Naval Architecture Archives - Marine Insight

What is Gunwale of a Boat or Ship?

Sudripto Khasnabis — Wed, 20 Mar 2024 11:38:29 +0000

Shipbuilding terminology owes its etymology to various cultures, practices, industrial influences, applications, and other factors. The gunwale of a boat, pronounced “gunnel” and not “gun whale,” is a seemingly simple yet critical vessel component.

On a boat or a ship, the gunwale denotes the upper edge where the hull and deck converge.

This article delves into the gunwale’s multifaceted significance, considering its historical origins, contributions to structural integrity and safety, and diverse modern-day applications.

The name gunwale borrows from a similar term called the gun ridge. Although nearly all boats feature a gunwale, this edge was initially known as a “gun ridge,” a band strong enough to support the weaponry employed on a warship (it does consider additional stiffening and load distribution characteristics to consider ship strength and stability).

In modern times, the association with onboard gun equipment no longer applies, but it remains a crucial design component with functional uses.

Generally speaking, docking and mooring are indebted to the gunwale. Fastening lines and fenders to this particular section (gunwale) secure the boat to a dock or another vessel.

In certain boats (and ships), the gunwale may be fortified (adding additional strength and protection) or broadened to accommodate fixtures like rod holders or cleats as well (image below). They also prevent wearing the shell plates at the edge or rim and any further structural compromises that may arise from long-term use.

In addition, the gunwale, for smaller boats, may also protect against water splashing or accumulating over the deck. This is when sailing in choppy waters, where waves can wash over the sides easily. Not to forget, sometimes, they may be used to access different parts of the boat (if wide enough, can be walked or stood upon) and store equipment (for example, in fishing boats).

So, in conclusion, it is important to note the function of a gunwale extends beyond just being referred to as the “edge”. It serves a range of purposes based on the vessel type.

Let me know your feedback, thoughts, and any other ship term you would like to read such an analysis for, in the comments below!

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Disclaimer: The author’s views expressed in this article do not necessarily reflect the views of Marine Insight. Data and charts, if used in the article, have been sourced from available information and have not been authenticated by any statutory authority. The author and Marine Insight do not claim it to be accurate nor accept any responsibility for the same. The views constitute only the opinions and do not constitute any guidelines or recommendations on any course of action to be followed by the reader.

The article or images cannot be reproduced, copied, shared or used in any form without the permission of the author and Marine Insight.

What is Gunwale of a Boat or Ship? appeared first on Marine Insight - The Maritime Industry Guide

How Deep Can Military Submarines Go?

Subhodeep Ghosh — Tue, 19 Mar 2024 09:02:36 +0000

Submarines are pressure vessels that can operate at submerged depths underwater. They are mechanically balanced by uniform hydrostatic pressure distribution acting on their surface.

Submarines are designed to withstand very high loads and pressures resulting from the hydrostatics of the water head at which they are immersed.

Any submarine design should always consider the theory of linearly incremental hydrostatic pressure and depth. Thus, when we choose a particular submarine design, its survivability is only at a certain depth, beyond which it collapses due to pressure loads beyond limit states.

Oxygen storage is a significant problem for submarines carrying living crew. All submarines are designed to carry onboard breathable oxygen depending on the number of crew and the vessel’s range, that is, the time it is expected to be underwater. This capacity is limited.

Moreover, at very high depths, the oxygen density increases due to climbing pressure gradients; hence, the exhaustion rate is also greater. Furthermore, various factors like propulsion, machinery, communication, ammunition, and power are fit to survive till some limiting conditions. Thus, for all practical purposes, submarines are designed to operate only to a certain depth.

Now, how much is this depth? The answer to this is highly relative and variable. It depends on various factors, like the vessel’s service, design, material properties, and the conditions in which it is expected to operate.

Conversely, based on the vessel’s requirements, the material and structural design metrics are also chosen so that at the desired conditions of operations, even at the upper spectrum of the margin of safety limits, the vessel remains intact and caters to its purpose.

Like all design states, there is a limit to the extent to which submarines can survive. The diving depth of a submarine that defines the submarine’s ability to operate and tread underwater is the most critical parameter taken into consideration right from the early stages of the design. This depth is not a single quantity and has various ratings or definitions. They are:

Normal Depth or test depth: This is the depth at which the submarine operates under normal conditions. Normal conditions can mean various aspects, ranging from the absence of a war or conflict to congenial weather conditions and sea states. Under these circumstances, the submarine is marked to operate at a range of depths and travels from one place to another within this range. This is also alluded to as the test depth, as the submarine is made to be run at such levels during sea trials. Test Depth has the lowest depth value of a submarine’s diving depth margins.

Maximum operating depth: This is the deepest permissible limit at which the submarine can operate under any circumstances to ensure intactness and functionality. During exigent conditions like wartimes or very severe weather conditions, the submarine can dive much deeper than normal conditions based on requirement. This rating marks the highest depth value the submarine can dive into without impairing its structural integrity, operability, and any aspect pertaining to its crew’s proper survival and sustenance. For all practical purposes, the maximum operating depth range is nothing absolute and can highly vary as designers specify this limit with some adequate margin of safety.

Design Depth: This is the critical point for a submarine that should not be exceeded even under the worst-case scenario. This is the maximum limit beyond which the chances of a structural collapse and overall damage in technical terms, including machinery failure, equipment malfunctioning, and loss in all communications, etc., are also very high. For all practical purposes, this can be considered the upper limit of the margin of the maximum operating depth.

Crushing Depth: This is the upper limit of the design depth and can be said to be the breaking point at which the submarine structure implodes due to high-pressure loads. It is taken at a margin greater than the design depth to ensure the safety margin.

Thus, these depth ratings can be arranged for a submarine design as Normal depth> Maximum operating depth> Design depth>Crushing depth.

Submarines’ highest depths have been well within the design depth for all practical purposes. Moreover, there is a distinction between how deep the submarines have been and how deep they can go, the latter pertaining to the limits of rated design depth and beyond and the former indicating the realistically recorded depth that has been attained.

Furthermore, this brings us to another contentious point: Submersibles and submarines, Which are also pressure vessels similar to submarines (but smaller and have different design characteristics), have attained greater depths.

Submersibles Trieste and Deepsea Challenger have marked their records in the history of mankind as having reached the Challenger Deep, the deepest point on Earth at the bottom of the Mariana Trench in the Pacific Ocean, boasting roughly a titanic depth of about 11000 m below mean sea level!

However, as submarines have different design configurations to cater to defence purposes, they operate at much shallower depths with a considerable margin of safety for defence purposes like stealth and climatic vagaries. Military submarines are designed robustly with high-grade material, a double hull construction, and an adequate amount of stiffening, like ribs and frames.

As the technical specification of any defence asset is highly classified, there is no absolute confirmation about how deep military submarines are designed to go. All available information about their capabilities is based on speculations, data leaks, limited government or high-level press reports, and technical estimations based on available design data, operating environments, and observed test depth performance.

Depending on the capability, defence vessels can dive a wide range of depths, most of the available values or figures within the design depth spectrum. Military submarines have been recorded to go as deep as 1500 m.

Russia’s (formerly Soviet’s) Akula-class submarines, the largest submarines ever built, were thought to reach maximum depths of 1200-1300 m below sea levels. The last of the class was decommissioned in early 2023.

Attack submarines belonging to the Yasen class are estimated to reach depths of about 600 m. In contrast, Ballistic missile nuclear submarines like the Borei class of Russia can reach depths of about 500 m.

US Navy also has an impressive fleet of powerful deep-dive submarines, with the Los Angeles class capable of plying at depths of up to 600-700 m. Their unclassified test depth remains at about 250 m. Ohio Class submarines, which are nuclear ones, are also believed to be capable of diving beyond 500 m, though their operational depth remains at 300m.

Virginia class submarines are believed to be the successors of LA class ones and have high technical capabilities. With test depths of about 500m, they are believed to be designed to tread even greater depths, 800 to 900m.

Nuclear-powered submarines, such as the Jin-class of China and diesel-electric Type 212 of the German Navy, are also powerful military submarines that can reach depths of up to 400 m.

Arihant-class submarines of the Indian Navy can also clock test depths of 300m and are believed to be capable of diving deeper under demanding circumstances.

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Disclaimer: The authors’ views expressed in this article do not necessarily reflect the views of Marine Insight. Data and charts, if used, in the article have been sourced from available information and have not been authenticated by any statutory authority. The author and Marine Insight do not claim it to be accurate nor accept any responsibility for the same. The views constitute only the opinions and do not constitute any guidelines or recommendations on any course of action to be followed by the reader.

The article or images cannot be reproduced, copied, shared, or used in any form without the permission of the author and Marine Insight.

How Deep Can Military Submarines Go? appeared first on Marine Insight - The Maritime Industry Guide

What is a Tumblehome?

Subhodeep Ghosh — Thu, 07 Mar 2024 06:58:16 +0000

The design of vessels is an interesting process and involves several typicality and eccentricities. The hull form and its various aspects comprise a crucial part of naval architecture.

As we know, a vessel’s hull form is well dependent on the requirements of the vessel, its service, and its capacity.

This article discusses a very interesting aspect of the hull form found in several vessels: the tumblehome.

What is a tumblehome?

Consider looking at the cross-section of a vessel. Its form depends on the type of the vessel. For finer-form vessels, the design is mostly tapering, with the upper parts wider than the lower area.

Similarly, for a fuller-form vessel, the cross-section resembles fullness throughout and has a more uniform bilge region, like in tankers or bulkers. For all practical purposes, in all conventional vessels, the cross-sectional frame at the midship, when viewed longitudinally, has the maximum beam or extent.

The cross-sectional forms become finer gradually as one moves towards the forward or aft region. Tumblehome deals with the cross-sectional characteristics of some fuller or semi-fuller hull forms.

Tumblehome is defined as the gradual narrowing or tapering of the hull above the waterline compared to its beam or maximum breath.

In simpler terms, when you look at the given cross-section view of the vessel, the decrease in the sectional breadth of the vessel towards the top, away from the maximum beam, is referred to as the tumblehome.

For all practical purposes, vessels with a tumblehome have a lower available breadth at the main or strength deck than the beam somewhere in or around the design waterline.

This is opposite to ship’s flare, the commoner design characteristic where the breadth increases above the waterline, and the main deck has a greater breath, making it the design beam of the vessel at midships.

Tumblehome is significant for a variety of reasons:

Ease in passing through or docking at specific channels, wharves, piers, and jetties where a reduced width at the top is advantageous.
Lowering the centre of gravity of the vessel and addressing stability problems in many designs
Accounting for an increased reserve buoyancy, the comparatively lesser hull volume at the top above the waterline leads to an increased draft compared to a similar design with a higher volume above the waterline.
In many naval vessels, along with stability, for stealth and weaponry purposes.

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What is a Tumblehome? appeared first on Marine Insight - The Maritime Industry Guide

Why Ships Sink – 10 Major Reasons

Ajay Menon — Wed, 06 Mar 2024 09:07:59 +0000

Do you have any idea on why ships sink? These massive superstructures weigh thousands of tons, can span hundreds of meters in length, and those responsible for moving goods worth billions of dollars, having an average lifespan of ten to fifteen years.

When building ships of massive dimensions, the risks involved also increase proportionately. The ship construction process can be fraught with a disaster waiting to happen, while the actual sailing on the high seas poses a major threat to the stability of the ships.

All manners of safety arrangements are undertaken by all shipping companies that run thousands of ships plying the oceans. But for an industry of such massive proportions, accidents do tend to happen due to avoidable causes, unpredictable natural elements or from rampant piracy.

In this article, we will closely examine 10 major reasons why ships sink.

1. Flooding

Flooding is the most common reason why ships sink. The scientific explanation behind how ships float is that the weight of a vessel is supported by the water it displaces when floating.

Mathematically,

Weight of the Ship =Volume of Water Displaced × Density of Water

The water that is displaced by the ship equals the volume of the ship that is submerged, and we can rewrite the equation as,

Weight of the Ship =Submerged Volume of the Ship ×Density of Water

When water is able to enter the vessel through openings in the hull or superstructure, the regions filled with water are no longer hydrostatically considered to be part of the ship. However, the weight of the vessel remains constant.

This creates an imbalance, where the weight of the ship is now larger than that of the displaced water. As a result, the vessel continually sinks lower in the water until it is completely submerged. Due to mounting water pressure, holds, walls and bulkheads may eventually rupture, which will lead to the vessel rapidly sinking.

2. Grounding and Collision

The ships are propelled by massive marine engines driving the propeller while the direction is controlled by the rudder. There have been many cases reported of grounding, which is bottom of the ship scrapping on the ground or on rocks near to the shore. However, the ship can sink after grounding in heavy or bad weather which will first damage the ship’s hull and heavy swell will take the ship to deeper water making it sink.

Also, ships are large structures that take time to respond to manoeuvring inputs from the bridge. On average, it may take a ship hundreds of meters to come to a complete stop, and time to turn effectively.

Given these circumstances, there is always a chance for a vessel to collide with other ships, tugs, ancillary vessels or floating structures such as port wharves if proper precautions are not taken.

Once a collision occurs, the hull of the vessel may rupture, leading to imminent flooding as discussed previously. In addition, there is a high chance that equipment such as the rudders or propellers may be damaged by the collision.

A collision can also lead to loss of cargo which can destabilize the ship leading to loss of stability which is explained in the next section.

3. Loss of Stability

All floating bodies have a metacentric height, that is defined as the vertical distance between the metacentre (M) and the vertical centre of gravity (G).

For ships, the vessel will remain relatively stable as long as this quantity remains positive. In the event it becomes negative, the vessel can capsize with the smallest of forces.

The metacentric height (GM) is directly related to a quantity known as the period of roll. This refers to the time that an oscillating body will take to come back to the original position of stability.

Vessels with very large values of GM will instantly reach an upright position, which can cause damage to the equipment and machinery owing to the large forces exerted.

On the other hand, very low values of GM will have extremely high periods of roll. In this case, the vessel has a high chance of taking on water through the deck. Thus, if the GM moves out of the safe region due to various conditions, there is a chance of the vessel sinking.

4. Poor Weather Conditions

Bad weather is exceedingly common for ships sinking, and contributes to nearly 75% of all other types of accidents. Due to the large unobstructed open space found in the ocean, wind speeds can reach the regions associated with typhoons or hurricanes. This can create massive waves that are able to capsize vessels.

Vessels can sink due to a few main reasons- wind and other forces forcing the ship to lean at dangerous angles to the port or starboard sides, waves on the deck adding weight to the vessel and forcing it lower into the water, or waves crashing into the side of the vessel and causing flooding.

Credits: manojmulchandani/YouTube

All these reasons force the vessel to take on water, which eventually leads to it becoming unstable and susceptible to sinking by the smallest of disturbances.

5. Negligence and Human Error

Fatigue, negligence and simple mistakes all contribute to a number of disasters at sea. These occur when ships are under-manned, have crews that are fatigued or are not properly managed.

As a result, simple avoidable errors are prone to occur. For instance, obstacles that float can get entangled in the rudder and propellers or can damage the hull.

If not spotted in time, the vessel can collide with them. In addition, if engine room measurements and adjustments are incorrectly made, there is a chance of the ship sinking due to a lack of thrust.

It is important that shipping and passenger lines take efforts to keep the crew well-rested and ensure that the vessel is adequately manned at all times.

Sometimes, a wrong judgement regarding technical aspects can lead to the stability of the vessel being compromised.

5. Faulty Equipment

On the open ocean, visibility can sometimes be low owing to mist or fog. In addition, waves can make it difficult to detect floating objects that may pose a danger to the vessel.

This is where modern equipment comes in, to guide the officers in the bridge in ensuring stability. However, incorrectly calibrated equipment is extremely dangerous, since the crew may use them to make key decisions.

In general, all equipment is to be routinely monitored and checked for accuracy at regular intervals. Although the preferred time interval between checks should be every thousand kilometres of the open sea or ocean sailing, cuts on spending can force companies to skimp on essential services. This can result in dangerous consequences that may cause the vessel to capsize and sink.

6. Improper Maintenance

Ships stay at sea for extended periods, often returning to ports once or twice in a month or so for loading supplies and refuelling. Corrosion, metal fatigue and prolonged exposure to harsh conditions can warp and damage the vessel. Without regular maintenance, there is a high possibility of an accident occurring.

For instance, the marine diesel engines that power modern vessels have extremely high ranges of operations RPMs. Under these conditions, the propeller shafts, rudders and propellers themselves can get damaged. In addition to vibrational loads, high-speed propellers are susceptible to cavitation, that occurs due to the boiling of water near the surface of the propeller. Thus, regular check-ups are required, else there is a chance of the propulsion systems getting damaged.

In general, small components are often the first to wear away, and thus comprehensive overall maintenance must be carried out diligently.

On average, ships with a lifespan of ten years have their full overhauls once in two to three years. If not carried out properly, it is possible that systems fail, leading to the vessel capsizing and eventually sinking.

7. Wartime Casualties

During the world wars of the early and mid-twentieth century, hundreds of ships and vessels were sunk. Torpedoes, underwater mines, depth charges, artillery fire etc. were responsible for the majority of these cases.

In addition to the actual wartime casualties, there continue to be accidents that occur because of undiscovered mines or floating charges that are still armed and highly dangerous.

In most cases of wartime sinking, torpedoes or explosives were used to rupture the hull, allowing water to flood the holds and drag the vessel down. To combat this, anti-torpedo protection such as toughened bilge keels were added to warships and commercial vessels plying dangerous routes. These softened the impact of the torpedo and sometimes deflected the main shockwave away from the ship.

8. Dock Mishaps

Docks and ports are cramped spaces that seek to maximize efficiency in the smallest of locations. Thus, ships need to be extraordinarily precise when manoeuvring, even with the aid of tugboats. However, considering the massive size of modern ships, there a multitude of port accidents that occur and sink ships.

For instance, if the port has not been correctly constructed, there is a high chance that a huge amount of water is compressed when a ship attempts to berth. The resulting hydrostatic pressure can rupture the hull and capsize the vessel. In addition, collisions with tugs, support vessels and the port wharf itself may damage the steel plating that makes the hull, which could sink the ship.

It is up to the port authorities to ensure that safety protocols are in place to control ships and guide them in manoeuvring around tight turns.

There are many cases of improper loading, leading to ship capsizing and sinking right on the jetty.

Piracy

Piracy at sea continues to be a menace, even though the ages of bearded pirates and ships are long gone. Modern-day pirates use sophisticated technology that rivals the navies of some countries.

Armed with missile launchers, torpedoes and interception devices, they are able to effectively board, loot and eventually sink the vessels that they attack. Generally, piracy results in the ship and the crew being held for ransom. However, sometimes the ships are too massive for the pirates to manage, and hence the bottoms are scuttled once the attack is complete.

Image Credits: imo.org

To combat piracy-related activities, several navies patrol the waters around dangerous zones such as the coastline and the Horn of Africa. These locations are a hotbed of criminal activity, and some countries have taken to setting bases up at strategic positions to protect ships passing through these waters.

Safety Measures to Prevent Sinking

Although ships are at the mercy of the elements, there are still steps that can be taken to prevent untoward incidents from happening. Regular maintenance and checks of individual components that make up the ship are essential to ensure that the vessel runs smoothly and has a long life.

Although cost-cutting is often the reason behind skipping checks, they actually reduce the life of the vessel, making it costly to the parent company. In addition, properly training the crew and having adequate personnel on board can reduce human error and negligence.

By making the crew aware of the safety protocol to be followed, the damage can be reduced, and lives can be saved. Along with this, properly designing the vessel can eliminate problems that are not apparent initially.

For instance, faulty propulsion valves have serious consequences, but cannot be identified during the sea trials. Also, properly plotting the route and following basic safety guidelines laid down by the SOLAS is essential to curbing accidents that may lead to a ship sinking.

Prominent Ships That Have Sunk

When talking of ships that have capsized, the most famous example that comes to mind is that of the Titanic. Built by Harland and Wolff and operated by the White Star Line, RMS Titanic set sail from Southampton on April 10th, 1912. While crossing the Atlantic, the ship struck an iceberg and promptly sank due to flooding. As the fore hull was damaged, the forward bulkheads took on water. As water filled the holds near the bow, the weight of accumulating water thrust the stern upwards. The building shear force on the hull eventually split the vessel in two.

Image for representation purpose only

An official inquiry into the cause for the sinking yielded information that the damage caused by the iceberg was far more serious than anticipated by the officers on the bridge, and that poor visibility and lax patrolling had led to the collision. As a result, no action was immediately taken, and evacuation was significantly delayed. In addition, inadequate lifeboats resulted in thousands of people losing their lives, as they were either stuck on the sinking ship or died of hypothermia due to the freezing cold ocean temperatures.

Another notorious tragedy was the sinking of the Costa Concordia on 13th January 2012 off the coast of Tuscany in Italy. Built-in the Fincantieri Shipyard for the Costa Crociere cruise line, the vessel was one of the largest ships built in Italy. During a cruise around the coast of Italy, the ship struck a rock which led to heavy flooding on the port side.

Image Credits: theparbuklingproject.com

Short-circuited electrical equipment resulted in a loss of power to the propulsion systems. In addition, the building water pressure forced the vessel into an irreversible list that eventually ran the ship aground, on the Isola del Giglio, located off the coast of Italy.

Evacuation started nearly an hour late and the rescue took more than six hours, which led to the death of thirty-two passengers. In addition, severe damage to the hull resulted in the ship eventually being scrapped at a shipyard in Genoa. The captain of the vessel was found guilty of manslaughter, as negligence had resulted in the ship running aground. Although the resulting deaths were considerably fewer than that of the Titanic, it served as a reminder that without the proper precautions and safety protocols, accidents can occur.

Over to you..

What are the main reasons a ship sinks?

Let’s know in the comments below.

Disclaimer: The authors’ views expressed in this article do not necessarily reflect the views of Marine Insight. Data and charts, if used, in the article have been sourced from available information and have not been authenticated by any statutory authority. The author and Marine Insight do not claim it to be accurate nor accept any responsibility for the same. The views constitute only the opinions and do not constitute any guidelines or recommendation on any course of action to be followed by the reader.

The article or images cannot be reproduced, copied, shared or used in any form without the permission of the author and Marine Insight.

Why Ships Sink – 10 Major Reasons appeared first on Marine Insight - The Maritime Industry Guide

Design Of Asphalt And Bitumen Tankers

Subhodeep Ghosh — Mon, 04 Mar 2024 08:13:15 +0000

With the population booming all around the world, rapid expansion and modernisation of human establishments, and a greater need for efficient connectivity in transportation, there is an increasing demand for roads. Whether it is a developed country or a third world, a rural or an urban area, a populated zone or a remote place, there is an ever-increasing requirement for the construction of roadways.

It is an undisputed fact that for the progress and prosperity of any country, proper and developed land-based connectivity is indispensable. Essentially, for any landmass, there should be free access from any corner to another unless there are some critical or hostile geographical constraints like mountains, dense forests, water bodies, and so on.

However, with advancing time, now even the adverse environments are getting access to people. In most countries, the road network is becoming prevalent across all routes and areas. So, unlike in the olden days, one does not need to worry about travelling from one tip of the country to another.

For the international trade supply chains as well, all forms of freight traded through air or sea need to be further re-transported from the terminals or ports and airports to their respective points as required.

In the US, the current federal fiscal fund allocation for asphalt or road construction is billed at an astronomical budget of nearly 100 billion US dollars.

In contrast, in populous countries like India, the annual government expenditures on major road and highway constructions are in the range of roughly 1,00,000 to 1,50,000 crore Indian rupees. Once again, all these whopping figures are likely to grow ceaselessly.

Hence, it can be said that for any nation, road or asphalt construction is itself a colossal industry and a vital organ of the economy.

A brief on asphalt construction

We must have all witnessed some form of road construction at some point in time or the other. For all practical purposes, most of the roadways are to date constructed out of a petroleum-based, gelatinous, residual or by-product material known as bitumen. This bitumen or asphalt is mostly prepared at very high temperatures of 150 to 180 degrees Celsius and is there in molten forms.

This concentrate has a very thick and sticky nature, and to this stone chips, pellets, gravels, sand, etc., are mixed well in mixers. This heated mixture is sometimes known as the tar or pitch and is laid over the desired areas in hot and semi-liquid form. Thereafter, in the areas where this is laid, a roller is usually run over to engender uniformity everywhere in a process commonly known as paving. After some time, the rolled and hot mixture cools off and hardens to give rise to smooth and solid surfaces for roads.

So, essentially, the bitumen acts as an adhesive for the constituents like stone, gravel, sand, etc. and binds them permanently. These kinds of road constructions are known as asphalt-based or bitumen-based works and have this very, very common blackish appearance.

Many roads are also built out of concrete instead of asphalt, where the former acts as the main binding medium. However, as concrete is more susceptible to damage under very harsh weather conditions, comparatively expensive and less procured than bitumen or asphalt, the latter type remains the most common type of road construction all around the world.

Introduction to Asphalt and Bitumen Carriers

Asphalt and bitumen transport is mostly local or regional as they are common and inexpensive, and every country is more or less self-sufficient in extracting, processing, and producing them. So, instead of intercontinental transport, they are limited to interstate and, at most, international routes. In most cases, asphalt and bitumen transport is limited to point-to-point voyages from one port to another. Asphalt trade through seas accounts for around 0.5-1% of the world’s maritime fleet.

So, asphalt and bitumen tankers are specialised tankers that are designed and constructed to carry asphalt or bitumen contents in the molten form at very high temperatures.

Everything from beginning to end associated with these special-type tankers is related to the temperatures. Asphalt and bitumen are required to be kept at an exceptionally high temperature, otherwise, they tend to pre-harden and be rendered useless.

Now, note that before paving roads, the temperature kept is from 150 to 200 degrees Celsius. This is the temperature that normal high flames can keep their contents in at atmospheric conditions. Moreover, the sticky, semi-liquid, and thick form of asphalt that is ideal for mixing the remaining contents binding them and also allowing for lower time to harden after rolling is best kept at these temperatures.

However, while transporting in ships, the thickness and density of this material need to be further decreased, or in other words, the nature of this asphalt needs to be kept even nearer to liquified form. Why?

The reasons are simple: The closer the contents are to liquefied form, the easier it is to carry as well as load and offload. The asphalt or bitumen tar, if kept in liquefied form, can be loaded as well as unloaded easily with the help of discharge pipes from the vessel, like oil or other forms of liquid cargo.

Furthermore, when the viscosity is lower of the cargo content, there is also a lesser tendency for the cargo to settle at the bottom and hamper not only the loading/offloading operations but also the uniform structural loading of the vessel due to excessive higher loads acting on the bottom areas of the vessel. Also, after offloading, stripping the cargo holds of the residues becomes a very big ordeal for highly viscous type cargo contents.

Hence, for all practical purposes, the cargo contents of an asphalt or bitumen tanker need to be kept at a continuously high temperature in the order of 250 to 300 degrees Celsius.

Let us now look into the core aspects of the design of these tankers next section.

Design of Asphalt and Bitumen Carriers

General

They are mostly small to medium-sized cargo ships with maximum capacities within 30000 dwt tonnage and with cargo designations including all related cargo content like asphalt, bitumen, coal-tar-pitch, creosote, and sometimes fuels for combination-type carriers, but that too within permissible characteristics like low inflammability.

The vessels usually has an elevated main deck in the way of the cargo holds/tanks that is off limits for the crew’s regular usage and has high-grade insulation systems for protecting the cargo from external conditions like freezing as well as preventing massive heat indices from escaping from the spaces to the outside environment.

Similar to other common types of cargo vessels like tankers or bulkers, they have a standard full-form hull type, often with transom sterns. For all practical purposes, all major machinery spaces, like the engine room, are placed at the aft along with the deckhouse above the main deck in the aft.

From a subdivision point of view, the vessels have standard divisions from a damage stability perspective and have well-marked spaces for cargo spaces, ballast, engine spaces, forepeak, and other utilities like freshwater or storage spaces.

Unlike containerships or ferries, they do not have tight schedules for voyages. They mainly have low to medium-speed 2-stroke or 4-stroke diesel engines, usually with a single-screw propulsion system, akin to tankers or bulk carriers. The propulsion system is connected to shaft generators and reduction gearboxes.

Though earlier designs had a single hull, since the contents of asphalt and bitumen tankers are considered hazardous and polluting, double-hull construction is being widely used for modern constructions similar to oil tankers.

Tankage And Heating Systems

Now, let us come to the specific and specialised characteristics of these kinds of carriers.

As mentioned above, bitumen and asphalt carriers need to be transported and continuously maintained at very high temperatures in the range of 200-300 degrees Celsius. Hence, these kinds of vessels are equipped with specialised cargo heating system arrangements.

Most of the heating of cargo is done through the means of thermal oil at very high temperatures. This thermal oil, in turn, is heated by mostly boilers or boiler-like heater electrical systems. Boilers are mostly fired by the Heavy Fuel Oil (HFO) used in main engine propulsion.

So, from the point from where it is being heated, this thermal oil is pumped to the cargo spaces through a special system of piping and is circulated and re-circulated around the cargo tanks through heating coils which are tubular structures transferring the heat to the cargo.

The number of such boilers or heaters depends on the capacity of the vessel. Sometimes, for colder outside temperatures, when rapid heat loss is a crucial problem, a greater number of boilers may be fitted to cater for the higher-level heating of the thermal oil. These heating units have a heating capacity in the range of 1000000 to 2000000 kcal/h rates. In most designs, operating under normal circumstances and external temperatures, one boiler unit should be sufficient to supply heat to the entire rated cargo capacity tonnage on board. The pumps for the same are also of high capacity.

They should run continuously with sufficient backup systems to maintain the temperature of the cargo to desired levels and also, at the same time, prevent settling or coagulation. Often in modern designs, the heat content lost during this circulation and re-circulation process is recovered as ‘waste heat’ and used for other utilities.

After heating, the next major ambit in the design of these carriers is the containment and transport of cargo. Storage of such high-temperature cargo is a very complex matter both in terms of structural as well as the overall vessel risk. Such highly heated cargo leads to tremendous thermal expansion and stresses on the hull that can lead to big-time structural failures.

Moreover, the direct connection of cargo holds to the entire vessel structure can trigger accidental overheating, heat leaks, and fires. So, bitumen and asphalt tankers are fitted with what are known as independent tanks. What are independent tanks? Independent tanks are holds that are not integral to the ship structure. In other words, they are neither permanently welded or is a component of the main hull structure.

These tanks are separately fitted and installed onto the vessel and are supported by plating, pads, bearings, washers, clamps and so on. Sufficient clearance is kept between the tank boundaries and the adjacent shell plating or structure at the sides and bottom to allow for maximum thermal expansion.

The fitting or installation of these tanks is very critical as any defect or error can lead to precarious frictional forces between the tank and the hull structure through the bearings or attached supports, leading to unbalanced loads or forces and, worse, risks like fire outbreaks due to heating.

Most of these tanks are numerous and not very big like LNG or LPG tankers and are collectively known as a single unit called blocks. The types of tanks are often classed as A, B and C. (omitted from discussion in this article).

Another very important aspect of the tanks is the insulation. The very high temperatures pertaining to these holds should be well contained; otherwise, they can be detrimental. On the less serious side, heat loss is also not desirable for the cargo, as already explained above. So, very high-grade insulation is provided to prevent the heat from escaping from the holds.

These insulations are multi-level tested and approved and are present in a specific level of thickness as recommended by the manufacturer as well as classification guidelines. In earlier designs, thick stuffings of wool or fabrics were used, but in almost all modern designs, synthetic and mineral-based insulation is chosen. Any form of cracks or faults in the way of the tanks and their surroundings are repeatedly inspected to prevent any kind of heat loss or leakage.

Outside the insulating layer of the tanks, a separate layer of water and air (space) is also provided to minimise heat transfer in modern designs. Most of the waste heat recovery takes place in between the insulation, heating coils, and tank boundary. The main cargo content is stored in the region known as the core. See the following simple schematic for tankage:

With increasing distance from the core, the temperature/ heat flow also rapidly reduces, as shown in the figure.

For bitumen/asphalt carrier designs, three modes of heat transfer- conduction, convection, and radiation are taken into account.

Most classification norms have special guidelines for these vessels. And along with special strength analysis, thermal analysis for these kinds of tankers is also mandatory to determine thermal stresses and loss of strength due to this highly heated cargo considering the highest level of temperatures and full-load capacity.

As per classification rules, most scantlings, especially in the way of tanks, are kept on the higher side to account for the thermal stresses, increased loads, and also higher fatigue strength values.

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Disclaimer: The authors’ views expressed in this article do not necessarily reflect the views of Marine Insight. Data and charts, if used in the article, have been sourced from available information and have not been authenticated by any statutory authority. The author and Marine Insight do not claim it to be accurate nor accept any responsibility for the same. The views constitute only the opinions and do not constitute any guidelines or recommendations on any course of action to be followed by the reader.

The article or images cannot be reproduced, copied, shared, or used in any form without the permission of the author and Marine Insight.

Design Of Asphalt And Bitumen Tankers appeared first on Marine Insight - The Maritime Industry Guide

A Guide To Naval Architecture

Soumya Chakraborty — Tue, 06 Feb 2024 06:19:31 +0000

Over the past century, naval technology has developed leaps and bounds. Ships and other sea-going vessels, along with the technologies of marine navigation and shipbuilding, have seen huge advancements, leading to the establishment of various dedicated fields of study.

Naval architecture is one such specialized field that is an integral part of the shipping industry.

What is Naval Architecture?

Naval architecture is the name given to the science and engineering of designing and manufacturing of sea-going vessels such as ships, yachts, powerboats, steamers, tugs, fishing boats, barges, warships, cruise ships, icebreakers and even submarines. In addition to these, the study of naval architecture also deals with designing and manufacturing offshore structures of all kinds, whether commercial or military.

Each of these structures, whether permanent, offshore, or movable, such as floating structures, has undergone vast changes with the development of this particular field of technology.

Naval architecture has been instrumental in the evolution of the new age sea machines and ports – some of these are very high-valued, complex pieces of engineering structures ever created by mankind.

A naval architect specializes in every facet of maritime activities, such as dredging, shipment and transportation, offshore drilling, etc. This field caters to the discipline of the shipping industry, from research and development to designing, building, and repairing all the machines mentioned above.

The naval architect is responsible for the development, economic feasibility, values, and safety of marine vessels and related units.

Read what naval architects do here.

It is of utmost importance that a naval architect is updated with all that is latest in the maritime field and stays connected with new developments and research. These professionals also have to be excellent at coordinating with other professionals who are experts in the marine discipline, such as scientists, marine surveyors, engineers of all departments, seafarers, accountants, mariners, and even entrepreneurs.

Industry experts can provide the best views on new, developing marine details and varying needs, and naval architects should learn how to incorporate these details while designing and manufacturing ships and other marine structures. Thus, teamwork is essential for the smooth functioning of this field’s operations.

A naval architect must also be extremely good at management and team coordination. Any person who engages in naval architecture should have patience, understanding, time management, man management, an eye for detail, and teamwork, among other things.

In terms of technical content, this profession is a beautiful blend of art and science, as it involves creative and artistic thought and an academic and knowledgeable mind. Working knowledge of other departments is an advantage that is welcome for anyone who wants to make a career in this field.

The naval architecture industry has had a long-lasting impact on the socio-economic status of the world. It would be safe to say that the developments that the marine world has witnessed over the course of the last century would not have been possible without the blossoming of the field of naval architecture.

How to Become a Naval Architect?

Note: The procedure of becoming a naval architect depends on the country one belongs to. One should be able to find information about their respective country by going through the website of some prominent maritime academies.

E.g. in India, the universities offering the best naval architecture courses of the country are:

Indian Maritime University, Visakhapatnam Campus
Indian Institute of Technology, Kharagpur
Indian Institute of Technology, Madras

One would have to qualify in the IMU-CET test (a common entrance exam) for being eligible to be offered admission to Indian Maritime University, Visakhapatnam Campus. For the IITs, one would have to secure a decent rank in the IIT-JEE (Advanced) examination.

There are other private universities that offer this course. Admission to these institutions can be secured by qualifying their respective entrance examinations.

What is the Ranking Hierarchy for a Naval Architecture Profession?

There is no fixed ranking hierarchy for naval architects. In a design firm, a fresh graduate naval architect can work his way up to the ladder to hold positions of highest technical responsibility in the organisation. The same holds for shipyards and classification societies. However, to make ones way to the tier 1managementt level of an organisation, management education is necessary.

What are the Main Software and Tools Used by Naval Architects?

It depends on what one is working on. At the initial design stage, software packages like NAPA and Rhino are widely used for surface modelling. Aveva Marine Initial Design, Maxsurf Modeller, Autohydro are used for stability analyses. Aveva Marine Initial Design is also widely used for hydrodynamic analysis.

Hydrodynamics and Resistance Calculations can be carried out using packages like Shipflow, ANSYS Fluent, and StarCCM. For seakeeping, manoeuvring, and diffraction analysis packages like StarCCM, OpenFOAM, WAMIT, ANSYS Aqwa and OrcaFlex are widely used.

In the production design stage, specific modules of packages like AVEVA Marine, FORAN, NUPAS CADMATIC, and NAPA STEEL are engaged in the process. The choice of software is a function of the type of vessel, its size, the requirements of the design, and other technical offerings of the package. ANSYS modules are also widely used for structural analyses.

Apart from these, it is important to note that a good hold over Microsoft Excel is necessary for a good designer, as a lot of preliminary data analyses, and naval architectural calculations are carried out in MS Excel.

How are the Job market and Prospects of Naval Architects?

The job market for naval architects depends on the country one is looking at. While the shipbuilding sector in India is yet to achieve its full potential compared to those other Asian and EU nations, there are opportunities for good talent in the country. The primary areas that employ naval architects in India are ship design firms, Classification societies, shipyards (public and private), and marine consultancy firms.

When one looks at similar opportunities overseas, they are better both in terms of the technical exposure and the pay packages. Many big ship-repair docks in the middle east, sub-sea oil exploration technology design companies, shipping companies in other Asian countries provide attractive opportunities, but also look for suitable talent and experience.

Future prospects can also include higher education and research work in areas of structural engineering, sub-sea engineering, naval architecture and ship design, etc. Reputed universities like –

Osaka University- Japan,
The University of New Orleans-the USA,
University of Southampton- UK,
University of Strathclyde- UK,
University of Michigan- USA, etc.

These universities provide world-class opportunities for higher education and research in the field of naval architecture.

What is the Lifestyle of a Naval Architect?

The lifestyle of a naval architect varies depending on various factors like work domain, job location, etc. The first few years of a naval architect are best invested in acquiring the required skills that would enable him/her to perform at higher levels of responsibility in the future. This may include working on specific software modules and gaining expertise in them, diversifying one’s experience through exposure to multiple kinds of projects, attending relevant conferences and industry conclaves, and keeping oneself updated with the latest technologies in the industry by subscription to the top journals. In the long term, when most of the learning is done, a naval architect acts as a conduit between the multiple functional stakeholders in a design project.

What are the Names of Some Popular Companies that hire Naval architects?

Some popular companies that hire naval architects in India are:

Public Sector Shipyards

1) Mazagon Dock Shipbuilders Limited

2) Garden Reach Shipbuilders Limited

3) Cochin Shipyard Limited

4) Goa Shipyard Limited

5) Hindustan Shipyard Limited

Private Sector Shipyards

1) Larsen and Toubro Shipbuilding

2) Reliance Defence Industries Limited

3) Tebma Shipyard Limited

Classification Societies

1. Indian Register of Shipping

2. Lloyds Register

Marine Design Consultancies and Firms

1) Vedam Design

2) Aries Marine Consultants

3) Marintek

4) Conceptia

5) Buoyancy Consultants

The opportunities increase manifold in the international arena. Some of the largest shipyards like Samsung Heavy Industries, Mitsubishi, Keppel Shipyard, Drydocks World-Dubai, Fincantieri and others of the top league provide world-class opportunities and exposure to naval architects. Most of the world class shipyards also offer the latest design experience in their respective design departments.

All the classification societies worldwide are the most suitable place to work for naval architects who look for specialisation in rule development, plan approval, and marine surveying. Apart from these, there are many software development companies that look for naval architects for providing better software solutions to their customers.

What Further Studies can a Naval architect do?

A naval architect can pursue a range of specialisations offered by various universities. Some of them are ship design, structural design, marine structures, hydrodynamic design and offshore structures design. The range of specialisations and course offerings vary according to the universities offering them. We’ve mentioned some of them previously.

What are the Famous Naval Architecture Colleges in India and abroad?

In India, the universities offering the best naval architecture courses of the country are:

1) Indian Maritime University, Visakhapatnam Campus

2) Indian Institute of Technology, Kharagpur

3) Indian Institute of Technology, Madras

4) AMET University, Chennai

Some of the universities that are globally known for their naval architecture courses are:

1) Osaka University- Japan

2) The University of New Orleans- USA

3) University of Southampton- UK

4) University of Strathclyde- UK

5) University of Michigan- USA

What are Some Famous Books that Naval Architects Must Have?

Though there is a range of books that a naval architecture can refer to, there are a few that every naval architect refers to in his/her career:

1) Principles of Naval Architecture (By Edward V. Lewis, SNAME)
2) Basic Ship Theory (By E.C. Tupper and K.J Rawson)
3) Introduction to Naval Architecture (By E.C. Tupper)
4) Ship Stability for Masters and Mates (By D.R. Derret)
5) Ship Construction and Welding (By N.R. Mandal)

What are the Differences Between Naval Architecture and Marine Engineering?

The difference is significant. The expertise of a naval architect lies in designing and building ships, submarines and other marine structures. Due to their complex engineering, a naval architect is a professional who brings together the contributions of a mechanical engineer, electrical and electronics engineer, material engineer, and other disciplines to suitably apply them on marine design. At any stage of the design or construction, the only go-to person who could have an overview of all the nuances involved is a naval architect, because he not only acts as a point of contact between all the involved engineering applications, but also has knowledge on Stability, Hydrostatics, Strength and Structural Design, Classification Society Rules, SOLAS Rules, Resistance and Powering, General Arrangement Layout, and all the design details in the project.

A marine engineer, however, is someone who specialises in operating and maintaining all the engineering systems used on a ship. When a ship is at sea, it is the team of marine engineers who keep the systems running and free from breakdown. A good marine engineer is also expected to know the design of most of the engineering systems used on ships. Every Chief Engineer on a ship is a graduate marine engineer.

What is the Average Salary of Different Ranks and Professions in Naval Architecture India and Abroad?

While there are no such ranks in the profession of a naval architect, some positions that naval architects hold in the Indian industry and worldwide are:

1) Designer to Chief Designer (Engineering / Stability / Systems / Structural)

2) Surveyor (Classification Society)

3) Marine Consultant

4) Production Manager as ranks above it (in shipyards)

5) Offshore Structures Designer

This is, however, a broad layout. There is a wide range of roles that are offered to naval architects, which depends on the organisation. But to sum it up, a naval architect, with years of experience or relevant management education is usually the most suitable professional for serving the highest hierarchical roles in the ship-building and maritime design industry.

Disclaimer: This is not a promotional post. The websites/books, if mentioned, are ranked randomly and not in any particular order. The authors’ views expressed in this article do not necessarily reflect the views of Marine Insight. Data and charts, if used, in the article have been sourced from available information and have not been authenticated by any statutory authority. The author and Marine Insight do not claim it to be accurate nor accept any responsibility for the same. The views constitute only the opinions and do not constitute any guidelines or recommendation on any course of action to be followed by the reader.

The article or images cannot be reproduced, copied, shared or used in any form without the permission of the author and Marine Insight.

A Guide To Naval Architecture appeared first on Marine Insight - The Maritime Industry Guide

How Much Cargo Can A Cargo Ship Carry?

Subhodeep Ghosh — Mon, 05 Feb 2024 09:08:49 +0000

The weight of a vessel is a very interesting aspect in the first place. Unlike all other physical objects, when we talk about the weight or mass of a vessel or any floating object in general, we usually allude to displacement.

This displacement, as we know, is nothing but the mass of the floating structure itself and is also equal to the mass of the water the vessel displaces to remain afloat, as per Archimedes’ principle. This quantity is also sometimes expressed in terms of volumetric displacement, which denotes the volume of the water displaced by the weight, which weighs the same as the weight of the vessel.

The displacement can be further divided as:

Lightweight
Deadweight

The lightweight is essentially the inherent weight of the vessel itself, including the structural weight of the ship, plus the weight of systems, machinery, equipment, cablings, piping, ducting, wiring, outfitting, and so on. Deadweight is the weight the vessel can carry: cargo, consumables, fuel, freshwater, ballast, people (passengers or crew), provisions, and other effects. Hence, a vessel without all the items in deadweight is basically in a lightship condition.

Though displacement is the common designation of any vessel, the size of a vessel is more specifically denoted depending on the type of ship for all practical purposes. When we speak about cargo and common types of commercial vessels like passenger ships, they can be referred to in more than one way, and that’s often confounding.

For instance, a passenger ship is usually referred to by the maximum number of passengers it can carry instead of the displacement. A 1000-pax ferry, for example, can hold up to a maximum of 1000 people. Deadweight tonnage is another very common term that refers to the maximum carrying capacity of the vessel in terms of weight, which is nothing but the deadweight measure of the vessel.

We have learnt in our previous articles about other standardised measures like Gross Tonnage (GT) and Net tonnage (NT).

To recapitulate, GT is based on the total usable internal space of a vessel, whereas NT is based on the space within the GT that is commercially revenue generating, that is based on spaces designated for cargo or freight or consumers (passenger ships).

They widely differ from the deadweight tonnage as they encompass the total carriable weight of the vessel, including other expendables of deadweight like fuel, lubes, ballast, water, consumables, etc.

Cargo ships that are laden with cargo are usually addressed on the basis of their purpose and utility.

Bulk Carriers and similar vessels

These vessels, mainly designated for transporting dry cargo in bulk format, are referred to in terms of their deadweight tonnage or, more commonly, the DWT tonnage. Hence, when we say that a bulk carrier is 100,000 DWT certified, it essentially means that the given vessel can hold up to a maximum of 100,000 metric tonnes of cargo in its holds.

As we know from several of our previous articles, bulk carriers range extensively in size from 500 tonnes to as much as a whopping 300000 tonnes. The Pacific Flourish is the largest bulk carrier in the present, with a maximum carrying capacity of almost 400000 tonnes!

The wider category of bulk carriers is the General-Purpose Carriers, which can carry more varied types of cargo but usually dry only. Similarly, other miscellaneous special sub-types of bulk carrier vessels include ore carriers, coal carriers, timber carriers, etc., and they are referred to in terms of their deadweight tonnage only. Apart from DWT, GT and NT are commonly used for dry cargo vessels.

Tankers and similar vessels carrying liquid cargo

Like bulkers, tankers are also referred to in terms of their deadweight tonnage expressed as DWT or tonnes, along with GT and NT. Crude oil carriers, gas carriers, chemical tankers, etc., all fall under this category. These are based on the maximum amount of liquid cargo the vessel can carry. Like bulkers, liquid cargo ships can also vary widely in size, ranging from as low as 500 DWT to as large as over 400000 DWT.

Containerships

They are one of the most common types of commercial cargo vessels where packaged cargo is in the form of standard containers. More than the overall displacement tonnage, they are mostly identified in terms of the maximum number of containers they can carry.

Remember the TEU units that we had discussed many times? Containerships are mainly designated in terms of TEUs. Hence, a 10000 TEU containership essentially means that the vessel can carry a maximum of 10000 1-TEU standard-size containers on board. Conversely, they also mean they can carry 5000 2-TEU or a combination of 5000 1-TEU + 2500 2-TEU containers.

Other types of vessels like Ro-Ro and Ro-Pax

Other types of commercial vessels can be described in different ways. Ro-Ro vessels that are mainly used to ship wheeled cargo like cars are defined in some special units like lane metres. By convention, 1 lane metre equals a deck area equivalent to 2 square metres.

Based on the vehicle sizes and the available lane metres, the total carrying capacity of a Ro-Ro can be deduced. Ro-pax vessels that are combinations carriers of vehicles, as well as passengers, can be defined as a combined measure of the lane metres and the number of pax-es it can carry.

Sometimes, these kinds of vessels are also defined simply as the number of vehicles they can carry. Other than these, they are referred to in terms of GT or NT as well.

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Disclaimer: The author’s views expressed in this article do not necessarily reflect the views of Marine Insight. Data and charts, if used, in the article have been sourced from available information and have not been authenticated by any statutory authority. The author and Marine Insight do not claim it to be accurate nor accept any responsibility for the same. The views constitute only the opinions and do not constitute any guidelines or, recommendations on any course of action to be followed by the reader.

The article or images cannot be reproduced, copied, shared or used in any form without the author’s and Marine Insight’s permission.

How Much Cargo Can A Cargo Ship Carry? appeared first on Marine Insight - The Maritime Industry Guide

What is Deck Plating on Ships?

Subhodeep Ghosh — Thu, 01 Feb 2024 10:15:35 +0000

Vessels are divided vertically by decks. These decks either extend fully and are flush with the primary structural members of the vessel or are partially disposed of up to some span.

Depending on the extent of their span, if they are significant, they contribute to the longitudinal and transverse structural strength of the vessel. In other words, they absorb a significant portion of loads, especially in the form of bending stresses.

Deck plating thickness can vary widely depending on a host of factors ranging from ship type to the region of disposition of the plate. However, for all practical purposes, deck plating thicknesses for any kind of vessel usually range from 4-5 mm to 20-25 mm.

The larger the ship type, the greater the scantling distribution of deck plates. Moreover, deck plating thickness also depends on the following:

Disposition
Highest magnitude of structural loads acting
Contribution to global strength

The deck plating in the way of cargo spaces, tankage, equipment, machinery spaces, and so on have higher thicknesses. Furthermore, the deck plating is given very high thicknesses in the way of openings like hatches. This is due to the factor owing to structural discontinuity or loss in strength due to the opening where it needs to be compensated. Similarly, the structural arrangement plays a very important role.

For continuous decks, the plating is given the highest number of thicknesses in the way of the midship region as the maximum level of stresses is incident there, in a longitudinal sense. For all practical purposes, about 40-50% of the deck extent in the way of midships is given the highest thickness. Likewise, locally, the scantlings of the deck plating need to be increased accordingly wherever there is an incidence of high localised loads or stress concentrations may occur.

For instance, in the way of some deck installations like a crane or gantry, the plating underneath and adjoining has a high thickness to absorb extra loads arising due to the equipment. Other critical points of stress concentrations occur due to structural discontinuities, and the scantlings must be increased accordingly—for instance, the connections between the main deck and the superstructure or deckhouse.

Decks that are continuous, contribute to the structural strength in global terms. They are given high thicknesses. For all practical purposes, the main deck, also known as the exposed deck or weather deck for all conventional vessel designs, forms the hull structure’s topmost boundary and intersects with the superstructure of the deckhouse.

This deck needs to have the highest level of load-bearing capacity overall and forms an intrinsic part of being a primary longitudinal strength member of the vessel. Hence, this is known as the strength deck. The main deck is always highly stiffened. These partial decks, in the way of machinery spaces, have very high levels of scantlings as they need to bear loads of machinery and engines.

For all practical purposes, decks in the deckhouse or superstructure have lower scantlings than the main hull structure as they do not participate in the global strength of the hull girder. However, the superstructure, as a whole, somewhat also contributes to the global strength of the vessel in what is known as the superstructure effect.

All requirements about the material, thickness, and necessary stiffening of decks are determined by classification rules and guidelines. Steel is the most common deck material and is mostly used in the form of grades like B, D, and E. However, depending on the requirement, these may change (for instance, in areas of high loading due to machinery or in the case of defence combat ships), and higher grades of steel are used.

Deck plates are strongly welded in both transverse and longitudinal manner. Simple hand welding, automatic welding, submerged arc welding, and friction stir welding are some common welding techniques used.

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What are Triple Hull Vessels?

Subhodeep Ghosh — Mon, 29 Jan 2024 07:07:56 +0000

Monohull vessels have been and will be synonymous with ships, come what may. This is owing to all kinds of reasons ranging from convenience to simplicity, low costs to large capacity, ease in construction to acceptability. However, over the years, there has been an escalated demand to explore unconventional design types in the quest for advancement.

Monohull vessels, despite all kinds of efficient designs, still lacked in terms of high speed and resistance to rough sea states. Moreover, depending on their design, the basis for monohull vessels is directly related to the buoyancy factor, which essentially means that for greater size and capacity, you have to increase the displacement. Furthermore, with all monohulls, there is always some calculated risk or problems in terms of seakeeping and stability characteristics, even if in very minimal degrees for a very safe design.

The concept of multihull vessels came in response to mitigate such challenges and delve deeper into the realm of unconventional designs for improved utility. Multi-hull vessels are vessels that are characterised by the construction of multiple hulls, either two or three, known as catamarans and trimarans, respectively. The advent and application of multi-hull vessels have been the collective result of three major requirements: i) speed, ii) stability and ii) capacity.

Catamarans or twin-hull configuration was the immediate result. This configuration accommodated two hulls, mostly symmetrical and identical, connected mostly by the main deck or some crucial structural member. In almost every vessel, the superstructure or deckhouse was mounted atop the main deck.

The advent of multihulls was incongruous with the evolution of high-speed planning crafts, which used the interesting concept of hydrodynamic planning effect and partial displacement to tread through waters at high speeds and increased propulsive efficiency. Combining both these developments was quite a game-changer where small to average-sized crafts for defence or passenger flourished dramatically. These high-speed craft had planing characteristics and were hydrodynamically manifold efficient. Moreover, they catered to the requirement of higher payload and capacity over a lesser displacement.

This lesser displacement required per unit payload coupled with high-speed planing characteristics and propulsive efficacy also significantly reduced resistance, both wave-making as well as frictional (due to lesser wetted surface area from each hull).

However, along with the many advantages, some disadvantages were there still. One of them was the high degree of stress that occurred in the way of the connecting cross deck, especially in rough sea conditions. These were mostly due to the torsional and transverse behaviour exhibited as a result of two hulls tending to behave independently. Moreover, these twin-hull configurations also exhibited high motions, including effects like slamming and pounding.

Also, the problem of hydrodynamic resistance was not mitigated at low speeds. The problem of fatigue was also quite significant in the way of the cross deck, especially when the separation between the two demi-hulls was above a certain limit.

Nevertheless, catamarans, or twin-hull configurations, have been common for the last several decades, and their numbers are increasing. Some years down the line, trimarans were proposed to further streamline this problem.
Trimarans are those vessels which essentially have a three-hull configuration.

These three hulls are connected by a single deck known as the cross-deck. For all practical purposes, there is a bigger main hull in the middle, and is, in turn, supported by two smaller side hulls, known as outriggers. However, some designs also have the hulls the same size as in the case of catamarans.

The main design philosophy of trimarans is nothing much different from the broad concept of multi-hull vessels: higher payload or tonnage capacity to displacement ratio. This essentially means that they are able to cater to higher carrying- capacity both in terms of weight as well as space-volume without a significant increase in the displacement that is required. This is a win-win situation for any kind of design as you are able to optimise everything that is ever ideally envisaged:

Speed
Hydrodynamic performance
Stability and seakeeping characteristics
Capacity
Greater deck area
Resistance and propulsion characteristics
Lesser required displacement
Lesser fuel consumption
Optimised distribution of loads and stresses

Design Philosophy of Trimarans

Trimarans were conceived based on the following design goals in mind that would ratify the reliability expectations from multihull vessels even further.

Managing the resistance even more, especially those stemming from low speeds and large ship motions, and further improving on the speed characteristics. The powering requirements also increase dramatically.
Reduce wetted surface area even further at similar displacements. This essentially means at even smaller displacements, the payload, as well as the available spaces and deck area, is increased. Hence, by making each of the hulls even more slender, a high value of payload can be maintained. This, in turn, even further improves on the resistance and propulsive characteristics.
The stability of the vessel is related to the previous point. A triple hull configuration caters for higher stability, as obvious. Hence, not only are we increasing the payload but also having the upper hand on stability while improving the resistance in tandem.

Consequently, the seakeeping characteristics of the vessel are also augmented, especially during rough sea states.

Flexibility in terms of design. When there is an availability of more space and deck areas, there is more amount of freedom to augment the arrangement.
Structural strength. This is one of the most crucial aspects associated with the design of trimarans. A 3-hull configuration increases the structural strength of the vessel manifold, both in terms of transverse and longitudinal.
All oncoming loads on the vessel are distributed more efficiently on the three hulls. As a result, the strength-bearing capacity of the vessel under all circumstances of sea states and motions of the vessel is improved. This also compensates in terms of increased higher usable payload even further. Safety and reliability also come hand-in-hand with strength. Henceforth, a greater strength translates to higher survivability.

Lastly, due to the above advantages, the reduced cost of the vessel in terms of lower material requirements as lighter structural weight can be commensurate to a better design.

Though mostly similar to conventional vessels, the initial design process of trimarans involves the following important aspects:

Deciding on the stability parameters like metacentric height. As the vessel is already inherently stable, GM height can be increased. Moreover, as per regulations, if the main deck height (and hence the above-water clearance) of the cross-deck(s), which is related to the GM itself, is more than 5% of the waterline length of the vessel, motions like slamming decrease significantly. Hence, trimarans offer much more freedom to increase the GM as compared to conventional vessels.
Deciding the dimensions of the side hulls. This is also closely related to the damage
stability criteria.
Designing the cross-deck is important, just like in the case of catamarans. The adequate stiffening of the same is also crucial.
Separation between the hulls based on resistance, strength and utility of the vessel.
Finally, meticulous allocation of the internal spaces optimising the design and the requirement.

However, multi-hull vessels become less feasible as vessel sizes increase due to a wide range of factors like lack of planing characteristics, lesser feasibility in design, complexity in construction, and so on. Nevertheless, many designs, especially within the gamut of defence vessels, passenger vessels, and other special types of vessels, have explored the feasibility of multi-hull designs with evolution over the years. They have been important successes, even if at a higher cost.

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What are Freeing Ports On Ships?

Subhodeep Ghosh — Thu, 25 Jan 2024 07:07:35 +0000

For exposed decks in ships, drainage is very important. Any form of accumulation of water can lead to a variety of problems ranging from stability to interference with other entities, structures, outfits, or machinery.

The main deck or weather deck has drainage holes or scuppers for the egression of water. However, the requirement is more when vessels have a significant bulwark arrangement in the way of the weather or main deck.

What is a bulwark?

A bulwark is a wall-like projection around the exposed deck and in line with the side shell plating such that it extends well above the main deck level. The purpose of a bulwark is for the protection of crew or personnel or passengers and deck cargo (if any) from falling off the sides. Moreover, bulwarks are also instrumental in protecting the exposed deck(s) from wave slaps and green water ingress during rough seas.

The height of these bulwarks adheres to certain regulations and guidelines based on the type of the vessel, service conditions, and other factors. For bulwarks above a certain height, a wall-like well is created with respect to the deck. This poses a higher risk for waterlogging as chances of drainage off the sides of the deck are absent.

Furthermore, the number of scuppers, drainage pipes, and so on are within certain limits, owing to strength and design requirements. Also, these openings are usually small (due to certain limitations on size with respect to deck strength).

In scenarios where deck flooding is quite significant, these are not fully effectual for complete drainage. Moreover, the horizontal openings on the deck plate have higher chances of being clogged, rendered inefficient, and obstructed in cases like icing.

Hence, in addition to the other drainage arrangements, some other means of water egress are necessary.

Freeing ports were introduced as per Load Line 1966 regulations to mitigate this problem. These are well-defined openings on the bulwark plate itself in certain numbers and intervals. They act as cut-outs close to the deck level such that any form of water accumulation onboard gets continuously drained.

The freeing ports should be designed and disposed of with the sole objective of rapidly clearing off-deck water under all kinds of external conditions. As there is no hard and fast requirement, freeing ports can come in any shape, though for all practical purposes, they are usually round.

However, as per standard, they should necessarily have rounded corners for heightened efficiency and minimising stress concentrations due to sharp edges.

The number, arrangement, and disposition of the freeing ports depend on the vessel type, size, design, nature of the deck, other means of drainage, and, of course, the type of bulwark.

Larger vessels, as expected, shall have a greater number of freeing ports than smaller ones. The configuration of the bulwark also plays an important role. When the entire exposed deck is abutted by a bulwark, the number of bulwarks is more than decks only partially covered by bulwarks.

Moreover, the height of the bulwark also plays an important role. Those bulwarks that have a greater height have more number of freeing ports as the chances of waterlogging are higher. The number of bulwarks is alone not a definitive parameter as each freeing port is also attributed to a size constraint.

The number as well as the size along with the disposition is optimised depending on the requirement. The overall or aggregate area of all the freeing ports for a deck is an important factor concerning designers. Let us look a little more into the important aspects of freeing ports.

Some important aspects of Freeing ports

The technical factors for the design, construction, and disposition of freeing ports are as per certain rules and regulations.

As far as the number of free ports is concerned, as mentioned above, it is as per the vessel design and the disposition of the bulwark.
The number of port openings should be maximised so as to ensure full drainage of water from the deck.
The freeing ports should also be decided based on parameters like sheer, camber, etc. In other words, the disposition of the freeing ports should be concentrated in areas with a greater chance of water accumulation.
The lowermost periphery or edge of the freeing port opening should be as close as possible to the deck edge or deck line. For all practical purposes, at least 2/3rd of the port opening should be at the lower half of the bulwark height in a vertical sense.
The interval between the ports (uniform or random) should be based as suited and catering to 100% drainage of water under all conditions.
Once the disposition and arrangement of the required, the area of the ports is decided in terms of the total area. As per Load Line convention guidelines, for vessels lesser than 20 m in length, the net area for freeing ports should be given as 0.7+0.035 X l, where l is the aggregate linear extent of all bulwarking in the way of the deck. For vessels longer than 20 m, this is given as 0.07 X l.
The vertical height of the bulwark is also important. For bulwarks extending more than 1.2 metres above the deck level, the areas of the freeing ports obtained from above shall be increased by 0.004 square metres with each 0.1-metre increment in height above 1.2. For example, if a bulwark has a height of 1.5 m above the main deck, the area (A) obtained from the above relations would be stated as A + 0.004 X 3A as there is an excess height of 0.3 m from 1.2 metres.
Likewise, when the bulwark length is less than 0.9 m in height, the decrease in area is also 0.004 square metres per unit, a 0.1 m decrease in height from the 0.9 metre reference.
In case of no sheer, the area calculated from above is increased by 5% with respect to what is obtained from above.
Similarly, for certain designs of trunks and superstructures, the requirement varies.
As per the rule, freeing ports having a large diameter above 230 metres should have intermediate railings or safety bars.
Some bulwarks also have shutters that can be controlled as and when required.
Although bulwarks are not primary or secondary structural members that contribute to the vessel’s strength, often, in many designs, they are kept as simple continuations of the side shell. Hence, for a considerable number of free ports or with ports having a significant size, sometimes additional strengthening is given around the openings as they pose a chance of reducing the structural integrity of the bulwarks and even localised areas in the way of the deck.
Though not very commonly necessitated, freeing ports is also related to stability and buoyancy requirements. We all know about reserve buoyancy. For all practical purposes, if the maximum volume of water entrapped in the way of the exposed deck (considering full water tightness) by bulwarks and superstructures/deckhouses is greater than the necessary design reserve buoyancy, the number of freeing ports is accordingly increased.
Some vessels, like fishing vessels, have special regulations for freeing ports.

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What is Freeboard on Ships?

Subhodeep Ghosh — Sun, 21 Jan 2024 08:20:44 +0000

We are all aware of the concepts of reserve buoyancy and draft, which are measures of the sinkage of the vessel. Freeboard is something closely related to these.

A freeboard is a minimum distance between the exposed deck edge and the waterline for a floating vessel. In other words, it is the difference between depth and draft.

The word minimum is crucial as the minimum value of the freeboard gives a picture of the safety margin before there is a risk of deck flooding and loss of buoyancy. For all practical purposes, freeboard is the inverse of the draft (maximum or service) and a margin for sinkage.

For example, if a vessel on an even keel has a depth of 10 metres and an average draft of 6 metres, the freeboard is 10-6=4 metres.

The freeboard is very similar to reserve buoyancy, which is the ratio of the enclosed hull volume above the waterline to the total hull volume. It gives a measure of the margin of safety for flotation.

The factors governing the freeboard are the same as those governing the draft.

The inherent conditions of the vessel’s loading and displacement.

A fully loaded vessel, having a higher displacement, has a greater draft and, thus, lesser freeboard than when it is in lightship conditions. The hull form of a vessel is also essential.

Consider a fuller-form vessel, for example, a tanker, and a finer-form vessel, for example, a frigate having the same displacement. Assuming a similar length, the finer-form vessel will have a greater sinkage. Thus, it will have a lower freeboard than the fuller-form vessel.

The cargo type

Vessels laden with denser cargo have higher sinkage and lower draft than vessels laden with lighter cargo, like timber. Similarly, the cargo distribution also defines the conditions of draft and freeboard.

The conditions of stability and sinkage

They are directly associated with the freeboard. Look at the figure below. For example, if the vessel has a trim by bow, the distance between the waterline and the forward is the least distance or clearance.

Thus, if this distance is 2 metres, the vessel’s freeboard is 2 metres. Likewise, if the vessel has heeled or listed, the freeboard is given from the side with the highest draft for a given condition of sinkage and trim.

Density

As we all know, the same vessel has a higher draft in freshwater as compared to seawater. The freeboard also varies accordingly.

Hydrodynamics

The draft of a vessel highly varies based on the wave dynamics and the mechanics of the flow, and subsequently, the freeboard is affected from time to time.

Depth of the hull itself

This factor is the only one not affecting the vessel’s draft. Depth purely depends on the design of the vessel itself. Moreover, design parametrical factors such as sheer and camber influence the depth.

A Brief on Freeboard assignment, minimum freeboard requirements and load line markings.

As per the IMO International Convention of Load Lines 1966, all vessels need to adhere to a minimum requirement for freeboard except for warships, some private vessels like pleasure yachts, fishing vessels, planning crafts of certain categories, existing cargo ships lesser than 150 GT, and very small vessels lesser than 24 metres in length.

The objective of this regulation is to ensure that the vessels have sufficient reserve buoyancy and margin for sinkage and stability.

The freeboard requirement concentrates on the minimum maintained freeboard and the risks for deck flooding under worst-case conditions.

In a broad sense, the standard freeboard values for a type of vessel take into account the following:

The vessel type, size and kind.

Larger vessels have a greater requirement for reserve buoyancy owing to their displacement than smaller vessels. Moreover, ships with heavier and denser laden cargo like stone or ore carriers experience higher drafts and have more potential risks of buoyancy loss due to sinkage, and hence mandate greater minimum values of freeboard compliance.

Similarly, other factors like hull-from, vessel service, nature of voyages, and so on influence the minimum criteria for freeboard.

Vessel layout and structural integrity

The vessel layout is directly related to damaged stability and subdivisions. Structural integrity or intactness is another very crucial factor taken into consideration. Vessels with more openings in the way of the deck(s), like cargo hatches or manholes, are at a greater risk of compromising on the reserve buoyancy due to more physical means of water entry into the hull.

Thus, they are to comply with higher minimum freeboard requirements.

Vessel construction and related design aspects like sheer or camber, bulwarks, etc.
Stability conditions
Operational requirements, areas of operation, crew and other effects
Superstructure or deckhouses: The extent of how they contribute to the necessary reserve buoyancy and the safety margin in case of vessel sinkage.

As per regulations guiding the conformity of freeboard, all ships are broadly categorised into two major types:

Type A
Type B

Type A ships are those ships that carry liquid cargo in bulk, such as tankers, product carriers, chemical tankers, LNG or LPG carriers, etc. Moreover, for all practical purposes, they have limited openings in the way of main decks, such as hatches.

From the stability and intactness point of view, most compartments are watertight and oil-tight. Also, due to the nature of liquid cargo stowed in bulk, the compartments in these kinds of vessels have low permeability.

Hence, for all practical purposes, these vessels are considered ‘safer’ from the reserve buoyancy point of view. This is because, due to the nature of the cargo and the low permeability in the spaces, the chance of sudden external water ingress and flooding in the event of flooding or breach is minimal.

During such damages, the liquid cargo maintains a pressure differential and seeps out gradually into the sea. Even when there is a significant amount of water ingress into the holds, the loss in buoyancy is not very critical, and full vessel sinkage, even if there, is gradual as such vessels are designed to carry liquid.

In many cases, since most oils are less dense than water, there is more outflow of oil as compared to water ingress, and thus there is a decrease in displacement and an increase in freeboard!

Furthermore, in Type A ships, as there are limited openings in open spaces such as the main deck, ingress of water from there in the occasion of severe weather, wave slaps, or other reasons causing deck flooding is not much.

On the other hand, Type B ships are all vessels other than Type A. Their conditions are taken differently from type A, depending on the requirement. For example, if there is a coal carrier, and due to a breach in the hull, there is rapid water ingress, the vessel gains more displacement, experiences buoyancy loss, and a decrease in freeboard that may ultimately result in sinkage.

Hence, as Type A vessels are safer, the minimum freeboard requirements are lesser than Type B.

As per regulations, tabular freeboards are given for both Type A and Type B ships. However, this is not the absolute freeboard that is applicable. To compute the minimum required freeboard, the value obtained from the corresponding table needs to be adjusted depending on the specifications and characteristics of the vessel based on certain procedures given as per the rules.

Since wood or timber is always classified as an exceptional form of cargo owing to its low density, the procedures applicable for such vessels regarding minimum freeboard requirements are differently stated.

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Frigate VS Destroyer- What’s The Difference?

Zahra Ahmed — Mon, 15 Jan 2024 06:02:24 +0000

Warships are an intrinsic part of any country’s naval fleet and differ in shape, size, functions, capabilities and structural configurations. Frigates and Destroyers are the most common kinds of warships in any naval force.

The main role of a frigate is patrolling and protecting larger vessels while the destroyer engages in direct combat with the enemy ships. Hence, destroyers are said to be a navy’s offensive arm, while frigates are considered to be the defensive arm.

Both Frigates and Destroyers were designed to be fast in order to escort and protect other vessels from air, land and underwater attacks; hence, some people use both terms interchangeably, but there is a difference between Frigates and Destroyers, which will be discussed in this article.

In simple terms, a frigate is smaller, lighter in weight and less armed than a Destroyer, which is larger, heavier and armed with a variety of ammunition. Secondly, a frigate is more common than a destroyer, with almost every navy in the world possessing frigates while only 13 countries have Destroyers, per Global Fire Power Index 2019.

Before delving into the differences between frigates and destroyers, let’s look at their history in brief.

Shedding light on the history of Frigate

In the beginning, Frigate was a term used for ships that were long, low and fast. So, vessels possessing these traits were called frigate-built. During the Age of Sail, a frigate was a full-rigged vessel with a single gun deck with a gun limit based on nationality.

Frigates were then used for patrolling, scouting and dispatching boats for bigger fleets and in commerce raiding. However, the term frigate vanished from popular use in the late 1800s, only to make a comeback in the Second World War.

During World War II, the British were in need of a ship for escorting its convoys of ships. The destroyers had pretty much a similar role as frigates in the Age of Sail. The Destroyers were swift and laden with torpedoes for intimidating capital ships like the battleships and cruisers; however, they were small in number.

The Patrol Boats were not fast enough and did not possess the range or needed seakeeping abilities for carrying out this crucial task and protecting convoys against enemy submarine attacks.

Hence, a class was formed which was not as fast or as heavily armed as the destroyer but still faster than the convoys. It was larger than patrol boats and could carry more fuel and endure harsh weather conditions at sea. Thus, the British used the term frigate for this new class of ships. Hence, frigates became ships that could outrun and outmanoeuvre enemy ships and had enough firepower to support themselves in battle.

Understanding the development of the destroyer

Destroyers are fast and manoeuvrable warships that escort larger vessels in a convoy, fleet, or battle group while defending these vessels against short-range attackers.

They were developed in the 19th century by Fernando Villaamil, a Spanish Naval Officer. Called the inventor of the destroyer warship, he envisaged them for the Spanish Navy to defend the fleet’s vessels from torpedo boats.

By 1904, the time of the Russo-Japanese War, the torpedo boat destroyers or TBDs were massive, swift and sufficiently armed torpedo boats meant to tackle other torpedo boats.

The term destroyer was used interchangeably with TBD and Torpedo boat destroyer since 1982, and it was eventually shortened to only destroyer by almost all navies by the time of World War I.

Destroyers are small in size compared to battleships but bigger than frigates. They usually have one smaller gun and many missiles, like anti-ship, cruise missiles and surface-to-air missiles. Advanced destroyers of today also have a helipad which aids with anti-submarine warfare.

Today, destroyers are heavily armed and armoured, perfect to face enemy ships face-to-face in a battle at sea.

Now that we have looked at how frigate and destroyer came into being, it is also important to note that in present times, the distinction between them has become blurred, thanks to the technological developments which have made all naval ships faster, more efficient, and better armed than earlier times. However, there still remain some differences between the two.

1. Most countries in the world have frigates but not destroyers

Since frigates are smaller and not very expensive to build, the navies of most nations in the world have them. Currently, 55 countries have frigates, with the most being part of the Chinese Navy, which has 52, followed by Taiwan with 24 and the U.S. with 22.

Meanwhile, only a handful of countries possess destroyers, with the U.S. leading the way with 68 destroyers in active service. Second comes Japan with 37 and then China with 33. Spain and Germany do not have destroyers; however, most of their frigates are quite identical to what other countries would classify as destroyers.

Some of the world’s biggest frigates and destroyers

Russia’s Admiral Gorshkov class frigate is said to be the world’s most powerful frigate, specialising in long-range surface attacks, anti-submarine warfare, escort missions and more that require the deployment of large destroyers.

Germany’s Sanchen class frigates have air warfare capabilities and are quite versatile, akin to destroyers regarding their firepower and displacement.

The epitome of Spanish naval excellence, the Alvaro de Bazan class frigates are anti-air warfare vessels built for escort missions.

World’s most powerful destroyers include the DDG 1000 Zumwalt-class multi-mission destroyers built for the U.S Navy. Said to the world’s biggest destroyers, they have a full load displacement of 15,656 tonnes.

The Type 055-class destroyers are capable surface combatants built by Jiangnam Shipyard and Dalian Shipbuilding Industry Company for the Chinese Navy. The first ship of this class was Nanchang (101), which made its first appearance during PLAN’s 70th anniversary parade in 2019.

Other prominent destroyers include the Arleigh Burke-class warships, Atago Class, Sejong the Great Class, etc.

2. Destroyers are comparatively larger and heavier than frigates

Another significant differentiating factor between a frigate and a destroyer is size. Destroyers usually measure between 150 to 160 m in length, and frigates are usually 130 to 150 m long.

However, even among destroyers, some can be humongous compared to others. Some small destroyers are the Royal Navy’s Type 45 Daring class and Russia’s Project 956 Sovremenny class, which are approximately 150 m long and 17 to 18 m broad.

The U.S Navy’s Zumwalt-class destroyer is 190 m long with a 24.6 m beam, weighing nearly 16,000 tonnes, almost twice the weight of smaller destroyers that weigh around 8000 tonnes a full load, while frigates roughly weigh around 4000-5000 tonnes.

Also, frigates like the Admiral Gorshkov class of Russia and the Sanchen class frigates of Germany are smaller but are nearly the same width as destroyers.

Per experts, since destroyers are big, they can generate the power for a more high-resolution radar and several vertical launch cells, providing theatre-wide defence for a carrier battle group. Also, nowadays, frigates are employed as escort vessels to safeguard lines of communication at sea or function as an auxiliary part of a strike group. Destroyers, on the other hand, are generally incorporated into carrier battle groups as the air defence component or used to provide land, air and missile defence.

3. Frigates are faster than destroyers

Frigates are designed to be fast, with higher speeds than destroyers and greater manoeuvrability. They usually have a speed of 30 knots, while destroyers can attain anywhere between 20 to 30 knots.

Due to being fast, frigates can position themselves to attack quickly or escape from danger if needed. Destroyers have powerful engines and sturdy hulls, but they cannot match the speed and manoeuvrability of frigates.

However, with advancements in naval technologies, there is not much difference in their speed. One of the fastest frigates is the Indian Navy’s Shivalik class, which can attain maximum speeds of 32 knots, while others can easily travel between 26 to 30 knots.

The colossal Zumwalt-class destroyer can reach up to 30 knots, which is still slower than the smaller Sovremenny and Daring classes, which can go up to 32 knots. The Zumwalt class is fast but not faster than most frigate classes.

4. Differences regarding weaponry and armament

Frigates and Destroyers are equipped with the latest weapons and defence mechanisms. Usually, frigates have surface-to-air missiles or SAMs, anti-submarine warfare or ASW torpedoes and guns for surface combat. They might also be armed with Vertical Launch Systems or VLS to fire long-range anti-ship missiles or AShMs.

Destroyers also have SAMs, guns, ASW torpedoes and VLS. Additionally, they may also be equipped with advanced electronic warfare systems such as radar jamming or decoy flares.

Royal Navy’s Duke Class frigates have ASW abilities along with the latest sonar equipment and torpedoes. Also, the ASW frigates have helipads for accommodating helicopters to tackle nuclear submarines.

The differences in weapons onboard frigates and destroyers differ due to their roles. For instance, frigates are smaller vessels unsuited to theatre air defence. They can be used for anti-submarine warfare roles and short-range air defence as part of a bigger surface group. On the other hand, destroyers can launch anti-ship and anti-aircraft-guided missiles like the US Navy’s Zumwalt and Arleigh Burke classes.

5. Destroyers are more costly to build than frigates

Destroyers are costlier than frigates since they need more crew members and have more weapons. A destroyer costs between $2-3 billion, and a frigate between $750 million to $ 2 billion.

US Navy’s Zumwalt class destroyer, DDG 1000, cost $4.2 billion, while the 2nd and 3rd destroyers of the class cost $ 2.8 billion and $2.4 billion.

Coming to frigates, they are cost-efficient, with the Royal Navy’s Duke class priced at £130 million per vessel. German Navy’s Sachsen class frigates, one of the most expensive frigate classes, cost around €2.4 billion for the 3 ships.

Conclusion

Frigates and destroyers have evolved with time as two distinct ship types made for distinctive roles in naval warfare. Frigates are light, swift and armed appropriately to patrol and protect larger ships of the navy.

At the same time, destroyers are designed to be bigger and heavier to protect themselves and also engage in direct combat at sea. Though they have some differences, they have some similarities, like advanced sensors and similar weapons, making both frigates and destroyers an essential part of a country’s naval fleet.

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Disclaimer: The authors’ views expressed in this article do not necessarily reflect the views of Marine Insight. Data and charts, if used, in the article have been sourced from available information and have not been authenticated by any statutory authority. The author and Marine Insight do not claim it to be accurate nor accept any responsibility for the same. The views constitute only the opinions and do not constitute any guidelines or recommendation on any course of action to be followed by the reader.

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10 Major U.S Shipyards Where Ships Are Built

Zahra Ahmed — Mon, 18 Dec 2023 07:00:35 +0000

The United States is home to the largest and finest shipyards in the world, enabling the construction of the sturdiest and most seaworthy vessels. Presently, the nation boasts 154 private shipyards, categorised as active builders, which are scattered across 29 states and the U.S. Virgin Islands.

Additionally, there are over 300 shipyards which engage in ship repairs and are capable of constructing ships but are not actively engaged in shipbuilding activity.

Most of the shipyards are situated in coastal states. However, some can also be found on prominent inland waterways like the Great Lakes, Ohio, and Mississippi.

According to a 2021 report by MARAD titled ‘The Economic Importance of the U.S. Private Shipbuilding and Repairing Industry’, the U.S private shipbuilding and repair industry directly provided 107,180 jobs, $9.9 billion in labour income and $12.2 billion in GDP to the national economy in 2019.

Let us go through the 10 major shipyards in the U.S. where ships are built.

1. Austal USA

Austal USA is a shipbuilder based in Blakely Island in Mobile, Alabama. It was formed in 1999 and has service centres in Singapore and San Diego and a technology centre in Charlottesville, Va. It constructs steel and aluminium ships and has a moving module production line.

It specialises in building high-speed vessels for transporting passengers, defence ships like the littoral combat ships used by navies around the world and fast ferries.

Austal USA has been contracted for programs which include the construction of a heritage-class cutter for the US Coast Guard, building ocean surveillance ships for the U.S Navy and also constructing a landing craft utility vessel, a towing, salvage and rescue ship, a medical ship and also independence-variant littoral combat ship programs.

It also supports the U.S. Navy’s unmanned vessel programs and is a key global support provider to the U.S. Navy, the Military Sealift Command and other clients.

Austal USA’s San Diego Service Center has a facility on the waterfront to accommodate small combatants and similar-sized vessels.

Austal USA, which began operations with less than 100 employees on a 14-acre facility, is now a recipient of 23 safety excellence awards, making it one of the safest shipyards in America and the world.

2. General Dynamics NASSCO

General Dynamics NASSCO has designed and constructed numerous ships in the industrial belt of San Diego since the 1960s.

It is also the only shipyard on the West Coast that provides a full range of services to its customers. Presently, it has facilities on the east and the west coasts of the US in 4 important ports: Bremerton, Mayport, Norfolk and San Diego.

It specialises in constructing support vessels for the US Navy, tankers and dry cargo ships for the commercial sector. It is also the principal provider of repair services for the U.S. Naval force.

General Dynamics facilities are capable of constructing commercial cargo ships, tankers and auxiliary ships for the Navy measuring 1000 ft lengthwise. It can service and repair any kind of ship sailing on the United States West Coast.

The main shipyard lies on the San Diego Bay with a 35 ft channel depth. It is spread over 86 acres of land and 47 acres of water and has 8 berths, which are 600 to 1000 ft long, 9 portal cranes, a floating drydock, 10 assembly areas, 5 production workshops, 2 inclined building ways, etc.

3. Newport News Shipbuilding

One of the biggest shipbuilders in the world, Newport News Shipbuilding has a long history of shipbuilding going back to 1886. It builds nuclear-powered ships for military and commercial use and specialises in constructing aircraft carriers, surface combatant ships and submarines.

It is a division of Huntington Ingalls Industries and came into existence as the Chesapeake Dry Dock and Construction Co. Till now, this shipyard has constructed over 800 vessels, including those for the navy and the commercial market.

Situated in Newport News, it is spread over 500 acres or 2.2 km2 of land. It is a major employer in the lower Virginia Peninsula, parts of Hampton Roads south of James River and the Middle Peninsula region, and some of North Carolina’s northeastern counties.

The shipyard built the USS John F. Kennedy, the 2nd Gerald R. Ford Aircraft Carrier, which was launched and christened in 2019. It is also building the USS Enterprise, which will be launched in 2025.

This shipyard also undertakes refuelling and complex overhaul work on the aircraft carriers of the Nimitz-class.

4. Philly Shipyard, Inc.

Earlier known as the Aker Philadelphia Shipyard, the Philly Shipyard is one of the leading U.S. shipbuilders, currently pursuing major commercial and government shipbuilding and repair projects. The shipyard is located in Philadelphia and is a preferred provider of oceangoing merchant ships.

It was established in 1997 through a public-private partnership between the U.S. government Agencies and the Kvaerner Shipbuilding Division. In 2000, it began construction of 2 container vessels. Soon, the shipyard grew, and between 2007 and 2011, it delivered 12 product tankers to AMSC and OSG.

In 2019, it delivered the CV3600 container vessel to Matson and was given the repair and maintenance contracts for FSS Antares and FSS Pollux, MARAD sister ships.

It also won the contract for design studies for the US Navy’s Common Hull Auxiliary Multi-Mission Platform program.

In 2020, it achieved another milestone when it bagged the contract to build 5 MSMVs for MARAD.

5. Bath Iron Works

Situated in the northeastern U.S., in Bath, Maine, this shipyard has successfully delivered more than 425 vessels since 1884. This includes far more surface combatants than any other shipyard in the U.S.

Right from the advent of the Second World War, Bath Iron Works constructed the lead ship for 12 non-nuclear surface combatants of the U.S. Navy.

Today, it is a shipyard offering a complete range of services, from the designing of vessels to their construction, maintenance and repairs. It supports destroyers and cruisers and has provided the Navy with highly advanced and great-quality surface combatants for over 100 years.

The shipyard aims to drastically reduce the hours for constructing warships by manufacturing outfitted modular ship units fitted on their Land Level Transfer Facility.

Bath Iron Works is also one of the biggest private-sector employers in Maine and is known as the leading designer of the Arleigh Burke or DDG 51 class of AEGIS destroyers.

6. Fincantieri Marinette Marine (FMM)

FMM is a part of the Fincantieri Marine Group, the U.S division of the Italian Enterprise Fincantieri. It has a long history of over 2 centuries and a record of building over 7000 vessels. Fincantieri has 18 shipyards on 4 continents, employing around 20,000 professionals.

The foundation of Fincantieri Marinette Marine was laid in 1942. It lay along the River Menominee in Marinette, Wisconsin and was built to meet the increasing market demand for naval ships in the U.S.

Since then, it has grown into one of the world’s biggest and most prominent ship construction facilities, having designed and constructed over 1500 ships over the years, ranging from vessels engaged in offshore exploration and production to maritime security, military sealift and polar operations.

FMM completed an expansion program which transformed its 550,000 sq ft. operations into a modern space with distinct areas for manufacturing, storage, and receiving areas and the capability for constructing the 7 Littoral Combat Ships using FMM’s automated manufacturing equipment and heavy lift capabilities.

FMM’s portfolio includes the US Navy’s freedom class littoral combat ships, constellation class frigates, mine countermeasure vessels, ocean tugs, the US Coast Guard’s response ships, icebreakers and buoy tenders.

7. Vigor Industrial Portland

Vigor has facilities at 12 locations and employs over 2500 professionals. It is a renowned name for ship construction, repair and fabrication in Alaska and the Pacific Northwest.

Vigor builds combatant crafts, aluminium workboats, barges, tuges, fishing vessels, and ferries. Vigor’s repair teams can handle offshore supply ships, aircraft carriers, cruise ships, floating drill rigs, etc.

Vigor’s 60-acre Shipyard is one of the biggest and most capable on the West Coast.

There are three drydocks and 15 piers with a total length of over 10,000 ft or 3000 m. The facility has 13 cranes, an 800-foot oversized buildway, and 150,000 square feet of fabrication bays.

8. Ingalls Shipbuilding

Situated in Pascagoula, Mississippi, Ingalls Shipbuilding is the biggest manufacturing employer in the region.

Ingalls was established in 1938 and is now a part of the HII. It employs around 12,500 people and is a major producer of U.S. Navy vessels.

For the past 85 years, it has designed, constructed and repaired amphibious vessels, cutters and destroyers of the U.S Navy and the U.S Coast Guard.

It is also the largest supplier of Surface combatants for the U.S. Navy and is building 4 classes of ships.

Ingall’s main focus has been naval vessels, and it has undertaken such projects for Venezuela, Israel and Egypt.

Ingalls also tried entering the diesel-electric locomotive market in the 1940s and produced hopper railroad cars in the 1980s, rolling out around 4000 units.

From the 1930s to the 1980s, Ingalls constructed type B ship barges in Decatur, Alabama.

9. BAE Systems Southeast Shipyards

BAE Systems Southeast Shipyards, Alabama, is part of the U.K.-based BAE Systems PLC, which builds warships, patrol boats, cruisers, destroyers, etc., used by European navies.

Possessing three full-service shipyards on the United States’ eastern and western coasts, BAE Systems Southeast Shipyards serve operators of commercial vessels and superyachts and also the U.S. Navy.

RightCowLeftCoast/Wikipedia

It is based in Jacksonville, Florida and has shipyards at Jacksonville, Mayport, Florida and earlier, Mobile, Alabama.

The facility in Mobile employed around 900 professionals, while the facility in Mobile employed around 800 people.

The Jacksonville shipyard caters to luxury yachts and commercial vessels, conversion, assembly of ships, and industrial and marine fabrication.

The Mayport facility repairs and maintains the U.S. Naval vessels. The facility at Mobile on the Gulf Coast offered dry docking and heavy-lift capacity for the biggest vessels; however, it was closed in 2018.

10. Fincantieri Bay Shipbuilding Company (FBS)

Fincantieri Bay Shipbuilding has a 63-acre facility custom-designed to handle major construction work, conversions, and the repair and maintenance of commercial, naval, and Coast Guard vessels.
FBS is a part of Fincantieri Marine Group and has a history of constructing ships in Sturgeon Bay, Wisconsin, since 1918.

The company operated under different names and tried its luck in different segments of the industry. In the 1970s and ’80s, it built Lake freighters. It constructed a modern freighter, MV Mark W. Barker, which was launched last year.

FBS specialises in designing and constructing large ships, including tug barges, cruise ships, dredges, ferries, platform supply vessels and offshore support vessels.

It is constructing a 5400 m3 bunker barge for bunkering LNG-fueled cruise vessels built in Europe that will sail from Florida to the Caribbean.

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Understanding “Making Way” And “Underway” Nautical Terms

Subhodeep Ghosh — Thu, 30 Nov 2023 08:58:32 +0000

This short article will briefly discuss an interesting topic: “Making Way v/s Underway.”

When describing vessels in water, we often say things like, “Look! The trawler is making its way near that bridge.”; “My uncle is presently underway through the Suez Canal on his tanker.”

Though these two terms sound very similar and are often interchangeably used by nine out of ten people, there is a significant difference.

Underway essentially means that the vessel’s speed relative to the water is zero or very low. Note the word “relative” carefully. However, just because the vessel’s speed is zero or low does not mean that the vessel is anchored, moored or stationed somewhere.

This is the second condition encompassing underway that states that the vessel needs to be necessarily free in all degrees of motion and ready to move or run adrift.

Now, consider the following simplest situation. A vessel is simply standing somewhere in the sea during idle time. It is not moored or anchored. However, the engines are not running, and the vessel is ideally stationary with respect to the water. This is a classic example of a vessel being underway.

Suppose in the above example, the vessel just starts its engines and tends to move at very low speeds. The speed is so low that the rudder action, which in turn is influenced by the hydrodynamic effects of flow, is rendered ineffective in changing course. What happens? She is still underway.

The reason was very low speeds, so the vessel could not use its power to change course. Thus, it is still underway irrespective of whether the vessel has the engine power supply on or not if its speed is insufficient relative to water.

Likewise, when a vessel is approaching a harbour or port and has shut off its engines, leading to very low relative speeds, it is still underway.

Now, consider a slightly complicated scenario. A river vessel is sailing downstream a river with very high current streams leading to a speed of more than 5 knots. Due to this inherently imposed speed, the vessel’s main engine is off, and it is just moving along with the flow.

What is this situation? It is again a condition of underway as the vessel’s speed relative to water is zero, notwithstanding the fact that it is moving at a good speed with respect to an observer on land.

Making way is just the complement of underway. When a vessel has considerable inherent speed relative to the water, it makes way. For all practical purposes, this means that the vessel is aided by some mode of propulsion or at least has some inherent high speeds. All ships sailing full steam and en route to their destination through deep seas are essentially making way.

Now, consider this situation. A vessel is approaching a port. The main engines are shut off, and the ship is still heading at some decent values of speed. This is again an instance of making way since the relative speed of the vessel is quite significant, and the vessel can change course easily at these speeds even though the power supply is absent.

Lastly, consider this trickier situation. A high-speed river craft is sailing upstream against high flows due to rough conditions. Even with the engine operating at full rated power, the vessel cannot make much progress against the flow.

Suppose the rate of flow is about 9 knots and the current power supplied by the engine is capable of speeding the vessel about 10 knots (in calm waters); the effective velocity is hardly a knot. Hence, due to the very low effective speeds, the vessel, with respect to an observer on the ground, is almost stationary or moving very slowly.

However, it is making way! Why? The answer is the imparted velocity of the vessel relative to the flow velocity. Hence, if the flow velocity is -9 Knots and the vessel’s surge velocity is, say, about +9.5 Knots, that’s still 9.5 knots with respect to the water even though from land, it is near zero.

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Disclaimer: The authors’ views expressed in this article do not necessarily reflect the views of Marine Insight. Data and charts, if used, in the article have been sourced from available information and have not been authenticated by any statutory authority. The author and Marine Insight do not claim it to be accurate nor accept any responsibility for the same. The views constitute only the opinions and do not constitute any guidelines or recommendations on any course of action to be followed by the reader.

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Types of Port Cranes

Hari Menon — Thu, 02 Nov 2023 07:19:39 +0000

Cranes are believed to have been in use as early as 3000 BCE. The earliest of them, called ‘shadoof’, were used to lift water from lakes and rivers for irrigating farmlands in Egypt. It consisted of a pole with a bucket on one end that was counterbalanced on a fixed support.

The Simple Crane

In its simplest form, a crane consists of a lever and a pulley.

Cranes at a fixed angle, with a single arm, were used in the early days to lift heavy loads. These days, modern cranes that can work from a few degrees angle to a nearly perpendicular position that can lift very heavy loads can be found everywhere, from construction sites to warehouses to seaports.

Stationary as well as mobile cranes help to move cargo from one location to another easily. Generally, cranes are counterbalanced to prevent them from toppling forward with the weight being lifted. Some of them have projecting arms or legs that can be planted firmly to the ground to help maintain stability and distribute weight evenly.

Here, we will focus on cranes that are used in seaports to lift heavy objects such as boxes, machinery, automobiles, and shipping containers.

How are Shipping Containers Loaded and Unloaded?

Cranes play a very vital role when it comes to lifting and stacking heavy objects in the port yard. They are also used to load heavy objects onto a ship.

If we take a gantry crane that is more common in seaports, it has a main supporting framework called the gantry, a boom or a long arm that goes over the ship with a spreader and a cabin suspended over the main framework from where the operator controls the crane. Here, the spreader is a movable clasp that is used to grip and lift cargo containers from and onto a ship.

Mobile cranes have trolleys that move on tracks along the quayside. There are rubber-tired gantry cranes as well. Containers are lifted from the ship and placed on truck beds or on the ground for reach stackers or forklift trucks to move them to their designated area. Port cranes are generally designed to lift weights ranging from 40 to 120 metric tons.

A mechanism called ‘spreader’ is used to attach and lock onto the four corners of a shipping container to lift it for loading or unloading. It locks onto the corner castings of a container using a twist lock mechanism.

Spreaders are designed to lift 20’, 40’, or 45’ containers. A single spreader can lift these containers separately or 2×20’ containers together. Double spreaders can lift single containers, 2×40’ or 45’, or 4×20’ containers in one move. Spreaders are used in different types of cranes to handle shipping containers.

A crane may be diesel-powered or powered by electricity. However, most modern cranes are electric-powered. Separate high-powered motors are used to move the boom, gantry, trolley, and hoisting mechanism.

The cranes used in seaports are generally classified as quay cranes and yard cranes. As their names suggest, quay cranes operate by the quayside, while yard cranes are found in the inner yards of the port.

Quay Cranes

When cargo ships berth along the quayside, large cranes are used to lift shipping containers and other cargo from these ships to shore or from shore to the ship (unloading and loading). The cranes used for this are generally called quay cranes. They are also referred to as Ship-to-Shore or Shore-to-Ship (STS) cranes, as the case may be.

Modern giant STS cranes are mostly classified based on their container lifting capacity from large ships that pass through the Panama Canal or otherwise.

Low-profile STS cranes are generally used in ports and terminals that are located close to airports. They have low, fixed booms. High-profile cranes have booms that can be lifted for ships to berth or, once they are fully loaded, to allow them to pass easily.

Let us look at some of the main quay cranes here.

Panamax cranes

Panamax cranes are used to lift or load containers onto ships large enough to sail through the Panama Canal. The booms of most such cranes can extend their reach up to 30 meters and lift to a height of about 38 meters.

They can lift a weight of about 50 – 65 tons, depending on whether it is a single or a double lift. With lifting speeds that can reach up to 125 meters per minute and a trolley speed of about 180 meters per minute, Panamax cranes are quite fast, too.

Post Panamax cranes

Post-Panamax cranes are used to load and unload containers from large ships, those usually too large to pass through the Panama Canal. Naturally, they are of higher capacity and have a horizontal reach of up to 45 meters and a lifting height of about 35 meters.

Like their Panamax counterparts, they can lift a weight of about 50 tons in a single lift and up to 65 tons in a double lift. Their lifting speed can reach up to 150 meters per minute. The trolley speed of Post Panamax cranes can reach up to 210 meters per minute.

Super Post-Panamax Cranes

With increasing global cargo traffic and as cargo vessels get larger and larger, the port cranes, too, have to keep up with these increasing loads. Ports compete with each other to attract cargo traffic and thereby increase their revenues. Under such a scenario, they cannot afford to have delays or cargo pile up. They should always be equipped to operate better and faster to keep up with competition.

Super Post-Panamax cranes that are used to load and unload shipping containers from very large cargo vessels have a reach of about 50 meters and lift to a height of about 40 meters. Their lifting speed is up to 175 meters per minute, while the trolley speed can reach up to 240 meters per minute.

Bulk Handling Cranes

The general feature of bulk handling cranes is that they have two buckets or grips that can grab bulk cargo, such as coal, mineral ores, grains, etc., for loading and unloading. The grabbing mechanisms used in such cranes are designed to suit handling specific products and conditions.

Gantry Cranes

Fixed gantry cranes generally straddle over a workspace – a space where shipping containers or other types of cargo are positioned for lifting and moving. Mobile gantry cranes that move on tracks or wheels are positioned to straddle over objects that must be lifted and moved.

Floating Cranes

These are large cranes fixed on floating platforms for loading and unloading containers from cargo vessels. These floating platforms are positioned by the side of a ship and used to lift heavy objects.

Tower Cranes

Tower cranes consist of a fixed base, a perpendicular mast, and a boom that rests on a rotating unit. Counterweights are used to balance the boom. The crane operator’s trolley usually rests on the boom from which he controls the crane. A hoist winch and a hook that moves along the boom are used to raise and lower the load.

Yard Cranes

Cranes that are used to move shipping containers and other cargo within a port’s yards are called yard cranes. They are used to move laden or empty containers onto trailers for overland transport or to the quayside for loading on board a cargo vessel. Different types of yard cranes are used to stack containers in the port yard.

Reach Stackers and Container Forklifts

Reach stackers and container forklifts are container handling machines used generally to rearrange or stack containers in a yard. They are also used to load or unload containers from trucks or rail cars.

These stackers and forklifts generally consist of a telescopic or retractable boom that is controlled hydraulically and mounted on a vehicle. A spreader at the tip of the boom is used to attach to the container for lifting or lowering.

Deck Cranes

Some small ships have deck cranes to lift and lower containers from and to the shore. This comes in handy at ports where cranes are not readily available or when the number of containers is less.

Modern cranes are designed for maximum speed and efficiency. They are used to complete loading and unloading within the shortest possible time, taking into consideration the safety of operating staff as well as infrastructure.

Multiple cranes may be employed to complete loading or unloading containers from a cargo ship within a stipulated time. Trained port crane operators are key to achieving this.

European crane makers are the leaders in port crane manufacture. Liebherr, the German-Swiss giant, Kone, and Kalmar – both based in Finland, are some of the major port crane manufacturers.

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Types of Port Cranes appeared first on Marine Insight - The Maritime Industry Guide

Naval Architecture Archives - Marine Insight

What is Gunwale of a Boat or Ship?

How Deep Can Military Submarines Go?

What is a Tumblehome?

What is a tumblehome?

Why Ships Sink – 10 Major Reasons

1. Flooding

2. Grounding and Collision

3. Loss of Stability

4. Poor Weather Conditions

5. Negligence and Human Error

5. Faulty Equipment

6. Improper Maintenance

7. Wartime Casualties

8. Dock Mishaps

Piracy

Safety Measures to Prevent Sinking

Prominent Ships That Have Sunk

Design Of Asphalt And Bitumen Tankers

A brief on asphalt construction

Introduction to Asphalt and Bitumen Carriers

Design of Asphalt and Bitumen Carriers

General

Tankage And Heating Systems

A Guide To Naval Architecture

Contents

What is Naval Architecture?

How to Become a Naval Architect?

What is the Ranking Hierarchy for a Naval Architecture Profession?

What are the Main Software and Tools Used by Naval Architects?

How are the Job market and Prospects of Naval Architects?

What is the Lifestyle of a Naval Architect?

What are the Names of Some Popular Companies that hire Naval architects?

What Further Studies can a Naval architect do?

What are the Famous Naval Architecture Colleges in India and abroad?

What are Some Famous Books that Naval Architects Must Have?

What are the Differences Between Naval Architecture and Marine Engineering?

What is the Average Salary of Different Ranks and Professions in Naval Architecture India and Abroad?

How Much Cargo Can A Cargo Ship Carry?

Bulk Carriers and similar vessels

Tankers and similar vessels carrying liquid cargo

Containerships

Other types of vessels like Ro-Ro and Ro-Pax

What is Deck Plating on Ships?

What are Triple Hull Vessels?

Design Philosophy of Trimarans

What are Freeing Ports On Ships?

What is a bulwark?

Some important aspects of Freeing ports

What is Freeboard on Ships?

The inherent conditions of the vessel’s loading and displacement.

The cargo type

The conditions of stability and sinkage

Density

Hydrodynamics

Depth of the hull itself

A Brief on Freeboard assignment, minimum freeboard requirements and load line markings.

The vessel type, size and kind.

Vessel layout and structural integrity

Frigate VS Destroyer- What’s The Difference?

Shedding light on the history of Frigate

Understanding the development of the destroyer

1. Most countries in the world have frigates but not destroyers

Some of the world’s biggest frigates and destroyers

2. Destroyers are comparatively larger and heavier than frigates

3. Frigates are faster than destroyers

4. Differences regarding weaponry and armament

5. Destroyers are more costly to build than frigates

10 Major U.S Shipyards Where Ships Are Built

1. Austal USA

2. General Dynamics NASSCO

3. Newport News Shipbuilding

4. Philly Shipyard, Inc.

5. Bath Iron Works

6. Fincantieri Marinette Marine (FMM)

7. Vigor Industrial Portland

8. Ingalls Shipbuilding

9. BAE Systems Southeast Shipyards

10. Fincantieri Bay Shipbuilding Company (FBS)

Understanding “Making Way” And “Underway” Nautical Terms