A dry dock is a structured area where the construction, repairs, and maintenance of merchant vessels and boats are carried out. This unique construction or arrangement allows water to be filled up in an area, also known as a lock, so vessels can be manoeuvred in and out of the area.

Once the vessel enters the dry dock, the gates are closed, and the seawater is drained out so that the hull and other parts of the ship, which have been exposed to seawater for a long time, are exposed for maintenance and repair work.

Dry Dock Survey

As per SOLAS requirements, all Merchant vessels require a complete survey of the hull in a dry dock twice within a 5-year period and an intermediate survey within 36 months at the earliest.

This includes maintenance of the hull, propeller, rudder, etc. and other parts which are immersed in water and are generally inaccessible by staff when the ship is sailing

For a passenger vessel, the bottom is to be inspected annually. Two such inspections in a period of five years must be carried out in dry dock, and the maximum interval between these inspections should be three years.

Types of Dry Dock

Different types of dry docks are used for repairing and cleaning a ship. The main ones are:

1. Graving dock
2. Floating dock
3. Marine Rail Dock
4. Shiplifts
5. Marine mobile lifts

Among these, the marine mobile lifts and ship lifts are mainly used for small vessels such as recreational yachts, tugs, pilot boats, etc.

Nowadays, there are mainly two types of dry dock procedures from the above list that are used for seagoing vessels:

1) Graving Dry Dock

This type of dry dock is normally constructed on land near coastal waters. It is rectangular and made of solid concrete, with blocks, walls, and gates. The vessel is shifted inside the dry dock and rested on the blocks. After the ship is in the required position, the gate is closed, and water is removed.

Related Read: Understanding Ship Stability During Dry Dock

In the past, the graving dry docks were constructed using stones and timber. Now, a steel and concrete enclosure is used, and a heavy steel gate is used to seal the dock to stop water ingress once the ship is standing on the blocks.

The gates can be in two parts, with each hinged to the sides and hydraulically operated, or one solid steel structure supported on a roller over the track, which can be retracted inside the dry dock walls when opening the gate.

Advantages of Graving Dry Dock

1. It can accommodate vessels of bigger sizes when compared to other dry docking systems.
2. It is cheaper to dry-docking a vessel of a similar size to other types.
3. The graving dry dock can perform retrofitting, modification, etc., which is challenging in other types.
4. Due to its location near the land, the graving dock is easily accessible for the supply of spares, machinery, and services.
5. New advanced graving docks have welding, hot-work and other workshops inside the dock on an elevated surface (above the water surface when the dock is filled), giving quick access and workflow in the dock.
6. Retractable ramps in new graving docks make it easy to supply spare machinery and save a lot of time and manpower to transfer them inside the dock.
7. A bigger graving dock can be used to repair more than two ships at a time, and some modern graving docks have two gates at both ends, making it easier to repair and re-float the vessel independently.

Disadvantages of Graving Dry Dock

• When re-flooding the dry dock, all the machinery and equipment needs to be taken out from the dock, which takes time.
• The maintenance cost of the graving dock increases as per the age of the dock and becomes very high.
• Any problem with the dock gate will make the whole dock non-operational

• The docking and undocking process in the graving dock takes time compared to other types
• If the dock holds multiple ships for repair, the complete operation needs to be stopped if any one of the vessels needs to be taken out of the dry dock as it will require filling of water for refloating

2) Floating Dry Dock

A floating dock is in the form of a “U” structure, mainly used in salvage to carry ships that have met with an accident and are damaged to an extent that has made them unable to sail further to a coastal dock.

However, many regular sea-going, small, and mid-size vessels are now dry docking in floating docks. Several “U” type floating docks can be joined to carry a large vessel.

The ship is brought near the channel where the floating dry dock will partly submerge itself, and the ship slides inside the dock.

Once the ship is in position, the floating dock is de-ballasted to drain the water from its hollow floors and walls, which support the vessel on the blocks arranged on the dock’s floor.

A valve is provided that can be opened to fill up the chambers with water and immerse the dock so that the ship can sail out.

The water is pumped out of the chamber, allowing the dry dock to rise, exposing the underwater area of the ship for maintenance or carrying out the ship repairs. 

Related Read: What is Ballasting and De-ballasting?

The floating dry dock is usually built using steel framing similar to that of seagoing vessels, with ballast tanks provided on the sides and bottom to raise and lower the dock.

Floating dry docks are commonly operated in sheltered harbours, where there are no waves or natural tidal activities.

Advantages of a Floating Dry Dock

1. They can be propelled to the location of a salvage vessel near the harbour
2. They are cheaper to maintain as compared to graving docks and can get a higher resalable return
3. They can be installed near or away from the shore inside the harbour, making them a portable and space-saving structure without taking space of the shore facility
4. The complete floating dry dock can be aft or forward trim by ballasting the dock, which further assists the ship or the damaged vessel which cannot be given a trim
5. Additional mooring equipment is needed for the floating dry dock to make it stable
6. The floating dry dock can be altered and increased in size in all dimensions by extensive retrofitting/ rebuilding
7. They can also be split into two different floating docks independent of each other

Disadvantages of Floating Dock

• The supply of store, equipment, and manpower is usually done from one access point gangway, which makes the operation slow.
• The maintenance cost of a floating dry dock is similar to that of a ship, as the hull is submerged in saltwater.
• The floating dry dock operation will be affected if there are tides or during windy weather.
• When re-flooding the dock, all the machinery and equipment needs are to be removed, which takes time.

Blocks Of Dry Dock

The blocks inside the dry dock play a critical role in taking the ship’s load and distributing it among the blocks placed below the keel plates. Every ship has a docking manual that will provide a guide block plan approved by the Ship Classification Society.

The shipmaster/ chief officer and the dry dock master must understand the blocking plan for the particular vessel and how the ship will behave under load when resting on the blocks, including various factors that can affect the load a block takes.

The blocks are usually constructed from one material so that their stiffness is similar. If the blocks are built from different materials, the force exerted on the blocks with a smaller elasticity module will squeeze them more than the stiffer block. This can lead to damage to the block or the ship’s hull, as the force distribution will be uneven.

The most common materials used for the blocks are:

• Concrete with steel
• Timber blocks
• Timber on top and concrete at the bottom

When a timber block is added to a keel track built of blocks with concrete or steel bases, the timber block will take a much smaller load than the others.

Apart from the keel blocks, side blocks are also arranged to support the ship. They are less stiffer than the keel blocks as a stiffer side block will overload the vessel and may damage the structure. The height of the slide blocks is usually similar or more than that of the keel blocks.

Important factors which affect the loading on the dry docking blocks are:

• The initial height of the block: The block’s height is a critical factor, as the load on the individual block will be determined by the load shared by all the other blocks. If the placement and height of the blocks are according to the ship’s hull, the load distribution will be even.
• The contact area of the block: The contact area of the block with the ship’s hull determines the load distributed on the block. If the contact area of the block is smaller in size, this means the load exerted on this block will be lesser than that with a larger contact area.
• The material of the block: As stated earlier, different materials will react differently to the load exerted by the ship. Hence, the material of the block used for the keel block and the side block plays an important role in aligning the ship in the dry dock.
• Placement of the block: The blocks in the dry dock need to be arranged according to the ship’s docking plan. Many types of equipment and parts can get damaged if the block position is not altered. For example, echo sounders, anodes, etc., the blocks need to be removed so that these equipment tools have space to settle once the ship rests on them.

Choosing A Type of Dry Dock

The criteria to select a type of dry dock  for a ship depends on the following factors: 

• The size of the vessel: The graving dock accommodates larger sizes than any other type. If the shipowner/ manager has to dry dock a large oil tanker, they will go to the graving dock. The Marine railway type can be used if the vessel is about 10000 tonnes. If a boat or small yacht of up to 250 tonnes needs repair in the dock, a mobile marine lift can be used.
• The condition of the vessel: If the vessel propulsion plant is not working or some damages can make a ship immobilized, floating docks are commonly used in such a condition
• Types of repair: The choice of dry dock type also depends on the type of repair the ship wants to undergo. For the regular scheduled dry dock, a floating dock can be selected; however, if there is major retrofitting or massive parts/ machine fitting is required, the graving dock is chosen as they are usually located near the shipyard and it is easy to move the material from land to dock as compare to the floating dock.
• Schedule of the Vessel: The location and the type of the dry dock will be decided as per the current schedule of the vessel and how easy it is for the ship to reach the dock after unloading all the cargo to the last port of call
• Budget: The most critical factor in selecting the type of dry dock is the budget allotted to the ship

Related Read: How Cost Estimation is done for Ship’s Dry Dock?

Requirements for Dry Docking

Stability is the most important requirement for getting a ship safely into a dry dock. The three important parameters which must be ensured before entering the dry dock are:

1) Adequate Initial GM:

When the ship touches the blocks, a reaction at the point of contact raises the centre of gravity “G” and reduces the metacentric height “G.M.” so that an adequate initial metacentric height is required to compensate for this.

2) Vessel to be Upright:

While entering the dock, the vessel must be upright, meaning there should be no port or starboard list when the ship touches the blocks. If the point of contact of the ship and keel blocks is outside the centre line of a vessel, it may force the ship to tip over.

3) Small or Moderate Trim Aft:

When making the ship’s keel sit on the keel block, a moderate trim aft is usually kept. As the water level in the dock lowers, the slight trim allows the stern and bow to ascend in tandem rather than simultaneously, which will reduce the load and pressure on a vessel’s hull and keel.

Related Read: 10 Types of Dry Dock Accidents That Can Occur in Ship’s Engine Room

Dry Dock Procedure

Once the ship manager selects the type of dry dock, the next step is to prepare the ship to enter the dry dock and carefully place the ship’s keel on the blocks provided on the dry dock floor. Some important points to note are:

• Make sure the ship is prepared to enter the dry dock by having the least ballast and no cargo carried on board
• If the floating dock is used, the ship’s movement will depend on the docking master’s requirements and the vessel’s condition. If the vessel is immobilized due to an accident, the floating dock will move towards it, and if the vessel is functioning correctly, it may propel inside the dock.
• Once the ship enters the dry dock, it is moored to the dock
• The docking master will inform the ship’s crew beforehand about the trim requirement they must maintain.
• Before emptying the dock, the ship and dock master must ensure that equipment like an echo-sounder or log sensor does not hit any blocks and is clear of any obstruction. For this, divers are sent to check that all such equipment is precise of the blocks
• The dock master will give the order to pump the water out from the dock, and slowly, the ship will sit on the keel  blocks
• The docking master and the ship’s crew must ensure the point of contact of the ship and keel blocks does not lie outside the centre line of a vessel as it may lead to the tumbling of the ship
• Once the ship sits on the dock, the cleaning and repairing process starts 

Related Read: Dry Docking of Ships – Understanding Stability And Docking Plan

Duties of Ship Crew Members During Dry Docking

While dry-docking the ship, the duty of the ship’s crew (under the guidance of the chief engineer and chief officer) will be:

• To keep the ship at minimum ballast condition
• To keep the aft trim as requested by the dockmaster
• To ensure the vessel is moored by assisting the dock crew once the ship comes inside the dry dock
• To keep a check on the stability of the ship while the water is lowered in the dock
• Once the ship is sitting on the blocks, the ship’s crew will pump out the ballast
• To prepare the vessel to connect to the shore power
• Once the dry dock water is pumped out, de-ballast tanks using gravity
• Remove the drain plugs from the bottom of the ship for various tanks

Related Read:

• Checks to Perform on Ship before Coming out of the Dry Dock
• What is Extended Dry-Docking of Ships?

Drydocking is one operation that allows the ship’s crew to learn areas that cannot be explored when the ship is sailing.

It also helps the ship manager to assess the condition of the ship’s hull and the machinery which are not accessible when the ship is in water.

Bringing the ship to the dry dock is a team effort between the ship’s crew and dry dock personnel. Proper communication is the key to safely laying the ship’s keel on the keel blocks.

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.

The Ultimate Guide to Dry Docks: Types, Functions, and Essential Requirements appeared first on Marine Insight - The Maritime Industry Guide

Dry docks are essential facilities for ship construction and repairs. Marine vessels are manoeuvred into the shipyard and then the submerged parts such as the hull are exposed for inspection and maintenance which is extremely important for expanding the life-span of a ship.

With the coming of new maritime technologies, efficient and sustainable vessels are being built to reduce the pollution caused by oceanic shipping.

Let us look at the 10 biggest dry docks in the world and their distinguishing characteristics.

1. CSBC Corporation- Kaohsiung shipyard

Founded in 1937, CSBC Corporation is the biggest shipbuilding company in Taiwan offering a plethora of services such as building commercial and official ships, naval vessels, offshore steel structures, manufacturing machinery, offshore engineering, assembling equipment, maritime transportation and others.

In the past three decades, the company has constructed different kinds of ships for its national and international customers hailing from Europe, Asia, Africa and America. It was owned by the government before being privatised in 2008.

Earlier known as the China Shipbuilding Corporation, the CSBC is presently headquartered in Kaohsiung and has a regional office in Taipei to solve customer queries. It has two expansive shipyards namely the Kaohsiung shipyard located in southern Taiwan, which is the biggest dry dock in the world and the Keelung dock lying in the north.

The Kaohsiung dry dock spans 950 m and is 92 m wide, with a draft of 14 m. Located near Taiwan’s biggest port, it is equipped with ultramodern technologies and equipment including state-of-the-art facilities for building efficient and sturdy vessels. The dry dock can simultaneously engage in the construction and repair of 4 ships weighing over 10,000 tonnes.

2. Hyundai Heavy Industries- Gunsan Shipyard

Hyundai Group’s shipbuilding corporation is the world leader in the ship construction sector and holds a 15% market share. The companies’ Gunsan shipyard is one of the biggest in the world, covering more than four kilometres along the coastline facing Mipo Bay in Ulsan, Korea.

A renowned manufacturer of marine propulsion systems, the shipyard has successfully delivered 2151 ships of varying sizes to 321 shipowners from 50 countries across the world since it became operational in 1974. In 2017, it reached a total production mark of 200 million DWT tonnes and delivered the world’s biggest container vessel, the CSCL Globe in 2018.

The shipyard comprises ten 700 m long and 115 m wide dry docks equipped with goliath cranes which allow the construction of ships of all sizes and hull types. Although the shipyard covers 1780 acres, it houses many warehouse facilities spanning 395 acres and is fitted with cutting-edge technologies and modern equipment such as mechanised steel cutting lines, a painting workshop, a metalwork factory and crankshaft shops.

Given the shipyard’s location, it is easily accessible from the sea and specialises in the construction of bulk carriers, container ships, oil tankers, product carriers, multipurpose cargo vessels, pure car carriers, roro vessels, chemical tankers, offshore rigs, and barges. It also provides transportation and marine engineering services.

The shipyard was closed in 2017 due to the recession in the shipbuilding industry however it will become operational in January 2023 as per news reports. The stakeholders plan to transform it into a major facility for manufacturing eco-friendly vessels and increase the country’s share in the growing global market of low-carbon ships such as those driven by ammonia and hydrogen.

3. Dalian COSCO shipyard

Founded in 2007, the Dalian COSCO shipyard is a joint venture of the China Ocean Shipping Group Company and Kawasaki Heavy Industries. Also known as DACKS, the shipyard is situated in Dalian, the maritime technology and industrial centre of northeast China.

It covers an area of over 1.89 million sq m along the 2500 m long coastline and comprises 2 dry docks, out of which one covers 700 m and is the longest dry dock in China. It also has a 180,000 DWT floating dock, 3 outfitting berths, a 250 m slipway and the biggest suit-assemblage factory in Asia measuring 125,000 sq m, three workshops, a pipe manufacturing factory and three paintings shops. The shipyard is operated by 2000 trained workers, including 300 engineers and technicians. After completion, the shipyard would have 2 docks and 4 quays.

It engages in the construction of large bulk carriers, VLCCs, container ships, Pure car carriers, LNG vessels, merchant ships etc. It also undertakes ship conversion services like VLCC to FPSO, VLCC to VLOC, the transformation of single-hull tankers into double hulls and so on. Presently the shipyard can repair over 200 ships of different types annually. It serves renowned shipping companies by building all types and sizes of vessels imbued with innovative maritime technologies.

4. Reliance Naval and Engineering Limited (R-NAVAL)- Pipavav Shipyard

Earlier known as Pipavav Shipyard Limited and Pipavav Defence and Offshore Engineering Limited, R-naval was acquired by Reliance Group in 2016. Possessing one of the largest shipbuilding and marine engineering infrastructures in the world, this Indian shipbuilding corporation is based in Mumbai and is the first Indian private enterprise to get a licence for constructing warships.

The shipyard is located in Pipavav, Gujarat and extends more than 500 acres with access to 750 m of the waterfront area. It has a 640 m long and 65 m wide dry dock capable of accommodating vessels weighing up to 400,000 DWT and incorporates a 100 m paved track for unloading machinery and other equipment from ships and barges using goliath cranes. It also has two mobile cranes with a combined lifting capacity of 1150 tonnes. This shipyard provides floating repair facilities and an additional 250 m long pier equipped with a level luffing crane.

A Special Economic Zone covering 95 hectares is located a few kilometres from the dry dock for making hull blocks. It houses numerous workshops, factories etc. Due to this facility, the dry dock has enough space for carrying out the repair, maintenance and assemblage work.

The shipyard is known for the construction and repair of bulk carriers, barges, naval vessels, platform supply ships, offshore units etc. It also has a facility for converting mobile offshore production units into mobile offshore production platforms.

5. Samsung Heavy Industries Co LTD- Geoje Shipyard

Samsung Heavy Industries is one of the biggest shipbuilding corporations in Korea and the world. It is present in the shipping and transportation sector including research and digitisation of port projects. Offering services such as maritime engineering, construction and delivery of vessels for shipping companies, building topside modules, drilling rigs, floating platforms, control systems for vessels etc, this company has manufacturing facilities in Korea and abroad.

Its Geoje shipyard is the biggest in South Korea and has the world’s highest dock turnover rate. It has 5 floating docks and 3 dry docks out of which the third is 640 m long, 97.5 m broad and 13 m deep. It can accommodate the world’s largest cargo carriers, VLCCs and undertakes the construction of highly-efficient ultra-large vessels. Built-in 1977, the shipyard covers 4,000,000 m2 and can handle repair, construction and conversion of 70 vessels annually. Its offshore facility deals with 250,000 million tonnes in a year.

Geoje shipyard mainly constructs special-purpose ships such as offshore vessels, LNG ships, oil drilling vessels, FPSO and FSOs, container ships, passenger ships and Arctic shuttle tankers. Presently the facility has concentrated on taking contracts for building LNG tankers and drilling vessels. Ships are built on the floating docks where novel methods such as terra-block technology are used for reducing construction time.

6. Hyundai-Samho Heavy Industries Co. LTD.

HSHI is the world’s fifth-biggest shipbuilding company based in Yeongnam, South Korea. It has increased the ambit of its operations from ship construction to manufacturing offshore plants. The company had built the first LNG powered crude oil ship in the world and is a dominant manufacturer of green energy vessels. Numerous LNG carriers, container ships, bulk carriers imbued with carbon reduction technology have been built by the corporation. It can construct about 40 ships annually at its various facilities.

Situated in Jeollanamdo, South Korea, the Hyundai-Samho shipyard has one of the biggest dry docks in the world. It covers about 3,300,000 sq m and comprises two dry docks with a construction capacity of 3.7 million gross tonnes annually. They are served by 5 goliath cranes and 2 mobile cranes. The shipyard houses a factory and automated facilities for undertaking construction and ship repairs. About 8 LNG carriers can be constructed by the shipyard in a year.

7. New Times Shipbuilding Co. LTD

New Times Shipbuilding Corporation Limited is a Chinese shipbuilding company situated in the Xingang Industrial Park in eastern China’s Jiangsu province. The Jinjiang New times Shipyard spans more than 1000,000 sq m on the 3200 m shoreline. It has its design institute, support facilities, two workshops, 2 outfitting jetties and 3 dry docks, the biggest being 588 m long and 106 m wide. It undertakes the construction, maintenance, and repair of bulk carriers, barges, tankers, cargo ships, Panamax size oil tankers, and chemical tankers along with manufacturing ship parts and control systems.

The shipyard has the capacity of constructing 100,000 to 300,000 tonnes class carriers and can build 5 million DWT every year. Currently, the corporation is focussing on taking contracts for building Aframax, Panamax and Capesize bulk carriers. The shipyard has a professional team of 5000 engineers and trained staff for providing efficient services.

8. China Shipping Industry (JIANGSU) CO. LTD

The China Shipping Industry is situated in the province of Jiangsu, China’s famous commercial and financial centre. The company is one of the renowned enterprises in the country specialising in the repair and maintenance of ships. Till now, it has successfully built more than 90 efficient maritime vessels for its customers. It has evolved considerably and shifted its focus to produce eco-friendly LNG powered vessels to overtake its Japanese and Korean competitors.

The company’s shipyard became operational in 2007 and enjoys a suitable position near the river Jia. Adjacent to the banks of river Yangtze, the availability of a well-protected natural 3500 m waterfront and deep waters make it a perfect facility for shipbuilding. It covers 4200 acres comprising four workshops, 2 floating docks, 3 administrative buildings and two dry docks measuring 530 m lengthwise and 136 m breadthwise with a draft of 14 m. A workforce of 2950 people and 29 engineers are behind the successful operation of the shipyard which engages in the construction of container vessels, tankers, non-submersible equipment, drilling rigs, engineering machinery etc.

9. Shanghai Jiangnan Changxing Heavy Industry Co LTD (SCH)

Established in 2006, Shanghai Jiangnan Changxing Heavy Industry is a prominent name in the shipbuilding industry. Its shipyard was located in the southern part of central Shanghai but was relocated to the island of Changxing near the mouth of river Yangtze in 2009. It manufactures all types and sizes of container ships ranging from 5000 to 10,000 TEU, bulk carriers weighing around 175,000 TEU, Very large gas carriers, LNG ships, offshore equipment, floating platforms and steelworks meeting the standards of distinguished classification societies. Conversion of civilian and military vessels is also undertaken at this facility.

The Jiangnan shipyard spans 1.48 million sq m and incorporates eight berthing facilities with a total berth length of 1870 m. It also has five outfitting quays and a dry dock measuring 580 m equipped with two large gantry cranes with a lifting capacity of over 500 tonnes, three mobile cranes for lifting blocks and a roll bending machine. Painting workshops and blasting service is also available. Since the facility has concentrated on building world-class container ships, it is known as the construction centre of container ships in China.

10. Shanghai Waigaoqiao Shipbuilding CO LTD

This company was established in 1999 and is owned by the China State Shipbuilding Corporation. Its shipyard covers approximately five million sq m of area for undertaking construction and repair works with a 4-kilometre long waterfront area. It also includes three outfitting quays, a 700-ton gantry crane, four cranes with a lifting capacity of over 500 tonnes and numerous blasting facilities, eight painting shops and 2 dry docks.

Recently, the facility delivered a 210,000 DWT Newcastlemax bulk carrier to the Foremost group based in New York. Since 2013, it has constructed 500 commercial ships with an annual delivery average of 499 DWT.

You might also like to read: 

• Top 10 Largest Cruise Ships in 2022
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• 10 Largest Container Shipping Companies in the World in 2022
• Top 10 World’s Largest Container Ships In 2022
• Top 10 Biggest LNG Ships of 2022

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.

Top 10 Largest Dry Docks in the World appeared first on Marine Insight - The Maritime Industry Guide

Dry dock is like a routine health check up for ships so that they live a long and healthy life. Dry dock schedule of every ship is laid down by the administration and every ship owner and operator has to follow the rules.

As much important it is to check conditions required for entering a dry dock, so much important it is to consider checks need to be done before the dock is flooded and ship is taken out of the dry dock. Let’s find out the exact procedure to be followed on a ship coming out of the dry dock.

It is extremely important to maintain a checklist of things and procedure to be done before undocking and not to miss any vital point which will lead to delay in undocking.

Following things must be checked by a responsible engineer and deck officers before water is filled up in the dock:

• All Departments in charge to confirm that repairs assigned under their departments are completed successful with tests and surveys are carried out

• Check rudder plug and vent and also check if anode are fitted back on rudder

• Check hull for proper coating of paint; make sure no TBT based paint is used.

• Check Impressed Current Cathodic Protection system (ICCP) anodes are fitted in position and cover removed

• Check Anodes are fitted properly on hull and cover removed (if ICCP is not installed)

• Check all double bottom tank plugs are secured

• Check all sea inlets and sea chests gratings are fitted

• Check echo sounder and logs are fitted and covers removed

• Check of propeller and rudder are clear from any obstruction

• Check if anchor and anchor chain is secured on board

• Check all external connection (shore water supply, shore power cables) are removed

• Check inside the ship all repaired overboard valve are in place

• Secure any moving item inside the ship

• Check sounding of all tank and match them with the value obtain prior entering the dry dock

• Check stability and trim of the ship. Positive GM should be maintained at all time

• If there is any load shift or change in stability, inform  the dock master

• Go through the checklist again and satisfactory checklist to be signed by Master

• Master to sign authority for Flood Certificate

• When flooding reaches overboard valve level, stop it and check all valves and stern tube for leaks

• Instruction to every crew member to be vigilant while un-docking

You may also like to read – What is Extended Dry-Docking of Ships?

Checks to Perform on Ship before Coming out of the Dry Dock appeared first on Marine Insight - The Maritime Industry Guide

The process of docking and undocking of ships might not seem like an important operation. However, it’s a process that is carried out more than once, not only by shipbuilding yards during the construction of a ship, but also as regular part of the ship’s lifetime. The understanding of the process of docking is specialised, and hence, not many naval architects or engineers are thorough with the inner details of docking. Professionals who are specialised in carrying out docking and undocking of ships are commonly known as Dock Masters.

But why is it important for ship designers to know about the docking processes? It is because, the process of docking is done by the aid of a series of drawings and plans, which are prepared by designers, based on certain calculations. Hence, knowing docking processes, docking calculations, and understanding how to read docking plans is an important skill for designers working in shipyards.

From time to time, it becomes important to carry out repairs in the underwater portion of the hull. Such repairs may include renewal of the sacrificial anodes, refit of the propellers, overhauling of the propulsion shafts, repair of rudders, underwater hull blasting to remove fouling, etc. In order to carry out these repairs, the underwater portion of the hull needs to be made accessible, which is the purpose served by a dry dock. It has also become a common practice in large shipyards to build their ships on dry docks, and float it out when ready for trials. For such procedures, the docking plans need to be prepared taking into consideration the increase in weight of the ship structure along the building time. Once the ship has been built, the dry dock is flooded and the ship is undocked. The calculations for undocking also play a major role in the process because it is during undocking that the the ship is at a risk of capsizing.

Stability during Docking:

When the ship enters a dry dock, it must have a positive metacentric height; and is usually trimmed by stern. The floor of the dry dock is lined with keel blocks, which are so arranged such that they can bear the weight of the ship. When the ship enters the dry dock, her centerline is first brought in line with the centerline of the keel blocks by using a combination of plum lines and Leica theodolite.

The dock gates are then closed and the water is pumped out of the dock in stages. Since the ship has a trim by stern, the stern of the ship will first sit on the keel blocks. The rate of pumping out water is reduced as the stern is almost about to touch the keel blocks. The reason is, it is from this stage of the docking procedure when the stability of the ship starts getting critical. The interval of time from when the stern takes the blocks to the moment when the entire ship’s weight is borne by the blocks is called Critical Period. We will understand the details a little later.

When the stern of the ship takes the blocks, it is fixed to the shores (sides of the dock). This is carried out from aft to forward so that by the time the entire ship takes the blocks, it is fixed to the shores. When the ship is completely borne by the blocks, water is pumped out quickly from the dock.

So what happens during the critical period and why?

When the ship’s stern just touches the keel blocks, part of the ship’s weight is being borne by the keel blocks. The contact between the stern and the keel block creates a normal reaction or upthrust. The magnitude of this upward normal reaction increases as the water level in the dry dock reduces. It is this upthrust that creates a virtual reduction in the metacentric height of the ship. Hence it is very crucial to maintain sufficient positive metacentric height before docking, lacking which, the ship may heel over to either side, or even slip off the keel blocks and capsize.

The purpose, hence, is to calculate the metacentric height of the ship at different stages of the docking process, and ensure that it does not fall below the safe limit. Follow the figure underneath, which shows a ship that has just touched the keel block by its stern. The location of the center of floatation (F) is known from the hydrostatic curves at the given displacement. Since the location of the stern is a known point, its distance from the center of floatation (l) can be calculated instantly.

The moment to change trim by 1 cm (MCTc) is a hydrostatic parameter that is obtained from the hydrostatic curves. So, for a known value of trim, the following equation is obtained:

The above figure shows the transverse view of a ship in the critical period, which has been inclined by an external force to an angle theta (Ɵ). The weight of the ship (W) acts vertically down through the center of gravity (G). The upward reaction force (P) acts vertically upwards through the keel of the ship. This is a normal reaction force, and is equal to the portion of the weight of the ship being borne by the keel blocks. For equilibrium, the remaining portion of the weight of the ship (W-P) will be supported by the buoyancy, which will act through the initial metacentric height of the ship (M).

What we have now, are three vertical parallel forces acting on the ship:

• Weight (W) acting downward.
• Keel block upthrust (P) acting upward.
• Buoyancy (W-P) acting upward.

The upthrust force (P) can be considered to have an effect similar to that of removal of a weight from the ship. This has the virtual effect of rising the center of gravity of the ship from the point ‘G’ to ‘G₁’. The metacentric height therefore reduces from GM to G₁M, as shown in the diagram below:

The virtual reduction in metacentric height at any stage of the docking process can be calculated by the following expression:

This calculation must be carried out for the condition when the ship has just touched the keel blocks throughout its length. It is at this point that the keel block upthrust is maximum, and the risk of tipping over or slipping from keel blocks is most likely if the metacentric height is too low or negative.

Docking Plans:

A docking plan is a document that is prepared for every ship during its preliminary design phase. All the information required to bring a ship to a dry dock are included in its docking plan. While most of the information is condensed into drawings, one must also refer to the textual references and notes provided, because they also inform us about the type of dry dock that is being used, and technical specifications of dry dock that should be met before the ship is docked.

The contents of a typical docking plan are discussed below:

• Table of Hydrostatics and Hydrostatic Curves:

The first few hydrostatics that must be checked before a ship enters a dry dock are:

• Forward draft.
• Aft draft.
• Longitudinal Center of Buoyancy.
• Moment to Change Trim by 1cm.
• Center of Gravity.
• Longitudinal Center of Floatation.
• Transverse metacenter.

Since it is not preferred to provide the information in an easily obtainable manner, a tabular form of hydrostatic data is more preferable than the curves. In case of intermediate values, interpolation methods are used, and then tallied with the curves.

• Docking Drawing – Elevation View:

The elevation view of the docking drawing gives the following information:

• Location of the Longitudinal Reference Point (LRP), i.e. the point from which all the longitudinal dimensions are measured.
• Location of Aft Perpendicular and Forward Perpendicular.
• Location of the end of skeg.
• Frame spacing.
• Longitudinal clearance required for removal of shaft.
• Longitudinal clearance required for removal of rudder.
• Location of draft marks along the ship.
• Location of the first and last keel blocks.

• Docking Drawing – Plan View:

The plan view would show the location of the keel blocks along the centerline of the ship. Most large ships with wide beam are also placed on a series of side blocks, and the layout of the same is laid out in the plan view. The position of every hull opening and hull protrusions (both, above and below the waterline) are also marked in this drawing, in order to make sure they do not interfere with the dock blocks.

• Cross Section at Propellers:

Sufficient clearance should be ensured between the propeller tip and the dock floor. There should also be adequate longitudinal and transverse clearances for enabling removal of the propeller. It is due to this reason, the cross sectional view of the propeller (usually looking forward) is provided in the dock plans. The centerline of the ship, centerline of the propeller disc, distance between the ship’s centerline and the propeller centerline, and keel line of the amidship is also shown in the same diagram, as illustrated below.

• Keel Profile:

The keel profile shows the elevation of the keel line along the ship’s length. This profile is used to determine the height of the keel blocks at each longitudinal position, taking into consideration the load distribution curve of the ship.

• Bilge Keel Clearances:

The bilge keel extends as an appendage from the sides of the hull. The distance from the bilge keel to the ship’s centerline must be specified in the docking plan. The height of the bilge keel from the ship’s keel is used to ensure there is sufficient vertical clearance available during docking and undocking.

Load Distribution and Block Pressure:

Since the keel blocks bear the weight of the ship, the load distribution curve for the keel blocks is derived from the weight curve of the ship, which is comprised of a combination of distributed and concentrated weights. The weight of the hull girder and superstructure are distributed along the ship’s length. But weights like that of machinery, equipment, transverse bulkheads, fuel oil, fresh water are considered as concentrated weights.

The figure above shows the nature of the weight curve for a ship (shown in blue). In case of dry docking, the buoyancy curve becomes non-existent. However, there is an important change that is made in the weight curve. If you notice carefully, when a ship is afloat, it is supported by buoyancy throughout its length. But a ship on a dry dock is not supported by keel blocks throughout its length. This is because of the shape of the ship’s hull. Notice in the figure below, that a significant length of the ship forward and aft are not supported by the keel blocks directly, due to the overhangs at the bow and stern.

Though the weight of the overhang regions is not directly exerted on the keel blocks, the total weight of the ship is supported by the total area of the keel blocks. To compensate for this effect, the weight curve of the ship is accordingly changed so as to transfer the weights of the overhang regions onto the region supported by the blocks (also called keel bearing length).

The maximum pressure that can be exerted on the blocks is a function of the material used for the blocks. This value being a constant, the minimum block area required for each block is calculated. If you observe the nature of the weight curve, it is usually high at the mid ship region and decreases at the forward and aft. It is due to this reason that the weight bearing area of the keel blocks increase as we move towards the mid ship. The pressure exerted on the keel blocks is called the block pressure, and the Average Block Pressure is the total weight of the ship divided by the total bearing area.

Now, docking plans are created for every ship taking into consideration the dry dock where it is likely to be dry docked during most of its major repair and refits. But there may arise situations where a vessel is to be dry docked at a different dock, where the docking plan is to be modified to suit the dry dock. There are a number of conditions that must be met in order to prevent any structural failure in such cases:

• The number of blocks may be different from the original docking plan, but the total bearing area must be sufficient to maintain the block pressure below the material safe limits. This ensures that the hull does not have excessive loads that could cause damage to itself.

• The floor of the dock has its own strength limits, which depends on the material of the dock floor. This makes the load on the dock floor per unit length a limiting parameter too. Now, if any block is removed or repositioned from the original plan, the load on the dock floor per unit length must be recalculated and checked for the given factor of safety.

• The dock floor is strengthened underneath by transverse frames that run along the breadth of the dock. When keel blocks or side blocks are repositioned from the original dock plan, it should be ensured that the new position of the block is such that it comes under a strength bearing member of the ship (bulkhead, longitudinal girder, etc.) and also sits on top of a dock floor transverse. This is to ensure that there is a proper stress flow from the ship’s hull to the keel blocks, and finally to the dock floor.

• It must be checked that the new positions of the keel blocks do not interfere with any underwater opening or protrusion. The heights of the new blocks should be calculated by interpolating the values of the two closest values from the original docking plan.

It is evident from the article, that the calculations and analyses that go into creating docking plans and executing the process require equal attention from aspects of stability, as well as the strength of the ship. Most of the failures in dry docking or undocking of ships have been due to

• Improper evaluation of loading of the ship.
• Improper loading of the ship during docking (concentrated weights like fuel oil, lube oil, fresh water, ballast water, etc. should not be stored in overhang regions during dry docking).
• Improper stability assessment of the ship during the critical period.

While these are the primary reasons, there are a series of many which can only be discussed in detail in courses that are designed specifically for dock masters. Today, dock masters use software to pre-determine the docking plans of ships, and the results are then tallied with the existing docking plan. Even then, this procedure remains one of the most crucial ones in the ship-building and ship repair industries, owing to its demand for extremely low margin for error.

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. 

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Drydock is one of the most crucial periods for a ship and its staff as it’s the time when all the major repairs and surveys take place. As per the regulations under SOLAS Chapter 1 Regulation 10, a commercial vessel has to undergo two inspections of its hull (outside of the ship’s bottom) in 5 years period conditioning; the time-gap between two of these inspections should not be more than 36 months.

The drydock also gives an excellent opportunity for ship management team to carry out repairs of the main and auxiliary engine, sea water pipes and system, intermediate and tail shaft, propeller, bow thruster and other similar machinery systems whose repairs cannot be performed at high seas when the ship is floating in the water.

Related Read: How to Perform Ship’s Stern Tube Integrity Test in The Dry Dock?

During the drydock, a ship has to take shore power to ensure that the work inside the ship, i.e. in the engine room and deck can be performed uninterrupted.

Related Read: How Cost Estimation is done for Ship’s Dry Dock?

Why ships need shore power?

When the ship sits on the keel blocks in the drydock and the water is removed from the dock to inspect the hull, the auxiliary engine-generators, which produce the electrical power, can no longer work due to non-supply of cooling water to the engine. To avoid overheating of moving parts of the engine, the auxiliary engine has to be switched off before the water is pumped out of the drydock.

Related Read: Dry Docking of Ships – Understanding Stability And Docking Plan

If the ship auxiliary engine and its alternator are included in a major maintenance of the drydock, it needs to be turned off to allow personnel to work on the machine.

The only alternative to shore power is to keep the auxiliary engines running, and that can be done if the shore team provides a separate portable cooling water piping system which can be attached to the inlet and outlet of the ship’s auxiliary engine cooling system. This set up is complex and requires pre-planning. The water provided to the vessel will typically be charged by the quantity (Metric Tonne) supplied to the ship’s system. Hence, shore power supply is preferred over this method.

Related Read: 25 Important Points to Consider While Securing the Engine Room for Dry Docking

Preparation and checks before drydock for receiving shore power:

A chief engineer needs to make sure the ship’s power receiving terminal is prepared well in advance of the drydock so that it can be connected to the shore power without any trouble.

Normally, the ship’s electrical engineer will prepare the ship’s power receiving terminal box and should do following things:

• Ensure the receiving box is not obstructed with any object, pipes or spares. It is usually located either on the deck near accommodation entrance or the emergency generator room
• If the box is not used or maintained for long, clean the box and ensure the safety door hinges and locks are functioning smoothly
• Ensure all the receiving terminals inside the box are present and in good working condition
• Ensure earthing cable is provided to earth the ship’s hull to shore earth
• Ensure measuring instrument such as voltmeter, phase sequence indicator, and tester etc. are present
• Ensure the indication of shore power (in the form of light bulb) is present and working
• Ensure a safety device (circuit breaker or fuse) is provided in the terminal to protect the MSB of the ship
• Ensure details of shore power requirement is pasted near the shore receiving terminal box, which includes required voltage, frequency, and method of connecting the shore supply
• Ensure the ship’s batteries are tested for full charging

Preparation and checks in the drydock before taking shore supply-

The process of receiving shore supply to ship is critical as unprotected connection may lead to accidents and wrong shore supply will hurt the efficiency and increase heat generation from onboard equipment.

Related Read: What is Alternate Marine Power (AMP) or Cold Ironing?

Following things to be checked before connecting shore supply to ship in a drydock:

• Check the cable drawn to ship for providing shore supply is in excellent condition
• Check the insulation resistance of the cable provided for the shore supply
• Check the insulation resistance of the shore supply box
• Check the polarity of shore supply using a voltmeter
• Check and ensure the frequency and voltage of shore supply are matching with the specifications required by the ship

Related Read:  How The Power Requirement Of A Ship Is Estimated?

• Check the phase sequence of the shore supply using phase sequence tester
• Check the tightness of the shore cable connector clamp to ensure they are not loose
• Ensure to display notice near the vicinity of ship’s receiving terminal box about high power cable in use
• Check and ensure the ship’s generators are disconnected from the Main Switch Board of the ship
• A responsible officer must check and record the energy meter reading provided on shoreside
• Ensure ship’s hull is earthed to the shore before supplying shore power to the ship

Related Read: How to Minimize the Risks of an Electrical Shock on a Ship?

Taking the Shore Supply-

Once all checks are performed by ship’s engineer and the ship is ready to take the shore power, take the following steps:

• Once the shore supply power is made available to the vessel, the light indicator provided in the terminal box will be ON
• Close the breaker to start the supply of the shore power to ship

Related Read: What are the Main Safety Devices for Main Switch Board on Ship?

• For checking the phase sequence, a bulb type phase sequence indicator can be used in which two lamps are connected to unbalanced load across the 3 phase via capacitor and resistors. The phase sequence will be considered “OK” when the right side lamp is bright, and the left side one is dark
• Another instrument used to measure PSI is a small portable 3 phase induction motor driven meter with a rotary pointer
• Check the frequency of the supply from the provided frequency meter or on the Main Switch Board of the ship
• Ensure to keep the emergency generator in manual mode to use the same if the shore power goes off abruptly and electricity supply is needed

Common problem faced by ship’s staff while taking shore supply-

1.  Shore supply switched on, but the ship is not getting power

• Check the three fuses connected between the ship’s terminal and Main Switch Board (MSB)
• Check the circuit breaker located in shore supply switchboard
• Check circuit breaker interlocks which are arranged in the system to avoid paralleling of shore and generator power

2.  Shore power trips during supply

• Faulty shore cable. Ensure the cables used for supplying power is of proper size and as per the maximum protective current value of the ship.
• Overload in the system. Ensure to correctly calculate the electrical load of the ship during the drydock using electric power balance table to avoid overload trip.

Generator circuit breaker trip: It is possible that the safety breaker for the generator trips the shore supply during the inspection or maintenance of generator’s interlock.

Related Read: Blackout Situation on a Ship: What are the First Steps that should be Taken?

3.  Wrong shore supply

Most countries have their local regulations which make the shore supply compulsory to avoid emission problems. If the voltage and frequency of shore power do not match with the ship’s rating, the machinery will operate at lower efficiency and may face overheating problems. The ship manager must ensure to choose a drydock, which can provide shore supply as per the ship’s requirement.

Related Read: 10 Technologies/Methods for Controlling NOx & SOx Emissions from Ships

* Sensitive electronic equipment such as controllers, navigation equipment etc. are prone to damage from power fluctuation. Try to switch off these systems while the using shore supply. If the equipment needs to be switched on, it is recommended to use battery supply for their operation

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. 

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The intention behind sending a ship to the dry dock at regular intervals of time is to inspect those parts which are technically difficult to access when the ship is at sea. One of the systems that is inspected during dry docking is the ship’s stern tube system, which carries the propeller shaft turned by the engine’s intermediate shaft, a configuration that propels the ship in the desired direction.

During dry dock, the stern tube is opened up for inspection of the seals, the stern cylinder, and the shaft. Overhauling and replacement of seals are done if their condition is not as per maker’s desire. After overhauling and boxing back the stern tube system, the next step is to make sure that it does not leak oil out to the sea or water inside the engine room, once the ship is water bourn. For this purpose, post overhauling inspections are carried out in the dry dock by experience marine engineers to make sure no leakages occur.

Modern ships are fitted with either oil lubricated or water lubricated stern tube systems. Both these systems have a different method of inspection which we will discuss in this article.

Water Lubricated Stern Tube System

For water lubricated stern tube system, following method can be used to inspect the integrity of the stern tube in the dry dock:

• In water lubricated stern tube, the seal housing is provided with a test connection which will be plugged all the time. Make temporary piping connection to this connection providing a pressure gauge installed in the pipe
• This type comes with a air inflatable seal. Connect an airline to that with provision of a shut-off valve
• Maintain air pressure of approx. 40psi to the inflatable seal
• Check and ensure the air pressure does not drop at rate of 10%/ hour
• Now supply water to the seal casing via test connection with twice the standard draught pressure of the ship
• Maintain the water supply for 20-30 minutes and check for any leakage
• Also check the complete seal assembly and mounting flanges for leakage
• If no water is leaking, the sealing is OK to undergo normal operation

Do remember to not rotate the shaft assembly once the inflatable sealing ring is inflated with air supply, as this will damage the sealing ring.

Oil lubricated stern tube system

For oil lubricated stern tube system, there are two designs available

1. 3 aft seals tube and
2. 4 aft seals tube.

Following method can be used to inspect the integrity of the 3 seals stern tube in the dry dock:

• If both high level and low level oil tanks are provided in the system, use the low level tank for filling the oil
• Align the oil feeding valves and feed oil in to the system from the low level tank
• Now open the drain plugs provided between the 2 and 3 seals of the aft seal assembly and check for any oil leak
• Open the drain plug between 4 and 5 seals of the forward seal assembly and check for any oil leak

• Feed oil manually to the chamber between 1 and 2 seals in the aft seal assembly and check for any leakages from seal 1 and drain plug provided in between 2 and 3 sealing chamber
• Close the drain of 2 and 3 sealing chamber and then feed oil to the line between 2 and 3 seals and fill the oil to the top of the plug. Check the level of oil is not dropping
• Similarly close the drain plug between 4 and 5 seals chamber and feed oil. Check for oil leakage from seal 5 in the forward area

Following method can be used to inspect the integrity of the 4 seals stern tube in dry dock:

• Feed oil from the stern tube tank keeping the oiling line valve closed for 3 and 3s seals
• Open the drain plugs of chambers 3 – 3s of aft sealing and 4 – 5 of forward sealing to check oil leakages
• Shut the drain plug of 3- 3s chamber and open oiling line valve to feed oil to 3 – 3s chamber in the aft sealing

• Open drain plug for 2 – 3 chamber in the aft sealing and check for oil leakage
• Feed oil to 1 -2 sealing chamber at the aft sealing and check for oil leakage from seal 1 and drain plug of 2 -3 chamber
• Now shut the drain plug of 2 – 3 chamber and fill oil from the top plug. Make sure the oil level in the top plug doesn’t drop
• Similarly shut the drain plug of 4 – 5 sealing chamber and fill it with oil. Check for leakages from seal 5 and area near the clamp ring

Once all the leak tests are satisfactory, engineer officer in-charge must ensure all the drain plugs are put on before bringing the system in normal operation.

Over to you..

Do you know any other important points that should be added to the article? Let’s know in the comments below?

How to Perform Ship’s Stern Tube Integrity Test in The Dry Dock? appeared first on Marine Insight - The Maritime Industry Guide

According to SOLAS regulation, every sea-going vessel has to undergo two dry docks within a period of 5 years. A ship in dry dock is a ship out of service. Dry dock is a complex process which is both expensive and time consuming. It is a necessary evil which ship owners, operators, and crew members have to go through when the time requires. With two compulsory dry docks within a period of 5 years, it is a stressful task for ship owners and personnel who have to go through a lot of planning and preparation for the drydocking activity.

Planning of dry docking starts several months before the scheduled date. A number of things needs to be arranged starting from the convenient place for dry-docking to arranging spares and on-shore maintenance staff. Moreover, it is often seen that ships have to take a totally different route for a suitable dry dock place as most of the time the desired facility is not available when needed. This is very common with larger vessels.

In order to deal with this situation, all major classifications societies have a special program called the “Extended Dry-Docking” or EDD scheme.

What is Extended Dry-Docking Program?

Under extended dry-docking program, ships have a privilege to extend their dry docking period from 5  to 7.5 years. This means that ships under this special program gets maximum dry dock interval of 7.5 years by replacing certain dry-dockings by in-water surveys (IWS) which are carried out by approved diving companies. A variety of factors are taken into consideration before approving a ship for extended dry-docking.

However, not every ship is allowed for the extended dry-docking program.

One of the major benefits of Extended Dry-docking program is that the ship is allowed to stay in water for a longer time increasing the availability of vessel for business. It also helps operators with increased flexibility in choosing the dry-docking window with properly planned maintenance programs and schedules.

Guidelines and Requirements for Extended Dry-docking Program

The maximum dry docking period is extended by allowing the qualified ships to undergo In-Water Surveys (IWS) which help to increase the period between two dry-docks. However, it is to note that only those ships which produce satisfactory results in these surveys are allowed to continue with the EDD program.

Each classification society has its own requirements to allow a ship under extended dry-docking period to ensure highest levels of quality and safety. Some of the main requirements for a ship to be allowed under this special program are:

– Presently, the extended dry-docking program is available for only container ships, general cargo ships, and multi-purpose dry cargo vessels. This means that ships such as tanker and passenger vessels and those subjected to Enhanced Survey Program (ESP) and Extended Hull Survey Program (EHSR) cannot opt for extended dry-docking.

In accordance with IMO resolution A744 (18), the scheme cannot be applied to Enhanced Survey Programme vessels – most bulk carriers and tankers – and under the SOLAS Convention it cannot be applied to passenger vessels.

– Ships belonging to all flag states cannot apply for the extended dry-docking program. The flag administration first needs to approve the type of vessel and the owner for the extended dry-docking scheme. A ship can apply for the EDD only if its flag state approves of the program.

– Age of the ship plays a major role during acceptance for the EED program. The ideal age for the commencement of Extended Dry Dock Program is between 0-5 years and less than 10 years. However, older ships can be considered for the program depending on the flag state, ship type, classification society and other design and operational factors.

– Inspection of hull and paint coating is one of the most important factors considered for extended dry-docking. The paint manufacturer provides the criteria for which the coating will be valid for 7.5 years. Several factors such as vessel speed, area of operation, vessel utilization, and idle time are taken into consideration while deciding the validity of the coating. High quality hull coating is an important requirement for extended dry docking.

– Anti-Corrosion system (corrosion protection) is an absolute must for EDD. Ships with high quality underwater coating are only allowed for the extended dry-docking. Moreover, sacrificial anodes attached to the hull must be capable for renewal in water and the impressed current corrosion protection system must be monitored for effectiveness. The ballast tanks must also have good coating condition.

– The quality and thickness of coating requirements are different across EDD providers. For e.g. GL has the following requirements for ships allowed for EDD program:

-> As criteria for the implementation of the “Extended Dry-Docking Interval”, at the time of new building, the corrosion prevention system for the bottom shell has to fulfill the following requirements:

-Dry film thickness of coating for 7.5 years has to be an average of 300 μm

-Anodes (Alu/Zinc) prepared for 7.5 years

Alternatively,

Impressed current system is to be installed and maintained

– >As criteria for the implementation of the “Extended Dry-Docking Interval”, for ships in service, the corrosion prevention system for the bottom shell has to fulfill the following requirements:

-Dry film thickness of coating for 7.5 years has to be an average of 250 μm

-Anodes (Alu/Zinc) prepared for 7.5 years

Alternatively,

If installed, in impressed current system, is to be maintained and documented in the Planned Maintenance Scheme

– The results of the in-water survey play an important role in deciding the next dry-docking schedule for the ship, even if the ship is under Extended Dry Docking Program. If the results of this survey are found unsatisfactory, then the operator is asked to book a dry-dock within one month of the IWS (In water survey).

Summary of Extended Dry-Docking (EED) Scheme 

– Dry-docking period extends from 5 to 7.5 years

– Dry-docking is replaced by In-Water Surveys (IWS) from authorized underwater inspection service providers

– Only those ship types and operators approved by Flag administrators are considered for dry-docking survey

– Not all types of ships can apply for EDD

– Generally ships of age not greater than 10 years are considered for EDD

– Special requirements for hull condition and paint coating thickness are required

– Proper ship corrosion protection system is a must

– Results of IWS decides the next dry-docking schedule

-Requirements for a ship to be approved for EDD will vary across EDD service providers

– Special surveys can be assigned to ships if required

– The scheme can be discontinued anytime if the ship doesn’t meet the stated requirements

DNV, one of the providers of Extended Dry-Docking, offer special recommendations to the ship owners who plan to opt for EDD for avoiding unscheduled dry-docking.

Further Reading:

• DNV EDD Notes
• LR EDD Guidance 

Extended Dry Docking is an excellent option for ship owners to avoid unscheduled and costly dry-docking, provided a well planned and documented maintenance/survey schedule is implemented.

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. 

What is Extended Dry-Docking of Ships? appeared first on Marine Insight - The Maritime Industry Guide

Preparing a ship for a dry dock is not at all an easy task. A lot of planning is required in order to ensure smooth repairing work along with optimum ship repair cost.

Every ship undergoes major repairing work during dry-dock period. Though there are several intermediate docking surveys and repairs scheduled in between, a five yearly dry dock is the one which involves major revamping of the ship.

Needless to say, dry dock is an expensive process which requires systematic and efficient planning and cost estimation to minimize overhead costs along with other unnecessary spending.

Cost estimation plays an important role in order to keep a check on a ship’s dry docking budget and to ensure a sensible quotation for the whole repair work. There are three important aspects of ship repair cost estimation:

• Cost Groups

• Cost Parameter

• Work Breakdown Structure

Let’s take a look at each of these aspects in detail.

Cost Groups:

Cost grouping in an integral part of cost estimation wherein the whole repairing process is divided into parts for the ease of cost quotation and work completion within the stipulated time. Cost groups also help to divide and assign work to different segments of the repair yard and to get individual quotation for each one of them, making the whole process smoother and manageable.

Cost grouping is mainly done on the basis of ship’s department. For e.g. deck, engine, electrical etc. Details of things included in each of these department are as follows:

Engine Room

• Main engine and propulsion machinery
• Boilers
• Engine room tanks
• Auxiliary Machinery
• IG System

Deck

• Accommodation area
• Navigation equipment
• Anchor and deck machinery
• Cargo gear
• Hull, rudder and tail shaft
• Cargo tanks, fuel tanks ,ballast tanks , and slop tanks

Automation

• Controls and automated systems
• Instrumentation jobs

Electrical

• Motors
• Panels
• PLC’s
• Main Bus Bar modification

Electrical jobs in all areas of the ship

Cost grouping is an excellent way to stream line the process of cost estimation and to avoid errors related to costing while planning a dry dock.

Cost Parameters

Cost parameter is an aspect of cost estimation which defines the total number of elements that are to be included for the final project cost. Cost parameters specify the limit and scope of activity during the repair work.

Cost parameters help in analyzing the scope of the work and also helps in considering each and every aspect taken into consideration for the dry dock.

Examples of cost parameters are:

• Dry docking fees and repair yard cost
• Agency cost
• Classification surveyors’ cost
• Cost of the stores
• Repair and maintenance cost
• Damage repair cost
• Cost of necessary spares

Work Breakdown Structure

Work breakdown structure is an extension of cost grouping which further helps in distribution of jobs and procuring cost estimation for each job.

Work breakdown structure helps estimating the time needed for whole process, including period of repair, dry docking period and lead time. It helps to figure out additional job quotations that would be required during the repair work. Based upon these parameters, quotations are asked for repair and spare from different agencies/yards, and eventually the best suited quotation is selected.

The work breakdown structure also helps the chief engineer to decide what all jobs can be handled by the ship’s staff within the stipulated time in order to save repair costs. This eventually helps in making the final quotation that is to be sent to ship yards.

A general breakdown of the structure would include

Engine room

• Maine engine and turbine
• Jobs on auxiliary machinery including generators, auxiliary condensers, steering system and engine room pumps and pipes.
• Work on auxiliary boiler without re-tubing
• Boiler survey, soot blowers, and chemical cleaning
• IG System
• COP control and valves
• Safety equipment
• Radio and navigation equipment
• Machinery and instrumentation controls
• Electrical work including motors and switch boards

Deck Side

• General expenses
• Anchor and chain
• Hull anodes and sea chests
• Tail shaft
• Painting
• Steel / shell
• Ballast tanks internal inspection / survey & anodes
• Accommodation
• Cargo gear, deck machinery
• COP and stripper pumps
• Tank washing machines and pipes
• Hydraulic pipes and valves
• Steel damage

By taking all the three parameters mentioned above into consideration, optimum ship repair cost estimation can be reached using the resources and manpower available on board ship.

Image Credit: zebecmarine

You may also like to read – What is Extended Dry-Docking of Ships?

How Cost Estimation is done for Ship’s Dry Dock? appeared first on Marine Insight - The Maritime Industry Guide

A ship’s dry dock is a hazardous place to work. In spite of providing a series of measures for ensuring personal safety to seafarers and dock workers, accidents still occur frequently. Blame it on human error, lack of knowledge, or insufficient safety equipment, at the end it’s the seafarers who have to suffer.

Several of causes are stated as reasons for accidents onboard ships during dry dock, both in the engine and deck departments. Though most of the causes are same for both the departments, the ship’s engine room turns into a highly “accident-prone” area during the dry dock.

Knowing all the operations and procedures for the ship’s dry dock is a must for the engine room crew. However, accidents do take place in spite of training and guidance. Mentioned below are some of the common causes of accidents that can take place in the ship’s engine room during dry dock.

Note: Most of these accidents also occur when the ship is sailing at the sea; however, their changes of occurrence increases greatly in the dry dock.

1. Fire

The most common and dangerous cause of accidents during dry dock, fire can lead to disastrous damage to both ship’s properly and lives of seafarers. Some of the main sources of fire in the ship’s engine room during dry dock are:

Hot Works: With a number of hot work jobs such as gas cutting, welding etc. taking place in the engine room, there are high chances of accidents taking place. Oily rags, oil spill, flammable material etc. provide the right environment for fire during hot works. Fire can also erupt because of hot works in the following areas:

• If painting or chemical work is being carried out on the adjacent plates/bulkheads
• In oil/cargo tanks are not properly cleaned and have flammable material remains
• In enclosed places are not gas freed properly
• If adjacent tanks and the opposite side of the bulkheads have flammable material
• If there are sounding pipes near the hot work areas
• If the oil spill is there in the area
• Welding in situ engine room plates
• During structural cutting

Apart from this, fire can also occur due to a short circuit of electrical connections in the engine room. During dry dock, the engine room is filled with several electrical connections for portable equipment such as blowers, grinders, drillers, lamps etc. Proper insulation must be provided for these electrical connections and care should be taken to ensure that no circuit is overloaded because of less number of points. An electrical officer must be asked to put more circuits and electrical boards to avoid overloading of circuits.

Additional read:

Basics of Fire Prevention on Ships

Free eBook – A Guide to Personal Safety on Ships

2. Injury Due to Falling of Load

With every possible machinery and system going under maintenance during dry dock,  a number of spare parts are lifted to and from the ship’s engine room. Falling of load on crew members has lead to several deaths in the past and thus wearing a helmet is compulsory in the ship’s engine room. Following points must also be noted while carrying a load to prevent accidents in the engine room:

– Minimum 2 people must be assigned for any kind of load-lifting using cranes. One person should operate the crane while others must assist to provide direction and warn others to avoid accidents

– Crew members should avoid walking under any load when it’s being lifted by the crane, even though he or she is wearing a helmet

3. Falling/ Tripping of Personnel

A number of spare parts, tools, equipment etc. are lying around in the engine room during dry dock. This makes seafarers highly susceptible to trips and falls which can be extremely harmful in several cases. Oil or small-sized spare parts lying on the floor plate are also one of the main reasons for falling/ tripping. Following points must be considered to avoid such accidents:

– The temporary railing must be provided around openings or plates which are removed from the engine room floor

– Put warning signs

– Clean slippery and oily floors as soon as possible

– Avoid running or walking in haste while using engine room ladder

– If the engine room skylight is open, put a railing around the same along with warning signs

Falling of personnel from height can also occur due to scaffold or safety harness failure. Thus, care must be taken to ensure that all platforms at height are properly secured and adequate safety measures are provided.

4. Back Injury

Though this doesn’t sound like a fatal accident in the first place, back injury is actually a very serious problem that has been bothering seafarers for a long time now. Lifting heavy loads is a part of engine room procedures and engine personnel often neglect the right posture while lifting such load. There have been a few cases in the past wherein seafarers have been forced to take bed rest for months or even quit sailing because of such injury. Following points must be considered to avoid back injury:

– Use cranes and chain blocks wherever possible. Do not life heavy load manually as much as possible

– Divide the load to be lifted in the following categories:

Heavy – Loads that require crane and chain blocks. ( If they are not available to ask for a portable hydraulic forklift to shift the load to the desired position or until the crane or blocks)

Moderate – If the load is moderate, 2-3 people should lift the load together.  Never lift it alone.

Small loads- These are loads which one person can lift. During this, one hand should be free especially when climbing or going down a ladder. The load must not block your vision.

Additional read:

How to avoid back injury on ships?

5. Accidental Start of Machinery and Systems

Accidents have occurred in the past when machinery and systems have been started accidentally while maintenance work was being carried out. Such accidents can be extremely fatal for those working in the machinery. In order to avoid such situations, ensure that:

– The machinery and systems under maintenance are isolated, logged and tagged out

– When doing maintenance on electrical machinery, shut the main switch and remove the fuse (if present) for additional safety

6. Enclosed Space Accidents

Enclosed spaces are dangerous areas to work because of the presence of toxic and flammable gases. There have been cases of accidents involving unconsciousness and death of seafarers even after the spaces were gas-freed. It is therefore extremely important that the enclosed spaces are properly gas freed and tested before entering.

Additional read

Procedure for entering enclosed space on ships

How to rescue a person from confined space?

7. Burns

Burns or Scalding are common occurrences in the ship’s engine room during dry dock. Steam pipes or hot oil are some of the main causes of burns. Also, during maintenance of machinery, heated parts can cause severe burns to seafarers.

Real-life accident: After dry dock entering, the boiler was brought to zero pressure before opening for maintenance. However, when the main steam valve body was opened, a lot of steam came out causing severe burn to the engine crew.

In order to avoid such incidents, ensure that the boiler vent is opened properly. Also, do not open the boiler immediately after the pressure reaches zero. Leave it idle for sometime before opening.

Burns can also be caused by chemicals and while performing hot works such as welding, gas cutting etc.

8. Failure of High-Pressure Components/ Failure or Lifting Equipment

Equipment and tools with high-pressure components are used during overhauling and lifting of engine room machinery and parts. Such high-pressure components can rupture or burst causing irreversible injury to engine room crew. In case of high-pressure pipe bursting, the jet from the system can puncture or piercer the skin causing very severe consequences. All these equipment should, therefore, be properly tested before using them.

 9. Electrical Shock

With several electrical connections present in the engine room for various tools and equipment, there are high chances of electrical shock to seafarers from improperly insulated wires and connections. Care must be taken to avoid overloading of circuits and coming in direct contact with any open wire.

Additional read:

How to avoid electrical shock on ships? 

Hazards related to electrical cable insulation in case of fire

10. Flooding

When the dry dock is complete, the dock is filled with water to start sea trials of the ship. While doing so, engine ship personnel must keep a close watch on all the recently repaired parts, valves, and mechanical systems for any kind of water leakage. There have been cases of engine room flooding and loss of lives in the past because of such incidences.

Over

10 Types of Dry Dock Accidents That Can Occur in Ship’s Engine Room appeared first on Marine Insight - The Maritime Industry Guide

Dry docking is a tough job for seafarers; thanks to the never-ending maintenance and repair work, surveys etc. But that doesn’t mean seafarers cannot spare sometime out of their super-busy schedule to click some splendid photographs.

Dry dock is a super-cool place to take some unique photographs. Seafarers know that they would rarely get such opportunity again, when the ship is out of water and almost all its parts are opened up for overhauling or repair.

Note: Next time when you are in a dry dock, don’t forget to explore your creativity with your camera.

Got some amazing photographs to share with us?

Send them to us at info@marineinsight.com or submit at https://photos.marineinsight.com

10 Splendid Dry Dock Photos Taken By Seafarers appeared first on Marine Insight - The Maritime Industry Guide