The anchors are as old as the ships themselves. They are those age-old devices used to haul a floating vessel to the ground, like the seabed or seafloor, when the vessel is required to be halted or stationed at some location for some requirement.

Anchors come in different shapes, sizes, types, and builds. Depending on the vessel size and type, the size and weight of the anchor vary accordingly. 

The anchors are usually stowed in an enclosure of the main hull, usually known as the anchor pocket.

When needed, they are lowered into the seafloor with the help of a chain-cable mechanism operated from onboard.

After the anchor is lowered into the seabed, it settles down by virtue of gravity into the undersea floor.

This creates a firm grip on the seabed, and the vessel is fixed to its location by the inertial weight of the anchor coupled with the fixity it creates on the seafloor. 

Though in modern times, technologies like Dynamic Positioning Systems or DPS have gained popularity, anchor still remains very common amongst vessels.

And for all vessels that use technologies like DPS, an anchor is still kept on board as a reliable backup source when any of these systems fail. Hence, the importance of anchors is indispensable. 

As an intrinsic part of the anchor systems, the anchor chains also have a great deal of importance. They should be sturdy, have strong connections and strength, and resist high loads. 

What do we mean by foul anchor?

Foul anchors are those where the chain (or the rope for ancient ships) becomes entangled about the entire structure, or the anchor gets enmeshed by some obstruction underneath the sea level.

The shank is the central vertical structure of the anchor. The crown is the lower part that embeds into the seafloor.

Flukes are at the ends of the fluke and further help in the settling process of the anchor. The topmost point of the anchor (atop the shank), where the chain or rope is attached, is known as the ring or hook.

In the first case of an anchor fouling, the rope or wire becomes entangled or entwined about the whole anchor structure.

This can be best visualised by this classic example. All of us must have, at some point in our lives, ridden or still ride a bicycle. 

And inevitably, nearly all of us must have experienced our chain being derailed from its slot over the paddle wheel.

If we continued for even a few moments after this debacle, the entire chain would get entangled miserably, and we would have a hard time getting things back to normalcy! 

Similarly, for a chain-release mechanism like the anchor chain system, there is often this risk of entanglement due to inaccurate action, erratic motions of the vessel, operational errors, or just unbalanced forces.

Hence, in these events, the chain gets entangled about the anchor, initially about the shank and later about the crown or base. This poses a great deal of risk to the functionality of the anchor system as a whole, rendering it ineffective. 

The second case of fouling of the anchor is in the event of any kind of obstruction or impediment underneath the sea surface. These can be because of barnacles, seaweed, cacti, moss, fern, and all other kinds of aquatic or marine vegetation. 

Similarly, there can be any kind of natural or geographical obstructions or some kind of artificial ones like wreckage parts or some structure. 

Fouling of anchors is a very cumbersome event, and recovering or reorienting the anchor back to the normal configuration is challenging. As the chains are quite heavy, any complex form of twist is almost impossible to unentangle by human effort.  The common practice is moving the vessel in different ways to change the alignment of the entangling rope or alter the state till it loosens up and becomes straight and taut gain.

This may involve moving the vessel back and forth or, in some cases, manoeuvre the vessel in different manners and suitably varying the engine power till it reaches a suitable position conducive to the fouled anchor.

In worst cases, the only option is cutting the tangled chains back on shore using welding or different cutting methods and thereafter, refitting the chain system. 

For fouling by other external means, the first technique of vessel motions is primarily used. Else, often the obstruction is removed by external intervention using underwater divers or other machinery-based means. 

You Might Also Like To Read-

• Introduction to Anchor Design
• A Guide To Types Of Anchors
• What are Mooring Anchors?
• What is Anchor Chain – Everything You Should Know
• What To Do When Your Ship Is Dragging Anchor?

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. 

What are Foul Anchors? appeared first on Marine Insight - The Maritime Industry Guide

Anchoring is one of the very frequent operations onboard ships. A number of variables and external factors influence the duration and location of an anchoring operation. While the type of seabed is of utmost importance during anchoring, soft muddy grounds or clay bottoms are best preferred. It should be taken care that the anchoring bottom is free of power lines, submarine cables, pipelines or rocks.

Various methods on anchoring include consideration of direction and strength of wind, current and tidal stream. Often good local knowledge helps a mariner determine required manoeuvres and actions to be taken while anchoring.

The two most prevalent methods for anchoring are –

i) Let Go

ii) Walk back Under Power

1) Let Go: This method is used in over a wide range of vessels including smaller crafts and pleasure yachts to larger vessels with tonnage varying up to 1,00,000 GT. The principle followed in this method is to let go or let the anchor slip with cable under its own weight from the hawse pipe. The weight on the cable, windlass brake holding power and momentum of the vessel are factors to be controlled by the vessel to ensure the anchor digs in and the cable is subsequently laid to extend backwards. While approaching the anchoring position the speed of the vessel over ground is brought to zero using engines and helm and at the same point anchor along with the cable is allowed to run out under its own weight.

Once the flukes touch the bottom or chain touches the ground the engines are moved astern or ahead according to the prevailing conditions of wind and current to attain astern momentum with respect to ground, which will stretch the cable. It can be paid under controlled application of brakes to control the length of cable from running out completely. Often under such conditions combined effects of wind and current vessel will tend to swing and fall astern as well.

Attention to be paid to the preferred direction of swing and the anchor on which side to be used. Care should also be taken to not allow the full cable to run out under weight or to allow the cable to pile up which can result is developing kink or twist in the cable. During approach to anchoring grounds it is a general practice by shipmasters to lower the anchor to water level so that when the brakes are released the cables is paid out freely. After a long sea voyage sometimes the anchor might get stuck in hawse pipe and not release down from the hawse pipe under its own weight. As a proactive and good seamanship practice one should always check the condition of the windlass brake liner before use.

On several occasions, often on old ships, due to repeated use brake liners were found completely worn out or below required thickness, consequently reducing the braking power significantly which led to cable running out completely under its own weight resulting in loss of anchor and cable both.

Uneven loads or excessive astern momentum after applying brakes can damage the windlass and its seat and foundation. Engines should be used to counter the excessive momentum of the ship and the state of the vessel loaded or in ballast should be always kept in mind while using engines. Prolonged kicks might develop sufficient momentum in a loaded vessel to drag anchor or even snap the cable. A loaded vessel is found to be more responsive to effects of current or tide whereas a vessel in ballast drifts substantially due to wind. Combined effects and directions of local conditions can be helpful while doing preparation for anchoring.

2) Walk Back Method: Most of the companies have their own guidelines for anchoring large ships such as VLCC’S or ULCC’S which should be followed without fail. Walk back method of anchoring is recommended and used mostly on vessel’s above 1,00,000 GT. The working principle is the same however cable is paid out using the windlass at a fixed speed. Upon approaching the anchoring position the speed upon ground of the vessel is brought gradually to zero and the anchor is lowered in water.

As it touches the bottom more length is paid and engines are given astern to develop slight astern movement to lay the cable nicely as the flukes of the anchor dig in the seabed. This method usually is of longer duration than the let go method; however it provides ship master’s with better control over the amount of cable paid and weight upon the windlass. It is important that correct assessment beforehand of tidal conditions, gusty winds or strong coastal currents are made by ship master to accommodate for the movement of vessel as the cable is paid out. In general design speed of windlass is about 30-35 feet/min., which is approximately 0.3 knots over the ground.

Also a windlass is designed to lift up to 3 -4 shackles along with the weight of the anchor. Walk back method prevents piling up or twisting of cable, which is paid under power and thus provides better control to master or pilot to ensure the anchor holds in and does not drag. However speed over ground of vessel must be diligently controlled to avoid excessive loads on windlass, which is being used with gear engaged.

What Are “Let Go” and “Walk Back” Ship Anchoring Methods? appeared first on Marine Insight - The Maritime Industry Guide

Anchoring is one of the many important operations coming under the responsibility of deck officers. It involves the use of critical shipboard equipment and requires high level of situational awareness. The key responsibility of the deck officer at an anchor station is to use the anchoring machinery and available man power for carrying out the operation safely and efficiently in accordance with the master’s instructions.

This article provides practical suggestions for deck officers on anchoring operations.

Communication

Proper and efficient communication between the bridge and the anchor station is the most important aspect of anchoring operations. The deck officer in charge should be thoroughly familiarised with the reporting procedures. While anchoring, it is as significant as to give clear commands to the crew members as it is to receive the same from the Master. It is also essential to update the status of the operation to the bridge, from time to time. Before starting the operation, the officer must be clear on:

1. The anchor to be used (Port or Starboard)

2. How many shackles are to be lowered

3. How the anchor should be lowered (letting go or walking on gear)

Preparation for Anchoring

Once the officer receives the command to prepare for anchoring, he must check on the following points:-

1. Presence of crew members wearing proper personal protective equipment (PPE) for assisting the anchor station

2. Confirming the anchor used for the operation (Port or Starboard)

3. The anchor lashings and bow stopper are removed prior commencing the operations

4. When using hydraulic windlass, make sure the pumps are started prior operation

5. Check the working of Windlass and its controls

6. If bow thrusters are likely to be used during anchoring, ensure that the required ventilations are open

7. Anchor day signal (ball) is ready for hoisting after terminating the operation

8. Walkie-talkies radios to be checked

9. Ensure that ship sides are clear of obstructions

Operation

Anchoring operations are of 2 distinct types.

a. ‘Letting go’ (dropping the anchor)

b. Heaving up (picking up the anchor)

In either case, the deck officer has 3 main responsibilities.

1. Operation of the Windlass

Normally, the operation of windlass is done remotely from the controls. It is best preferred that the windlass operation is carried out by the deck officer, provided the controls are positioned near the ship’s side or in such position that he can keep a look at the anchor and its chain while operating the controls. Otherwise, it is preferred to assign the duty to a skilled seaman guided with clear instructions.

2. Visually checking the anchor and its chain

As the officer is in charge of reporting the position and stay of the anchor and its chain, it is recommended to keep a visual check on the same by himself. Any uncertainties or out of ordinary action observed during the anchoring should be reported to the Master in no time.

3. Keeping a track on how many shackles are lowered

Tracking the number of shackles lowered is done by visually observing the ‘kender’ shackle of the chain. Kender shackle is bigger in size and is usually marked in different colour patterns or numbers for easy sighting. In modern ships, the length of the chain below the hawse pipe is digitally displayed on the control panel, however it is better to have a visual check than to rely on it. If the officer is operating the windlass, a crew member can be assigned for the duty.

Remember – 1 shackle is 27.5 meters.

Reporting

Reporting is another vital duty of the deck officer in charge of the anchoring operations.

The duty officer acts as the eye of the Master in anchoring; hence every single status of the operation should be updated to the Master. The most significant factors to be reported are:-

1. Anchor position

While anchoring operations are underway, the anchor-chain position is a matter of high concern. The positions are reported normally in

a.   Clock format – Considering the bulb as 12’o clock, the position to be reported with reference from the bulb. The positions on starboard side will be 1’o clock, 2’o clock etc. and port side will start from 11′ o clock

b.  Cardinal Points – Reporting using the points system with every point 11.25 degrees. Example – 2 points on starboard bow.

2. Chain Stay

Along with the Position, the stay of the chain is also to be reported. Stay of the chain is the tendency of its movement. While reporting the following terms are to be used for the respective observations.

a. Short stay – when the chain is leading in a short range from the ship’s side.

b. Medium stay- When the chain is leading in a medium range from the ship’s side.

c. Long stay- When the chain is leading in a longer range from the ship’s side extending from the hawse pipe.

d. Up and Down – When the chain is vertically leading parallel to the ship’s side. It will not extend and will be leading vertically downwards from the hawse pipe to the seabed.

Example of reporting – Position 2’o clock, long stay. 

Different officers have different reporting styles. It is good to use the way an individual is comfortable with, as long as the Master and the rest of the anchoring team is clearly able to understand.

In normal cases, while letting go the anchor, the chain needs to be stretched out for the anchor to hold the vessel. After dropping the anchor, the chain stay will be longer. When the anchor is holding to the seabed and the chain is settling down, the stay comes gradually to medium and then to a short range. Finally the chain will go up and down which means the anchor is holding and the chain is settled down.

Safety

The deck officer in charge is responsible for the safety of the equipment and the crew members involved in the anchoring operation. The officer has to watch out for himself and his crew during the operation. Unsafe practices should be corrected and the officer should be able to lead the crew and guide them on doing the operation safely.  Regarding safety, the following points should be noted:-

a. Use of proper PPE including safety helmet, gloves, goggles, and ear muffs (if needed)

b. While checking the anchor and its chain, find the apt position from where you can observe the anchor and avoid leaning over from the ship’s side.

c. While letting go the anchor, stay well clear from the windlass

d. While lowering/heaving the anchor on gear, do it in a gradual speed and avoid sudden and repeated alteration of the speed of windlass and its direction of movement

Anchoring is a crucial and highly practical operation. In most of the cases, theoretical guidelines and bookish knowledge are helpful only to an extent. Situational awareness and spontaneity of the officers, and their instant decision making capability helps to carry out the operation fruitfully. A good knowledge of ship’s maneuverability and the limitation of the equipment involved will further help the officer to make such spontaneous decisions. The competency of the officer is decided upon his ability to consider the situation, command his crew and to assess the orders give by the Master, to carry out the operation safely and efficiently.

Have we missed any important duties of deck officer that can be added to this article? Let’s know in the comments below.

Responsibilities Of Deck Officer During Anchoring Operation appeared first on Marine Insight - The Maritime Industry Guide

Surrounding circumstances and conditions are probably the greatest variables when the ship is at sea. It may become necessary all of a sudden to drop anchor in an emergency in case of steering failure, probable collision, manoeuvring in shallow waters etc.

Usually, letting go (dropping of anchor) is done to reduce the speed of the vessel as swiftly as possible to prevent any forthcoming mishap. When such an action is taken at sea, there’s barely any time to walk back the anchor which means the action to be taken by the responsible officer is to be firmly made in limited time.

Letting Go (Dropping) Ship Anchor in an Emergency

The following points must be kept in mind when letting go anchor in an emergency:

1. The Officer must be at the forecastle with a portable VHF, a torch and their paraphernalia to release the bow stoppers. While clearing away anchor in the previous operation, the brakes as well as the bow stoppers must be checked for efficient operation.

2. The Ship sides must be checked for boats, skiffs, tugs, barges and other such obstructions, especially below the anchor; obviously, this is to be done to prevent harm to a third party.

Watch: Ship Anchor Drops on Tug Boat

3. The Officer must be in constant parley with the Bridge to relay and receive orders to and from the Master. This includes information about where and which anchor to let go and how many shackles as well.

4. The Officer must open the take and let the anchor run out directly from the hawed pipe, as and when the required information is received. There’s no time to walk back anchor in this case due to probable imminent danger.

5. The cable must be checked at all time to count the number of shackles passed as per orders from the bridge.

6. In case there’s too much cable paid out without keeping an eye on it, the anchor tends to hold tight causing the cable to part by the vessel’s momentum.

7. In case there’s less cable paid out, the anchor won’t really make the required full contact with the seabed, defeating the very purpose of dropping it in the first place.

8. The number of shackles paid out is normally in the region of two to three times the depth of water. The whole point of this emergency operation is to enable the ship anchor to drag along the seabed bottom, providing maximum resistance to the movement of the vessel without causing damage to the anchor or the vessel.

9. The Officer undertaking the operation must be at all times aware that there is another anchor at his disposal which might need to be used.

As with any emergency operation, dropping anchor under the circumstances requires swift action that can prevent any imminent danger. The handling of the vessel and her anchor will differ as per the characteristics but the above points give a general direction to the procedure that is required in such a case.

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. 

9 Points to Remember When Dropping Ship Anchor in Emergency appeared first on Marine Insight - The Maritime Industry Guide

As we learned in the article on types of anchors, nautical equipment that is used to restrict structural or vehicular movement in the water using a combination of weight and friction along the bed of the ocean or seafloor is known as an anchor.

Its primary purpose is to provide a mechanism for ships and boats to hold their position either during berthing and mooring operations at ports, or for large offshore installations such as semi-submersible oil rigs to remain stationary above an oil deposit.

To do so, the anchor grips on to any rocks or debris at the bottom of the ocean or sea, to provide a pivot about which the vessel will remain stationary.

Along with this, anchors can also increase the drag of any vessel in situations where it is so required. When trailing behind the ship, they serve as an artificial drag mechanism.

By letting the anchor follow in the wake of the ship, the entire vessel is stabilized against any abrupt wave motions during storms. This is a key factor in preventing green water loading and bow slamming. Green water is a technical term for any water present on the upper deck of the ship.

Bow slamming refers to the large forces exerted on the fore hull of the vessel by waves during storms. By allowing the anchor to absorb huge amounts of load and redirect forces away from the hull of the ship, the vessel can remain relatively stable even during unfavourable conditions.

Importance of the Anchor Chain

As seen, the anchor plays a major role in a vessel and offshore operations. However, it can only function as long as it remains attached to the floating structure.

Considering the tremendous amounts of force applied to the connection between the anchor and the ship during routine berthing or anchoring conditions, conventional methods of securing the anchor will eventually fail under the extensive stress.

The anchor chain refers to the component that attaches the anchor to the boat or structure and is usually referred to as the anchor rode (or anchor cable). It is superior to conventional methods in terms of strength and load-bearing.

The purpose of the anchor rode is to secure the anchor to a part of the vessel in such a manner that it can be easily hauled up when the need arises.

It also plays a major role in absorbing a certain portion of forces away from the main structure and anchor head. For instance, during storms or other similar weather conditions, the vessel or offshore rig tends to pitch and heel. This motion can intensify, causing damage to the vessel.

To dampen these forces, the anchor rode is designed to absorb a certain amount of the load. Since anchor chains and cables are built to withstand large forces on them, they are not drastically damaged or deformed by such loads. This absorption of forces away from the main structure and anchor is known as dampening.

Important factors to keep in mind while selecting or designing the anchor chain are the

• maximum permissible loads,
• ease of storage, and
• the expected length of the rode.

The stresses need to be checked for every unit of the rode. Metal chains have links as their primary unit component, while ropes and cables have fibres.

Ease of storage is another key factor in rode design. If the anchor rode cannot be reeled back in and then stored securely, it could lead to damage of the hull.

Every vessel or offshore installation has a rough idea of the operating locations, and consequently the maximum and minimum depths of the waterbodies at these locations. Based on these, the anchor rode is manufactured at a particular length at which it must be securely fastened.

The ratio of the length of the anchor rode paid out, and the actual depth of the waterbody is known as the scope. It represents a trade-off between vessel drifting and vertical forces on the anchor.

Scopes are usually in the range of 5:1 to 7:1. Shorter rodes have lesser slack, hence the ship does not easily drift off due to the natural wave motions. However, since the angle between the seabed and anchor rode is nearly ninety degrees, shocks and jerks are directly transferred to the rode and subsequently the vessel.

If the scope is increased beyond a certain value, it would drastically decrease the forces on the vessel, but would also allow the vessel to drift out into a larger region.

Forces on the Rode (Or Anchor Cable)

To decide the material and structural requirements used while designing the chain, it is important to analyze the various forces acting on it. The major forces acting on the rode include tensile, compressional, vibrational, torsional, thermal and chemical forces.

Tensile forces refer to loads that attempt to elongate any structure in the longitudinal direction. Conversely, compression refers to loads that contract the entire structure.

Vibrational loads arise due to machinery and other vessel components that have high frequencies of operation. For instance, the anchor chain located near the engine is subject to large strains since the engine vibrates at a high rpm.

Torsion refers to the twisting of a structure when one end is kept fixed. This causes distortion when the individual links or fibres get knotted. Since a large weight acts at the other end of the chain, deformations can occur.

Thermal forces arise because of temperature changes that occur near the anchor. Between the day and night, varying weather conditions could heat or cool the rode. This hot-cold cycle can induce thermal stresses that cause material fatigue. Lastly, chemical forces occur due to the corrosion of the material forming the rode, either due to rusting or because of exposure to organisms in the water.

The right blend of materials must be used to manufacture the anchor rode. Broken connections can be extremely dangerous during berthing operations for ships and offshore installations. Two common methods of designing the anchor are used: metal links known as chain rode or ropes known as an anchor cable.

Anchor Cable/Rope

In this type, the individual units are fibres running along the length of the entire rode. They are twisted for added strength and are often covered in some form of the sheath.

These types of rodes are extremely lightweight and flexible since they are essentially made of rope. Also, they can absorb large amounts of loads because of the high yield stress. However, the biggest disadvantage of using anchor cables is that they are prone to chaffing and can wear out easily.

Rubbing against underwater debris, or friction generated between adjacent cable fibres are major causes of this form of degradation. Another common problem with this type of anchor rode is that it can split apart when the internal stresses exceed the permitted levels.

These types of anchor rodes are used for small boats, watercraft, and lightweight vessels. Larger structures place undue stress on the fibres that may result in them giving away in the middle of an operation. There are several methods of manufacturing anchor cables that are more resistant to loading.

The most common type of cable is the twisted cable. Two or more individual cables are twisted against each other until they form a single, strong cable. The benefit of this method is that it increases the strength without increasing the production time considerably.

The issue is that there may be the partial unravelling of the cable when forces are applied on it. The second type is the braided and double braided cable. In this style, the individual fibres are twisted together and braided, instead of just the cables.

Double braided cables have an internal braided core that is then covered by an outer braided sheath. The benefit is that this type of anchor cable is extremely strong. However, the time taken to manufacture the cable can be labour intensive.

Natural fibres such as hemp and jute are rapidly being replaced with synthetic fibres that are considerably stronger. Polyamides are a common material for cables, and a well-known variety is Nylon. It has a high resistance to damage from exposure to UV from sunlight and has a near 30% elasticity that makes it suitable to absorb and dissipate forces.

A replacement for nylon cables is polyester, known by its commercial name Dacron. These nearly possess the same strength as Nylon but are not as elastic. To overcome this lack of dampening, a longer rode can be paid out.

Polyester is better than Nylon when it comes to retaining its length and overall shape when it is exposed to water. In addition, it has better resistance to damage from UV exposure and abrasion.

A slightly less common alternative is polypropylene, which is preferred since it floats in water. However, it is not as strong and is extremely sensitive to UV exposure. A common replacement for the standard synthetic rodes is the combination of reinforced polymer braided with conventional nylon or Dacron.

By doing this, the strength to weight ratio of the rode becomes considerably large, while keeping the overall length and scope the same. These reinforced anchor cables are common in offshore installations and are used by tug boats to pull various structures in ports.

Anchor Chain

The anchor chain is made up of multiple link segments that resemble closed loops. Each loop is connected through to its neighbouring loops, creating a chain of any given length.

The major advantage with this type of anchor rode is that it is resistant to the wear and tear that is extremely common with anchor cables. Because it is generally made of metal, the rubbing action between two adjacent links will cause only small deformations over long periods.

Compared to the problem of chaffing with cables, the chain rode can withstand almost all types of friction-related deformations with the application of lubricants. Most lubricants eventually come off as a result of continuous exposure to water. However, this merely requires the anchor to be wound back up, and the required links to be coated in grease.

Although common lubricants such as WD-40 are used, their toxic effects on the marine flora and fauna because of chemical exposure have gradually resulted in them being switched out for grease and other types of lubricants.

Another advantage with the anchor chain is that it can compactly fit in the anchor chain storage locker, because of the individual weight of each link. Unlike rope or cable that tends to be elastic, and hence more difficult to coil up, the individual links are much easier to store.

However, the biggest problem with using chains, especially for large structures such as ships or offshore installations, is that the anchor rode becomes extremely heavy. When this is combined with the weight of the anchor itself, the total mass of the system comes to a few tons.  To be able to haul up this weight, heavy-duty motors or cranes are required, that can complicate the operation.

Another issue is that metal does not absorb as much energy compared to cable or ropes. Because of this, it is often not able to redirect any jerks or other disturbances being generated from the ocean bed or seafloor. If the entire chain abruptly becomes taut because of natural wave motions, a massive shock can be transmitted to the vessel or structure, that can cause failure and metal fatigue over time.

An interesting aspect of anchor chains is the catenary action of weighted links. Since each link weighs a sizeable amount, the entire chain tends to sag or fall in the middle because of this weight. Catenary refers to the natural shape that a chain takes when it is suspended between two points.

The benefit of this catenary action is that it decreases the initial angle between the seafloor or ocean bed and the anchor rode. Because of this, a certain amount of forces and loads are absorbed and dissipated away from the structure and anchor. However, this only takes place as long as the angle remains small and there are acceptable ranges of loads.

This type of anchor rode is mainly used for large vessels and offshore installations. This is because these structures are considerably heavy, displacing several tens of thousands of cubic metres of water. If a cable rode is used to anchor these structures, it will eventually chaff and simply break apart.

Heavy-duty metal chain links are used that can withstand the enormous loads placed on the chain. Common materials that are used in manufacturing the individual metal links include high carbon steel and heat-treated high carbon steel. The latter is known as the transport chain or G70 and has an exceptional strength to weight ratio that makes it ideal for such purposes.

Combination of Cable and Chain Anchor

Considering the various parameters involved in the pure chain and rope designs, a combination of both types of anchor rodes would be able to eliminate certain disadvantages.

This is used in large offshore structures and large cruisers. The combination works on the principle that the chain portion of the anchor rode would be present in areas where abrasion of conventional cables is likely to occur. This would ensure that the overall integrity of the structure remains intact, while not affecting the dampening effect of the rode.

Thus, the chain portion is attached directly to the anchor stock, while the cable forms the rest of the rode. In general, the junction between the chain and cable is the weakest portion in the rode, and specialized methods of joining both types of rodes must be used.

A galvanized connection is used to cover the junction, and the cable fibres are partially connected to the chain. Along with this, the cable can be spliced directly into the chain.

Another advantage in using a cable-chain combination is that the angle between the bed and anchor rode decreases, which in turn decreases the vertical loading on the floating structure. However, it only works in moderate to light underwater currents. Otherwise, the chain is not heavy enough to remain on the ocean bed.

The solution is to pay out a longer rode that will aid in dissipating a certain amount of energy away from the anchor. The risk of drifting increases with a proportional increase in the rode length, and it is advisable to optimize the length of anchor rode paid out based on these parameters.

Anchor Chain Marking

The scope of the anchor rode plays an important role in balancing the amount of drift and forces borne by the chain or cable during anchoring operations. Thus, it is important to have an accurate value of the length of the anchor rode paid out. To measure this, specialized markings are present on the anchor rode, so that the length paid out can be visually identified by the anchor operator and other personnel.

The most common methods of marking the anchor rode are- plastic marker elements or painted sections.
Plastic elements such as zip-ties and blocks are fairly common owing to the ease of setting up and replacing these components once they wear off.

In addition, since they are made of plastic, they have a higher life on the seas compared to paint and other methods. Coloured zip ties are knotted at regular intervals (the standard is 25 feet or slightly more than 7.5 meters) and they indicate the length that has already been paid out.

Colour codes indicate the length and are generally composed of white, red and blue based on maritime standards. However, the issue with plastic components is that they can get caught in the windlass and other anchoring equipment.

Moreover, they can break apart if continuously rubbed on the hawsepipe and tethering spool. The broken plastic portions can end up polluting the waters and pose a grave environmental hazard that cannot be overlooked.

Paint is another fairly common method of marking anchor chains. This follows a three-colour system, similar to the plastic tie method. Each of these colours indicates a specific digit and a significant number of the length of the anchor rode.

The functioning is similar to the markings of resistor bands on electric equipment. Each of the three bands in a certain order can represent a unique number, based on the determined marker differences.

For instance, a certain ship operator decides that the difference between two adjacent painted marks on the anchor rode is to be 25 feet. Then, a certain order of the three bands will indicate a unique multiple of 25, that can be used to identify the length of the rode paid out.

Painting these bands is a common approach, especially since environment-friendly paints are easily available on the market. However, the only issue with this method is that the paint can wear off rather rapidly owing to the harsh climates it is exposed to. To combat this wear and tear, frequent coats must be applied, and the bands must be made wide enough so that even if the paint flakes off, there is still a sizeable portion left to correctly identify the anchor rode length with.

Anchor Chain Stowage Arrangement

From the previous discussion, it is evident that the anchor chain plays a vital role in conjunction with the anchor. However, since modern anchors are made from metal or from a rope, they stand a high chance of wear and tear related issues, such as rusting or chaffing.

The solution is to constantly monitor the anchor rode whenever it is hauled back on to the vessel.

For this, special stowage arrangements have to be made such that the rode is kept safely away from corrosive substances and so that it can be easily accessed for either maintenance or to paid out with the anchor.

Anchor chains are stored in a chain locker set deep within the hull of the vessel. These are ventilated enclosures that are used to store the anchor while it is not in use, and to house the remaining length of the anchor chain while it is deployed. It can be accessed by engineers and personnel for routine checks or long-term maintenance.

Generally, the floor of the chain locker is reinforced, so that it can bear the extra weight of the metal rode. To haul the chain out of the locker, a series of heavy-duty motors and gears are set up on the deck in pairs.

The reason for the pairing of the anchor stowage equipment is so that there are individual components for the port and starboard side anchors. In the event of mechanical failure, if both anchor lines were operated by the same windlass, it could leave the vessel prone to drifting. The windlass is the technical term used to define the motor that lowers or lifts the anchor chain.

Along with the windlass, a secondary spool is present in front of it, on the deck. The purpose behind this is to ensure that the individual links do not get entangled while being moved. It straightens the chain and slowly feeds it out of the vessel. There is a locking mechanism present on this spool so that the chain can be fixed at the desired length once it is deployed.

Lastly, the hawsepipe or cat’s hole is the gap in the hull through which the anchor rode is paid out. It serves three main purposes- to feed the anchor chain, to house cleaning equipment for the rode, and to hold the anchor head in place. As defined, the hawsepipe allows an outlet on the port and starboard sides for the chain to be lowered or lifted into the chain locker.

Moreover, when the chain is hauled out of the water, there is a high chance that it may be littered with subsurface gravel, mud and even living organisms. To get rid of this organic matter, hoses are fitted along the mouth of the hawsepipe, so that the rode can be cleaned before storage.

Finally, the anchor is firmly held on to the side of the hull by the locking mechanism provided on the hawsepipe. It also restricts the movement of the anchor head, which would otherwise cause damage if left unattended, especially during storms.

Anchor rodes play an important role in securing the anchor to the vessel or structure. Without the right choice of type and materials, there can be serious consequences for the structural integrity of the anchor system. Based on the type of linking, anchor rodes can be broadly classified into cable and chain types.

Cables are preferred for lightweight and small boats, whereas chains are common for larger structures such as ships and offshore rigs. Modern anchor rodes combine both these types to improve durability, dampening effects and overall strength of the anchor.

The scope is a measure of the ratio of the length of anchor paid out and the depth of the waterbody. By choosing the right type of anchor rode based on the vessel size and overall operating conditions, and by opting for the right materials to manufacture the rode with, the life of the anchor system can be increased.

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 Anchor Chain – Everything You Should Know appeared first on Marine Insight - The Maritime Industry Guide

A merchant vessel is said to be having a “dragging anchor” when the vessel drifts without holding power inspite of being anchored. Dragging anchor has been the reason for several accidents such as collision, grounding, or stranding.

Merchant vessels stay at anchorage for various reasons:

• Waiting for berthing prospectus
• Cargo discharge and loading
• For carrying out maintenance , hatch cleaning
• Waiting for Instructions from owners or charters
• Quarantine etc.

The main reason for a vessel dragging its anchor is because of rough weather conditions. In such situations, it is extremely important for seafarers to collect all necessary information to familiarise with the situation and prevent dragging of anchor as much as possible. Some important parameters that needs to be considered are:

• Prevailing weather condition of that particular area
• Safe position for anchoring the vessel
• Wind and tidal behaviour of that area
• Contact information of port authorities in case of assistance required etc.

At most ports, it is inevitable for a vessel to wait at anchorage and the time at anchorage can be for days or even weeks. During such times, the master and ship crew should identify possible dangers to the ship and make all the necessary preparations.

A vessel dragging anchor is a threat to its own and also to other vessels in the vicinity, often leading to an emergency situation such as collision, grounding or stranding, depending on the manoeuvrable condition of the ship.

In such situations, a quick assessment of the situation can only be achieved by a vigilant bridge watch, contingency plan to tackle any emergency, quick response and good judgment of the situation. It may take some time to weigh the anchor and restore the vessel to its full manoeuvrable condition, but no serious accident should happen if there is enough sea room and time to do so.

Following points should be considered by a seafarer prior anchoring where dragging anchor is predicated:

• Take on heavy weather ballast, taking in to account the stability of the vessel and depth of water below the keel
• Pay out more anchor cable depending on the size of the vessel and weather condition
• Keep a safe distance from other anchored ships, shoals and other dangers, leaving room for manoeuvring
• Weigh anchor and shift the vessel to different position away from the vicinity of other vessels, provided prior permission is received from VTS of that area, port authorities and owner’s orders
• Increase the efficiency of the bridge team by adding an extra lookout
• Keep the main engines standby for manoeuvrability

How to assess the vessel is dragging its anchor?

• Check the ship’s position at frequent intervals, to confirm if the vessel is outside the swinging circle. Use all available means, both visual and electronic equipment such as GPS, RADAR and ECDIS, to make the appraisal of the situation. If the vessel deviates from the circle, it is likely to be dragging its anchor
• The bow cannot stand against the wind
• Check anchor chains for slipping, a small pole with a cloth as flag like arrangement can be tied to the links to understand the slipping of anchor chains
• Extra vibration and weight on anchor cable
• Check the speed over ground (SOG) when the vessel is swinging, the SOG can increase variably and this should not be misinterpreted
• Check the course recorder for figure of eight motion locus
• Also monitor the position and distance of vessels nearby. In case if they are dragging counter measures to be taken to safe guard own vessel

What actions to be taken if the vessel has started dragging anchor?

• Master to be informed, do not hesitate to call him at any time of the day, his experience and decision making authority is vital in any give situation
• Inform engine room and start the main engine with the permission from the master and give power to windlass if it is not already given. Make the vessel ready for manoeuvring
• Stop all cargo operations and prepare vessel for manoeuvring. Let go cargo barges and crane barges if they are alongside
• Inform and alert Vessel traffic system (VTS) and other vessels nearby about the condition and inform about the actions taken. Seek permission for re-anchoring
• Start heaving up the anchor and once the vessel’s manoeuvrability is restored, shift the anchorage position where drifting can be safer or take to the open sea
• Deploy more cablse or drop a second anchor (not recommended for big vessels) before the speed of dragging of the vessel increases. This can stop the small vessel from dragging anchor at very early stage before the ship is pressed to leeward side with increasing speed
• Use bow thrusters, main engine and steering to manoeuvre. It becomes more difficult to weigh anchor when the vessel is pressed more to the leeward side and takes considerable amount of time. Use bow thrusters for stemming the wind. Do not override the anchor especially in shallow waters as the vessel may impact on the anchor during pitching.
• If the scenario permits, let the vessel drag in a controlled manner. But this is not recommended in areas where offshore work such as oil and gas operations are being carried out, which can result in damaging the submerged pipe lines, cables etc.
• Release the bitter end and let go the anchor completely, when weighing of anchor is not possible. A ship without minimum of 2 anchors is not considered to be sea worthy, a careful assessment is to be made prior making this decision
• Call (tugs) for assistance. This is possible only if the weather permits

Most accidents collision or grounding happens while the vessel is at anchor mainly because of no early prediction of dragging anchor. Time plays a vital role in area of high vessel density and this time lapse results in difficulty in restoring the manoeuvrability of the vessel. Ensure that proper contingency plan is set in place to control such incidents and avoid arising of any emergency due to dragging anchor.

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What To Do When Your Ship Is Dragging Anchor? appeared first on Marine Insight - The Maritime Industry Guide

Anchors play a critical role in the maneuvering of ships and aid them in safely docking at ports and on the high seas. To keep an entire vessel (weighing a few hundred tons) in place, a heavyweight known as the anchor head provides the resistive forces.

Have you ever wondered how such a heavyweight is lowered and raised from the ocean bed or seafloor?

A mechanical device known as the anchor windlass is used for this very purpose.

A windlass refers to any pulley or mechanical system used to shift large weights in a vertical or horizontal direction. It was invented by the ancient Greek scientist Archimedes and was used for general purposes such as to draw water from wells or to aid in lifting heavy construction equipment.

As technology advances have placed larger demands on the shipping and goods transport industry, heavier anchors required to stop larger ships have also been pressed into service.

Owing to this, advanced anchor windlass systems have also been used to effectively operate the anchor and associated machinery. In this article, we will examine what an anchor windlass is, and how it operates.

Basic Design of a Windlass

A windlass is any device used to move considerably heavy weights using a pulley system. A barrel with a chain or cable wound around it is operated using a belt or crankshaft. This shaft provides a circular motion that is able to lift heavy weights without having to expend the energy needed to normally haul it.

The crank can either be operated manually (as in the case of drawing water from wells) or using a motor (used in large construction cranes) and is attached to the barrel in such a way that it can rotate about a central axis.

The principle behind using a pulley design is that large weights can be lifted by distributing the load between multiple cables instead of a single chain. Thus, by exerting a limited amount of effort, a considerably heavier load can effectively be raised.

The issue with using such types of designs is that a large strain is placed on the cable or chain used to shift the load. In case the mechanism is stopped midway through operation, adequate steps have to be taken to prevent the cable from breaking under tension.

Most materials can suffer from fatigue or stress-related failure under loads of tension. Thus, for an anchor windlass that has to lift a weight of nearly a ton, specialized mechanisms have to be used to ensure that the weight of the anchor head is taken off the anchor rode while the operation is stalled. This will be discussed in further detail in the below sections.

Where is the Windlass Located?

On ships and large vessels such as container vessels or oil carriers, the windlass is located in a specialized location at the fore of the ship, known as the windlass chamber or room. However, some vessels also have the windlass positioned on the forecastle deck.

The benefit of having the windlass on the deck is that it allows a higher degree of control while operating the device. In addition, space that would have been occupied by a windlass chamber can now be effectively used for storage, which is a high-demand commodity on board any ship.

Having the windlass on the deck would also make it more accessible in the event of emergencies. Personnel on board would find it easier to operate, especially in the case of a manual or partially-manual system, if the windlass is positioned on the upper deck as compared to a closed room.

However, having the windlass on the upper deck also raises the possibility of damage due to the elements. In general, the forecastle deck is subject to green water loading (rare, but still a possibility) and bow slamming.

Green water loading refers to any water that accumulates on the deck of the ship as a result of high waves. Although the forecastle deck is designed to prevent this, natural elements such as waves are unpredictable, and there is still a high chance of getting the windlass equipment wet.

Another issue is bow slamming.

During storms, the fore of the vessel is sometimes momentarily lifted off the water surface, and then comes crashing down at the base of the ship’s bow.

This jarring impact can have adverse effects on an open windlass system. Lastly, the issue with having the windlass on the upper deck is that it presents a safety hazard that can obstruct personnel movement.

On small crafts, a windlass is not present, as the anchor head does not weigh a lot. For medium-sized vessels, a single windlass is often used to control the anchors on the port and starboard side.

This is a simple mechanism, that uses a single windlass drum to control the anchor rode for both sides. However, for larger ships that require a higher degree of precision, the anchors on both sides are given separate windlass systems.

Such a design is known as a split windlass and is effective in executing tight manoeuvres while the ship is either at a port or while it is at sea.

How an Anchor Windlass Works

An important point to note about the naming of the word “windlass” is that it generally refers to only horizontal motion of the weight.

The “capstan” is the equipment used for vertical motion. To be used effectively, a windlass is often combined with a capstan to afford a larger degree of control to the captain or personnel manning the winch.

The setup is used to release, hold and manipulate the anchor chain, which is made up of metal links. These links fit onto notches or grooves on the central windlass barrel that releases the links gradually.

Although the windlass can be controlled remotely from the bridge of the vessel, it can also be manually cranked using a system of levers and brakes present adjacent to the windlass.

To release or lower the anchor into the water, there are two possible methods of manipulation- powering down the anchor or allowing the head to fall freely.

Each has its own benefits, although the powered option is often used on ships and large vessels. The powered option uses the windlass to slowly revolve in a direction that pays out the anchor chain. Once the markers on the anchor chain indicate that the required length has been paid out, the crank operator can then apply a braking action to the windlass barrel.

The benefit of using this method is that the heavy falling anchor head does not suddenly exert a large force on the hull of the ship, because of the gradual lowering of the large weight. Thus, a larger amount of control is exercised.

In addition, it is also possible to position the anchor head to the required location by manipulating the windlass controls. The free-fall option is more commonly used on small and medium crafts.

This is because they have a relatively low freeboard, that allows the surface of the water to dampen the force of the falling weight. However, it can still cause a small amount of flooding on the deck, or create large oscillations that could pose a problem to the stability of the vessel.

The advantage of using the free-fall option is that it is considerably faster than having to slowly crank the winch. However, there is almost absolutely no control over where and how the anchor lands in the water.

The various components that make up the anchor windlass broadly include- the winch, dog clutch, chain wheel drum, pawl bar, and hawsepipe.

As discussed earlier, for reeling out the anchor rode, a crankshaft rotates the windlass drum. This cranking motion is provided by a winch positioned next to the windlass itself.

The winch is powered by an electric or steam-based motor that winds a strong cable around it. The drum on which this cable sits is known as the winch drum. As this drum rotates, it turns a dog clutch, that can be engaged or disengaged by the windlass operator.

This clutch is attached to the larger windlass drum known as the mooring drum or chain wheel. When not in use, or during an emergency, the dog clutch can be disengaged.

The clutch rotates the chain wheel on which the large anchor rode is moored. There are grooves cut out in the chain wheel, to allow for the rode links to be properly gripped. The mooring drum uses a gypsy to secure the anchor rode in place, so that the links do not slip.

As the winch rotates the chain wheel, the rode is slowly paid out through the hawsepipe, which is an opening located on the side of the hull on which the anchor head sits. However, when it is time to hold the anchor rode in place, a pawl bar is used to grip an anchor link and restrain the entire rode.

This pawl bar is often replaced by a device known as the Pelican Hook or the Devil’s Claw. These use a hooking mechanism to secure the link and keep it in place.

However, these mechanisms cannot be released while still under tension. As the entire setup remains under tension, the chain wheel is put in reverse so that the pawl bar can be safely disengaged. Once this is done, the entire anchor can be lowered or raised by the operator.

The controls behind the entire anchor operation are operated using hydraulics in addition to a manual safety override. For instance, the winch drum and chain wheel have hydraulic brakes that can be controlled by the operator using a systems console.

However, in case of a systems failure, there is a provision for a manual override wheel that enables the drum to be stopped. This provides an additional layer of safety, especially since mishaps involving heavy anchor heads and the rode can be fatal.

The manner in which the anchor windlass operates is through the following steps given below:

• The electric motor turns a winch that rotates the winch drum.
• The dog clutch is first engaged and then activated using the winch.
• The clutch begins to crank the chainwheel in a specified direction, and at a specified speed.
• The gypsy is used to contain and control the anchor chain during the entire operation.
• The chain is lowered through the hawsepipe until a desired rode length has been achieved.
• A pawl bar or Devil’s Claw is used to restrain the anchor rode in place.
• To release the pawl bar, the chainwheel relieves it of any tension from the rode by being put in reverse.
• The chain can then be lifted by simply reversing the direction of the winch drum.
• Safety Precautions and Conditions

Maintaining safety is essential while working with heavy machinery such as the anchor windlass. To obtain a factor of safety in the operation of the anchor windlass, the windlass must be able to completely raise or lower the anchor head at any speed within its given operating rpm range.

In addition, the maximum torque applied on the chainwheel or anchor drum at any time must always lie safely within the operating ranges, and not at an extreme value.

In addition, the location of the windlass must always lie within safe operating environments. For instance, if a windlass or the chain locker is located within the deck inside the chamber, there must be proper provisions to ventilate the rode.

There is a high chance for the growth of microorganisms on the links when the chain is stored in a dark and closed room.

To get rid of any waste or organisms on the chain, small hoses are attached to the hawsepipe, such that the chain hauled into the chain locker is cleaned.

Related Reading: Important points for windlass maintenance 

Along with this, if the setup is stored within the deck, there is a chance of the chain links twisting and entangling the entire setup. Thus, there must be sufficient provisions to separate individual links and stop the entire process.

In the case where the windlass is constructed on the forecastle deck, there is a high chance that wind and waves may damage sensitive equipment on board.

Thus, when not in use, the anchor windlass must be covered or protected with water-proof and insulated materials. This includes tarpaulins lashed on to the deck or a stiffened polyester enclosure.

In addition, the various pipes and components of the windlass must be sufficiently illuminated and demarcated, so as to prevent any mishaps due to their odd location.

Any sharp edges that may come in contact with personnel or passengers must be ground down to within an acceptable radius of curvature. By following these strict safety protocols, it is possible to safely use the windlass anchor without causing any accidents.

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.

Anchor Windlass – Understanding Design And Operation appeared first on Marine Insight - The Maritime Industry Guide

What is an Anchor?

An anchor refers to a nautical or marine equipment intended to restrict vehicle or structural movement in the water. Anchors achieve their purpose by either using their weight to hold structures in place, clamping on to the bed of the waterbody, or using a combination of both these techniques.

In addition, anchors can also act as drogues (positive drag mechanism) for ships and other such vessels during storms. They provide a restoring drag that keeps the vessel stable and steady and prevents slamming of the bow or flooding through green water loading during unsteady conditions.

Bow slamming refers to the fore of the ship violently striking the water surface due to large waves that can cause structural deformations and failure.

Green water is a technical term for any water than is present on the upper decks of a vessel due to the partial flooding as a result of the natural motions of waterbodies.

Although naval architects generally try to reduce drag as much as possible while designing moving structures to increase their straight-line speeds, drag can slow vessels down during storms so that they remain under the control of their propulsion system. This prevents the rolling motion of waves from damaging vessels or other structures floating on water.

Conventionally, anchors were found onboard large vessels such as general cargo ships and tankers, to hold them in place either while being moored to the dock at the port, or if they required to be at a complete standstill in the middle of a sea or ocean.

With the advent of oil rigs and other sub-sea structures deployed in the middle of large water bodies, anchors are used to connect these large semi-submersible structures to the seafloor.

Generally, anchors are meant to be temporary so that they can be reeled back on to the structure when the need arises. However, certain offshore structures require permanent anchors to keep them connected to the bed of the waterbody since they remain at a single location for extended periods.

What Are Anchors Made Of?

Anchors are generally made of metals resistant to long-term corrosion that use suitable methods of protection such as electroplating and galvanization.

However, they can also be made from fibre-reinforced composites or polymers such as carbon-fibre. The advantage of using such materials is that they have a high strength to weight ratio. This means that compared to generic metals, even light reinforced composites structures can handle enormous amounts of load or strain.

However, the disadvantages of using such anchors are that the cost of development and large-scale manufacture is considerably more expensive. Besides, some mooring methods utilize the weight of the anchor to aid in holding down the structure still.

Since composites are extremely light, these types of anchors provide a negligible effect in such situations. An upcoming field of research is the use of multi-layer crossed fibres in composites to provide slightly better weight properties, without adversely affecting the strength of the anchor.

Basic Anchor Design

Modern anchor designs that are extremely stable and able to easily grip on to surfaces are generally derived from three standard designs that have been used from the 10^th century onwards.

These are the – Fluked, Admiralty and Stockless anchor designs that are often still in use for small crafts and lightweight boats.

The fluked design uses flukes attached to the central arm of the anchor, commonly referred to as the shank. Flukes are structures similar to the tines of a fork, that are used to provide grip and weight to the anchor.

This design was most commonly used in ships belonging to the early British and Viking sailors. Books and casual diagrams depicting anchors in drawings often use the fluked design for inspiration, as it is mistaken for the structure of modern anchors. This is one of the most basic designs that use the weight of the anchor to drive the flukes into the bottom of the ocean.

The admiralty design uses two flukes attached to the central shank by arms perpendicular to the main axis. A long bar attached to the intersection between the shank and chain links is known as the stock. It is used to pull the anchor towards the ocean bed or floor until one of the flukes finally digs into the bottom and settles in.

Due to the descent, the fluke is forced into the bed under its weight and the additional force from the stock. However, the issue with the admiralty design is that it can foul up the anchor owing to the arm that is not embedded in the ocean bed.

To overcome this, modern designs incorporate arms that can collapse onto the central shank. By doing so, the anchor changes into a single shank and fluke design that can be stowed easily and will not foul up the anchor when deployed.

The main change from the standard pattern of admiralty anchors was the stockless style of an anchor. It involved a basic admiralty anchor design that had projections along the bottom which forced the flukes to sink into the ocean bed or floor.

However, despite these additions, the holding power of the stockless anchors is less than their admiralty counterparts. What makes them widely used these days is their ease of storage. They can be quickly hauled up and made to rest against the hull.

The chain or rope forming the links connecting the anchor motors to the shank is reeled in through a hole in the side of the hull known as a cat’s hole or hawsepipe. The convenient design of the stockless is what makes it common on modern ships despite being a relatively old design.

Permanent Anchors

Offshore structures are often deployed for long periods, where they remain in a single location with minimum movement. Due to the expensive and extremely sensitive nature of the equipment used by oil rigs and energy harvesters, they cannot afford to move by more than a few millimetres.

Also, the risk of damaging important components or causing oil leaks require these structures to be anchored in such a manner that underwater currents and small waves are not able to easily dislodge and move the entire setup. Permanent anchors are used in this regard to restricting the movement of such structures. Also, a specialized class of tug boats known as Anchor Handling Tugs (AHTS) often use this anchor line to tow these semi-submersible structures from one location to another for deployment.

In general, such anchors are not meant to be frequently moved and spend extended periods at the same spot. However, when the time comes to move the floating structure, the anchors often need to be reeled back on the surface or towed using an AHTS.

In such cases, to dislodge the anchor, a trip line is attached to the head and is connected to the structure. In the event of the anchor head being stuck to the seafloor, the trip line can be used to provide an additional force to move the anchor. Sometimes, explosives or small, controlled charges are used to disturb the bed of the ocean.

The anchor is then hauled back up to the surface. In addition to these two methods, some types of anchors use detachable heads that can be left on the seafloor after the operations are completed, and when it is time to move the structure. The anchor chain and stock are reeled on to the structure leaving the head behind.

The problem with such a type of anchor is that it leads to pollution of the ocean floor, especially if the metals are toxic to marine flora and fauna. Besides, there is a risk of accidentally disengaging the head from the rest of the anchor while the structure is still in operation. The most common method of dislodging the anchor is by using a trip line aided with contained charges deployed close to the ocean bed.

It is important to finalize the number of anchors to be used to tether any structure. From the study of mechanics of a body, it is known that using a three-point anchoring mechanism, any structure can be completely held stationary. This is because forces from any direction can always be countered by the alignment of the anchors in such a system.

The common type of anchors used in such permanent deployment situations is the mushroom, auger, high-holding, and deadweight methods.

Mushroom Permanent Anchors

Mushroom anchors, as the name suggests, are shaped like inverted mushrooms, with the head being laid in the sea or ocean bed. This style of anchor utilizes its weight, suction power and relative friction between the bed and anchor head to keep itself firmly attached to the strata of the ocean floor. However, it only works in conditions when mud, silt or sand are prevalent on the floor of the ocean.

Other materials such as rock and sand are not able to provide the adhesion required to keep the anchor firmly attached to the ocean floor. The science behind how this system works is that the anchor uses a derived version of the Archimedes Principle on soft, granular or viscous media such as mud and sand.

Since these materials cannot generally hold up the weight of an anchor (these weights can reach up to several tonnes for ships with abnormally high displacements), they allow the head to sink in until it has displaced enough strata material to equal its weight.

Due to the sheer size of such anchors, these could easily account for several meters of depth in the ocean or seafloor. They can resist almost all types of wave motions and even the most severe of storms.

To remove them, the sand or mud surrounding the anchor is dislodged, until the adhesive attraction between the head and the strata material is weak enough to be broken by the anchor hauling force provided by the motors on the structure.

While the strength provided by these anchors makes them very useful in restricting motion, they can only work in regions where the floor of the ocean or sea provides sufficient suction to drag down the anchor. This makes them ideal in regions close to beaches or lagoons.

Auger Permanent Anchors

The auger type of anchors makes use of the physics behind the high retention power of screw design, and their ability to remain locked in a position for extended periods. These anchors consist of large threaded heads that are drilled into the bed of the sea or ocean where the structure is to be installed.

Often instead of directly being driven into the ocean floor, a casing is first attached to the bottom of the ocean, with grooves cut into it. The casing and screw heads are often made from titanium or similar alloys and materials resistant to rusting and corrosion from exposure to water and underwater organisms.

The reason for using titanium is that it is ideal for creating strong and unreactive components such as riser joints in oil rigs. However, the relative abundance of titanium and the extensive treatment of the materials used in the production of this type of anchor tends to make the process of manufacture and set up expensive.

Another problem that arises while setting up the anchor is that ready access to the case and screw head must be provided, since perfect alignment is required, and any errors in drilling the ocean or sea bed can lead to damage to the equipment. Thus, this type of permanent anchor is mainly used in regions that are shallow and located close to the shore or have low-tides that make it possible to access the casing and head.

Issues can also arise when the bottom stratum is made of soft pliable materials such as mud, silt or sand. Since the screw works on the principle of friction between the casing and head, such materials do not generate sufficient traction for the screw to properly grip the ocean or sea bed.

The screw and its casing will continuously swivel without actually being able to anchor the structure. However, despite so many restrictions on the location and deployment of this type of anchor, it is considered to be one of the strongest methods of permanently anchoring any structure. In operating environments where all the basic requirements are met, these anchors are commonly found.

High Holding Permanent Anchors

High holding types are a class of anchors that are characterized by their High Holding Power (HHP) or Super High Holding Power (SHHP). These anchors are used in the oil and gas industry to tether large semi-submersible structures or to hold down underwater pipelines running across the ocean bed or seafloor. Such anchors are considerably larger and heavier than their counterparts.

To be declared as a high holding anchor, they must exhibit strength and retention capabilities equal to twice the normal values of conventional anchors. The conventional anchor considered for reference purposes must be the same weight as the HHP anchor being tested. To achieve this tag, three tests must be conducted successfully, and the anchor must be tried in a minimum of three different types of soil. Compared to the previous two types of permanent anchors, this classification ensures that the anchor functions in any type of condition.

Similar to HHP anchors, Super High Holding Power is a classification that guarantees that the tested anchor can withstand a minimum force equivalent to four times that of a normal anchor weighing the same. Test conditions from the HHP testing are applicable in this case as well.

Once the tag of HHP or SHHP is provided to the anchor being tested, a 25% reduction in weight is allowed under maritime rules. Due to the holding power of these types of anchors, this reduction is often not drastic. To lay down this type of anchor, pennant wires and tugs are often required, owing to the sheer size and weight.

An interesting point about these styles of anchors is that HHP and SHHP only classify the holding power and can be applied to both permanent and temporary anchors. In that case, the conventional anchor used as a reference must also be considered to be either temporary or permanent so that the tested values translate accurately into the real world.

Deadweight Permanent Anchors

These anchors are the simplest and most cost-effective method of tethering down floating structures to a single place. They employ the weight of dense structures such as solid metal blocks or concrete bricks to provide a downward force.

The only issue with this type of anchor is that it requires to be relatively larger than normal anchors so that it can successfully hold down large semi-submersibles, oil rigs, and other offshore installations. In such a case, it can be difficult to transport and store the large anchor on the structure and to lower it gradually to the ocean bed.

This type of anchor is similar in structure to a mushroom anchor in the fact that they use their weight to hold down the structure on the surface of the water.

Like mushroom anchors, deadweight anchors can function better if there is an inherent suction or downward pull of the weight. That way, the anchor head is buried several meters in the ocean bed and becomes firmly lodged in the strata.

Also, it is better than mushroom anchors in the fact that it can operate in absolutely any sort of environment without the explicit need for any suction or adhesion. This makes them a cheap option to moor or berth large structures at a single place.

If we compare mushroom and deadweight anchors of a similar structure, the mushroom type is always more effective due to its smaller size and the ability to get dragged down into the mud or soil. With the large size of the deadweight anchor, it can be difficult to operate. It makes up for this with is the ability to work in any condition of the ocean bed or seafloor.

Temporary Anchors

As the name suggests, these anchors are intended to be used for short periods. Generally, they are used to berth and moor vessels or to stop them dead in the water for various reasons.

Unlike permanent anchors, simply attaching a heavyweight to the anchor line is not sufficient, since reeling back these anchors then become next to impossible. Hence, temporary anchors rely on the clamping or hooking of the anchor into the seafloor or ocean bed.

To do this, it uses a combination of its weight and gravity to drive a set of flukes or pointed shafts designed to embed themselves in the bottom strata. Most modern temporary anchors derive their basic design from the fluked, admiralty and stockless anchor.

Since temporary anchors are used to tether ships and other crafts, they do not need to be made of expensive materials such as titanium. Since they can always be hauled back on to the vessel in a matter of minutes, they are often made of metals or alloys that do not easily rust and are coated with a basic layer of zinc or some other cheaper non-corrosive metal.

Carbon fibre or other reinforced polymers also serve the purpose of hooking and clamping on to the ocean bed, due to their high strength to weight ratio.

To remove the anchors of ships from the seafloor or to dislodge it from the material at the bottom of the ocean, tripwires are used to provide an additional moment of pull. They also serve as an extra source of the force that can haul the anchor head quickly to the surface if the need arises.

To embed the anchor, they are let down till they touch the ocean bed while the ship is still slowing down. It is essential that they quickly catch on to debris, small rocks or cracks in the ocean bed before the vessel comes to a complete halt. Once this is done, they must be able to settle in and prevent motion due to light waves and currents.

In general, for ships at sea that have set down their anchor for some reason, small movements due to waves are of no importance and do not affect the ship, crew or goods in any way. However, for moored or ships berthed at a quay or port, they must not shift from their position. Any extensive movement can lead to damage to both the hull of the ship and the port itself. To prevent this from happening, tugs and additional mooring lines are employed to support the anchor in holding the vessel steady.

Common types of temporary anchor designs used by boats and ships include Northill, grapnel, Herreshoff, Danforth, Bruce and plough anchors.

Northill Temporary Anchor

The Northill anchor is a lightweight design that is not commonly in use these days owing to superior modern designs. It is a combination of a standard anchor and a dual plough design on either side of the central shank. This plough design serves to catch on to any rough surface at the bottom of the sea or ocean that can be used as a mooring point.

However, owing to its shape and severe limitations, it is not commonly found, except in use by seaplanes and other light crafts. The issue with the Northill design is that it depends on one of the two plough blades catching on to some debris or rock at the bottom.

This can require quite a bit of time since unlike conventional anchors, there are only two blades to work within this design. Moreover, nothing is tethering down the anchor other than its inherent weight. Thus, it works only in regions where the ocean bed has a rugged terrain.

Grapnel Temporary Anchor

This style of an anchor is similar to grapnels used in the military or rock climbing. A central metal arm consists or multiple shorter pointed arms known as tines (generally four in number) that grip on to the surface of the ocean bed. It is ideal for rough bottom structures that have several ridges or cracks providing places for the tines to hold on to.

What makes the grapnel style useful is the fact that no matter how the anchor settles down, it will catch on to the ocean bed due to the multiple tines attached to the central arm. However, it does not work in mud, soil or other loose material that makes up the bottom of the ocean. This is because the tines of the anchor are not able to grip and simply lift off the bed when there is a slight movement.

Another problem with this type of anchor is that it can be difficult to retrieve once it is embedded. This commonly occurs when the anchor head or flukes get stuck in rocky or coral conditions. However, with the use of a trip line, it is possible to haul such anchors back to the vessel.

While being stowed back on the vessel, it may damage other components due to its ungainly design. Hence, these anchors are generally hung from the side of the ship itself or are simply stowed onboard small crafts and water boats and then thrown off when the need arises.

Herreshoff Temporary Anchor

Similar to the basic Admiralty anchor used in ships and other vessels, the Herreshoff is a common version of this design. It uses the same principle as the Admiralty but is more manageable. It can be disassembled into three pieces or more for easy storage and can be put back together without any major requirements. This enables the anchor to be quickly and easily deployed.

Like the Admiralty, this faces the same problem of the anchor head being fouled up due to the natural motions of the ship as a result of waves and light currents. Improved designs are implemented in the Herreshoff anchor so that the arm which is not attached to any debris or rocks at the bottom can be collapsed against the shank. This allows the anchor to freely function without the idle arm getting in the way of the anchor cable.

Danforth Temporary Anchor

The Danforth is a lightweight, cheap and easily storable design that uses two triangular blades or flukes attached to the shank to hook or dig into the ocean bed. The gap between the flukes allows for the anchor to grip onto debris and rocks instead of simply acting as a sail against the water currents. Also, the shank and flukes are hinged, so that the orientation of the flukes can be changed depending on the type of material on the seafloor.

This design uses a tripping line attached to the fluke tips so that the orientation can be varied as the anchor reaches the bottom. Based on research, the ideal angle for embedding the flukes into the bed is 30 degrees. Thus, till the anchor reaches the bottom, the entire anchor is dropped as a single vertical structure to reduce drag and sail effects.

Once the anchor sinks completely, the flukes are oriented correctly and are then allowed to sink into the ocean bed or hook on to the corals or rocks at the bottom.

The design is lightweight and can be folded in on itself for easily being stored away. This makes the Danforth a common design for small crafts operating in regions with shallow to moderate depth so that the trip lines can be employed.

Bruce Temporary Anchor

This type of anchor is commonly referred to as the claw because of its shape and design. It is used to hook into the rocks at the bottom of the ocean and then settle in. However, it does not work when the material at the bottom is loose sand, silt or mud. Also, weeds and other structures can entangle the claw of the anchor without providing any actual anchoring force. Instead, they tend to impede the recovery of the anchor when it is time for the vessel to move on.

The original Bruce claw design is a relatively redundant design that is now being given up for more practical designs. More modern designs incorporate a claw similar to a spade that can grip most types of materials at the bottom. They incorporate a roll bar to provide additional stability to the anchor head till it can latch on rocks or debris on the ocean bed. Designs such as Rocna, Vulcan and the Ultra utilize this spade design to provide the necessary anchoring force.

Plough Temporary Anchor

Similar to a plough employed in agriculture, this design of anchors uses flat blades or plates attached to the central shank. The aim is for the blades to dig in and grip the ocean bed. Often, in place of a single plate at the end of the shank, three to four blades running perpendicular to the centreline are used. Modern designs utilize an arched shank that can be used to quickly embed the plough in the bottom strata.

The main problem with the plough anchor is that it does not work well in mud, soil or loose materials that comprise the ocean bed. This is because they are simply dragged along the bottom when the ship moves without any resistance whatsoever until they catch on to a rock or similar debris at the bottom. Similarly, with a slight upward force owing to normal wave motions, the plough blades or plates can dislodge itself and pop out of the ocean bed. Hence, ideal conditions are required for this style of anchor to work.

Modern takes on the plough anchor include the Delta design which comprises of an arched shank that is rigid and a combination of either plates or blades that are attached to it. Unlike conventional plough anchors that use a hinged shank, these are single structures that use the weight of the anchor and its inherent design to grip on to the ocean bed.

In Conclusion

Other types of equipment that are used in conjunction with an anchor to hold down a vessel or installation floating on the surface of the water include riggings (such as trip lines), anchor chains and ropes, stowage equipment etc. Anchor chains and ropes are an important factor in determining the reliability of a given anchor since these provide the only connection between the structure and anchor. They must be able to withstand tremendous amounts of force both in tension and contraction. Similarly, trip lines must also be strong enough to apply force on the anchor to orient it in a particular direction.

The bottom line to any anchor design is that the original three standard designs (fluked, admiralty and stockless) have been derived and changed over time with the advent of new technology and requirements. Depending on whether we wish to use permanent or temporary anchors, the basic principle remains the same. All that changes are the design styles depending on factors such as time of being submerged and the material found on the ocean bed or floor.

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.

A Guide To Types Of Anchors appeared first on Marine Insight - The Maritime Industry Guide

Mariners consider anchoring a ship to be an art. In fact, it’s also a form of science for it involves a sense of pivot, around which, a ship turns and imparts the stalling force to the ship.

While berthing a ship alongside a jetty or a pier in tidal or windy conditions, the role of the ship’s anchor is extremely vital.

Preferably, a ship must always approach the berth or a jetty stemming the tide (reduce the effect of the tide by cutting it) to ensure better control of the vessel. If the opposite is done when the ship is berthed, i.e. if the ship approaches the berth or jetty with the tide at its stern, the rudder effect is minimized as the tide plays with the stern.

Related Read: What Are “Let Go” and “Walk Back” Ship Anchoring Methods?

To turn the vessel, which is coming up the tidal estuary along with the tide, the anchor is dropped on the side towards which the vessel has to be turned. If the vessel is planned to turn on the starboard wheel, the starboard anchor is dropped. Likewise, if it’s planned to turn on the port wheel the port anchor is dropped.This is done to avoid the anchor chain going across the stern of the vessel after the swing.

But before dropping the anchor, the ship’s speed is reduced to around 3 knots or less to minimize the chances of chain damage or damage to the ship’s equipment and hull.

For a ship having a normal right-handed propeller, which comes up with the tide, the starboard anchor is dropped so as to take the advantage of the canting, i.e., swinging of the stern due to transverse thrust ( which is essentially a sideways force acting on the stern of the vessel moving forward or astern). The ship is brought up with the help of the anchor ( i.e. her way has stopped and the vessel is riding only on her anchor).

Related Read: How Dredging Anchor is Used for Maneuvering Ships?

Generally for obtaining maximum holding power of the ship’s anchor, the total anchor rode (The vessel is attached to the anchor by the rode, which is made of chain, cable, rope, or a combination of these) should be 4 to 7 times the depth of the water the ship will be anchoring in.

If the anchor is designed to hold on the horizontal pull (like fluke or claw type anchors), more chain is paid out to give a lower angle of pull and the sag of the chain will give enough catenary effect to hold the ship. The final position of the vessel is assessed beforehand so as to keep enough leverage of the swing.

Once the anchor drag has stopped, the helm is kept hard over to the starboard and the tide starts pushing to the starboard quarter, turning the ship 180° to the starboard facing the tide. Once turned, the anchor is slowly weighed up. Then, by stemming the tide the ship is brought close to the jetty at an angle of 20° – 25° and the head rope is passed.

If a tugboats are available to assist the berthing, it is placed on the stern side in the quarter of the opposite end to the ship’s side that is coming alongside. Pivoting the bow with the head-rope, which has now gone ashore and is ‘bar-tight’, the ship is brought alongside the jetty with the tug gently pushing the stern till the time the stern-line is safely ashore and the second officer has started heaving in.

Related read: What are Anchor Handling Tug Supply Vessels (AHTS)?

If the head rope becomes too tight, minor slack or adjustments are given from the shore to prevent it from parting. If there is no tug in the vicinity, a jollyboat takes the line ashore from the stern. If the jollyboat is also unavailable, the ship’s stern is brought closer to the jetty with the help of the engines, with repeated slow kicks while pivoting the bow with the head-rope.

A pilot feels blessed if the ship has a bow and stern thrusters in such cases. These equipment tools make the job of a pilot much easier.

Have questions? Let us know in the comments below.

How a Ship is Berthed Using An Anchor? appeared first on Marine Insight - The Maritime Industry Guide

Ship’s anchors can be used not only for berthing but also during maneuvering through channels and other similar areas with restriction in movement. Dredging anchors is a method which is used to assist a ship in maneuvering during unavailability or inability of tugs to assist as required.

A dredging anchor sniffing the bottom of the ship would hold the bow steady while allowing a ship to move fore and aft, this would shift the ship’s pivot point forward. Then, to overcome the anchor’s drag, propulsion is used giving good steering at low speed.

Today, modern ships have bow-thrusters to control the bow while going ahead or astern. While piloting in the narrow confines, in restricted waters or maneuvering vessels in somewhat constricted space, bow thrusters or tugs can be handy.

Sometimes ships have to cross stern first (i.e., moving backward) through the restricted channel between ships or buoys, using engines and bow thrusters. Now since the stern cants (moves laterally sideways) while a ship comes astern due to transverse thrust, a towing tug is employed in this case at the stern and the engine is used sparingly just to adjust any deviation in the desired direction of motion.

At the bow of the vessel, a checking tug is also deployed to control it and prevent it from swinging waywardly. The checking tug also comes in to play in stopping the momentum of the ship lest its engine doesn’t respond in time.

Now what happens when there is neither a bow thruster nor a tug to check the bow? The towing tug is necessary as the ship will invariably deviate with every second of the engine running astern due to the transverse thrust. In such an emergency situation the anchor becomes the rescuer.

The anchor is dropped at short stay where the cable is almost vertically down up to the anchor and taught. The anchor barely digs in when the ship is put to astern and the anchor is dragged over the sea bed. The pivot is shifted to the bow near the howse-pipe, making it easier for the towing tug at the stern to exert more moment of force as its distance from the pivot has increased. Also, the bow is prevented from “Yawing”.

The objective of this operation is to drag the anchor over the soft mud (like the drag-heads of the suction dredgers) and not to dig the anchor deep into the mud. Otherwise the cable will come under huge strain and can part when engine is run astern or when the towing tug tows. The machineries involving the anchor on the forecastle, like the windlass, the bow-stopper or the brakes can also get damaged.

Ideally the length of the cable should not be one and a half to two times than that of the depth of the water. Moreover, it is generally advised to have a thorough knowledge of the sea or river bed before performing this operation. Recent survey charts in this case can become extremely helpful.

Do you know any other way in which ship’s anchors are used for maneuvering ships? Let us know in the comments below.

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How Dredging Anchor is Used for Maneuvering Ships? appeared first on Marine Insight - The Maritime Industry Guide

The operation of a ship is a complex activity, especially when it is being carried out away from immediate help and at the mercy of nature. Optimum performance can therefore only be achieved by using the available workforce in an efficient manner.

The very core aspect of watchkeeping is to minimize any prospect of human error and thereby reduce the risk of damage to the ship or cargo. More than often, the time at anchorage is considered to be a time to relax. However, depending on the area in which the vessel is operating in, the anchorage might be a time to be extra vigilant.

Seafarers who have been on a vessel anchored outside the Port of Calabar (Nigeria) can relate to the extent to which watchkeeping at anchorage is troublesome, or anchorage at Singapore for that matter where traffic is abundant and where small errors might lead to full-scale disasters.

At anchorage, it is solely up to the Master to decide whether the watch is to be kept on a deck or on the bridge. As otherwise, the officer on watch (OOW) has to ensure that all measures are taken for the safety of the vessel, its cargo and crew.

Here are a few procedures for watchkeeping at the anchorage:

 1. Calculate the Swinging Circle

Swinging Circle (M) = L.O.A + Length of Cable – UKC

1852.3

The swinging circle might vary with the changes in tidal levels and in the weather. However, it is important to have a fair idea of the radius around which the ship might move about.

2. Follow the Master’s Standing Orders

Every ship’s master writes their own standing orders based on the ship, the experience of its officers, the trade patterns which in turn determine the standing orders. These orders reflect the Master’s requirements based on past experiences with the ship and his contemporary workforce, therefore making it imperative that the orders are followed to prevent any anomaly or to maintain a set grade of performance. Clearly, the master puts faith in the officer when saying “Call me if in doubt” and expects the officer to do so if required and in ample time.

3. Keep a Check on your own Ship and other Ships in the Vicinity

Keep a close watch on your ship and other ships in the vicinity lest they start dragging after anchoring. Dragging might occur due to changes in tidal levels, changes in weather or due to the brake giving away to a lot of yawing. The danger here is primarily to ensure that your own vessel does not drag and also to double-check if there are other vessels drifting towards your vessel. Use the bow stopper when at anchor to minimize any probability of a blunder.

4. Keep a Constant Check on the Ship’s position. This point is generally laid down in the Master’s Standing Orders and almost always mentions the intervals at which the position must be plotted on the chart. Use the GPS or the Radar or both to determine the exact position of the ship, which, very obviously, helps to determine if the ship is stationary or dragging.

5. Display Appropriate Lights

This enables other vessels to know that you are anchored, therefore making it evident that they should not anchor too close to your vessel and also give them an indication of proximity if dragging occurs.

6. Keeping a Constant VHF watch

 If slated to receive a pilot on board or for information on vessels in the area, it is very important to keep a constant VHF watch. The coast authorities generally promulgate extremely useful information that might be integral to the safety of the vessel. Wreckages, vessel information, ETA to pilot etc are necessary data that optimize operational procedures.

7. Alert Nearby Vessels When Required

If another vessel seems to be coming close to your own vessel, get their attention on the VHF or by flashing the Aldis lamp. Use any available means at the time to bring to their attention regarding the grave nature of the situation and avert any danger that may be impending.

Watchkeeping at anchorage might seem to be an easy task, for there is barely any movement. However, the very fact that the vessel is halted makes it vulnerable to a variety of dangers. As is done usually, the OOW must be vigilant at all times and use the assistance of additional lookouts if necessary.

In areas prone to piracy, the importance of alertness cannot be stressed more. The ship being stationery makes it open to attacks and pilferage. And very little can be left to the imagination in case the pirates attempt to board the vessel when it is anchored!

Responsibility and diligence in the part of the OOW will keep the vessel safe and away from harm. That is to say that the OOW should basically just do what he does on an everyday basis and thereby keep the dynamics going.

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.

Responsibilities of Deck Officer When Ship is At Anchorage appeared first on Marine Insight - The Maritime Industry Guide

When it comes to ships, anchoring is an important aspect that should be taken seriously. In the absence of anchors, ships would continuously adrift leading to huge wastage of resources like energy and also increase chances of accidents. In order to avoid these problems, mooring anchors are used to enable the ship to halt effectively whenever required in the port or harbours and if required, even in the middle of the ocean or the sea.

Types of Mooring Anchors

Initially, only one major type of mooring anchor was used. However, there have emerged several other types of mooring anchors as well.

The different types of mooring anchors are as follows:

• Conventional Type (Upside Mushroom Type): As the name suggests, these mooring anchors are shaped like inverted mushrooms that provide them with the ease to penetrate the surface of the ocean floor. They can be used for any type of underwater surface and their weight holding capacity is also good.

• Dead-Weight Type: Dead-weight mooring anchor types are the simplest and the most uncomplicated anchors to be used in today’s times. These anchors are known for their utility more in rough underwater surfaces. The anchors are quite bulky and are capable of being used for heavier ships. This type of mooring anchor is also cost efficient.

• Screw-in or Blades Type: In this type of mooring anchor, the blades or wings are fitted to the sides of the anchor which help in deeper sinking of the anchor. Anchoring of this type is quite popular in today’s times as these mooring anchors are faster to reach the ground depth as compared to the other variations. This factor could be regarded as the main selling point for such anchors. In addition, this type of mooring anchor is also quite cost-efficient and smaller as compared to the other variations of mooring anchors.

• Multiple Mooring Anchors Type: These types of mooring anchors have multiple anchors that are raised from a common rode (the anchoring cable) and then used for penetration into the subsea areas. The amount of anchors used in the mooring anchor system varies between three and more. They offer prompt anchoring services that has made them quite popular in today’s times.

Unlike other means of transport, ships function on an unpredictable natural resource, making it important that the method of stopping a ship can more than adequately tackle the unpredictability of water at any given point of time.

You may also like to read-What are Jack Up Drilling Rigs?

What are Mooring Anchors? appeared first on Marine Insight - The Maritime Industry Guide