Since childhood, we have been intrigued by this question: How are ships ‘parked’ upon their arrival in ports, jetties, and piers? Unlike cars, they can’t simply be put off gear and parking brakes! Ships don’t have brakes in the first place.

Ships need to be fastened and fixated soundly for conducting all kinds of shore operations such as cargo loading/unloading, refuelling, bunkering, ballasting/deballasting, boarding/deboarding, maintenance, repairing, and often for idle times based on voyage schedules and berth or workforce availability.

So, mooring or the system of securing a vessel soundly for the purposes mentioned above is indispensable in studying ships and offshore structures. 

Differences between mooring, docking and anchoring

It is common to get confused with the terms mooring, docking and anchoring and may use them interchangeably. But there are stark differences between them. 

Anchoring is the system of securing a vessel amid the sea when the ship is not near the vicinity of a permanent structure. In other words, when a vessel requires to be fastened or stranded for various purposes in the deep waters, anchoring is used so that the vessel does not drift away in the action of hydrodynamic forces present in various forms. For anchorage or anchoring, anchors, those heavy weights as old as the history of ships, have been used for a very long time.

However, in recent times, vessels can be secured anywhere in the seas with the help of in-situ dynamic positioning systems (DPS), which are automated systems that can keep the vessel affixed to a particular coordinate without the help of anchors.

In the traditional systems of anchors, the heavyweight is suspended from the vessel and is allowed to settle onto the seabed. This fixity of the weight in the seabed and the resultant high degrees of tension created in the strong anchoring lines, which are heavy-built lock chains, helps keep the vessel in its position. The size of the anchors depends on the size of the vessel.

Docking, on the other hand, alludes to the hauling of the vessel entirely away from the water to a dry area adjacent to the surrounding waters for various purposes such as maintenance, repair, refitting, or even disposing of an old vessel. Here, for all practical purposes, the vessel is suitably shifted to an enclosed area, and the water is then drained off, leading to a dry surface. The term ‘dry docking’ is often used for repair and maintenance work. 

Now, mooring again is the fastening of a vessel to any shore or land-based structure with the help of suitable mechanisms such that the vessel is not subjected to free motion. This land-based structure may include berths, jetties, piers, wharves, quays, etc.  

Components of Mooring 

The basic components of a typical mooring system are as follows: 

Mooring Lines 

These are the main components of any mooring system. In earlier times, ropes were mainly used as mooring lines. However, steel or high-grade synthetic materials have been widely used. The main requirements of any mooring line should be high strength and elasticity. The forces transmitted from the ship structures are transmitted directly to these mooring lines. 

The net effect on the lines becomes manifold from this static load coupled with the random dynamic behaviour from the tendency of motions or environmental loads acting on the ship. So, these mooring lines’ material and sizes are carefully chosen based on the vessel and the type of mooring arrangement. 

All mooring lines are characteristic of a Safe Working Load or SWL based on their properties. Like all other structures, these mooring lines have a definite breaking strength with a safety factor margin. Steel hybrids of high grades are often used, and common materials such as Polyamide or HMPE are used for synthetic.

Generally, lower elastic or higher rigid but greater strength lines are used for larger vessels, and higher elastic or less rigid materials are used for smaller ships. The reason is that heavier vessels, due to their greater inertia, have a lesser tendency to respond to external forces and, thus, are less subjected to random motion parameters than smaller vessels. Therefore, when these lines have higher flexibility, they can cater to smaller ships more prone to motion when moored. HMPE and steel have low elasticity, whereas other materials, such as polyamide, have greater elasticity. 

Mooring Winches

On the shoreside, the mooring lines are joined to the winches. These winches act as end supports for these lines and help in handling and directing the lines as per requirements. The winch system controls the tension and extension of the mooring lines. The mooring lines are commonly operated by electro-hydraulic power that uses hydraulic pressure to control the tension and traction forces on the lines. The main component of the winches is cable drums, either oriented horizontally or vertically. The size of the drum once again depends on the ropes. 

Driving Systems

The winches are operated by electrical and hydraulic mechanisms. These are mainly dedicated engines or motors that supply the power to the winch through torque. In turn, the power supply is from the shore supply main lines. These systems’ capacity is as per the capacity and configuration of the winch and related mooring lines. 

Vessel fittings or attachments

 At the other end of the mooring lines, they must be tightly secured to the vessel structure. These attachments are usually on the main deck but can sometimes be placed in subsequent decks. Once again, based on the type of vessel, the number, size, type, and configuration of these fittings are present. The fittings associated with these mooring are all designed and constructed per standard IACS guidelines based on the vessel and the related mooring system. Usually, the fitting used are chocks, bollards, fairleads, bitts, etc. 

Fenders

Now, despite the mooring lines, vessels often tend towards motion and, as a result, can be prone to hit on the adjacent shore or dock structure to which it is secured. Such impacts can result in damage to the shore structure as well as the vessel. So, for the same reason, the vessel and the shore structure are padded with a securing arrangement known as fenders, which absorb impact energy in the event of a collision or strike. The design of the fenders is once again based on the vessel type and size. They are usually made of rubber, wood, or high-grade synthetic polymers. 

Competence of a mooring system 

Now, for a mooring system, the main job is to secure a vessel in its position when berthed safely and also ensure that the vessel is kept sound from collisions or damages due to vessel-structure interactions due to external dynamic forces. Moreover, the mooring arrangement should be such that for various port or dock operations, there is never a problem. So, for a good mooring system for a given vessel, the main characteristics can be listed as follows: 

• Symmetrical nature of the vessel and uniformity of position
• Maximum possible resistance against the rotational and translatory motions of the vessel. 
• Uniformity concerning the shore connections or winches such that the tension forces of the entire mooring arrangement remain more or less in equilibrium without any mechanical imbalance on both the ship structure and the shore. 
• Maximum space to cater for the minimum motions of the vessel without any hindrance, how sound the arrangement may be.  
• Reliability
• Safety
• Ability to cater continuously round the clock for a single vessel stranded for a long time or multiple ships coming to be secured at the same arrangement without structural fatigue or failure. 
• The capability remains intact under all weather conditions when the forces imposed on the lines and the attachments are very high. 
• Having provisions for surplus or spares when required or in the event of a partial failure. 

Types of mooring (Based on configuration) 

Mooring can be of various types: 

• Single-Point Mooring
• Multi-Point Mooring
• Standing Mooring 
• Running Mooring
• Mediterranean Mooring 
• Canal Mooring 

You might also like to read

• How Baltic Mooring of Ship is Done?
• What is a Mooring Buoy?
• 6 Common Mooring Methods Used For Ships
• 10 Important Points For Ship’s Mooring Equipment Maintenance
• How to Adjust the Load Sensors on Mooring Winches?
• What is Mediterranean Mooring of Ships?
• 10 Important Points to Remember During Mooring Operation On Ships

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 is Mooring of Ships? appeared first on Marine Insight - The Maritime Industry Guide

Mooring operation is one of the important tasks that seafarers have to perform on ship’s deck. Technically, the operation may seem simple but there are several dangerous associated with it. As a seafarer, you must have heard about “Death Traps” on ships and how crew members have lost lives during mooring operation.

Working on the ship’s deck is not an easy task. Deck crew has to consider various safety precautions and understand working of deck machinery and systems, along with cargo operation equipment. When it comes to mooring operations, additional precautions need to be taken to ensure personal and crew members’ safety.

Mentioned below are ten points that must be considered while handing mooring operation on ships:

1. Don’t Allow Any Extra Crew Member on the Deck: Ensure that no extra personnel are present at the mooring station except those who are involved in the operation. Anyone who is not assisting in the mooring operation must be asked to leave the mooring station for his/her and other’s safety.

2. Consider Weather Condition: Before planning the mooring operation, consider the weather condition by taking factors such as wind and current. The ship’s master and responsible officer must have the details of current and future weather data before commencing the mooring operation.

3. Have knowledge of Snap Back Zone and Rope Bight: All personnel involved with the mooring operation should be aware of the snap back zones and rope bight. Click here to know more about this.

4. Check All the Mooring Equipment: Check all the equipment (mooring winch, drums, windlass etc.) involved in the mooring operation for any kind of problem. Proper routine maintenance is the key to ensure smooth running of mooring equipment and systems. Don’t forget to check the load sensors of mooring winches. 

5. Check the Tail of Mooring Line: If the mooring wire line is provided with tail (short lengths of synthetic fiber rope which are placed in series with the vessel’s winch-mounted wires to decrease mooring line stiffness and thus to reduce peak line loads and fatigue due to vessel motions) ensure same size and material of tails are used for all lines in the same service (breast, spring and head lines). Different tail size and material would lead to uneven load in the mooring line.

6. Tend One Line at a Time: Only one line should be tended at a time during mooring operation. If this is not done, it may increase the load in the other tended lines. If two lines are tended together it may lead to overloading and breakage. Follow the orders of the master or responsible ship officer properly to avoid any kind of mishap.

7. Keep a Check on the Mooring Line Load: Ensure that the allowable breaking load in any of the mooring lines does not increase 55% of its Maximum Breaking Load (MBL). This is to prevent the line from breaking.

8. Avoid Mixed Mooring: Mixed mooring is extremely dangerous. Generally, mooring lines of the same size and material should be used for all leads, if this is not possible due to the available equipment, all lines in the same service, i.e. breast lines, spring lines, head lines and stern lines should be of the same size and material. The use of mixed moorings comprising full length synthetic ropes used in conjunction with wire should be avoided.  If a synthetic rope and a wire are used in the same service the wire will carry almost the entire load while the synthetic rope carries practically none.

9. Keep a Continuous Check: Load on the mooring lines must be checked continuously even after the mooring operation is over. If there is any change in the ship’s ballast condition, the lines must be slacked or tightened accordingly. The condition of the rope material should also be checked to foresee unfortunate accidents.

10. Arrange Mooring Lines Symmetrical: All mooring line must be arranged as symmetrical as possible with the breast line. The breast line should be perpendicular to the longitudinal centre line of the ship and the spring line should be  parallel to the longitudinal centre line.

The above mention list is not an exhaustive one but does cover all the important points that must be taken care of without fail during mooring operation. Do you know any other important points that must be considered during mooring operation to ensure smooth operations and safety  of crew personnel? Let us know in the comments below.

10 Important Points to Remember During Mooring Operation On Ships appeared first on Marine Insight - The Maritime Industry Guide

Each vessel has been designed with mooring arrangements such that ropes and wires of recommended strength can help it moor safely alongside a berth, floating platform, buoy or jetty. Fundamentally a vessel has to be positioned alongside a jetty or a berth, between mooring buoys, to a mooring buoy, to another ship or barge and then made fast using her own anchors, mooring lines or shorelines.

Some very common methods of mooring are Mediterranean mooring, Baltic mooring, Running mooring, Standing mooring, Spider mooring buoys, Single-point or single buoy mooring, Conventional or multi buoy mooring, Ship to Ship Mooring

While Moored alongside a fixed or floating jetty or a sea berth there are various forces acting on the vessel such as wind, current, tide, wave action, swell, surging induced due to passing ships and trim of the vessel.

The spring, breast and head lines prevent the vessel’s movement against the action of these forces. The directional effect of these need not be unidirectional. It can be multi-directional or at various angles to the vessel.

The resultant direction of these forces often changes with changes in direction of onshore/offshore winds or tidal streams, currents upriver and down streams. Thus a combination of breast ropes, head ropes and spring ropes is the best method to counter these forces and keep the vessel safely alongside.

Often mixed moorings are observed as some terminals based on local conditions and experiences require vessels to use more lines than they are designed for. Thus the method in which wires in conjunction with soft ropes with different SWL and construction are used as well is termed Mixed mooring.

The simplified resultant of these forces would tend to move a vessel in the transverse or longitudinal direction with respect to the jetty. Thus spring lines prevent the longitudinal motion and the breast lines check the transverse motion.

It is always preferred to avoid mixed moorings due to variable loads and elasticity of various kinds of ropes and wires which lead to different strains or weights on the lines. This can result in excessive loads on some lines than others and eventually part them putting the vessel in danger. However,  for safety reasons or in a desperate situation shipmasters or pilots may have to resort to mixed moorings.

Vessels sometimes also use the seaward anchor in conjunction with mooring lines to haul the vessel out of the jetty while casting off or while making fast the vessel alongside use the seaward anchor to assist the control of the rate of lateral movement towards the berth. This manoeuvre can be carried out with or without the assistance of tugs.

Ship to Ship transfer operation involves mooring alongside two different or same sized ships for cargo transfer. During this operation, either one of the ships is at anchor or both are underway.

The mooring arrangement depends on the size of the ships. A vessel either at anchor or stopped and maintaining a constant heading is approached by the manoeuvring ship at an angle of approach as smaller as practicable. The region of approach is usually abaft the beam of the constant heading ship.

During the approach as the manoeuvring ship comes closer, it steers a course parallel to the heading or course of the other ship and reduces the horizontal distance between ships to less than 100 metres. Once this state is achieved the manoeuvring ship uses engine and rudder movements and reduces this distance further until the fenders touch each other.

The two ships thus then make parallel contact and the lines are passed respectively as per the mooring plan. As a common practice during the approach, the wind and sea are preferred to be from ahead or at very small angles to the bow.

Single buoy or single point mooring: Often larger ships that cannot approach ports and terminals are berthed outside the port limits or in sheltered anchorages and the cargo transfer carried out with the help of Single-point or single buoy moorings.

The basic principle of the buoy is to keep the position of the vessel with respect to the buoy steady and at the same time allowing vessels to swing to wind and sea..

Often a tug is provided at the aft to keep the ship at a fixed angle and distance from the buoy. The buoy is fixed by positioning it in the centre of four anchors connected to it. The ship is made fast to the buoy with the help of a single chain or two which is secured onboard to the bow stopper.

In general, while approaching Single point or single buoy moorings weather is a major criteria in determining whether to berth the vessel or not. Calm seas with low swell and wind force below 15kts are considered favourable to make an approach. Presence of strong tidal current limits the interval for berthing and unberthing.

The headway approach has to be slow often less than while at the same time approaching at a smaller angle to the buoy and then gradually hauling in the buoy messenger rope and pulling the vessel slowly towards the buoy using engine kicks at short intervals to control and maintain headway along with mooring winches to haul in the vessel when she nears about 150-200 meters from the buoy.

For unberthing the chain is released from the bow stopper and a short kick on the engines going astern swings the bow to starboard for right-handed propellers thus clearing the vessel of the buoy. Tug’s assistance can also be sued to pull the vessel astern and clear it of the buoy. Know more about single point mooring here. 

Conventional buoy or multi buoy mooring: In this method, the bow of the ship is secured using both her anchors whereas the stern is secured to buoy around it. In the approach firstly vessel approaches the final berthing position from forward at an angle of 90 degrees to her final direction of berthing.

The starboard anchor is then let go first at a pre-decided spot while the ship is making headway. The required amount of cable is paid and the astern propulsion too operated simultaneously to stop the vessel. Once the vessel is stopped in the water port anchor is let go and thus vessel positions her stern along the centerline bifurcating the buoys.

For aligning the vessel along this centerline port cable is paid out and starboard cable heaved in with astern propulsion. The helm and engines are to be carefully used during this manoeuvre to ensure the stern is swinging clear of any of the buoys.

During unberthing, the anchor cables are heaved in to move the vessel forward and the weight is taken on windward lines while casting off other lines to prevent swinging of the stern into the other buoys. This manoeuvre requires skill and efficient operation of the ship’s crew as well as of the mooring equipment as often weight of the lines can be immense.

Read on baltic mooring here.

Mediterranean mooring: For this type of mooring, a pre-calculated position is determined and approached using engine movements. The bow initially is made to cant towards the berth and the starboard anchor is let go in that position.

After this, the engines are run astern and the port anchor is let go at the designated spot. The vessel falls astern and swings to starboard. Thus vessel is held by both the anchors as it approaches the quay. Stern lines are then passed. Moorings are kept tight by using the anchor cables.

The positioning of the vessel is such that mooring is completed with around four shackles on each anchor. Often tide is used to control the drift of the vessel towards the quay while positioning it by heaving or paying out on one of the anchors. Read more on mediterranean mooring here.

Running Mooring: This manoeuvre takes a relatively short duration compared to the Mediterranean mooring and offers more control of the vessel. The vessel’s starboard anchor is let go at a position approximately four to five shackles from the final position of the bow and around 9 shackles paid out while moving ahead on engines.

Then as she falls astern with the tide the port anchor is let go and the starboard anchor is heaved onto five shackles. This method restricts the swinging room and reduces the load on the windlass.

Standing Mooring: This is practised during crosswinds. As the vessel is stopped the port anchor is let go and with the tide around 9 shackles are paid out. The starboard anchor is let go and simultaneously port anchor heaved on.

Thus the port anchor is kept on 4 shackles being generally the flood anchor and starboard on five as it is the ebb anchor. This vessel takes longer duration and provides less control over the vessel. The load on the windlass is more as compared to running moor.

Over to you..

Do you know any other important mooring methods that can be added to this list?

Let’s know in the comments below.

6 Common Mooring Methods Used For Ships appeared first on Marine Insight - The Maritime Industry Guide

What happens when there is not enough space at the wharf for a number of ships or boats to be moored? Or what happens when there is a ramp at the stern of the ship (like a car carrier) that connects it to the hold? The answer is that the ship has to be moored perpendicular to the wharf with its stern transom (surface) lying parallel to the jetty. Such “end on” to the quay berthing is called “Mediterranean Mooring”.

Mediterranean mooring, also known as “med mooring”, is a technique for mooring a vessel to pier at a perpendicular angle. The ship thus occupies less space as it is connected to a fixed length of pier along the width rather than its length. The disadvantage of Mediterranean mooring is that it is more likely to result in collisions and that it is not practical in deep water or in regions with large tides.

Mediterranean mooring can be done in two ways. Now the boats or crafts like yacht can be berthed bow to or stern to with the wharf depending upon the convenience or preference of the crew but in both cases an anchor is dropped from the opposite end of the one that is approaching the jetty in such a way so that that the end remains fixed and the anchor can be hove up and hauled out.

CASE 1: (Berthing Stern to)

At first the place where the ship’s stern is to be brought alongside is located. A firsthand knowledge of the shore line is required, like if there is a protrusion or not at the underwater section or the bed is shallow or shoaled. In that case the stern first approach is aborted and the bow first approach is tried. For a vessel having normal right handed propeller the wharf is best kept on the port side and the distance is kept more than seven ships length.

The ship is at first kept parallel to the berth and then it is brought astern. The point of berthing is now generally abeam. All through the astern movement the rudder is kept to hard over port so as to get the maximum canting effect. As the ship falls astern, the bow will naturally cant to starboard due to transverse thrust. The Starboard anchor is dropped in such a way so that the scope (it’s the ratio of the length of the anchor rode and the vertical distance from the bow of the vessel to the bottom of the water or the bed) is 7:1 (approx). So if the sea bed is 10 m down from the bow, a distance of 70 m is required.  Smaller crafts with shorter anchor chain will try to make this distance as much as practicable.

The chain is let to fall free so that the anchor digs at the sea bed in the first attempt. It is ensured that there is no snag in the rode (it’s the length of the anchor line or chain) and that there is enough length of the chain to reach the berth. The anchor must be dropped away from the other anchor lines or the lazy lines, which are used to retrieve heavy pre embedded bow lines substituting the anchor. Otherwise fouling of the anchor chains or these lines can be quite a cumbersome affair during sailing.

Meanwhile hand fenders are arranged along the sides to protect the hull of the ship/boats on a windy day from colliding with the other crafts that are docked already. The vessel is slowly brought astern keeping in mind that the wind is not on- shore. Otherwise the fall cannot be restricted. Off shore winds are of great help as they dampen the stern board movement and the vessel will have a tendency to stop without much use of the ahead movements on the telegraph.

When the wind is athwart, the first line ashore will be the one from the windward side. In this case if the wind pushes the starboard hull the starboard quarter line is to be sent ashore first. Then the other rope from the opposite end is thrown ashore and ensured that both the lines are” doubled up” i.e., the lines are made to take a turn on the shore bollard and are sent on board. This helps the crew while hauling out as only casting one end of the line from on board the line can be retrieved with the winch without any shore assistance. On a windy day the first shoreline is sent ashore by a small motorboat or a dingy so that the vessel can be warped in with the help of its winches. While hauling in if the bow swings corrective counter measures are taken with short kicks of forward movements and necessary helm or holding the anchor a bit, as the case may be. The lines ashore are fast in such a way that the angle between them is wide enough to restrict any swing of the stern due to any surge in the wave or wind. It is best to set another pair of lines across the stern to the shore.

The boarding ramp is employed for the crew to step out from the stern. Also cars and trucks loaded in the car carriers can be loaded or unloaded.

CASE 2 ( Berthing Bow to):

Docking “Bow to” is much easier though as the pilot or the master has much more control over his ship as he steers in letting his stern anchor far off the berth so as it holds the stern during the stay. A line from each quarter is hitched to the chain aft to restrict any side wards play. Two lines are passed ashore from the port and starboard bow at a wide angle as in the previous case so as to make fast the bow to the jetty. This type of bow fast approach is done if there is an underwater shoal below the jetty or there is a protrusion.

In both cases the anchor is snubbed when there is only a boat length difference between the quay and the bow or stern.  Engines are also given accordingly so as to avoid any untoward collision.

Do you have any more information on Mediterranean mooring? Let us know in the comments below.

What is Mediterranean Mooring of Ships? appeared first on Marine Insight - The Maritime Industry Guide

What happens when there is a strong onshore wind and you have to berth a ship without the assistance of tugs to a pier or jetty that is not strong enough to bear the impact or is not sufficiently ‘fendered’?

Watch the video below to understand the process:

Do you have more information on the baltic mooring process of ships? Let us know your thoughts in the comments below.

How Baltic Mooring of Ship is Done? appeared first on Marine Insight - The Maritime Industry Guide

Single point mooring (SPM) is a floating buoy/jetty anchored offshore to allow the handling of liquid cargo such as petroleum products for tanker ships.

SPM is mainly used in areas where a dedicated facility for loading or unloading liquid cargo is not available. Located at a distance of several kilometres from the shore facility and connected using sub-sea and sub-oil pipelines, these single-point mooring (SPM) facilities can even handle vessels of massive capacity such as VLCC.

Single point mooring (SPM) serves as a link between the shore facilities and the tankers for loading or offloading liquid and gas cargo. Some of the major benefits of using SPM are:

• Ability to handle extra large vessels
• Doesn’t require ships to come to the port and thus saves fuel and time
• Ships with high drafts can be moored easily
• Large quality cargo can be easily handled

How Single Point Mooring (SPM) Work? 

The offshore-anchored loading buoy is divided into different parts having dedicated functionality.

Mooring and anchoring systems, buoy bodies and product transfer systems are the main parts of the SPM.

The SPM is moored to the seabed using a mooring arrangement, which includes anchors, anchor chains, chain stoppers etc. The mooring arrangement is such that it permits the buoy to move freely within defined limits, considering wind, waves, current, and tanker ship conditions. The buoy is anchored to the seabed using anchor chains (legs) which are attached to the anchor point (gravity based or piled) on the seabed. Chain stoppers are used to connect the chains to the buoy.

The part of the Single Point Mooring System (buoy body) which is floating above the water has a rotating part which connects to the tanker. The rotating part allows the tanker to get stable at its desired position around the buoy. The tanker is usually moored to the buoy by means of a hawser arrangement, which consists of nylon or polyester ropes shacked to an integrated hook on the buoy deck. Chafe chains are connected at the tanker end of the hawser to prevent damage from tanker fairlead. The mooring systems used for such offshore operations follow the standards put forth by Oil Companies International Marine Forum (OCIMF).

The product transfer system is located at the heart of the mooring buoy. The system transfers products to the tanker from the Pipeline End and Manifold (PLEM) (geostatic location) located on the seabed. Flexible hoses known as risers connect the subsea pipelines to the buoy’s product transfer system. The buoy is connected to the tankers using floating hose strings, which are provided with breakaway couplings ( A particular type of coupling with a breakpoint which will break at a predetermined break load, activating internal valves which will automatically close at both ends and prevent further release of products.) to prevent oil spills.

Single Point Mooring Systems use a swivel system which connects the Pipeline End and Manifold (PLEM) to the buoy. The product swivel system provides the flexibility of movement to the tankers during the transfer of products. This movable pipe-connection system prevents premature hose failure due to traction or bending stresses.

General overview of how single point mooring (SPM) system works

• The tanker ship is moored to the buoy for loading or unloading of cargo.
• A boat landing space on the buoy deck provides access to the buoy for setting up the connections and securing the ship.
• Fenders are used to protect the buoy from unexpected movement of the ship due to bad weather.
• Lifting and handling equipment on the buoy allows for handling of hoses connections and safety tools.
• Once the connections are made, valves are operated from the electrical substation.
• Necessary alarm systems and navigational aids are provided as safety precautions.
• Liquid cargo is transferred from the geostatic location (Pipeline End and Manifold (PLEM)) to the tanker using the product transfer system of the single-point mooring system.

A General Video on Single Point Mooring Operation

Additional Reference 

Single Point Mooring Maintenance and Operations Guide 

Single Point Mooring Maintenance and Operations Guide sets out guidelines for operators of SPM terminals and provides a framework and set of procedures that are based on the extensive experience of several companies. It primarily deals with the two most common types of SPM, the CALM (Catenary Anchor Leg Mooring) and the SALM (Single Anchor Leg Mooring).

You may also like to read – How Subsea Components Of ROV Sustain Tremendous Seawater Pressure?

How Single Point Mooring (SPM) Offshore Operation Works? appeared first on Marine Insight - The Maritime Industry Guide

Mooring winches are used to tie the ship to the berth when at a port. While loading and unloading the cargo on the ship, the mooring winches tighten or loosen suddenly. Any extra tightening or loosening of the mooring winches can lead to dashing of the ship with the berth or any other form of accident.

For this reason, load sensors are used on the mooring winches. Load sensors sense the tension on the mooring winches and adjust the tightening and losing accordingly.

However, it is important that these load sensors are adjusted properly to get accurate results. The article will explain how to adjust the load sensors on the mooring winches.

Adjusting Load Sensor

Winches consist of strain gauges that sense the load. This strain gauge produces a small voltage when the load is applied to it. The voltage produced will be different for different loading conditions. This voltage is then calibrated to give out the readings on the panel of the winches. These gauges are required to be calibrated from time to time and the procedure for the same is as follows.

1.      A tool is fabricated as shown in the diagram with the dimension specified. The dimension may vary with different sizes of the winches; proportional dimensions may be calculated accordingly.

2.       There are 2 holes in the rope drum and the measurement between the holes is 200 mm for the picture shown which may also vary with different winches.

3.      For fabricating cut 2 pieces of plates 10-15mm thick and weld a distance piece of 25 mm between them, and in the bottom a plate to be welded for placing the hydraulic jack as shown.

How to Fill in the Formula?

The following calculations and measurements have to be taken and put which is marked in blue.

The example given above is for the MW 300 EA winches.

The winch tension is noted, a winch MW 300 EA is pulling 300 KN, and an MW 120 EA 120 KN etc.

The drum diameter is checked and noted. It can be measured on the winch or can be taken from the manual by checking the mechanical dimensions.

The rope diameter is measured and noted.

The distances from the centre of the shaft to the position where the hydraulic jack is to be positioned are measured and noted.

Finally, the jack piston area is to be calculated cm2.

Download your own formula calculator below.

Winches Formula Calculator

Procedure

1.  After all the measured values are inserted we need to get the jack load and the maximum pressure to be applied by the hydraulic jack.

2.   Before adjusting safety precautions are to be taken to avoid any accidents.

3.   Bridge is informed that you are working on the winches.

4.  Proper signs and placards are displayed for men at work so nobody will switch on the power by mistake.

5.  Electrical permit to work to be filled and instructions should be followed so you don’t miss any safety point and prevent an accident.

6.  Switch off the power to the winch after putting the tool as seen in the picture.

7. The rope is made slack and a voltmeter is mounted between GND and SIGN. Trimmers P7 and P5 are adjusted until you have 0 V DC.

8.  The reading should be zero as there is no load on the gauges, but if it shows any reading then it should be adjusted to zero as specified in the above point.

9.   Now engage the clutch and apply the pressure with the help of a jack. The pressure applied is already calculated in the form above.

10.   When the maximum pressure is reached, check the reading in the voltmeter by mounting the two leads between SIGN and GND.

11. Now adjust trimmer P6 amplification by turning with a small screwdriver until you have approximately 3 V DC and the value on the “Load meter” in the control panel is maximum.

12.  Release the hydraulic pressure and now the reading on the control panel should read approx. 0 V DC.

13. If reading is not zero then re-adjust trimmer P5 load sensor for fine-tuning.

14. It is recommended to put back the pressure again to be sure that it goes back to max value.

How to Adjust the Load Sensors on Mooring Winches? appeared first on Marine Insight - The Maritime Industry Guide

Correct operation of the mooring equipment onboard is indeed important for the overall safe operation of a vessel in port. Mooring, being such a critical operation, reminds us of the fact that any unforeseen event could prove dangerous and sometimes fatal.

In order to implement safety and avoiding lives to be at risk, it’s imperative for ship’s personnel to maintain high standards of integrity of the mooring equipment. A better way will be to incorporate all the parts of the mooring equipment into the ship’s planned maintenance system.

Let’s see how to adhere to the maintenance of the mooring mechanisms onboard –

1. Make Checks Prior Mooring – After an extended sea passage or a passage undertaken in heavy seas and prior to mooring operation, ensure to check the following –

i.         Any physical damages to the mooring mechanism.

ii.        All controls, linkages and the operating levers are well oiled, greased and free / easy to use.

iii.       Ensure that all the brake drums and linings are suitably dried and clean of salt deposits.

2. Do Frequent Greasing of Moving Parts  – All rotating parts of the mooring equipment, which would include rollers, fairleads, winch drums, deck stands etc. must be moved and lubricated on a frequent basis. Multipurpose grease is the best lubricant for such applications (check the vessel’s lubricating chart for the right application). Normally, high pressure grease guns are used for this kind of work.  Particular attention must be given to the roller fairleads and deck stands as these often suffer from little use and thereby are neglected. Rollers should turn smoothly and must be checked for integrity as corrosion may have weakened them.

Tip – Always check the grease nipples before application and make sure the nipples are free of rust, salt and grit. Change the nipples if necessary.

3. Check Brake Liners – Regular inspections must be made of the winch / windlass brake linings for wear and tear. Oil, heavy rust and moisture on the brake linings or the drums could seriously reduce the brake holding capacity of the winch and in some cases as much by 75%. To remove the moisture in the linings, apply the brakes lightly while running the winch (remember to avoid excessive wear and tear during this operation). Oil has the tendency to get impregnated into the lining itself which is difficult to remove. Thus the only option would be to change the lining as early as possible. Remember that the brake holding capacity of the winch is dependent upon the type of mooring pattern used.

4. Check Break Drums : Whenever brakes are opened up for any reason, ensure that the brake drum is thoroughly checked / examined for build up of rust or other worn out brake material. The part to be de-scaled and fitted with the replacement as required.

5. Check Brake Linkages – The brake linkages should be checked for free movement. If the linkages are not free then there would be a loss of brake holding capacity. This would create a wrong impression to the operator that the brake has been applied fully, but in fact has not or the brake mechanism is hardened up from lever bars ,which have a tendency to build up high stresses on some mechanical parts of the brakes.

6. Inspect Gear / Hydraulic Oil – Inspect the gear oil regularly through the inspection cover in the winch / windlass. Whitish color of the liquid means the liquid is contaminated and requires to be changed immediately. Use the replacement oil that is recommended by the manufacturers.

 7. Carry Out Regular Visual Inspection: Ensure that regular inspection of the synthetic mooring hawsers, heaving lines, messenger ropes, etc. is carried out for damages, chafed areas, kinks and loose ends. Also make sure that each mooring rope carries a certificate from the manufacturer. Additionally, check that the ID number of each certificate is conspicuously marked / embossed on an identification plate and subsequently attached to the end of the corresponding mooring hawser. If the hawser is not supplied with the certificate, then the vessel has all the right to reject such a supply and inform the office / purchasing department.

8. Clear Walkway: An important part of the mooring operation is to have the deck completely free of obstructions and oily residues. Therefore, it is essential to keep the decks clean, dry and if possible have anti-slip paint coatings over the deck surface, as and how required. Often there have been cases where the support brackets for the gratings (for winch operation) have been found neglected and therefore are heavily corroded making the area most unsafe to step on. Officers should include such neglected yet critical areas for planned maintenance in order to prevent an unforeseen event when least expected.

9. Do Proper Marking and Labeling: Marking the mooring equipment is another important aspect for a safe and effective operation. The ship’s officers should ensure that the bollards, fairleads, rollers, etc. are marked with their safe working limits. Additionally, the winches and windlass shall be marked for rotating direction of the drums (render / heave), braking capacity, test dates and ID numbers of the equipment subsequent to the certificates carried onboard.

10. Maintenance of Steel Wire Mooring Ropes – It is essential to grease and lubricate the steel wire mooring ropes at regular intervals as rust will reduce the strength of the wire in a very short period of time. Lubricating such ropes require special grease, normally oil based compounds. An effective greasing is carried out by removing the entire wire out of its stowed position and applying the lubricant generously throughout the length of the rope. It is also important to note that the wire should be turned end to end regularly to reduce wear and prevent corrosion. Visual inspections are equally important and should be carried out regularly with special attention to areas with dark patches. Any wire shall be replaced if it is damaged to the extent that more than 10% of the visible strands in a length of a wire equal to 8 diameters are broken.

These are some of the important points that must be considered while carrying out mooring equipment maintenance. Do know any other important points? Let’s us know in the comments below.

10 Important Points For Ship’s Mooring Equipment Maintenance appeared first on Marine Insight - The Maritime Industry Guide