Mooring Equipment

Mooring Equipment is the set of fittings and mechanisms aboard a ship that are used to warp and secure the ship when it is moored at a dock, at the wall of a lock, to buoys, or alongside another vessel.

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.

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.

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.

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.

Mooring line
Mooring line connects to the anchor and keeps the structure afloat. Mooring lines are mainly made from wire, fiber rope, and chain.

Mooring anchor
Your mooring system relies heavily on the strength of its anchor. The holding capacity of each anchor, which should generally be at least three times the weight of your service anchor, depends on the water depth, seafloor soil properties, and type of anchor you use.

Mooring chain
The mooring chain connects the anchor to a floating buoy or watercraft. Experts recommend that your mooring line be three times the length of the water’s depth and a quarter inch thicker than your service chain.

It’s also a good idea to invest in mooring line supports to protect the line from chafing, as well as mooring whips, which are solid fiberglass rods that keep your watercraft a safe distance away from the dock edge to prevent damage during unfavorable weather conditions.

Although you can also choose from various mooring lines, cables, and ropes, stick with a chain for permanent moorings in waters up to 328 ft (100 m). For waters deeper than 984 ft (300 m), choose a stainless steel cable or wire rope. For ultradeep waters (more than 6,560 ft or 2,000 m), use a combination chain, wire, and synthetic fiber line for maximum strength.

Mooring buoy
The mooring buoy, heavier than a standard buoy, floats in the water away from the shoreline. The buoy allows boats to be moored in deep water instead of shallow water or to be moored to a pier.

Mooring anchor
Boat dock systems can use several types of anchors:

Deadweight anchors use weight as their holding power to settle at the bottom of the sea and are the simplest type of anchor.

Mushroom anchors look like an upside-down mushroom, are made of heavy cast iron, and are best for freshwater and smaller motorized water vehicles. If you get a mushroom anchor, find one coated with PVC to act as a bumper and prevent damage to your watercraft.

Pyramid anchors are similar to mushrooms, except they’re shaped like a pyramid and become embedded in the seafloor quicker than the mushroom anchor. They’re used in shallow waters.

Helix anchors consist of helically shaped stainless steel plates attached to a central shaft and use rotation during installation in the ground. They’re more eco-friendly and work best for marinas and residential systems in waters no greater than 60 feet.

Piling anchors drive a single structure into the seafloor for maximum stability and minimal side-to-side movement.

It is expected to get confused with the terms mooring, docking, and anchoring, and they may be used 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 needs to be fastened or stranded for various purposes in 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 traditional anchor systems, the heavyweight is suspended from the vessel and 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, help 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.