Anchor and mooring systems - Essay Example

Anchor and mooring system are used to hold the ships and the floating platforms in position and prevent movements caused by the wind and current. Given most sea vessels and ship are incapable of breaking, only anchorage systems and mooring can be used to slow down and hold the ship into position to avoid moving (Lekang, 2007). The unregulated and unwanted movements caused by wind and the current can cause grave consequences and repercussions including damage to property if the ship is not properly anchored or moored.

Floating production systems and offshore drilling units located in deep sea require a high level of anchorage in order to maintain a firm position against the high tides, currents and wind present at high depths. Anchoring systems and mooring therefore perform a crucial function in maintaining the stability of the sea vessels without which there exist costly ramifications (Blackwell & Blackwell, 2011). This paper discusses the operation of anchors and mooring systems, their fabrication and classification.

Operation Anchor and mooring system consist of the anchor, the mooring line which is used to transmit force from the moored vessel to the anchor and the tension system or the attachment point on the moored vessel or floating work platform. The mooring line can be made from either a chain or wire rope. In some cases the anchor line is made from the combination of the chain and wire rope with fiber line or rigid element included (Blackwell & Blackwell, 2011). In shallow waters of depth up to 100m, chains are usually preferred for permanent mooring.

Steel ropes have a higher elasticity and is preferred at greater depth than 300m. Synthetic fiber ropes on the other hand is the lightest among the three choices and is used for anchorage in deep waters of up to 2,000m. The anchor usually provides the majority of the holding capacity or the resistance to motion even though the other components of the system are also at play in contributing to the anchorage of the vessel or the floating work platform (Dokkum, 2010). The portion of the anchor buried under the sea has a significant contribution to the whole system especially when a chain is used as an anchor line.

The portion of the anchoring system excluding the attachment point on the vessel or the floating work platform is known as the ground leg. The ground leg is inclusive of the anchor, anchor line and other auxiliary devices (Blackwell & Blackwell, 2011). The anchor line (chain or wire rope) is connected to the windlass mounted on the sea vessel or the floating platform. The windlass can be either of vertically or horizontally designed. Most anchor and mooring systems use a vertically designed windlass mostly known as a cap an.

The capsan is composed of a gypsy; drive wheel notched in order to fit the chain links. The chain is drawn along the deck from the capsan through a pawl and dropped down through the hawse pipe in the deck which exits at the ship's bow. The chain is then dropped down and a shackle is used to connect the chain to the anchor. The hardened steel pins of the shackle pass through a hole drilled in the anchor central shank (Scott, 2011). Material and methods of fabrication A number of materials can be used to make an anchor ranging from large blocks of rocks to sacks of sand.

Commercial anchors are made from pig iron which are fabricated to form cast iron anchors. Steel anchors are also made through drop forging of carbon steel. Both the cast iron and forged steel anchors