2016年2月20日星期六

Breif introduce of Marine Anchor

Marine Anchor




Definition
1, with specific shape, was thrown into the water can meshes into the subsoil provides holding force, thus by anchor chain of ship or other floating system left in the predetermined area of the apparatus.
2, with a specific shape, was thrown into the water to buried in the subsoil, providing grip and easy from out ,through anchor chain or cable, to stable ship or other floats tethered in the waters of special equipment.

Summary
Anchor is to have a specific shape, thrown into the water can quickly gnaw into the subsoil providing grip strength, through the top of anchor chain or cable, will leave the ship or other floating system in the predetermined area of special equipment. Anchor is the main parts make anchor force. The shape of anchor is special, usually made of forged steel or cast steel. The anchor consists of anchor body and anchor bar, anchor consist of anchor shackle, anchor shank, anchor crown, anchor arm, anchor fluke.
The number and weight of anchor are determined according to the number of outfitting capacity, or according to the ship's displacement, upper water is affected by wind area, resistance, anchoring depth and the length of anchor chain. A ship with three main anchor (two bow anchor and a spare anchor). Submarine anchor of superstructure use short shank anchor, so as not to equip difficult. Anchor in the rated weight conditions to ensure maximum grip strength and in any dropping conditions of various subsoil can rapidly meshing, heaving up anchor and easy to emerge from the subsoil, close to the broadside of hiding anchor when should be hawse pipe, anchor points, or anchor frame fit well with.
Commonly the merchant vessel use stockless anchor

Basic requirements of anchor
Anchor is main device to tie the ship, its performance directly affect ship’s reliably captive, so the performance put forward very high requirements.
1 .grasping force
This is the most basic performance requirements. Measurement of the performance of the ship's anchor holding performance is usually referred to as the grasping force coefficient. Holding force coefficient is equal to the quality of the anchor in the anchor in the subsoil caught in the air force divided by the anchor. According to common sense, the greater the quality of the anchor, the greater its grip strength; but most of the anchor with the quality of the increase, the coefficient of its grip force is a downward trend in the determination of the anchor should pay attention to the characteristics of the.
2 .can adapt to a variety of different subsoil quality
Generally, due to the vast area of navigation, the bottom of the ship is very large, so the configuration of the anchor type requirements can adapt to a variety of bottom.
3. solid structure
Ship in the process of anchoring and mooring may bear a variety of complex load, so anchor structure should be strong enough to ensure the safe use.
4, good stability, easy to merge
Ship in anchor mooring process, due to the wind direction and the direction of the flow changes around the ship cast anchor rotary, uneven ground the anchor force and cause anchor turn over and was pulled out of the subsoil, so good stability for the anchor is very important. Anchor bar with stability is better, but the collection inconvenience anchor. In some cases, such as ship to load or a sudden increase in anchor may still is from the subsoil in pull out, thus requiring anchor with re meshing subsoil characteristics.
5 into soil short distance
Anchor is thrown into the water after, in cable affects the fluke gradually meshes into the subsoil, from the beginning to all mesh into the subsoil play maximum grip the distance shorter is better.
6 small pull force
The anchor, the anchor pull out from the subsoil in force as small as possible, this will help reduce the burden of the anchor machine.
7 good self-cleaning
The anchor in the anchor from the subsoil, should not have a lot of dirt, otherwise it will increase the burden of the anchor machine. At the same time anchor in the process of removing the water, the soil should be basically clear clean.
8 convenient collection
General anchor used in the hawse pipe, usually without rod rotating claw anchor is easier to be accepted into the hawse pipe, anchor rod and fixed claw anchor that are the anchor frame.

Many types of anchor, according to its structure and shape is divided into: stock anchor, stockless anchor, high holding power anchor and special purpose single claw anchor, double fluke anchor, grapnel anchor, bacteria anchor, floating anchor; divided by setting, the location and use: bow anchor, stern anchor, spare anchor, shift anchors, position anchor, back beach anchor and deep-sea anchor, mooring anchor etc.

Anchor structure
Like Hall anchor, composed of anchor shaft, anchor body and shaft pin. Both the upper and the lower anchor hole, the upper part of anchor hole connecting shackle, anchor hole at the lower part of body is connected by a pin shaft .The anchor body is composed of two anchor fluke and anchor crown .anchor crown in hole can make the anchor stem through that hole has two and a half round groove, the pin shaft can rotate in the groove. To prevent the anchor stem and pin to emerge from the crown, with two cross pin pinned, and the cross pin and the anchor crown welded by welding. The prominent part of crown on both sides called help catch make fluke easily buried in subsoil.

Foundation of anchor selection
Ships anchors and anchor chains according to ships type and sailing waters, ship outfitting number in the column data to select.
The number of ship outfitting, is a parameter that reflects the hull can be wind, fluid flow force.
Cargo ships, bulk carriers, oil tankers, ferries, trailing suction dredger is equipped with devices according to the selected N. By the number of outfitting look-up table derived from a ship should be the weight of the anchor in a matching number, each anchor and chain level, length and diameter,
Usually more than ten thousand ton ships are equipped with 3 main anchors, 2 bow anchor, 1 for preparation of anchor. Ships sailing in narrow, curved and water potential complex channels are also equipped with stern anchors to control the swing of stern when necessary.

Anchor test
All anchor and main parts shall be made by the authorized factory in accordance with the relevant regulations. The anchor cast steel parts can be carried out by stretching test according to the same furnace molten steel, the same specification, the same heat treatment procedure and the total weight not exceeding 3T. At least 1 samples were drawn from each batchA set of 3 impact specimens shall be taken for each batch of steel castings used for high holding anchor, and the test shall be carried out at 0 degree. The average impact work is not less than 27J. The forged steel parts shall be manufactured and tested in accordance with the relevant provisions.

Heat treatment should be carried out when a single piece is more than 3T. The welding material approved welding anchor assembly, according to the approved welding procedure by certified welders. All finished anchors shall be inspected, weighed and tested in the absence of paint.

Installation requirements and test methods for anchors
Anchor and anchor chains, swivel, before connecting the mounting ring should be carefully reproduces the ship inspection product number, manufacturing factory product number and anchor quality. In accordance with the requirements of the drawing, the specification and quantity of the inspection can be shipped on board, and record the number of each.

Anchor of the visual inspection should be carried out prior to painting, anchors and the part surface there should be no cracks, pores, trachoma and other defects enough to affect strength of anchor, to not affect the strength of surface defects allowed to repair welding repair.

Anchor shape and size of the margin of error is 3%, but the sum of each ship bow anchor actual quality shall not be less than standard anchor weight sum of; each new bow anchor when equipped with quality limit of error is 7%; bolt bending in 1m length does not exceed 3mm; the rotary angle of the flukes allowable deviation for -0.5o~+2o; when meet the anchor quality deviation, size of each part of the allowed deviation is 4%, but the maximum value shall not exceed 20mm.

The ship anchor can be divided into several ways, such as mooring anchor, auxiliary ship operation anchor, emergency anchor and so on.

1. mooring anchor
The ship for loading and unloading of goods, such as wind and tide, waiting for a berth, and need moored at anchor. Mooring anchor can hold. Loose the appropriate length of anchor chain, anchor and anchor chain grasping in force to resist ship of water and wind and waves on the ship's force. According to natural conditions of anchorage, can be divided into single and double anchor mooring systems.

2 .auxiliary ship maneuvering anchor
In the narrow waterway navigation, sometimes with anchor help turn around or steering, relying on berth or emergency avoidance away with drag anchor to control the bow, control the hull or brake reducing speed. The general maneuvering anchor chain is not long, mainly from the block affection , do not request the anchor hold completely.

3 .emergency anchor

In the narrow channel traffic density larger waters, sometimes for emergency avoidance can drag (double) anchor brake to reduce the speed of ship, to avoid collision or collision loss is reduced. If ship ran aground, along direction of anchor under refloating transport, hauling chain to assist light. When ship encountered large waves, wind and air stagnation can be anchored and loose chains of proper length to increase the ship drifting resistance and is beneficial to control the bow, to assist the ship resistance big waves.

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