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The principle, function, type and daily inspection of anchors

The principle of anchor

The structure from top to bottom is the anchor shackle, bolt, anchor rod, anchor handle, anchor wrist, and the symmetrical parts on both sides are called anchor claw. The anchor claw is the most important part of the anchor to grab into the soil. When the ship breaks down, the anchor sinks to the bottom of the water under the traction of the anchor chain. At the bottom of the water, due to the action of the anchor rod, the plane of the anchor wrist will be perpendicular to the bottom of the water, and the anchor claw will be in contact with the bottom of the water at this time.

The length of the anchor chain of the ship is often greater than the depth of the water, so the anchor chain on the bottom part is in a flat state. When the ship is disturbed, such as when the top wave, the anchor chain will be pulled, and the anchor at the bottom is at the anchor chain connection. At the same time, the anchor's own gravity acts on the contact point between the anchor claw and the bottom of the water, and the combination of the two forces makes the anchor move diagonally downward, which is the process of anchoring into the soil. After the anchor is pulled into the bottom of the water, it can provide the ability to moor the ship. It should be noted that this ability can not only be completed by an anchor, but also a long anchor chain also plays an important role.

The role of the anchor

The main function of the anchor is to fix and stabilize the ship, which can be seen from the following aspects:

1. For the anchor to work, the most basic condition is to hook something on the seabed.

If the anchor chain is not long enough, the anchor will not work. If the seabed is flat, or the anchor hook is not fixed, or the hook is not strong enough, if the wind is calm, it's okay, but once the waves are too large, the anchor can't hook things, and the anchor will lose its function. , this is called "walking the anchor". It is very dangerous for the ship to walk the anchor during the anchoring period.

2. The weight of the anchor chain is negligible for the ship, and that point will not play a big role.

Generally speaking, the anchor chain is straight when the ship is anchored. Do you think there will be any friction in the anchor chain at this time? If you are at the seaside, you will find that there are many small fishing boats, and the anchor chain is a thick rope.

3. Viewed from the top of the ship, the anchor chain is straight, but there is a section under water that is nearly parallel to the seabed. In fact, it is the anchor attached to the seabed to provide grip, and then passed to the ship through the anchor chain to resist the current. , The influence of external loads of wind and waves on positioning. The reason why there is a section close to the seabed is to take into account the influence of the force, and there is a section close to the seabed, which can provide a margin, which is acceptable within a certain range.

The weight of the anchor is not large, but there are regulations on the size of the anchor for the size of the ship. This is because of the gripping force that the anchor can generate and the factors of its own inertia, the anchor chain friction also plays a role.

type of anchor

There are many types of anchors. According to different structures and uses, they can be divided into rod anchors, rodless anchors, high-holding anchors and special anchors; merchant ships mainly use rodless anchors for bow anchors, and stern anchors sometimes use rod anchors. and dovetail anchors.

1. Rod anchor

Also known as the naval anchor, this kind of anchor is an early anchor, also known as the naval anchor. This kind of anchor has a simple structure, a large grab-to-weight ratio, and a good bottom grabbing stability, but the anchoring operation and storage are not convenient. The anchor catch is easy to entangle the anchor chain and scratch the bottom of the ship. This kind of anchor is not easy to be used as the first anchor of commercial ships, and is generally used for small boats or sailing boats.

2. Rodless anchor

Also known as mountain anchors, the common ones are Hall anchors and Spek anchors, which are rodless anchors with movable anchor claw (about 45° forward and backward along the anchor shaft). The anchor rod and anchor arm of the rodless anchor are cast separately. Anchor claw, anchor crown and anchor arm are cast in one piece. The anchor stem is inserted into the rectangular hole of the anchor crown, and the pin shaft and the horizontal pin are positioned in the two semicircular grooves at the lower part of the anchor crown to realize the purpose of the anchor stem being rotatable.

3. Large holding anchor

High-holding anchors combine the advantages of rod anchors and rodless anchors, and are generally rod-claw anchors. The most commonly used anchors are Martens anchors and Danfoss, which are characterized by wide and long staggered claws, deep gripping soil, and good stability, so as to obtain greater gripping force, and the grip-to-weight ratio can reach 11 to 17 times. But the anchor claw is weak and easy to deform. And because the unearthed resistance is relatively large, it is generally only suitable for engineering ships, and some are used as spare anchors or tail anchors.

4. Special anchor

Special purpose anchors commonly used for permanent moorings such as pontoons, buoys, light boats, floating docks and pontoons. There are single claw anchors, screw anchors and mushroom anchors.

Daily inspection of anchors

1. Anchor inspection

1) Check the wear and deformation of the anchor shackle, and pay attention to whether the cross pin is loose, and carry out inspection and maintenance.

2) Pay attention to whether the anchor claw is bent, whether the rotation is flexible, whether the angle is normal, and check and maintain it.

2. Anchor chain inspection

1) Usually use the left and right anchors in turn.

2) Pay attention to whether the anchor chain mark is clear, if it falls off, it should be made up in time.

3) Check whether the swivel is flexible and lubricate it in time.

3. Windlass inspection

1) Always check if the brakes are good.

2) Refuel and test drive before each use. Before the steam windlass is used, the water accumulated in the cylinder should be discharged until the steam is sprayed from the drain hole, and then test the drive.

3) The clutch is often refueled to ensure light and flexible operation.

4) Pay attention to the wear of the teeth of the sprocket and the thread of the worm.

4. Chain controller

The friction surface of the chain brake is often oiled, and the rest should be painted with anti-rust paint. Frequently check the tightness of the base-to-deck connection. The chain ejector checks the integrity of the handwheel protective cover, and the rotating parts are often refueled.

The above content is the anchor principle, function, type and daily inspection popularized by the editor of The anchor is an indispensable equipment in the operation of the ship. On ordinary ships, there are usually one anchor on the port side and one on the starboard side, plus a spare anchor to prevent the port or starboard anchor from being lost. There is an emergency backup. Special purpose ships may be equipped with more than 5 anchors, such as engineering ships, salvage ships, etc.