What Is Anchor Chain

 

Anchor chain refers to a special chain that connects the anchor and the hull and transmits the anchor's grip. It is often composed of anchor end links, intermediate links and end links. According to the structure of the chain link, it can be divided into two types: the anchor chain with gear and the anchor chain without gear. The strength of the former is larger than that of the latter. According to the manufacturing method, the anchor chain can be divided into cast steel anchor chain and electric welding anchor chain. The length of the anchor chain is measured in sections, and the standard length of each anchor chain is 27.5m. The internodes are connected with connecting links or connecting shackles. Usually, the chain length of the main anchor on each side of the 10,000-ton ship is about 12 knots.

 

The main function of the anchor chain is to connect the anchor and the ship, and transmit the anchor's holding force to the hull; when anchoring, the anchor chain thrown out has a certain weight, which can exert a certain degree of external force on the ship in the water such as wind and current. Buffering effect; the anchor chain in the horizontal bottom part maintains a level force on the anchor, which is conducive to the reliable bottom grasp of the anchor. At the same time, this part of the anchor chain can also provide a part of the anchoring force due to the blocking effect of the soil.

 

Contents:

H1. What is Anchor Chain

   H2. Types of Anchor Chains

   H2. The composition of the anchor chain

       H3. Anchor chain links

       H3. Anchor link

           H4. Anchor link

           H4. End link

           H4. Middle link

   H2. Anchor chain sign

   H2. Anchor chain accessories

   H2. The function of the anchor chain

   H2. Construction Features

 

Types of anchor chains:

 

The anchor chain can be divided into two types: Stud Chain and Studless Chain according to the structure of its links. The chain link of the chain anchor chain is equipped with rungs. When the size and material are the same, the strength of the chain with the chain is larger than that of the chain without the chain. The chain link of the gearless anchor chain has no rungs and is only used for small ships. The specification stipulates that when the diameter of the anchor chain provided as required does not exceed 17mm, it can be replaced by a non-stop anchor chain with the same test load, or a steel wire rope or fiber rope with the same breaking load.

Stud Chain

Studless Chain

The anchor chain is divided into cast steel anchor chain, electric welding anchor chain and forging anchor chain according to its manufacturing method. The cast steel anchor chain has high strength, good rigidity, small deformation, wear-resisting, the crosspiece is not easy to loosen, the service life is long, and it is suitable for mass production. The disadvantage is that the process is complicated, the cost is high, and the impact resistance is poor. Electric welding anchor chain is made of round steel material that meets the requirements and is welded. It has the advantages of advanced and simple production technology, low cost and good quality. Forged anchor chain has good impact toughness, but the manufacturing process is complicated, the cost is high, and the quality is unstable.

 

At present, electric welding anchor chain has been most widely used on merchant ships. Anchor chains are almost all manufactured by flash welding, and cast anchor chains are rarely used. Except that most of the anchor chain accessories are forged parts, the forged anchor chain has been basically eliminated.

 

The steel grade of the anchor chain used for the production of the anchor chain is divided into three grades: M1, M2, and M3 for electric welding, and two grades for cast steel anchor chain, M2 and M3. Add A (such as AM2) before the corresponding code to indicate a gear chain, and B to indicate a gearless chain (with two levels of BM1 and BM2). The higher the steel grade, the greater the tensile strength. AM1 grade anchor chain steel is killed steel, AM2, AM3 grade anchor chain steel is fully killed and fine-grained steel. For the same ship, if steel with high strength is used, the size of the chain link can be appropriately reduced.

 

The composition of the anchor chain:

 

A complete anchor chain is firstly composed of many anchor chain links connected to each other to form a certain length of anchor chain links, and then several anchor chain links are connected by connecting links or connecting shackles to form the entire anchor chain.

 

Anchor chain links:

 

The chain link (Chain Link) in the anchor chain includes the common link (Common Link, C), the enlarged link (Enlarged Link, EL), the end link (Open End Link, E), the swivel (Swivel, SW), the end Shackle (D Type End Shackle, ES), connecting link (KS) or connecting shackle (JS) and so on. The size of each link is represented by the diameter of the round steel of the link.

 

Chain Link Type



Ordinary links are the most numerous links in the anchor chain, and are standard links that characterize the size and strength of the anchor chain. The size of the anchor chain is represented by the chain diameter (Chain Diameter, mm), and the chain diameter (d) is the diameter of the ordinary link in the corresponding anchor chain. The size ratio of ordinary chain links with gears is: diameter d, width 3.6d, length 6d. The enlarged link mainly plays the role of size transition in the anchor chain, and its size is increased by 10% compared with the ordinary link in the corresponding anchor chain. The end link is an enlarged open link in the anchor chain, which is used to match the connection of other links and play a role in size transition, and its diameter is 1.2d.


Detachable Joining Link or Detachable Joining Shackle is used to connect the front and rear anchor chains. The connecting link is a detachable link, there are two forms: one is the Kent type (Joining Link Kenter-type), also known as double half type or Kenter Shackle (Kenter Shackle, KS), The diameter is d, the length is 6d, and the width is 4.2d. It is a kind of link specified by our country's norms and national standards; the other is a C-shaped (Joining Link C-type, also known as a loose type). Since the diameter of the connecting link is the same as that of the ordinary link, it can be directly connected with the ordinary link. When assembling the connecting chain, clean all parts, apply butter to prevent rust, connect the two sides of the anchor chain and assemble, insert the tapered pin (TaperPin) into the pin hole, and use the anchor chain to punch and fix it. The pores are sealed with a Lead Plug.



Detachable Joining Shackle Type


Joining Shackle (JS) is a detachable D-shaped shackle. In order to ensure the connection strength, the diameter of the connecting shackle is increased to 1.3d, then both sides of the shackle are connected to the end chain ring in sequence, the chain ring is enlarged, and then the ordinary chain ring is connected to ensure a smooth transition of size. The end shackle is directly connected with the anchor shackle at the front end of the anchor chain, with a diameter of 1.4d.


The horizontal pin of each D-shaped shackle in the anchor chain is generally an approximate elliptical cylinder without thread. As shown in below image, the horizontal pin is fixed with a conical pin perpendicular to the shackle plane, and the pin is sealed with a lead block.



Joining Shackle Drawing File



Anchor link:


The length of the anchor chain is measured in "Length or Shackle". my country stipulates that the standard length of each anchor chain is 27.5m, and there are also 25m sections in practice. In countries that use the imperial system, 15 fathoms are used as a section, and the public limit is 27.5m. A complete anchor chain consists of three types of links: anchor end link, middle link and end link. Except for links with swivel rings, the number of links in each anchor chain should be an odd number to ensure that the connecting links or connecting shackles can lie flat in the sockets of the sprocket when passing through the windlass sprocket. successfully passed.


  1. Anchor link


At the front end of the anchor chain, the section of the anchor chain whose ES is directly connected to the anchor shackle of the first anchor is the first section of the anchor chain. In addition to ordinary chain links, there are generally anchor chain accessories such as end shackles, end chain rings, enlarged chain rings and swivel rings, as shown in Figure 5 (a). In order to facilitate maintenance, these accessories are often composed of a detachable anchor chain segment, called a swivel set, which is connected to the chain link body through a connecting link (or shackle). There are various forms of link matching of the chain link group, and a typical form is shown in Figure 5(b). The opening direction of the end shackle can be determined according to the user's requirements, most of which are in the same direction as the anchor shackle (towards the anchor) to reduce the wear and blockage between it and the lower anchor lip when the anchor is lifted.


According to regulations, the anchor chain should be provided with a swivel at one end of the connecting anchor. The purpose of setting the swivel is to prevent excessive twisting of the anchor chain when mooring. The ring pin of the swivel should face the middle link to reduce friction and jamming. The ring bolt and its body should be on the same centerline and can rotate freely. A new type of connection accessory, Swivel Shackle (SW.S), is also often used now. One is Type A, which is directly installed on the anchor to replace the anchor shackle. The other is Type B, which is located at the end of the anchor chain to replace the end shackle and is connected with the anchor shackle. After the swivel shackle is provided, the anchor end chain link may not be provided with a swivel and an end shackle, as shown in image below.



Anchor link type



  1. End link


The end link is the last link of the anchor chain and is connected to the anchor dropper. Under normal circumstances, the end link is not equipped with a swivel, and the end link is connected to the anchor abandoner, and its matching form is shown in Figure 6. In order to be able to use the two ends of the anchor chain in a planned way, the chain ring configuration form basically the same as that of the anchor chain link can also be used, with a swivel ring, but no end shackle, at this time, the ring bolt of the swivel ring should also face Intermediate link.


end link drawing


  1. Middle link


The middle links are the anchor links between the anchor end links and the end links, as shown in below.


middle link drawing

If the middle links are connected by connecting links, all the links are ordinary links. If a link shackle is used, the open part of the link shackle should face inboard. China national standards stipulate that the sections of the anchor chain with gears are connected by Kent shackles, and the sections of the anchor chain without gears are connected by connecting shackles. The enlarged chain link of the gearless anchor chain is a gearless ring that is one gear larger than the ordinary chain link.


Anchor chain sign:


The anchor chain mark is a mark that represents the number of anchor chain links painted on the connecting link (or connecting shackle) and its adjacent links. It is used to know and master the length of the anchor chain outside the ship or in the water in time when the anchor is dropped and lifted.

The anchor chain connected by connecting links is usually marked with the following methods (as shown in below):


connecting link drawing


Indicates the first section: wrap the metal wire (or white steel ring) on ​​the rungs of the first chain link before and after the connecting link between the first and second sections, and apply white waterline paint on the two links to connect Chain links painted in red.


Indicates the second link: wrap the metal wire (or white steel ring) on ​​the rungs of the second link before and after the connecting link between the second and third link, and on all the links between the two links Painted white waterline paint, connecting links painted red.


Section signs representing sections three to five and so on.


Starting from the sixth section, repeat the method from the first section to the fifth section to mark.


The last one or two sections can be marked with red or yellow paint as a hazard warning that the anchor chain will loosen to the end, so as to guard against losing the anchor. In order to be used as a sign to know that the anchor has entered the hawse drum and has been twisted into position when the anchor is twisted, white paint is generally applied to several chain links corresponding to the sprocket or chain stopper when the anchor is twisted into position.


Anchor chain accessories:


Kent shackles, connecting shackles, A-swivel shackles, B-swivel shackles, end shackles, swivels!


Anchor chain accessories:



The function of the anchor chain:


The main function of the anchor is to fix and stabilize the ship. From the following aspects:


  1. For the anchor chain to work, the most basic condition is to hook things 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 lose the anchor during the anchoring period, because the main engine is usually stopped when the ship is anchored. If you start the ship immediately, it will take time. dangerous. Therefore, there is the concept of anchorage. Anchorage, the implication, is relatively rough under the sea, and in addition, it must be able to shelter from the wind.
  2. The weight of the anchor chain is negligible for the ship, and that little friction will not play a big role. Generally speaking, when the ship is anchored, the anchor chain is straight, which is basically the effect of friction. If you are by the sea, you will find a lot of small fishing boats, their anchor chains are thick ropes.
  3. Viewed from the top of the ship, the anchor chain is straight, but there is a section under water that is close to parallel with the seabed (in fact, it is close to the seabed). The anchor provides the grip, and then transmits it to the ship through the anchor chain to resist the influence of the external load of the current, wind and waves on the positioning. The reason why there is a section close to the seabed is to consider the influence of the force. Think about it, an anchor, the anchor chain is straight and easy to pull the anchor. And there is a section close to the bottom of the sea, which can provide a margin within a certain range.


Construction Features:


The anchor chain is made up of many chain links, and the size is expressed in terms of chain diameter (mm). According to whether there is a brace in the middle of the chain ring, it is divided into an anchor chain with a file and an anchor chain without a file. The anchor chain can be made by forging, casting and welding. The marine anchor chain is composed of several "sections" (shackle), each section is 25.0-27.5 meters long, and the sections are connected by links or shackles. After the anchor is hoisted, the chain is stored in the chain locker at the bow. The specifications of the anchor chain are determined according to the ship construction standards.