How is the anchor chain fixed on board?
The anchor chain plays a vital role in the navigation and mooring of ships. It is a key component connecting the anchor and the ship. We often say "the ship stops at the anchor", but in fact the anchor is only the part that grips the ground. What really bears the huge pulling force of the ship is a complete set of "anchoring system", and the anchor chain is one of the most important parts of this system.
Many people may be curious: How is an anchor chain that is tens of meters or even hundreds of meters long and weighs tons per section fixed on the ship? Is it welded directly into the hull? What if the chain breaks? This article will answer you one by one from the aspects of structure, installation, fixing method, safety device, etc.
1. Overview of anchor chain: It is not a "dead chain"
First of all, we need to understand that the anchor chain does not exist alone, but is installed in the entire "anchoring equipment system". This system generally includes:
Anchor: inserted into the seabed to provide grip;
Anchor Chain: connects the anchor to the hull;
Chain Locker: storage space for the anchor chain;
Chain guide (such as rollers, chain pipes): guides the anchor chain in and out;
Windlass: controls the retraction and release of the anchor chain and provides tension;
Anchor chain brake and chain lock device: used to fix the anchor chain and prevent it from sliding.
Therefore, when we talk about "how to fix the anchor chain", we actually mean: how the ship can firmly lock the anchor chain to the hull structure while being able to release and recover it flexibly.
2. The layout structure of the anchor chain on the ship
1. Position of the anchor chain: The anchor chain is generally arranged at the bow, connecting the hull and the main anchor. The main anchor is located in the anchor holes on both sides of the bow, and the anchor chain passes through the chain hole (Hawse Pipe) on the deck and enters the chain locker inside the cabin. The chain locker is a reinforced chain storage space, generally located on the inner side of the ship's front cabin near the waterline. The anchor chain is naturally stacked in the chain locker by gravity.
2. The structure of anchor chain: A whole anchor chain is composed of multiple links, generally measured in "links". Each link is 27.5 meters long, and each link is connected by a Kenter shackle.
The following key components are also installed between specific links:
Unloading device: such as elastic connector, buffer;
Positioning device: such as chain stop wedge or block;
Color marking: Color marking is applied on the link to help the crew identify the number of links released.
3. How to "install" the anchor chain on the ship
Overview of the installation process: The anchor chain is not welded once when the ship is built, but is detachably installed on the hull through professional processes.
The main installation steps include:
① Connecting the anchor and the anchor chain:Use "anchor connector" (such as bow shackle, end shackle, etc.) to connect the anchor chain head to the anchor.
② Leading the chain into the chain pipe:The anchor chain is passed through the anchor hole → chain pipe → anchor windlass → chain compartment through lifting equipment or traction. Avoid jamming or kinking during the whole process.
③ Fix the chain tail:The tail end of the anchor chain is connected to the "chain tail fixing device" (usually the anchor chain tail lock or emergency release pin) inside the chain compartment to ensure that it will not fall off under maximum tension.
④ Debug the anchor windlass:After the anchor chain is installed, it needs to be repeatedly retracted and released through the anchor windlass to ensure that it runs smoothly and has moderate friction. This process is also very technical. Generally, when a hydraulic anchor windlass is installed on board for the first time, the manufacturer needs to send professional technicians to the ship for installation and debugging.
4. Detailed explanation of the anchor chain fixing method
The anchor chain must not only be fixed firmly, but also be able to be released quickly in an emergency. Therefore, its fixing method has both strength and operability, and is mainly divided into the following categories:
1. Chain Stopper: The anchor chain brake device is installed between the anchor windlass and the chain pipe. It is a chain clamping device that can be manually or hydraulically controlled. The function is: to take over the anchor chain tension after the anchor windlass stops working; to prevent the anchor chain from accidentally slipping out; to reduce the burden on the anchor windlass and extend its service life. Common types include wedge-type, claw-type, and hydraulic locking brakes.
2. Bitter End System: This is the last "safety". The chain tail is generally fixed to the reinforced steel plate structure in the chain compartment, using the following devices:
Slip Pin: Inserted into the chain tail connection hole, it can withstand huge pulling force;
Guillotine Release: In the event of power failure or mechanical failure, the chain tail can be released manually or pneumatically to anchor and save yourself;
Pin shaft + safety chain combination: more common in small and medium-sized ships.
3. Chain Stop Wedge: Located between the chain guide wheels at the anchor windlass, there is a wedge that can lock the anchor chain to prevent the chain from sliding during tilting or rotation.
5. Coordinated system for anchor chain retraction and fixing: Anchor Windlass
In order to make the anchor chain go up and down, it depends on the anchor windlass, the "power heart".
1. Functions of anchor winch: Anchor lifting refers to recovering anchor chain and anchor, anchor dropping refers to controlling the anchor chain to be released freely or slowly; brake refers to maintaining tension in the anchored state; manual/electric/hydraulic control is to cope with different energy consumption scenarios.
2. Precautions during operation: When dropping anchor, the anchor should be released section by section and the number of links should be recorded. When collecting anchor, ensure that the anchor chain is clean, without entanglement or wear. The anchor winch must be turned off after the brake device is locked to avoid chain slip accidents.
6.Safety and emergency mechanism of anchor chain fixing
The anchor chain system is a typical high-risk component that "concerns the safety of the entire ship". Its fixing system must have the following characteristics:
1. Double redundant design: Under normal circumstances, it is controlled by the anchor winch, and in abnormal circumstances, it is taken over by the brake, chain tail lock, etc.
2. Emergency anchoring capability: In the event of sudden power outage, engine failure, loss of control of the ship, etc., the crew can quickly cut off the chain tail and let the entire anchor chain and anchor fall freely to prevent the ship from running aground.
3. Regular inspection system: check whether the brake is flexible, check whether the chain tail pin is rusted or stuck, check the lubrication of the anchor machine and the operation of the motor.
7. Summary: Anchor chain fixing is a technical job and also a "safety"
Through this article, we can see that the anchor chain is not simply "welded" on the ship, but is fixed and released in a controlled manner through a set of complex and scientific systems. This system needs to have sufficient mechanical strength and respond quickly in an emergency. In short, the anchor chain is fixed by multiple structures such as the anchor machine, brake device and tail lock; its fixing method takes into account safety, operability and maintainability; each ship should formulate the most suitable anchor chain fixing plan according to tonnage, navigation area and frequency of use; daily inspection, maintenance and testing cannot be ignored, which is a guarantee for the safety of the entire ship.