# Shark jaw and towing pin The Ultimate FAQ Guide

Shark jaw and towing pin, known as the hydraulic chain stopper or shark jaw. It is a chain stopper that holds the anchor chain or steel cable firmly and under bears, just like shark teeth.

It extends off the deck in working condition and retracts below the deck to be flush with the deck in non-working condition, keeping the deck clear and unobstructed.

## What is the function of Sharkjaw and towing pin?

The shark jaws is a unique device for anchor handling towing Supply vessels to support the anchor and chain line during anchoring and towing operations for the platform, reducing the friction between the anchor chain line and hull and increasing the life of the chain line.

At the same time, the guide pin system can play a limiting role in avoiding the sliding and swaying of the chain rope on the stern of the ship, improve the ship’s stability in operation and protect the safety of the seamen.

## How does the guide pin system work?

The main function of the towing pin is to guide the chain line for anchoring and towing to ensure the safety of personnel.
It is located between the shark jaws and the stern roller. The retaining pin has two individually retractable bollards.
The bollards are generally cylindrical in shape and can be raised and retracted by hydraulic cylinders.
The bollards are usually cylindrical and can be raised and retracted from the deck by hydraulic cylinders. Some of the top of the bollard has a rotatable cover (Fig. 3) to prevent the chain from crossing the bollard.

## What types of sharkjaw and guide pin anchor handling tug supply vessels?

Sharkjaw device has two forms as follow:

1) Fork type:

The shark pliers are of the same structure, cylindrical, with forked jaws at the upper end and a forked jaw at the lower end.

The upper end is a forked jaw, and the lower end is a cylinder driven.

The lower end is a cylindrical body that can be moved up and down in the cylindrical cylinder by a cylinder.

The fork opening is V-shaped and can be replaced with different clamps depending on the fork jaws are V-shaped, allowing different clamping devices to be changed for different chain or cable diameters.

2)Triplex shark jaw type:

Shark jaw with a linkage structure.

There are two flipping and retracting jaws

When flipped up the cable is held between the two jaws.

When not in use, it When not in use, the jaws are lowered to be flush with the deck.

The two jaws are separated by a top pin between the jaws lifts the sagging chain up to The top of the two jaws can be easily dismantled to remove the buckle.

## what consists of a shark jaw and guide pin?

shark jaw, towing pin, casing, hydraulic pump station, and electronic control cabinet and control panel located.

## how does the shark jaw and towing pin tug supply vessel design selection?

The selection of equipment parameters should consider the owner’s requirements for the working conditions of the vessel and cost control. The main factors to be considered are equipment Safe working load (SWL), lifting height, and the suitable chain diameter. The following are Several types of platform vessels with towing equipment Shark jaw and towing Pin Equipment parameters:

The Safe Working Load (SWL), the maximum allowable load that the shark jaw can support, is the basic performance indicator. The design of the shark jaw needs to be compatible with the functional parameters of the towing winch.

According to the China Classification Society Marine Towing Guidelines, the braking device of the towing winch should have a static holding force corresponding to 1.1 times the maximum breaking load of the towing cable to which it applies, i.e., the static holding force of the first layer of the towing winch drum is determined by the maximum breaking load of the chain cable. Therefore, the design safe working load of the shark jaw device for holding the chain cable. 

### Fork type or triplex type?

The shark jaw with fork construction is a relatively more advanced shark jaw equipment, as it is a vertical takeoff and landing, it can greatly reduce the size of the box Some ships can be equipped with four forked shark jaws at the same time.

This increases the maneuverability of the vessel in different operating conditions.

The adjustable jaws are also available in a variety of sizes. In addition, the adjustable jaws can be adapted to a wider range of diameters and sizes of chains.

However, they are more expensive and do not contribute to the cost of the vessel. cost control.

The Linkage Shark jaw is more used in domestic design designed for AHTS vessels the structure form is simpler than the forked shark jaw. However, it occupies space; generally, one vessel equips one linkage shark jaw anchor handling tug supply vessels.

### Layout

The placement of the shark jaw assembly is related to the towing winch, the location and height of the drum, and the structure of the hull compartment under the stern deck are closely related.

The layout of the shark jaw is closely related to the position and height of the towing winch drums and the cabin’s structure under the stern deck.

It should be placed on the stern of the triple-use workboat near the stern roller.

near the stern of a triple-use workboat, with sufficient below-deck

There should be sufficient space under the deck for structural reinforcement. The placement of Guide pins should be positioned appropriately close to the stern to minimize the impact of the chain on the vessel movement during operation should be minimized.

Generally, the distance between the towing pins and the center of the stern rollers is usually 3.5.5 mm.

In general, the distance between the stopper and the center of the stern roller is 3.5.5m, and the distance between the two hydraulic

The spacing between the two hydraulic pins is 1.5m.

### The lifting

The lift is the maximum working height at which the shark jaws and guide pins lift the deck.

The maximum working height of the deck. In general, the working height of the shark jaws on the deck is limited by the strength and position of the lower collection of the deck. It cannot be set too high, usually around 500mm.

The working height of the stopper pin is governed by the operating height of the towing machine. The height of the anchor roller or secondary winch must be less than that of the straightened wire rope not held in shark jaws.

However, in general, the strength is inversely proportional to the lift. The strength is inversely proportional to the lift, so a reasonable lift should be selected depending on the situation.

The lift height should be selected as appropriate.

Hydraulic pump units

The hydraulic pump station and control system of the shark jaw unit should be equipped with a separate hydraulic pump station to ensure that its operation is not affected by other equipment. The pump station should be close to the shark jaw to reduce piping.

The control system of the shark jaw needs to have the following functions.

The ability to upper and lower the left and right jaws individually.

The ability to raise and lower the left and right stop pins independently at any height.

The ability to quickly retract the stop pins and jaws in less than 1 second to avoid impact from the chain line.

A remotely controlled console should be set in the direction of the cockpit towards the transom, which can be operated visually and remotely for the shark clamp.

The support structure of shark jaws

The huge load of the shark jaw and towing pin device must be transferred to the hull structure through the housing. Therefore, the box of the shark jaw needs to be set in the strong structure area of the hull and connected with the surrounding transverse bulkhead and strong longitudinal truss. The panel of the shark clamp hull is generally a 50~60mm thick high-strength steel plate, and the butt welding with the deck surface needs to open x-shaped or U-shaped bevel deep fusion welding through. The box can be surrounded by welded structures extending to the longitudinal trusses or bulkheads to transfer the load to the hull structure.

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