TRIPLEX - SHARK JAW SYSTEM.

This equipment has been installed with the objective of safe and secure handling of wire and chain and to make it possible to connect/disconnect an anchor system in a safe way.

Most vessels are provided with a double plant, - one at the starboard side and one at the port side of the aft deck.

The largest plants installed in the vessels today have an SWL of 700 tonnes and they are able to handle chains of the size of 7” or wires with diameter up to 175 mm.

Two control panels are installed in the aft part of the bridge console close to the winch operating panels. The panels are located in port side and in starboard side referring to the respective plant. The port side panel serves the port side TRIPLEX shark jaws and pins and the starboard side serves the starboard side TRIPLEX.

Before any operation of these panels it is most important that the operator has studied the manuals and made himself familiar with the functioning of the plant and that any operation complies with the navigator’s instruction. If an order has been indistinct or ambiguous the operator MUST ask for correct info to avoid any doubt or misunderstanding of the operation to take place.

This instruction of the TRIPLEX plant has been adjusted to comply with the latest layout and to describe exactly the plants as they appear in the latest and future new buildings and where the company has decided to modify the existing plants in order to comply with safety.

The layout is mainly TRIPLEX but APM has added quite some changes to the plant in order to improve and optimise the safety and reliability.

The manufacturer, TRIPLEX, has not implemented this modification as a standard version in their basic plants. The development of this modification was prepared and completed by APM based on experience.

The Danish Maritime Authorities have approved this improvement.

Operation

To oblige accidents most possible an operating procedure has been prepared.

The operator must carefully study this procedure in order to obtain and ensure full understanding of the function of the plant.

The marks welded on the links indicate whether the jaws are locked or not. The links MUST pass 180 degrees to achieve “Locked position”.

If any irregularity in this respect should occur due to e.g. wear down it will be indicated clearly, as the marks are no longer aligned.

It is as a fact ALWAYS the deck crew who make the final decision if the jaws are locked or not. As they have to convince themselves by visual check of marks and upon this turn a lever outside the crash barrier as a confirmation to the operator on the bridge. When this has been performed the jaws are to be considered “Locked”.

After the acceptance from the deck the bridge operator can not operate any part of the shark jaws.

The only option for overruling this condition is the “Emergency release”- buttons!

Emergency operation

In cases of power failure (Black Out) it is still possible to operate the shark jaws as the plant is supplied from the vessel’s emergency generator.

Should even the emergency power supply fail it is possible to release the jaws by the

“Emergency Release” system. In this case the system is powered by nitrogen loaded accumulators located in the steering gear room and from the vessel’s 24 volt battery supply. The accumulators are reloaded at each operation of the hydraulic power pack for the TRIPLEXsystem.

Maintenance and inspections

The maintenance and frequent inspection of the shark jaws system is very important and should be complied by the vessel’s programmed maintenance system, please see procedure 15, 1345:

Triplex Shark Jaw – Control Measurements (Supply Vessels).

Defects or damages are often revealed during inspections or lubrication.

Special attention should be shown to the lower part of the shark jaws – trunk. In spite of drainage from this compartment the environment is rather harsh and tough to the components located at the bottom of this area. Hydraulic hoses and fitting are constantly exposed to salt water as well as the suspension of the shark jaws components.

A procedure concerning the treatment of the hydraulic hoses and fittings has been issued, -

Densyl tape.

The shark jaws trunk is often used as “garbage bin” for various items such as mud from anchors, used rags, mussels from chains, chopped off split pins, remains of lead and much more. Due to that fact it is very important to clean this compartment frequently.

Check of “Lock”- position

It is very important to make sure that the shark jaws links are able to reach the correct position when in “Lock”- position. The links have been provided with indication marks that have to be aligned when locked and a special ruler is included in the spare parts delivered along with the equipment. This ruler is used to check that the links are well above 180o.

Ref. Chapter 1, Section 7.2.4, - drawing B-2209 section C.

Please see procedure 15, 1345: Triplex Shark Jaw – Control Measurements.

Also refer to wooden model for demonstration.

This check has to be performed frequently and should be comprised by the Programmed Maintenance System on board the vessel. If the equipment has been exposed to excessive load or at suspicion of damage check must always take place and the result entered in the maintenance log.

The shark jaws may often be exposed to strokes and blows from anchors tilting or other objects handled.

Safety

It is most important to oblige safety regulations and guide lines connected to the operation of the plant.

Ensure that all warning signs are located as per instructions - ref. Chapter 1, section 1.

If maintenance or repair work has to be performed inside the shark jaws compartment the plant MUST be secured in order not to operate the unit unintended or by accident. This includes the emergency operation as well.

To eliminate the risk of emergency release of the system the accumulators have to be discharged by opening the return flow valve to the power pack. This will ensure safe access to the shark jaws compartment.

In case repair or check is performed inside the trunk and the jaws are in upper position it must not be possible to lower the jaws as the compartment leaves no room for both the jaws and a person. This may require mechanical fastening of the jaws. (No former accidents reported).

Guide Pins / A-pins

Together with the shark jaws plant two guide pins are provided. These pins are to ensure guidance of wires and chains.

The guide pins are hydraulic operated from the power pack common with the shark jaws. The rollers on the guide pins may be manufactured as single roller or divided into two rolls.

To ensure proper operation of the guide pins it is very important that they are well greased at all time. In case the rollers are not able to rotate they will be damaged very fast and they will damage e.g. wires as well. Good maintenance and greasing is essential to ensure good and safe performance.

A central lubricating plant has been installed in the steering gear room for the greasing of both the shark jaws, guide pins and the stern roller. Daily check of this greasing unit is important to ensure sufficient lubricant in the reservoir.

Rather too much lubrication than too little.

Wire Lifter

The wire lift is located just in front of the shark jaws and is a part of the same unit. This item is used to lift a wire or chain if required in order to connect or disconnect.

Stop Pins / Quarter Pins

The stop pins are located on the “whale back” in order to prevent a wire or chain to slide over the side of the cargo rail. They function exactly as hydraulic jacks controlled from the shark jaws panel on the bridge.

The stop pins are often exposed to wear and strokes from the wires and the wear may sometimes cause need for repair. Especially the collar and bushing may require repair as a wire could have ground the bushing and created burrs which prevents the hydraulic piston from proper operation. Due to that fact it is important to frequently check the functioning of the stop pins and to ensure proper greasing. If these pins are not used for a period they easily get stuck.