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Cargo hoses for chemical tankers - Care and maintenance

A modern cargo hose represents skilled engineering and, unless wrongly used, can be relied upon to contain the cargo. Nevertheless, it should always be treated as the weakest link in the cargo containment and transfer system, so correct handling and use of hoses is important.

Use and handling may differ from type to type of hose, or by manufacturer. The types of hoses normally encountered are either metallic, composite, PTFE (polytetrafluorethylene) or polypropylene.
A ship's own cargo hoses are frequently used on board chemical tankers, during loading and discharge of cargo at a terminal, during cargo transfers between ships and during tank cleaning. A ship should have on board appropriate manufacturers' material describing the hoses carried, and specifying any limitations in their use.

Certificates, marking and testing of cargo hoses

A ship's own cargo hoses must be tested and certified as required. The minimum requirements for the construction and testing of ships' cargo hoses are specified in the MCI Codes. All cargo hoses are required to be designed for a bursting pressure not less than 5 times the maximum pressure that the hose Will be subjected to during cargo transfer operations. New lengths of cargo hose, before being placed in service, should be tested hydrostatically at ambient temperatures to a pressure not less than IX times its specified maximum working pressure, but not more than two fifths of its bursting pressure.

A manufacturer's test certificate will provide information about the hose's construction method, its performance range and its nominal sizes. While in service, hoses should regularly be visually inspected, and they should be pressure tested at least annually. Test results should be recorded in a cargo hose condition log book.

Cargo hoses are required to be marked with their specified maximum working pressure, which should not be less than 10 bar gauge. Hoses used in the transfer of cargoes at other than ambient temperature should be marked with the applicable minimum and maximum service temperature range.

Cargo compatibility

Hoses used for the transfer of chemical liquids and vapours during cargo handling operations should be compatible with the nature and temperature of the chemical. Any limitations of the cargo properties and temperatures listed by the hose manufacturer should always be observed.

Handling, connection and use

When a hose is being moved about the ship it should always be lifted and carried. It should not be dragged over the ship's fittings such as pipework or walkways, or rolled in a manner that twists the body of the hose, nor hoisted on a crane or derrick using a single wire strop about its mid-length. Hoses should not be allowed to come into contact with hot surfaces such as steam pipes.

connecting loading arm at chemical tanker

Fig: Connecting shore loading arm to the ship’s manifold onboard a tanker.

Cargo transfer hoses may contribute to cargo contamination therefore hoses should be properly cleaned in between different cargoes.

To ensure cargo tank readiness, thorough check by senior officer must be carried out prior tendering Notice of Readiness for loading.

Cargo lines are the main concern while loading high specification cargoes. It is important that cargo lines, drains and dead ends are adequately cleaned along with the cargo tanks.

Octopus flanges (if fitted) are to be opened for additional checks and to verify the condition of the cargo lines. On completion of steaming the cargo lines, the quality of the effluent condensate at the flange will provide a good indication of the line cleanliness.

Octopus flange at chemical tanker

Fig: Octopus flange at a chemical tanker

Before connection, cargo hoses should be examined for any possible defects that may be visible inside the hose or on the outer covering. These may include signs of blistering, abrasion, flattening or evidence of leaks. Hoses with any damage should be assessed and a positive decision made on whether they can continue to be used safely. Seriously damaged or leaking hoses should not be used.

Gaskets used between hoses and at the ship's manifold should be checked for suitability before use. Flanges on both the hose and manifold should be checked for cleanliness and good condition. Bolts and nuts used should be of the correct size and material, with a bolt fitted to every hole in the flange and tightened correctly.

Cargo hose support

Fig:Cargo hose support

When in use, a cargo hose should be properly supported along its length to avoid excessive bending of the hose or its weight hanging from the manifold connection. This is especially important when significant tidal or draught variations can cause the relative heights of the ship and shore manifolds to alter a great deal, and the hose support to require frequent adjustment.

Fendering, stools or chocks can be used to provide support under the hose, particularly at the manifold and at the shipside rail. When a hose is supported from above, bridles and saddles should be used to spread the load, and may require more than one supporting point. A single wire strop should not be used to support a cargo hose near its midlength. Protection should be provided at points along the hose where chafing or rubbing could occur.

Hoses should not be subjected to pumping pressures that exceed the rated working pressure. If this happens, the hose should be replaced by another, and retested before any further use. After use, hoses should be depressurised and drained before disconnection.

Ship / shore insulation, earthing and bonding

It is essential that the cargo hose does, not provide the primary path for static electricity between the ship and the jetty, otherwise there is a possibility of a static electricity discharge at the manifold when offering up the hose for connection or when breaking the connection after the cargo transfer. The necessary electrical discontinuity should be achieved with an insulating flange or a single length of non-conducting hose in the hose string between the ship and the shore.

Storage and maintenance

After they have been used for cargo transfer, hoses should be washed out, drained and dried. They should be stored horizontally on solid supports. If hoses are stored in the open, they should be protected from direct sunlight. No attempt should be made on board to repair damaged or leaking hoses.

Related Info:

Cargo line leakage countermeasures

Checklist for handling dangerous liquid chemicals in bulk

Recommended temperature monitoring equipments onboard

Practical example of solving tank cleaning problems

Pre-cleaning /washing of cargo tanks

Risk & hazards of chemical contamination onboard

Checklist for handling dangerous liquid chemicals in bulk

Cargo compatibility and reactivity of various chemical cargo

Poisoning and required first aid treatment onboard

Chemical tanker safe mooring practice

Determining presence of contaminants in chemical cargo

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