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Safe practices when handling noxious chemical cargo -Chemical tankers procedure

Chemical tanker procedure : It is essential on chemical tankers that everyone knows his ship's safety precautions thoroughly prior handling noxious chemical cargo. Also the master/chief officer must assume responsibility for this. Guidelines listed below are for general reference, prudent mariner should also aware of ship specific limitations.

Before loading /unloading:

1. Have cargo tanks to be loaded well ventilated and checked for any toxic vapours so that tank inspection can commence without any danger or undue delay.

2. Portable (dry powder) fire extinguishers to be placed on deck ready for use. Take off covers etc and make other fire fighting equipment on deck ready.

3. Check cargo hoses to see that they have not deteriorated, that flange connections are intact, that there is an electrical bond between hose flanges and that the working pressure for the hose is marked on it. If there is any doubt about the hose's condition, find out when the hose was last pressure tested . After connection of the hose to the ship's manifold the flange should be pressure tested for tightness with air at 6-10kp/cm 2 (shore valve closed). With corrosive and toxic cargoes a protective cover should be placed over-the hose flange connection. A drip pan should also be there.

4. Establish communication routines with the terminal operators regarding flow rates, emergency stops, topping up, general alarm etc.

5. Keep unauthorized people away from the cargo deck and hoses. Check that vapour release/admittance to the cargo tanks is unobstructed (P/V valves moveable, lids opened, flame screens unclogged etc).

6. Keep hatch lids closed except when taking ullages, sampling etc.

7. See to it that everyone engaged in cargo handling is wearing the correct protective clothing (depending on whether there is danger to the skin on contact or inhalation of vapour )

8. Avoid getting the blast of vapour in your face when taking ullages during loading. Do not stand "upwind" or "downwind" of an ullage hole but stand beside it with the wind across your face.

9. Keep pump rooms ventilated with fans running during cargo transfers.

10. Keep moderate loading rate during the first phase of cargo transfer to an empty tank (not necessary with inerted tanks), particularly with petroleum products of the type kerosene, jet fuel. The liquid velocity should be kept well below I m/s in the cargo piping until the liquid covers bottom framing or about 0, 5 m above bottom. (Risk for static electric charges and incendive sparks )

11. The final ullages should not be taken before 30 min after loading is finished if conductive tape is used (when possible static electric charges are likely to have been dissipated). Non-conductive tapes to be preferred.

12. Never go down into a pump room without reporting to someone on duty when leaving and on returning.

13. Never work alone in confined spaces!

14. Have breathing apparatuses on deck ready and available when handling toxic cargoes.

15. Remember that an explosimeter only indicates the risk for explosive conditions - toxic conditions may arise at far lower concentrations than detectable by an explosimeter instrument. Use also a toxiometer for health readings.

16. Never wash and steam a tank simultaneously. Many explosions have proved this to be a dangerous combination, electric charges are a likely reason. It might be dangerous to enter a tank containing oxidizing vegetable oils (e g castor seed oil, cotton seed oil, ground nut oil, linseed oil) during the last phases of discharge. There are indications that conditions with lack of oxygen in the tank atmosphere may develop. Use a breathing mask with fresh air supply or forced ventilation.

17. Use one "half-mask" and one emergency mouthpiece with nose clamp . The maker will be able to advice on types of filters for the cargoes in question. For escape purposes a better equipment is handy air bottles with masks for short time use.

18. Air compressor for recharging of breathing air bottles (200-300 atm) should be standard equipment on chemical tankers.

It should be borne in mind that individual ship has got own characteristics and limitations may involved handling various chemical cargoes . The master and all personnel in all cases must be aware of cargo/ship information that has been given and comply with relevant safety procedures.

The following reference publications are provide useful information :

Requirements of MARPOL Annex II for chemical tankers

MARPOL Annex II contains extensive regulations about the loading, carriage and discharge of noxious liquid cargoes, as well as the treatment of cargo residues remaining on board, washing of empty tanks and the final disposal of the contaminated washing medium.

Ship shore safety guideline for handling bulk chemicals

Ships should remain adequately secured in their moorings. Alongside piers or quays, ranging of the ship should be prevented by keeping all mooring lines taut: attention should be given to the movement of the ship caused by wind, currents, tides or passing ships and the operation in progress.

Cargo pump room hazards

On tankers equipped with a cargo pump-room, this is a potentially hazardous enclosed space. Pump alarms and trips, level alarms etc. should be tested regularly, and in any case before commencing cargo handling operations, to ensure that they are functioning correctly. The results of such tests should be recorded.

Cargo hoses handling ,connection and use

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.

Cargo handling safety equipments

A breathing apparatus (compressed air type 200 atm) should be kept ready for immediate use if sudden entry into a gas-filled pump room should become necessary. Eye washing bottles available on deck and in pump rooms. Explosimeter and toximeter available.

Various stages of cargo loading operation

Commencement of loading should be slow and, before the full loading rate is used, both ship and shore must be satisfied that the lines are correctly set and that there is no leak in the system. At the start of loading, and at regular intervals throughout the process, a check should be made that cargo is not leaking anywhere.

Procedure for discharging dangerous chemical cargo at sea - various restrictions

Operation of ships transporting noxious liquid chemicals in bulk , which when accidentally released into the sea from tank cleaning or deballasting operations may pose a serious threat to marine enviroment and therefore justify the application of special anti pollution measures that need to be considered.

Restriction of radio equipments and other mobile devices in cargo working areas

During medium and high frequency radio transmissions significant energy is radiated, which can create a danger of incendive sparking by inducing an electrical potential in unearthed steelwork. The use of medium or high frequency main radio transmission equipment should therefore be prohibited in port and during ship to ship cargo transfers.

Isolation of cargo tanks and piping systems

When a single parcel of cargo is carried in several tanks served by a common pipeline system, containment within each tank depends upon the tightness of the inlet valve. Due to the pressure differential on either side during sequential loading into or discharge from such tanks, the tightness of a single valve should not be relied upon to prevent the entry or escape of cargo.

Ship shore cargo connection safe method

The connection at the manifold of hoses or metal cargo arms for cargo handling is the primary cargo connection between ship and shore, and it is essential that both parties take proper care preparing for the connection. Flange faces, gaskets and seals used at this point should be clean and in good condition. Minimum standards for hoses are laid down in the IBC Code.

Venting of cargo tanks safety procedure

Venting of cargo tanks during cargo transfer or cargo related operations must be carried out in accordance with applicable international, national, port and terminal regulations. Tank vent system outlets are located at a safe distance from all areas where personnel who are not involved in cargo work may be present, to ensure that toxic vapours are diluted to a safe level of concentration before they can reach such an area

Ship to ship transfer operation

The ship to ship (STS) transfer of cargoes carried on chemical tankers is a frequent operation, and the following section addresses some special safety aspects of the preparations and procedures that may be found necessary for STS operations.

Cargo unloading operation safety precautions

Just prior to commencing discharge the responsible officer should check that the cargo pipeline system is set correctly, that correct valves are open, that valves not being used are closed, and that the cargo venting system is appropriate for the cargo operation

Liaison between ship and shore

Operations concerning cargo handling, tank cleaning and pre-wash, ballasting and bunkering require an exchange of information between the ship and terminal before the ship arrives or after arrival.

Ship checks prior to arrival

When approaching a port to load or discharge cargo, there are important checks that be made by the ship in time to allow any necessary work to be done:

Preparing a cargo tank atmosphere

For some cargoes the IBC Code requires vapour spaces within cargo tanks to have specially controlled atmospheres, principally when the cargo is either air reactive resulting in a hazardous situation, or has a low auto-ignition temperature, or has a wide flammability range

Preparation for receiving nitrogen from shore

Care should be taken to ensure that the valves on the loading line between the shore manifold and the ship's tank are operated in the correct sequence, so that the ship is in control of the nitrogen flow. The ship should station a crew member at the loading manifold valve during the operation

Cargo care during transit

Regular checks on tank contents should be made to detect an unexpected change in liquid level. Cargoes that need cooling or heating must be monitored daily and a temperature log kept. Some cargoes are liable to self-react under certain conditions . Cargoes that may self-react should be monitored daily in order to detect any abnormal behaviour at an early stage.


Related Info

Liaison between ship and shore

Ship shore safety checklist while alongside a terminal

Cargo hoses handling ,connection and use

Checklist for handling dangerous liquid chemicals in bulk

Cargo compatibility and reactivity of various chemical cargo

Poisoning and required first aid treatment onboard

Determining presence of contaminants in chemical cargo

Chemical tanker safe mooring practice

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