Oil and chemical tankers: the English of the ship

Words you will use every day (28)

Cargo tank

A tank built into the hull for carrying the liquid cargo. Numbered from forward: No. 1 port, No. 1 starboard, No. 1 centre.

Slop tank

A tank that receives tank washings, dirty ballast and residues so that they are not pumped into the sea.

Ullage

The empty space measured from the top of the tank down to the liquid. Tankers usually measure ullage, not depth of liquid.

Sounding (innage)

The depth of liquid measured from the bottom of the tank. Ullage plus sounding equals the tank height.

Manifold

The row of pipe ends and valves on deck, amidships, where the shore hoses or loading arms are connected.

Drip tray

The tray under the manifold that catches drips when hoses are connected or disconnected; it must be plugged and empty.

Cargo pump

The pump that discharges the cargo ashore: centrifugal pumps in the pump room, or deepwell pumps in each tank on product and chemical tankers.

Pump room

The space below deck that houses the cargo pumps; an enclosed space with its own ventilation and gas detection.

Stripping

Draining the last of the cargo from the tank bottom and the lines with a small pump or an eductor.

Crude oil washing (COW)

Washing the cargo tanks with the crude oil cargo itself during discharge, so that sediments go ashore with the cargo.

Inert gas system (IGS)

The plant that fills the cargo tanks with gas low in oxygen (flue gas or from a generator) so that the vapour cannot burn.

Oxygen content

The percentage of oxygen in the tank atmosphere. Below 8 per cent the mixture cannot explode; entry needs 21 per cent.

P/V valve

Pressure/vacuum valve on each tank: lets excess pressure out and air in, so the tank is neither over-pressured nor collapsed.

Vapour return line

The line that carries cargo vapour from the tank back to the shore during loading, instead of venting it to the air.

Closed loading

Loading with all tank openings closed; ullages and samples are taken through vapour-locked fittings.

Ship-shore safety checklist

The list of checks agreed and signed by ship and terminal before cargo operations start; from the ISGOTT guide.

Loading rate

How fast the cargo comes on board, in cubic metres or tonnes per hour; it is reduced when topping off.

Topping off

Filling the last part of a tank slowly to the planned ullage without overflowing.

Segregated ballast tank (SBT)

A ballast tank with its own piping, never used for cargo, so ballast water stays clean.

Oil Record Book

The MARPOL log where every cargo, ballast and residue operation is recorded and signed.

Flash point

The lowest temperature at which a liquid gives off enough vapour to ignite. Below 60 degrees C the cargo is "volatile".

Gas-freeing

Ventilating a tank with fresh air until it is safe to enter and safe for hot work.

Bonding

Connecting metal parts electrically so that static electricity cannot spark. On the cargo connection it is done separately on each side of the insulating flange, and that flange is never bridged.

Emergency shutdown (ESD)

The button or signal that stops cargo transfer at once, on the ship and at the terminal.

Vetting inspection

An inspection by an oil major (through the SIRE system) that decides whether the tanker may carry their cargo.

Pre-wash

On chemical tankers, the mandatory washing of a tank after certain cargoes, with the washings discharged ashore.

Cargo compatibility

Whether two chemical cargoes may be carried in adjacent tanks or through the same lines; the IBC Code and the compatibility chart decide.

Hydrocarbon gas

The vapour given off by oil cargo, measured with a gas detector in per cent of the lower flammable limit.

Ten things you will hear

1. Commence loading at a rate of five hundred cubic metres per hour.Cargo control room to the terminal, start of loading.
2. Stop cargo. Stop cargo. Stop cargo.Emergency stop, said three times on the radio; everybody stops.
3. Topping off number three port, reduce the rate to two hundred.Chief Officer to the terminal when the tank is nearly full.
4. Ullage in number two starboard is one decimal five metres.Deck watch reporting a tank to the cargo control room.
5. Inert gas pressure eight hundred millimetres, oxygen four per cent.Engine or cargo watch reporting the IGS readings.
6. Vapour return line connected and open, ready to load.Manifold watch confirming to the CCR before loading starts.
7. Close the manifold valve and drain the line before disconnecting.Chief Officer to the deck crew at the end of discharge.
8. Watch the drip tray, there is a small leak at the flange.Deck watch to the pumpman; tighten the bolts, keep the tray drained.
9. The tank is gas-free, oxygen twenty-one per cent, no hydrocarbons, permit issued.Before tank entry or hot work.
10. Vetting inspector on board at zero nine hundred, all records ready.Master to the crew before a SIRE inspection.

Numbers are said digit by digit on board: "one decimal five", "channel one six", "zero seven three zero". Train your ear in listening practice.

Safety on oil and chemical tankers

• No naked lights, no smoking, no mobile phones in the cargo area. The cargo area is a hazardous zone by definition.
• The inert gas system keeps the cargo tank atmosphere below 8 per cent oxygen; a tank is entered only when it is gas-free at 21 per cent oxygen, with a permit and a standby person.
• Static electricity ignites vapour. The ship-shore cargo connection is broken electrically, by an insulating flange or one length of non-conducting hose, so that stray current cannot spark there, and metal gauging equipment does not go into a non-inerted tank for 30 minutes after loading.
• The ship-shore safety checklist is completed and signed before cargo work starts, and repeated during the operation.
• The emergency shutdown and the ship-shore communication (radio or link) are tested before the first valve is opened.
• Chemical cargoes need cargo-specific PPE: chemical suit, gloves, face protection; the safety shower and eyewash at the manifold must work.
• SOPEP equipment and scupper plugs are in place during any oil transfer; a spill on deck is contained first, reported second.

What recruitment tests ask

• The oxygen limit for an inerted tank (below 8 per cent) and for entry (21 per cent).
• What the P/V valve, the vapour return line and closed loading are for.
• Ullage against sounding, and how figures are read over the radio.
• MARPOL Annex I: the Oil Record Book, slop tanks, segregated ballast, when oily water may be discharged.
• The ship-shore safety checklist, static electricity and the insulating flange, ESD.

Sit the tanker knowledge test: 30 questions for your rank

The full test mixes up to eight questions on oil and chemical tankers with the STCW areas for your rank group, under a 30-minute clock. The names of commercial tests are used on this site only to describe what our training prepares you for.

Quiz: 10 questions on oil and chemical tankers