Sea cargo reference
Chemical Tankers
A pump and a line for each tank. The notes below cover the cargo, the way the hull is arranged, and the limit that puts a ship in this class.
- Ship's gear
- Self-discharging, often with one pump per tank
- How capacity is counted
- Deadweight tonnes (DWT)
- Usual size
- Commonly 5,000-50,000 DWT
- Cargo type
- Bulk liquid chemicals
Chemical tankers
These are the most demanding tankers. They carry bulk liquid chemicals, many of them corrosive, toxic or reactive.
Tanks are stainless steel or specially coated. Each tank usually has its own pump and pipeline, so cargoes never share a line. One ship may carry twenty or more parcels, each with its own handling and compatibility rules.
They trade under the IMO IBC Code, which classes the ship by the hazard of the cargo it may carry. Washing between cargoes is exacting, and the previous cargo history decides what may be loaded next.
Cargo on board
How the hull is arranged
- The IBC Code sorts these ships into three types by the hazard of the cargo. Type 1 is for the greatest hazard. It must meet the hardest damage standard, and its tanks sit furthest inboard from the shell. Type 2 covers cargo that is appreciably hazardous and needs strong preventive measures. Type 3 covers a lesser hazard and needs a moderate degree of containment.
- Tanks are stainless steel or coated, so the cargo cannot react with the tank wall.
- A double hull keeps cargo tanks off the sea, with ballast space on the sides and bottom. MARPOL requires this on oil tankers.
- The cargo sits in several tanks. Longitudinal and transverse bulkheads limit how far the liquid can slosh.
- An inert gas system holds the tank atmosphere below the oxygen level at which the vapour could catch fire.
- Cargo pumps and a fixed pipeline meet a manifold amidships, so the ship pumps its own cargo ashore.
- Tanks for cargo that must stay warm enough to pump carry heating coils.
Why this trade uses it
- Large volumes of liquid move with no packaging.
- The ship pumps itself out, so a terminal needs pipes and tanks rather than heavy cranes.
- Separate tanks let several grades travel on one voyage without mixing.
Settle these points before you fix
- Washing tanks between cargoes costs time and money. What the ship carried last decides what it may load next.
- Oil majors vet ships on top of class and flag rules, and that vetting decides who will take the ship.
- Pollution liability is heavy. Ship and terminal both follow strict transfer rules.