Chemical tanker
A chemical tanker carries different types of liquid chemicals in bulk. The chemicals are transported under atmospheric pressure and at low temperatures (max 80°C). The size of these ships can vary between rather small ones (5.000 DWT or less) to bigger ones (over 40.000 DWT). This is considerably smaller than an average crude oil or product tanker because of the usually smaller amounts of chemical cargo and the sometimes much smaller ports where the ship loads or unloads.
The tanks are often heated either to lower the viscosity of the cargo for pumping or to prevent it from solidifying.
A chemical tanker also has relatively more and smaller tanks than an oil tanker to accommodate several different kinds of relatively small volumes of cargo at the same time. Depending on material compatibility the cargo is transported in a stainless steel tank or a tank coated, with epoxy or zinc for example. Thus, acids can be transported in a stainless steel tank, while most vegetable oils can also be carried in epoxy-coated tanks.
Because differing cargoes impose differing safety requirements, there are three different types of chemical tanks, Type I for the most dangerous chemicals, type II --for less dangerous chemicals,, and type III for relative safe chemicals, this classification being based on relative hazards to the marine environment.
The structural arrangement of a type 1 chemical tanker is made to the highest standards possible. This type of tanker is allowed to transport cargo’s that are considered to have severe environmental and safety hazards.
Figure 4 shows the requirements for the double hull that IMO has set for the type 1 chemical tankers. Type 1 ships have the largest distance between the cargo tank shell and the outer hull. The size of the tanks is also restricted; a type 1 cargo tank should not exceed 1.250 m³. A cargo tank must also be separated from fresh water tanks, the accommodation, other cargo (depending on chemical type) and the engine room.
Chemical tanker type 1
This tanker type is allowed to transport all possible cargoes. In practice, however, ships allocate space to types 2 and 3 cargoes because the offer of type 1 cargoes is too small to make a type 1 tanker profitable. Most ships have type 1 chemicals in the centre tanks and type 2 or 3 chemicals in the wing tanks. The maximum tank capacity for type 1 substances is 1.250 m3.
Chemical tanker type 2
The structural arrangement of type 2 tankers corresponds to a lower level of precaution. This type of tanker is allowed to transport cargo’s that are less dangerous. The requirements for the hull spacing of a type 2 tanker are shown in Figure 5. The maximum tank capacity for a type 2 substance is 3.000 m3.
Chemical tanker type 3
The structural arrangement of a type 3 tanker corresponds to the lowest level of precaution. The requirements for the hull spacing of a type 3 tanker are shown in Figure 6.
There is no limit to the tank capacity of a type 3 tanker.
