" parcel chemical tankers" =
Parcel tankers are deep sea vessels equipped with compartments designed to carry shipments of various sizes. The temperature and other specifications of the compartments can be regulated according to the specific requirements of the type of liquid being transported.
And I can add that sometimes certain compartments or tanks are made of stainless steel in order to accept special cargoes which would not be suitable for lined (read: painted) tanks. Quite often "heating coils" are fitted on the bottom to regulate the temperatures indeed as Ruud described above.
Some vegetable oils and also palm oil with a certain PH degree.
For aviation fuel e.g. no stainless steel is required as the paint systems would be resistant to that.
You can understand that stainless steel tanks are extremely expensive and these are usually fitted in tankers which have longterm charters to carry a specific cargo.
Sulphurs has been transported over years ago by the Stella Duval,[Theodora Tankers now TBS] and other products as bitumen, pitch, coal-tar products, vegetable oil, phosphorus, chemical and petroleum product transportations; I\'ve sailed for them and as well for GB[Gebroeders Broere]same cargoes.;-)
When I worked on the chemical tanker Hallanger, we had 32 tanks and we could carry 12 different types of cargo. we also had 3 different types of tank coating. It was down to the piping system, we could load the 12 different types without cross contamination???