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A chemical tanker is a type of
tanker ship designed to transport
chemical
A chemical substance is a form of matter having constant chemical composition and characteristic properties. Some references add that chemical substance cannot be separated into its constituent elements by physical separation methods, i.e., w ...
s in bulk. As defined in
MARPOL
The International Convention for the Prevention of Pollution from Ships, 1973 as modified by the Protocol of 1978, or "MARPOL 73/78" is one of the most important international marine environmental conventions. MARPOL 73/78, MARPOL is an amalg ...
Annex II, chemical tanker means a ship constructed or adapted for carrying in bulk any liquid product listed in chapter 17 of the
International Bulk Chemical Code.
[ ARPOL Annex II, Chapter I, Regulation 1/ref> As well as industrial chemicals and clean petroleum products, such ships also often carry other types of sensitive cargo which require a high standard of tank cleaning, such as palm oil, vegetable oils, ]tallow
Tallow is a rendered form of beef or mutton fat, primarily made up of triglycerides.
In industry, tallow is not strictly defined as beef or mutton fat. In this context, tallow is animal fat that conforms to certain technical criteria, includ ...
, caustic soda
Sodium hydroxide, also known as lye and caustic soda, is an inorganic compound with the formula NaOH. It is a white solid ionic compound consisting of sodium cations and hydroxide anions .
Sodium hydroxide is a highly caustic base and alkali ...
, and methanol.
Oceangoing chemical tankers range from to 35,000 DWT in size, which is smaller than the average size of other tanker types due to the specialized nature of their cargo and the size restrictions of the port terminals where they call to load and discharge.
Chemical tankers normally have a series of separate cargo tanks which are either coated with specialized coatings such as phenolic epoxy or zinc paint, or made from stainless steel. The coating or cargo tank material determines what types of cargo a particular tank can carry: stainless steel tanks are required for aggressive acid cargoes such as sulfuric and phosphoric acid
Phosphoric acid (orthophosphoric acid, monophosphoric acid or phosphoric(V) acid) is a colorless, odorless phosphorus-containing solid, and inorganic compound with the chemical formula . It is commonly encountered as an 85% aqueous solution, w ...
, while 'easier' cargoes — such as vegetable oil — can be carried in epoxy
Epoxy is the family of basic components or cured end products of epoxy resins. Epoxy resins, also known as polyepoxides, are a class of reactive prepolymers and polymers which contain epoxide groups. The epoxide functional group is also coll ...
coated tanks. The coating or tank material also influences how quickly tanks can be cleaned. Typically, ships with stainless steel tanks can carry a wider range of cargoes and can clean more quickly between one cargo and another, which justifies the additional cost of their construction.
Classification
In general, ships carrying chemicals in bulk are classed into three types:
Type 1
Tankers intended to transport products with very serious environmental and safety hazards requiring maximum preventive measures to prevent any leakage of cargo.
Type 2
Tankers intended to transport products with appreciably severe environmental and safety hazards requiring significant preventive measures to preclude an escape of such cargo.
Type 3
Tankers intended to transport products with sufficiently severe environmental and safety hazards to require a moderate degree of containment to increase survival capability in a damaged condition.[ BC Code, Chapter 2, 2.1 General/ref> Most chemical tankers are IMO 2 and 3 rated, since the volume of IMO 1 cargoes is very limited.
]
Main characteristics of chemical tankers
Chemical tankers often have a system for tank heating in order to maintain the viscosity
The viscosity of a fluid is a measure of its resistance to deformation at a given rate. For liquids, it corresponds to the informal concept of "thickness": for example, syrup has a higher viscosity than water.
Viscosity quantifies the inte ...
of certain cargoes, typically by passing pressurized steam through stainless steel 'heating coils' in the cargo tanks. These coils circulate fluid in the tank by convection, transferring heat to the cargo. All modern chemical tankers feature a double-hull construction. And most have one hydraulically driven and submerged cargo pump for each tank with independent piping, which means that each tank can load separate cargo without them being mixed. Consequently, many ocean going chemical tankers may carry numerous different grades of cargo on a single voyage, often loading and discharging these "parcels" at different ports or terminals. This means that the scheduling, stowage planning and operation of such ships requires a high level of coordination and specialist knowledge, both at sea and on shore.
Tank cleaning after discharging cargo is a very important aspect of chemical tanker operations, because cargo residue can adversely affect the purity of the next cargo being loaded. Before tanks are cleaned, they must be properly ventilated and checked to be free of potentially toxic or explosive gases. Chemical tankers usually have transverse stiffeners on deck rather than inside the cargo tanks, in order to make the tank walls smooth and thus easier to clean using permanently fitted tank cleaning machines. Cargo tanks, either empty or filled, are normally protected against explosion by inert gas
An inert gas is a gas that does not readily undergo chemical reactions with other chemical substances and therefore does not readily form chemical compounds. The noble gases often do not react with many substances and were historically referred to ...
blankets. Nitrogen is often used as inert gas, supplied either from portable gas bottles or a Nitrogen generator.
Currently, the latest chemical tankers are built by shipbuilders in Japan, Korea or China, where the large majority of stainless steel chemical tankers are built, as welding stainless steel to the accuracy required for cargo tank construction is a difficult skill to acquire. Nations with minor builders include Turkey, Italy, Germany and Poland.
Notable major chemical tanker operators include Stolt-Nielsen
Stolt-Nielsen Limited (SNL) provides transportation and storage for liquids, notably specialty and bulk liquid chemicals. It also has an aquaculture division that grows turbot and other fish and fish products.
Founded in 1959, corporate services ...
, Odfjell
Odfjell SE is a company specialising in worldwide seaborne transportation and storage of chemicals and other speciality bulk liquids. The Odfjell fleet comprises more than 80 ships in total. The ships transport around 600 different kinds of l ...
, Navig8 and Mitsui O.S.K. Lines
Mitsui O.S.K. Lines ( ja, 株式会社商船三井, Kabushiki-gaisha Shōsen Mitsui; abbreviated MOL) is a Japanese transport company headquartered in Toranomon, Minato, Tokyo, Japan. It is one of the largest shipping companies in the world.
...
(MOL) chemical tankers, ASM. Charterers or the end users of the ships include oil majors, industrial consumers, commodity traders and specialist chemical companies.
See also
* Ship transport
Maritime transport (or ocean transport) and hydraulic effluvial transport, or more generally waterborne transport, is the transport of people ( passengers) or goods (cargo) via waterways. Freight transport by sea has been widely used throu ...
* List of tankers
This is a list of tankers. The list includes merchant tankers as well as naval tankers that do not fall into more specialized lists such as List of replenishment ships of the Royal Fleet Auxiliary and List of Type T2 Tanker names.
*Former ...
References
External links
IBC Code
Chemical tanker Companies
{{DEFAULTSORT:Chemical Tanker
Ship types