A chemical tanker is a type of tanker ship designed to transport chemicals in bulk. As defined in MARPOL 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.[1] 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, caustic soda, and methanol.
Oceangoing chemical tankers range from 5,000 tonnes deadweight (DWT) 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, while 'easier' cargoes — such as vegetable oil — can be carried in epoxy 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.
Oceangoing chemical tankers range from 5,000 tonnes deadweight (DWT) 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, while 'easier' cargoes — such as vegetable oil — can be carried in epoxy 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
Type 1 ship is a chemical tanker intended to transport Chapter 17 of the IBC Code products with very severe environmental and safety hazards which require maximum preventive measures to preclude an escape of such cargo.Accordingly, a type 1 ship should survive the most severe standard of damage stability and its cargo tanks should be located at the maximum prescribed distance onboard from the shell plating.
The quantity of cargo required to be carried in ship < 1,250 m3 in any one tank.
Tank locations :
Cargo tanks shall be located at the following distances inboard – MEAN OF DOUBLE BOTTOM HEIGHT TO THE BASE LINE OR MOULDED LINE (ABOVE THE BOTTOM PLATE).
From the side shell plating, not less than the transverse extent of damage (B/5 or 11.5m whichever is less), and from the moulded line of the bottom shell plating at centerline, not less than the vertical extent of damage (B/15 or 6 m whichever is less), and nowhere less than 760 mm from the shell plating. This requirement does not apply to the tanks for diluted slops arising from tank washing.
Type 2
Type 2 ship is a chemical tanker intended to transport Chapter 17 of the IBC Code products with appreciably severe environmental and safety hazards which require significant preventive measures to preclude an escape of such cargo.The quantity of cargo required to be carried in ship < 3,000 m3 in any one tank.
Tank locations :
Cargo tanks shall be located at the following distances inboard – MEAN OF DOUBLE BOTTOM HEIGHT TO THE BASE LINE OR MOULDED LINE (ABOVE THE BOTTOM PLATE).
From the moulded line of the bottom shell plating at centerline, not less than the vertical extent of damage ( B/15 or 6m whichever is less), and nowhere less than 760 mm from the shell plating. This requirement does not apply to the tanks for diluted slops arising from tank washing.
Type 3
Type 3 ship is a chemical tanker intended to transport Chapter 17 of the IBC Code products with sufficiently severe environmental and safety hazards which require a moderate degree of containment to increase survival capability in a damaged condition.[2] Most chemical tankers are IMO 2 and 3 rated, since the volume of IMO 1 cargoes is very limited.There is no filling restriction for chemicals assigned to Ship Type 3 Cargo Tank.
Tank locations :
Cargo tanks shall be located at the following distances inboard – MEAN OF DOUBLE BOTTOM HEIGHT TO THE BASE LINE OR MOULDED LINE (ABOVE THE BOTTOM PLATE).
No requirement
Hazards of carrying noxious liquid chemicals at sea
Toxicity is the ability of a substance, when inhaled, ingested, or absorbed by the skin, to cause damage to living tissue, impairment of the central nervous system, severe illness or, in extreme cases, death. The amounts of exposure required to produce these results vary widely with the nature of the substance and the duration of exposure to it. ....
Vapour given off by a flammable liquid will burn when ignited provided it is mixed with certain proportions of air, or more accurately with the oxygen in air. But if there is too little or too much vapour compared to the air, so that the vapour-and-air mixture is either too lean or too rich, it will not burn. ....
Self-reaction: The most common form of self-reaction is polymerisation. Polymerisation generally results in the conversion of gases or liquids into viscous liquids or solids. It may be a slow, natural process which only degrades the product without posing any safety hazards to the ship or the crew, or it may be a rapid, exothermic reaction evolving large amounts of heat and gases. .....
Acids, anhydrides and alkalis are among the most commonly carried corrosive substances. They can rapidly destroy human tissue and cause irreparable damage. They can also corrode normal ship construction materials, and create a safety hazard for a ship.....
The poison is a very toxic substance which when absorbed into the human body by ingestion, skin absorption, or inhalation produces a serious or fatal effect. Poison may enter the human body orally, by inhalation, or by skin contact. After being absorbed by the body it may affect certain organs or give a general poisonous effect. Lately the cancerogene effects of some industrial chemicals have been noticed. This has led to significant reductions of hereto accepted TLV- values in many countries.
Additional precautions for specific cargoes are necessary and should also be incorporated in the ship’s cargo handling procedures....
The consequences of a chemical tanker ranging along a jetty or breaking away from a berth could be disastrous, especially during a cargo transfer involving multiple different chemicals. Correct and sufficient mooring is therefore of the utmost importance.
If an unauthorised craft comes alongside or operates in an area which may create a danger, it should be reported to the port authority and, if necessary, cargo transfer operations should cease. .....
During cold weather, precautions should be taken to prevent equipment and systems from freezing. Attention should be given to pneumatic valves and control systems, fire lines and hydrants, steam driven equipment, cargo heating systems, pressure/vacuum valves etc......
During medium and high frequency radio transmissions significant energy is radiated, which can create a danger of incendive sparking by inducing an electrical potential in unearthed steelwork.
Improper closing and sealing of cargo tank hatches can be a major cause of cargo contamination. A properly closed and sealed tank hatch/opening will prevent sea water ingress and maintain a positive pressure Nitrogen blanket in the ullage space. ....
Emergency towing-off wires ( fire wires) ,Ship’s readiness to move Deckhouses and superstructures safety precautions .....
Static electricity is generated by friction that occurs between different materials during relative motion. Electrostatic charges can then accumulate in materials which are poor conductors of electricity or which are good conductors but are insulated.....
On chemical tankers the entry of personnel into cargo tanks is a more common practice than on oil tankers as a result of the requirement for inspections between grades etc; despite this, it is essential that the necessary checks are conscientiously made and recorded prior to entry in order to ensure the safety of personnel, enclosed space rescue equipment must be made ready for immediate use.
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