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Cargo compatibility and reactivity for ships carrying dangerous chemicals in bulk

Transporting of dangerous and noxious liquid chemicals in bulk involved various risk factors. Between some chemicals violent reactions may occur if the chemicals are mixed in certain proportions. The result may possibly be an eruption and tank rupture. Such an occurrance must be prevented. Water may also have to be considered in this respect.



Leakages through bulkheads occur at times in any tanker. Normally, however, such leakages are only minor seep ages. They will not cause any violent reaction due to the great disproportion in mixture from dangerous proportions. But legislation as expressed in the IMO Chemicals Bulk Code ref (25), and in the US Coast Guard Rules ref (18) and Appendix 3 expressly prohibits the placement of inter-reactive cargoes on both sides of a bulkhead. There must be an empty tank, a cofferdam or a tank with a cargo neutral to both products in between. This requirement causes some headaches in cargo planning. "Diagonal contact'' between tanks is normally considered as sufficient separation between reactive cargoes.

More important, however, is the complete separation of piping systems so that one product cannot inadvertently be pumped into another. To this effect strategic pipe bends may have to be removed and blind flanges fitted on each pipe end. Modern chemical tankers will have blind flange valves fitted . Such a blind flange valve must have a double separation between the products with a drain in the interspace. A single blind flange is not acceptable. Remember also to separate drain lines or slop connections to avoid the possibility of cargo mixing.

The cargo inter- reactions may be of type:

a) Chemical reaction: Strong ( inorganic) acid plus alikali (or water) causes heat, e g sulphuric acid plus caustic soda or water. Therefore sulphuric acid may not be carried in tanks bordering the side shell or filled ballast tanks. Similarly sulphuric acid may react with a number of hydrocarbons except parraffines (petroleum oils). Amines ( aniline, diethylamine) may react with esters ( butyl, acetate, ethyl acetate). Caustic soda will react violently with acrolein, acrylonitrile and allyl alcohol.

b) Oxidation : An Oxygen-rich compound like propylene oxide may react with an amine (e g diethylamine) or an aldehyde (e g acetaldehyde). An ether (e g ethyl ether) may react with oxygen and from a peroxide which is an explosive hazard. The ether should be inhibited and carried in an inerted (N 2 ) tank.

c) Auto- reaction : Certain hydrocarbons compounds have a tendency to polymerize with time, accelerated by heat, light, sometimes air or other matter such as rust. Polymerization means that several molecules of the same kind binding together to bigger molecules. The compound tends to become more viscous or eventually solidify. Heat is liberated , which accelerates further polymerization.

Chemically most cargoes are monomers, which means that they, before any polymerization, consist of single molecules.


Toxic vs edible products

Toxic products must never get mixed into edible products for human or cattle feed! In this case minor seepages between tanks might prove disastrous.

IMPORTANT: Edible products should never be loaded with bulkhead to bulkhead contact with toxic cargoes! The piping systerns should be entirely segregated or provided with double blind flanges.



Related Info:

Cargo compatibility chart for handling dangerous liquid chemicals in bulk

Cargo handling safe practice for chemical products

Risk with noxious liquid cargo contact

Poisoning and required first aid treatment onboard

Determining presence of contaminants in chemical cargo

How take a sample of noxious liquid cargo ?



Recommendations

Closed loading requirement of various grade liquid chemicals and related considerations

Handling various grade liquid chemicals during loading

How to prepare a cargo loading or discharge program ?

How to avoid solidification in cargo tanks ?

Cargo line clearance requirement for chemical tankers

Cargo segregation requirement for chemical tankers

How to arrange disposal of tank cleaning waste ?

Restrictions on discharge cargo residue into sea

Retention of slops on chemical tankers

Vapour emission control requirement for chemical tankers

Handling self reactive chemicals

Handling of toxic chemical cargoes

Cargo handling safe practice for chemical products

Ship & terminal pre-loading meeting prior loading /discharging

Cargo compatibility and reactivity of various chemical cargo

Poisoning and required first aid treatment onboard

Determining presence of contaminants in chemical cargo

Checklist for handling dangerous liquid chemicals in bulk

Loading / stress computer for chemical tankers

Requirements of various grade chemical cargo heating

Cargo handling safe practice for chemical products

Ship & terminal pre-loading meeting prior loading /discharging

Cargo compatibility and reactivity of various chemical cargo

Poisoning and required first aid treatment onboard

Determining presence of contaminants in chemical cargo

Checklist for handling dangerous liquid chemicals in bulk

Loading, discharging & care of Phenol - Safety guideline

Hazards of Phenol - safe handling of Phenol on chemical tankers.

Handling benzene & methanol safety precautions

Personal protective equipments for carcinogens & cyanide-like cargoes onboard chemical tankers

Handling ACRYLONITRILE safety precautions

handling ISOCYANATES safety precautions

Loading, carrying & discharging of Sulphuric acid - regulatory requirements & special handling methods

Product characteristics & special arrangements for carrying Phenol onboard


Reference publications:

  • API/ASTM-IP Petroleum Measurement Tables
  • Vols. I, II, VII, VIII & XI/XII
  • Ship’s Ullage and/or sounding tables.
  • Ship’s “Trim and Stability Data/Manual” (Approved by Class)





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