Transporting of dangerous and noxious liquid chemicals in bulk involved various risk factors. Chemical cargoes can be very dangerous, most of them being flammable and/or toxic, some of them extremely so. 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.

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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:

1. Edible oils Heating Instructions
   Heating instructions should also be detailed, and these should state the in-transit temperature, loading/ discharging temperature and the allowed daily rate of increase of temperature. Rapid heating of certain grades can cause scorching of the cargo, and overheating the cargo can promote oxidation, hydrolysis, scorching and discoloration of the cargo. Rapid heating can also cause an increase in FFA content, which causes the load to turn sour, and is used as a measure of cargo quality, especially for palm oil.


2. What is putrefaction process of liquid chemicals ?
   Most animal and vegetable oils undergo decomposition over time, a natural process known as putrefaction (going off), that generates obnoxious and toxic vapours and depletes the oxygen in the tank. Tanks that have contained such products must be carefully ventilated and the atmosphere tested prior to tank entry . .....


3. Carriage of inhibited flammable chemical products in cargo tanks
   In certain conditions of heat, pressure and in the presence of Oxygen, some chemical cargo types can become viscous and possibly solid and dense in nature. This self reaction can cause some cargoes , especially in the presence of high temperatures and Oxygen, to begin an exothermic reaction, becoming self heating and rapidly expanding which may result in possibly disastrous consequences for the vessel.


4. Cargo sampling safety precautions
   Cargo samples are evidence of the condition of the product during the various phases of transport (storage at terminal, arriving on board, loading, passage, discharging). This procedure describes sample-taking procedures and the legal background. Suitable PPE is to be worn when taking samples. Sample bottle to be flushed prior collecting sample. .....


5. Cargo segregation requirement for chemical tankers
   In the case of two or more liquid chemical cargoes which react with one another in a hazardous manner, segregation must be done The product data sheets, together with the BCH/IBC Codes are to be studies carefully to determine the compatibility restrictions when carrying different groups of cargoes.


6. How to avoid solidification in cargo tanks ?
   Solidification in the cargo tanks can occur when solidifying cargoes are stowed adjacent to “cold cargoes” or cold ballast water in adjacent spaces. Tank bottoms must therefore always be checked for hard factions especially when carrying vegetable and animal oils, at regular intervals throughout the voyage and always prior to arrival in the discharge port.


7. Cargo compatibility and reactivity of various chemical cargo
   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.


8. Determining presence of contaminants in chemical cargo
   To maintain product quality onboard modern chemical tankers any contaminants in the cargo need to be observed. Following guideline may be useful determining various product contaminants in noxious liquid chemicals.


9. Ship shore cargo connection safe method
   The connection at the manifold of hoses or metal cargo arms for cargo handling is the primary cargo connection between ship and shore, and it is essential that both parties take proper care preparing for the connection. Flange faces, gaskets and seals used at this point should be clean and in good condition. Minimum standards for hoses are laid down in the IBC Code. The hoses should be in good condition and installed with gaskets which are suitable for the chemical product to be handled.


10. Venting of cargo tanks safety procedure
    Cargo tanks of a chemical tanker are required to be provided with venting systems to prevent both over and under pressurisation of the tank. Two types of venting system are specified by the Code, namely “open” and “controlled”.


11. Ship to ship transfer operation
    The ship to ship (STS) transfer of cargoes carried on chemical tankers is a frequent operation, and the following article addresses some special safety aspects of the preparations and procedures that may be found necessary for STS operations.


12. Ship shore safety checklist while alongside a terminal
    Due regard should be given to the need for adequate fendering arrangements. Ships should remain adequately secured in their moorings. Alongside piers or quays, ranging of the ship should be prevented by keeping all mooring lines taut: attention should be given to the movement of the ship caused by wind, currents, tides or passing ships and the operation in progress. Wire ropes and fibre ropes should not be used together in the same direction (i.e. breasts, springs, head or stern) because of the difference in their elastic properties.


13. Cargo compatibility chart for handling dangerous liquid chemicals in bulk
    Determine the group numbers of the two cargoes by referring to the alphabetical listing of cargoes and the corresponding groups. Many cargoes are listed under their parent names: unless otherwise indicated, isomers or mixtures of isomers of a particular cargo are assigned to the same group.


14. Cargo handling safe practice for chemical products
    Check cargo hoses to see that they have not deteriorated, that flange connections are intact, that there is an electrical bond between hose flanges and that the working pressure for the hose is marked on it. If there is any doubt about the hose's condition, find out when the hose was last pressure tested .


15. Risk with noxious liquid cargo contact
    Different chemicals affect the human body in many different ways. A general information and some practical advice are available in Appendix,7, of "Medical first aid guide for use in accidents involving dangerous goods" published by IMO, WHO and ILO ref (36).


16. How take a sample of noxious liquid cargo ?
    Cargo samples are evidence of the condition of the product during the various phases of transport (storage at terminal, arriving on board, loading, passage, discharging).For protection against possible cargo claims it is very important that cargo sampling is correctly carried out.
    

More 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)

Related Info:

• Recommended temperature monitoring equipments onboard



• Signing a Bill of lading & related problems



• Issuing notice of readiness and related guideline



• Cargo claims and issuing letter of protest



• Statement of facts



• Avoiding cargo claims - Chemical tanker procedure

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