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Sea transport of dangerous & noxious liquids in bulk

Chemicals are involved in everything from agriculture to complex manufacturing - providing the world with such things as pharmaceuticals, detergents, insecticides and fertilizers, synthetic fibres and rubbers, and packaging materials. The increasing demand for these chemical products throughout the world has led to the development of sophisticated ships capable of carrying a wide range of specialty cargoes in bulk, often in smaller quantities or ‘parcels’. While some chemical tankers are specifically constructed to carry less sophisticated chemicals, such as methanol, the term parcel tankers usually refers to the more complex parcel/chemical tankers.

chemical tanker navigation at sea
Chemical tankers primarily transport organic and inorganic chemicals as well as vegetable oils and fats. The total global volume of chemicals is estimated at approximately 60 million metric tonnes per year. In addition, the transportation of vegetable oils, alcohols, molasses and lubricating oils amounts to 40 - 45 million tonnes per year.

Chemical tankers are complex and technologically advanced
The transportation of chemicals is technically and logistically different from the transportation of oil and oil products. Chemical tankers are more advanced in many ways. The cargoes may be hazardous and noxious chemicals or such products as edible oils and fats. A common characteristic of these cargoes is that they tend to be high value and require sophisticated handling for safety, health and loss prevention reasons.

Modern Chemical tanker underway

Fig:Modern Chemical tanker underway

The ships are complex and technologically advanced due to the degree of subdivision created by 50+ cargo tanks. They are inherently more robust vessels compared to bulk tankers. This large number of cargo tanks, sophisticated cargo operating systems and supply of deck services enable them to carry a broad range of chemicals, in accordance with the requirements of the International Code for the Construction and Equipment of Ships Carrying Dangerous Cargoes in Bulk (IBC/BCH Code), and in strict accordance with anti-pollution regulations under MARPOL Annex II.

Every chemical cargo carried requires careful consideration during the planning process and loading. Some are temperature sensitive some are semi-gases, some need to be inhibited, and some are sensitive to water. Checks also need to be made regarding the chemical ship type, (for instance category I, lI or III), tank coating compatibility, cross compatibility with other cargoes carried, environmental controls if required (inerting).

In addition, tank construction type for containment, venting requirements, gauging equipment, vapour detection, compatible fire protection medium, heating requirements, inhibition requirements, density limitations of the product in relation to the cargo tank, and pumping requirements are important considerations. Most of this information is set out in the IBC or BCH Code.

In addition, the vessels also need to take into account the information contained in safety data sheets, applicable load-line zones encountered during the voyage, changes in sea/harbour water densities, bunker quantities and disposition, the loading sequence of each grade, final quantities/ullages, charterers’ options on cargo lift requirements, segregation requirements, valve line-up and the line-up and sequence of concurrent ballast operations.

Most early chemical tankers were slightly modified product tankers, in which the main variation was coating of the cargo tanks. Although many of the products shipped could be carried quite safely in uncoated mild steel tanks, the need to maintain product quality, to minimise the potential for discoloration, and to facilitate tank cleaning between cargoes led to tank surfaces being coated with an impervious material.

As the shipment of bulk chemicals developed, different countries involved with the trade developed regulations to minimise the risk to the ship, its crew and the environment, and applied them to their own ships and ships trading to their ports. These regulations were not an the same, and it was extremely difficult for a ship and its crew to comply with them all. To establish an international standard for the safe design, construction and equipment of chemical tankers, IMO developed the Bulk Chemical Codes. It was a major step forward.

A ship that complies with the IMO Codes is issued with a Certificate of Fitness that is recognised internationally, and enables the ship to trade worldwide carrying the cargoes for which it is approved.

The cargoes now carried in these ships range from petrochemicals used as feedstock for plastics or synthetic rubbers and fibres, industrial acids and alkalis, alcohols and solvents, highly refined lubricating oils and lubricating oil additives, to detergents, animal and vegetable oils, and edible products such as fruit juices or wine. Furthermore, certain refined petroleum products that were previously considered to be oils are now classified as chemicals under IMO marine pollution or toxicity regulations, and must only be carried by chemical tankers.

Chemical tanker cargoes

Chemical tanker cargoes may be divided into four main groups:

Petrochemicals :
This is the collective name for organic chemicals derived from crude oil, natural gas and coal. Organic chemicals are those produced from living or once-living organisms, petroleum and natural gas (marine animals and plants) and coal (plants). It is now possible to synthesise organic chemicals from inorganic chemicals to the extent that 'organic chemicals' really means those compounds based upon the element carbon. But the term does not include the simplest carbon compounds such as carbon dioxide, carbon monoxide and the carbonates.

Alcohols and carbohydrates :
Alcohols may be derived from hydrocarbons or produced by fermentation.

Vegetable and animal oils and fats :
Derived from the seeds of plants and from the fat of animals and fish.

Acids and inorganic chemicals :
Inorganic chemicals are those that are not produced from living or once-living organisms. However, a number of inorganic chemicals such as sulphur and ammonia can be manufactured using petroleum as the raw material. Acids may be organic or inorganic.

Hydrochloric Acid Storage Guidelines
Hydrochloric acid should be stored in a cool, dry, well-ventilated area in tightly sealed containers protected from exposure to weather, extreme temperature changes, and physical damage.

Hydrochloric acid is considered a strong oxidizer and steps should be taken to separate hydrochloric acid and hydrochloric acid products from incompatible materials such as copper, brass, bronze, galvanized steel, tin, zinc, oxidizers, combustible materials, plastics, rubber and some coatings. Contact with metals causes erosion and the formation of flammable hydrogen gas. The heat generated from the exothermic reaction of metal and hydrogen chloride or hydrochloric acid could cause ignition of combustible materials

DANGER – Explosion Risk

Other Info pages

Cuprous alloys for shipbuilding of seagoing chemical tankers
Copper and its alloys corrode in many cargoes and may contaminate them, e g styrene, phenol, vinyl chloride, aniline, ammonia solutions etc. Check your cargo against information . Particularly aggressive are the ammonia compounds; they cause inter -crystalline corrosion of cuprous alloys very rapidly. The object in question disintergrates very soon. ....

Use of magnesium and alluminium alloys as sacrificial anodes
Alloys of magnesium and aluminium should never be used in the cargo tank area, due to their poor corrosion resistance in such environments. .....

Introducing rubber lined tanks for the transport of phosphoric acid, waste acids and hydrochloric acid
In recent years a number of ships have been fitted with rubber lined tanks, for the transport of phosphoric acid, waste acids and hydrochloric acid. .....

Tools for shipboard maintenance

Although grit blasting and the use of mechanically powered tools are not normally considered to fall within the definition of hot work, both these operations should only be permitted under controlled conditions. ......

Sea transport of various liquid chemicals at sea
Chemical tankers primarily transport organic and inorganic chemicals as well as vegetable oils and fats. The total global volume of chemicals is estimated at approximately 60 million metric tonnes per year. In addition, the transportation of vegetable oils, alcohols, molasses and lubricating oils amounts to 40 - 45 million tonnes per year. .....

stainless steel as shipbuilding materials for chemical tankers
Iron, steel Mild steel and high tensile steel is, and will continue to be the most important material in the building of chemical tankers and their cargo tanks.Steel is attacked by only a few products, mainly acids and, of course ballast and washing water. Steel itself contaminates very few products, one of them being high purity caustic soda. .... ....

Types of various chemical tankers at sea
modem chemical tanker is primarily designed to carry some of the several hundred hazardous products now covered by the IMO Bulk Chemical Codes. The following general types of chemical carriers have developed since the trade began: ....

Related Info:

What is toxicity and associated health hazard onboard chemical tankers ?

What is reactivity of noxious liquid chemicals while carrying at sea ?

What are the most corrosive liquid chemicals transporting at sea ?

Static electricity -How they generate & required safety precautions

What is putrefaction process of liquid chemicals ?

Defining specific gravity (Density), flash points,Ffammable / explosive Limits, Viscosity ,vapour pressure/boiling point,freezing point/melting point,solidifying/non-solidifying states of chemical cargoes

Requirement of Material Safety Data Sheets (MSDS) for chemical cargoes carried at sea ?

Chemical tanker familiarization training for newly joined crew member

IMO codes guideline for modern chemical tankers

Following reference publications provide useful guidance and international regulations for carrying hazardous chemicals at sea.

Main Info pages!

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