Marine Engineering Study Materials

Pollution of the sea by chemicals

Carriage of liquid chemicals in bulk is covered by SOLAS chapter VII, Part B, chemical tankers used for carriage of such cargo have to either;

• Comply with the international code for construction and equipment of ships carrying dangerous chemicals in bulk (IBC) code when the tankers are built after 1^st July, 1986.

Or

• The code for the construction and equipment of ships carrying dangerous chemicals in bulk (BCH) when the vessels are built before 1^st July 1986.

The chemical tankers accordingly must have either “International Certificate of Fitness for the carriage of dangerous chemicals in bulk” or “Certificate of Fitness for the carriage of dangerous chemicals in bulk” to facilitate prevention of pollution of the sea.

These codes take into account the materials of the tanks, pipes and fittings, which can withstand actions of the chemicals carried, construction details, type of pumps and other equipment suitable for handling the chemical, tank cleaning, and ventilation of the tanks and prevention of the hazards to the ship’s personnel. A chemical tanker should carry a list of cargoes, which can be carried in its tanks. Unlisted cargo must not be carried. Ships must have emergency towing arrangement.

Ship’s master must be informed about the physical and chemical characteristics of the cargo for its containment and action to be taken in case of emergency such as pollution of the sea.

Ship’s personnel must be trained in all operation of the tanker including loading, transfer and discharging of cargo, tank cleaning, pumping out, gas freeing, venting and emergency procedures. Ships must carry chemical resistant protective clothing for use of personnel. Equipment for treatment of personnel, who are exposed to dangerous chemicals, must be readily available.

Noxious liquid substances means any substance indicated in the pollution category column of chapter 17 or 18 of the IBC code or provisionally assessed under the provisions of regulation 6.3 as falling into category X, Y and Z dealt in Annex II of MARPOL 73/78.

Special measures are required when carrying chemicals falling under categories X, Y and Z are given below, to prevent pollution of the sea.

Maximum Tank Residue in Liters after Loading

Construction Date	Category
	X	Y	Z
Before 1st July 1986	300	300	300
On or after 1st July 1986 but before 1stJanuary 2007	100	100	100
After 1st January 2007	75	75	75

 

Discharge Criteria for Noxious Liquid Substances (NLS) Falling in Categories X, Y and Z

The relevant tanks to be emptied to the maximum extent in accordance with the procedure described in the Procedures and Arrangements (P & A) Manual before any pre-wash or discharge procedure.

Discharge of NLS, which have not yet been categorized or ballast water, or tank washing or other mixtures containing such substances, the following shall apply.

1. Ship must be en-route at minimum 7 knots speed.
2. Discharge to be through under water discharge outlet. Outlet not exceeding the maximum designed rate for ships built before 1^stJanuary 2007. This requirement is not mandatory in the case of category Z substances.
3. Minimum 12 nautical miles from the nearest land and minimum depth 25 meters.
4. No discharge in Antarctic area.

Also the ships carrying NLS must have “International Pollution Prevention Certificate for the Carriage of NLS” and Shipboard Marine Pollution Emergency Plan (SMPEP) for NLS.

See Also:

Special Areas in Marpol 73/78

 

Reference

“SHIP SAFETY AND ENVIRONMENTAL PROTECTION” BY GAUTAM SEN