Question.

During routine soundings it is found that leakage into a cofferdam is occurring from an adjacent deep cargo oil lank.

(a) As 2nd Engineer state the procedure for directing safe entry by the engine room staff to ascertain the cause of leakage.

(b) If the leakage persists discuss EACH of the following options:

(i) Leave the cofferdam to flood with oil:

(ii) Flood the cofferdam with sea water;

(iii) Seal the cofferdam and pressurize with air pressure:

(iv) Pump the leakage to bunker tanks.

Answer

(a) Since the cofferdam is an enclosed space, safe entry procedure must be applied as stated in the Code of Safe Working Practices (pp.54-60) - also M 1345, The procedure is listed under 6 headings as follows:

(i) A competent person should make an assessment of the space and a responsible officer to take charge of the operation should be appointed;

(ii) The potential hazards should be identified;

(iii) The space should be prepared and secured for entry;

(iv) The atmosphere of the space should be tested; ;

(v) A permit to work system should be used;

(vi) Procedures before and during the entry should be instituted.

(b)

(i) Leaving the cofferdam to flood with oil is acceptable since the cofferdam

is there to provide positive segregation i.e. a safety barrier in case of a leak. Therefore, the cofferdam is performing the task assigned to it.

(ii) Flooding the cofferdam with sea water is probably a better option than (i) since it is safer for adjacent spaces to have the cofferdam-filled with sea water than the more dangerous oil and vapour.

(iii) If the cofferdam were sealed and the ullage pressurised with air then there would be a danger of the tank rupturing (consider the effect on the hydrostatic load diagram).

(iv) To pump the leakage to bunker tanks would be very dangerous since the crude oil has a lower flashpoint than bunker oil. Of course, it could be possible that the cargo oil is fuel oil