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