A vessel was being prepared for Methanol loading by steaming out the cargo tanks for chloride removal. After steaming out the cargo tank, the duty officer went inside the tank for inspection and found deformed bulkheads.
The survey revealed that the tank’s forward bulkhead buckled in way of the 5 upper corrugations for up to a maximum of 30 cm on top and buckling reducing towards lower parts. Similarly longitudinal bulkheads port and starboard were buckled out by approximately 15 cm on top which was reducing towards lower area. Aft bulkhead, deck and bottom were found without any deformations.
Discussions on board concluded that proper ‘steaming out procedures’ were not followed:
- As per ship staff, P/V valve malfunctioned and did not open.
- Tank’s pressure sensor was not working. Sensor found out of order at the time of survey.
- Access hatch should have been kept open during steaming out, which was not done.
- Improper watch maintenance during steaming out operation as nobody realized if steam was coming out from the tank or not.
As a result of the above the follwoing should always be taken into consideration in similar situations:
- Ensure proper maintenance of the P/V valves and other relevant equipment, ensure redundancy of the P/V protection. The P/V valves should be checked each time the cargo tank is to be loaded or unloaded.
- Follow ‘steaming out procedures’ including proper ventilation and proper supervision of the steaming process
Source: DNV
Officer of the Watch 
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