An Oil Tanker (VLCC – Very Large Crude Carrier) was discharging its cargo. Ballasting was planned in the early hours of the day in order to correct the trim/List. The engine room got flooded to a level of two metres above tank top (to just below the engine room floor plating). Had the flooding incident lasted a few minutes longer, serious machinery damage could have resulted. The incident was reported to occur during ballasting operations, when the configuration of pumping from and to ballast tanks was altered. During this process the cover plate of the sea chest strainer was blown off as the wing nuts (clamps) slipped. This resulted in seawater ingress into the engine room.
Engine room personnel instructed the cargo officer (Deck officer on watch during the cargo operations) in charge of ballasting to stop the ballasting operations (without mentioning reasons).
As per company procedure, the overboard suction valve and overboard discharge valve were opened to ‘de-energize’ the pumping system. Since a direct connect between open water and engine room got created the situation went worse. Sea water started flooding the engine room spaces more forcibly than before. This caught the engine room personnels immediate attention and immediately the cargo officer was instructed to close overboard valves. Thus the ingress of water was reduced and other contingency measures were followed. Emergency Bilge Suction valve was put in use to reduce the water level in the engine room bilges. Terminal and port controls were alarmed appropriately and the incident was logged in Engine room Logbook.
- Malfunctioning of one of the actuators of the valves in the ballast pipelines caused the valve to close in 1.5 – 2 seconds (normally 15 – 20 seconds)
- This created a pressure shock in the ballast system
- Subsequently, this pressure shock caused the cover plate of the sea strainer to blow off
- The actuator of the valve which was closing in 1.5 – 2 seconds was replaced by vessel crew in early 2014 without verification of the opening/closing time of the valve
- Communication between engine room personnel and bridge personnel was not sufficiently detailed
- This resulted in incorrect actions being taken which caused a worsening of the situation
- Ballasting procedure of manufacturer was not followed. The recommended procedure described that pump(s) should be stopped before operating valves in the ballast lines. This was not followed
- Introduced vessel-specific procedures for ballasting and added this instruction to the official document list of vessel
- Following the hierarchy of control, the company recognised it could not eliminate nor substitute the ballast process on board. Therefore, it focused on the following engineering controls by: − Improving visual presentation for valve operations on the bridge/Cargo Control Room (CCR) to emphasize valve position and open lines in the ballast system introduction of interlock system to eliminate simultaneous operations of valve(s) and pump(s)
- The Engine Department should try out the emergency bilge suction valves and record the same in the engine room logbook. Most cases, the Engine staff do not test the proper functioning of this valve and carry out a table top drill for the same
- Sea chest and other sea water line filters need proper attention when tightening them after filter cleaning. The clamps has to be tightened even and proper in ‘opposite first’ fashion. It is always essential to put the sea water line filters in use and test them against leaks after purging out air effectively. If you choose to keep the sea-chest filters isolated after cleaning as a standby, ensure that the sea chest cover nuts are tight and there are no leaks after change over
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