201153 Human error causes oil spill

One of our tankers was discharging cargo alongside at an oil terminal in USA, when an overflow of Low Sulphur Marine Gas Oil (LSMGO) occurred from the vent pipe of the starboard Diesel Oil (DO) storage tank. The overflow was stopped immediately and spill control measures initiated, however some of the oil had flowed over the gutter plate and escaped overboard. Spill abatement and control measures were carried out by the Qualified Individual (QI) under the supervision of the USCG.

Result of onboard investigation
In preparation for internal transfer of LSMGO, the junior engineer independently chose to prepare the receiving (DO storage) tank and line up the valves and the fuel oil (FO) transfer pump just before the end of the evening watch, which was about to be handed over from the third engineer to the fourth engineer. Observing that there was a small quantity of remnants in the receiving tank, the junior engineer decided on his own that it would be prudent to transfer this into a drain tank. As per established procedure, he inspected and confirmed that the line from the FO storage tank (which temporarily contained the LSMGO to be transferred the next day) was isolated, opened the suction to the receiving tank and inlet valve of the drain tank, and started the FO transfer pump (vertical shaft, centrifugal type) locally from the bottom platform. This transfer should have taken only a couple of minutes. Once the receiving tank was confirmed to be empty, he proceeded to stop the transfer pump locally and shut the inlet valve of the drain tank.
Unfortunately, on this occasion, the junior engineer did not press the stop button hard enough to deactivate the motor. The design and location (below  the bottom plates) of the FO transfer pump was such that, apart from the indicator panel in the control room (ECR), the only reliable method to ascertain its status was to look at the exposed portion of the drive shaft from inside the bilge space, as its motor does not generate sufficient noise to be audible above the engine room noise. Believing that pump was now stopped, the junior engineer reopened the suction valve of the FO storage tank and the inlet valve of the DO receiving tank in preparation for the transfer the next day. Other stop valves along the line were normally kept open for  convenience, and it had become the established practice to route and control transfers by operating valves at the pump.
The junior engineer then went to the ECR, where the watch was being handed over, but did not inform either of the watch engineers about the transfer preparations that he had executed. He also failed to check the ECR panel to confirm the status of the pump, which was now transferring LSMGO from the FO storage tank to the DO storage tank. At the same time, the fourth engineer, having taken over the watch, was concentrating on the inert gas plant and cargo pump turbines, and did not notice the status of the fuel oil transfer pump on the rear ECR panel. After about an hour, the DO storage tank began to overflow. The fact that the transfer pump was operational was only noticed when the fourth engineer was informed about the spill by the C/O from the deck.

Lessons learnt
1. Operation of valves and pumps associated with the fuel system are to be only carried out under the direct supervision of the watch keeping or senior engineer. This task is not to be entrusted to the junior engineers or ratings.
2. The Chief Engineer to include strict instructions in his standing orders that any internal transfer including those from/to drains tanks must be carried out with his permission and under direct supervision of the duty engineer.
3. The internal transfer checklist as part of the SMS must be properly used.
4. The duty engineer must exercise strict control over all activities undertaken by the personnel during his watch and must ensure that he is informed of all the activities being performed in the engine room.
5. Any pump must be reliably checked after stopping to confirm that it has actually stopped. Where pumps and system are started by local control buttons/ switches which do not have indicators, a positive means of identification of the state of the pump must be obtained from the ECR or by other physical means.
6. Senior engineers are to ensure that all personnel are sufficiently trained in the fuel pumping and piping system, especially where specific  arrangements have been made for segregating LSMGO in emission control areas.