Lessons Learnt: Hydraulic Oil Spill

Vessel Type: Bulk carrier

Incident description

While the vessel was discharging a cargo of grain, it started to rain heavily requiring the closure of the cargo hold hatch covers as is customary for water sensitive cargoes. The hatch covers were hydraulically operated hinged panels and during the closing procedure, the main hydraulic supply line ruptured causing oil to spray onto the deck, which then flowed aft with the rain water along the side of the main deck. As the deck scuppers where plugged, the oil was initially contained, however, water accumulation adjacent to the accommodation ladder up to the level of the raised deck edge plate resulted in the oil spilling over the ship's side into the harbour. The crew reacted quickly and efficiently in dealing with the spill and reporting the incident to the port authorities.

Analysis

The leak was found to originate from a small pinhole in the hydraulic pipe, which was protected with anti-corrosive tape. There was no indication of improper maintenance and it was thought that the leak occurred either due to a manufacturing defect or moisture somehow becoming trapped inside the tape which could promote hidden local corrosion. Keeping deck scuppers plugged for the duration of a vessel's stay in port is good practice. However, in conditions of rain it is important that the crew regularly remove any water collecting within the main deck containment, preferably by being drained or transferred into a designated slop tank. In this case, the vessel was fitted with deck drain valves for just this purpose. The excessive amount of water pooling at the after end of the main deck removed any effective deck containment in the event of an oil spill. Although the spill amounted to only a few litres of hydraulic oil, such pollution incidents could potentially expose ship owners and crew to heavy penalties and risk of prosecution.

Lessons Learnt

• Leaks from hydraulic systems associated with cargo hold hatch covers, cranes, pumps and other deck machinery are a common cause of oil spill incidents
• Although keeping deck scuppers plugged in port is good practice, excessive quantities of water should not be allowed to accumulate on deck
• Procedures for maintaining the integrity of deck containment and the proper use of drain valves and transfer equipment should be included in crew anti-pollution training
• The prompt and effective response of the crew was instrumental in mitigating the effects of the pollution
• Remember! A drop of oil in the sea is a drop too many