201038 Oil leak from fuel pump return line

Oil leak from fuel pump return line
MARS Report 201038

The vessel was en route and operating in UMS mode. The duty engineer entered the engine room at 06:50 to man the engine room and discovered fuel oil spraying around the main engine top, middle and lower platforms, as well as around the flywheel area. Under the influence of the main engine turbo-charger air intake and the engine room ventilation blowers, the oil mist was being carried right across the machinery space, increasing the fire hazard. The main engine was immediately stopped and the ship's engineers began the job of tracing the source of the leak.

It was soon established that the leak originated from a failed joint at a pipeline flange on a fuel pump oil return line. It was also observed that the joint (which had been opened during a recent drydocking) and the fuel pump inlet pipe bosses were not covered with approved splash prevention screening, as required under Solas. This was apparently due to an oversight in the case of the flange and due to the awkward shapes of the castings on the fuel pump body. All fuel oil inlet and return pipes were checked and it was found that some of the bolts required about half a turn of the nuts to obtain proper tightness.

Root cause/contributory factors
1. Lack of standards: insufficient data on engine vibrations, lack of recommended tightening torque on fuel oil piping connection fasteners;
2. Although the vessel had been in operation for less than six months since the last dry-docking, it was evident that excessive vibrations caused some flange connections to become loose;
3. Inadequate application of splash-prevention screening at key locations.

Corrective/preventative actions
Procedures initiated in the fleet for:

1. Better monitoring of the assembly process during building as well as during the post-drydock commissioning trials;
2. Regular checks to be carried out on flanges and tightness of bolts and providing data on recommended torque settings for fasteners on pressurised oil systems;
3. Investigating the possibility of installing some form of spray guard/deflector around fuel pumps to deflect any leakages away from hot surfaces;
4. Use of spray deflection measures around the flanges. These used with the deflectors would enhance the level of protection provided;
5. Investigating the possibility of fitting some kind of oil mist detection system around the top of the main engine or utilise the oil mist detection capabilities of some CCTV systems to raise alarms;
6. Incorporating nut locking arrangements such as locking tab washers or drilled bolt head and locking wire arrangements.