202010 Planned maintenance interval revised

A tanker had finished a discharging operation and crew were carrying out pre-departure checks and preparations while awaiting the
pilot.

During these checks, an engineer started up the main engine lube oil separator. An alarm indicated an excessive amount of water in the clean oil outlet of the separator. The engineer immediately reported this issue. Further checks found that the main engine lubricating oil had been contaminated with fresh water. The Master cancelled the departure to allow time to further investigate the anomaly, and notified the company, local authorities, harbour master, charterer, and classification society of the delay, as
required in the SMS.

The investigation revealed that the solenoid valve on the main engine lube oil separator had malfunctioned. The internal orifice of the solenoid valve had allowed leakage through to the clean oil outlet and sump tank oil.

Although the maintenance interval for the lube oil separators was set at 4,000 hours or at least once a year, there was no detailed guidance to vessel crew about solenoid valve maintenance and inspection requirements. It was not anticipated that the internal components of solenoid valves could become worn beyond specifications within this period.

Lessons learned

• The company decided to reduce the time interval for scheduled maintenance to 2,000 hours or at least once every six months. Further, the internal components of solenoid valves were to be replaced annually.
• The main engine lube oil separator system was to be fitted with an additional automatic control solenoid shut-off valve on the clean oil outlet line to the sump tank.