A major charterer has noticed a significant increase in the number of incidents involving failure of engine connecting rod bolts in four stroke auxiliary engines. In most cases these incidents resulted in catastrophic damage to auxiliary engine components with some of them resulting in engine room fire and human injury.
The charterer noted that planned maintenance systems do not always capture the maintenance routine of connecting rod bolts as specified by the makers. A lack of experience, knowledge and skill of the personnel involved in the tightening of the connecting rod bolt was also observed. The importance of proper tightening was not understood or appreciated, resulting in the manufacturer’s specified tightening procedures and recommendations related to stage-wise tightening not being complied with.
In addition to compliance with manufacturers’ recommendations, the charterer has recommended that precautions in place for this work should include but not be limited to:
– Effective supervision by a senior engineer who should not be involved in the work;
– Close inspection of the connecting rod bolt, its threads and pitting on the contact surface of the bolt head;
– Thorough cleaning of landing faces of the bolt head and nuts prior to assembly;
– Bolts are given a good surface finish to reduce stress raisers;
– Tightening of the connecting rod bolts using correct tools and manufacturer recommended torque/ hydraulic pressure;
– Tightening of bolts done in stages as recommended by the manufacturer;
– Calibration of the tightening tools such as torque spanner and gauges on hydraulic jacks before use;
– Retightening checks of bolts to be carried out after stipulated time of test run of auxiliary engine as specified by the maker;
– Locking of the nuts, if applicable has been completed and checked thoroughly;
– Connecting rod bolts management systems on-board the vessels are in place in order to ensure that worn and discarded bolts are appropriately disposed of and never reused in error;
– Bolts are procured from the original equipment manufacturer;
– Ensure adequately skilled personnel are involved and are aware of the correct tightening procedure, and
CHIRP Comment
This charterer’s advice is most useful. CHIRP has an open invitation to ship owners, managers and charterers to share their experiences and advice on lessons learned.
