On Board Grinding of Crankshaft of Yanmar S185L-ST Engine A prominent shipping business in Saudi Arabia reported a major accident involving Auxiliary Engine No. 2, a Yanmar S185L-ST diesel engine used for power generation onboard MV THE ABLA. Crankpin No. 1 suffered significant damage as a result of the big end bearing failure that led to the accident. To assess the damage and perform the required crankshaft repair, RA Power Solutions dispatched a team of two skilled experts with calibrated measuring tools and portable onsite crankshaft grinding equipment. In order to evaluate the crankshaft's condition and repair it without removing it from the engine block, the team boarded the ship. Initial Inspection and Damage Assessment During the initial inspection of crankpin No. 1, the following observations were recorded: ● The big end bearing had failed, and bearing material was found firmly embedded on the crankpin journal surface. ● The crankpin surface had deep scoring marks, multiple bearing lines, and a rough finish. ● The radius fillets on both sides of the crankpin were damaged and had lost their original profile. ● Considering the seriousness of the accident, all connecting rods were dismantled, and every crankpin was inspected. ● Dimensional inspection of the remaining crankpins did not show any abnormality. ● After removing the embedded bearing material, the hardness of crankpin No. 1 was checked and found within the acceptable limits. ● Crack detection was carried out using a high-intensity Magnaflux torch and Magnetic Particle Inspection (MPI) equipment. No cracks or surface abnormalities were detected. ● Crankshaft deflection readings were also taken and found within the permissible limits. The absence of cracks and abnormal hardness readings was an important finding, as there was a possibility of surface damage due to the severe bearing seizure. Crankpin No. 1: Dimensional Inspection Before Repair Crankpin No. 1 had a standard diameter of 140 mm and a bearing width of only 62 mm. Detailed dimensional measurements were taken before starting the grinding operation. S. NO Crankshaft Details 1. Engine Make Yanmar 2. Engine Model S185L-ST Engine 3. Crankpin Diameter Standard 140 mm 4. Crankpin Bearing Width 62 mm 5. Name of Vessel MV THE ABLA The measurements confirmed excessive wear and ovality. The deep scoring marks and embedded bearing material also required substantial machining to restore the journal surface. Crankpin Grinding and Repair by RA Power Solutions After completing the inspection, RA Power Solutions decided to carry out onsite crankpin grinding without removing the crankshaft from the engine. The following repair procedure was adopted: 1. Initial Grinding to 0.50 mm Undersize The crankpin was initially ground to 0.50 mm undersize with the objective of removing the deep scratches, scoring marks, and embedded bearing material. However, after completing the initial grinding operation, some deep line marks were still visible on the journal surface. 2. Further Grinding to 1.00 mm Undersize Considering the remaining surface damage, the decision was taken to grind the crankpin by an additional 0.50 mm. Finally, crankpin No. 1 was ground to 1.00 mm undersize. Special attention was given to maintaining the required diameter, ovality, and surface finish. 3. Final Dimensional Inspection After completing the grinding operation, the crankpin was inspected again using calibrated measuring instruments. The final measurements confirmed that the crankpin had been restored to the required dimensional accuracy. Supply of Undersize Bearing and Engine Recommissioning After completing the crankpin grinding operation, RA Power Solutions supplied a matching 1.00 mm undersize bearing from its available stock. The new bearing was installed, and the necessary checks were completed before the engine was put back into operation. The repair was successfully completed without removing the crankshaft from the engine block or sending it to an external workshop. This helped reduce the repair time and avoid the high costs associated with crankshaft dismantling and transportation. Special Features of Yanmar S185L-ST Crankpin Repair The successful completion of this repair demonstrated the importance of specialised equipment and experienced technicians, particularly when working on small-diameter crankpins with limited bearing widths. The main features of the repair work included: ● Nearly Five Decades of Experience: RA Power Solutions has extensive experience in crankshaft inspection, grinding, and machining of marine and industrial diesel engines. ● In-House Machine Manufacturing: The company manufactures its own portable onsite crankshaft grinding machines and has been using this equipment for more than 25 years. ● Compact Machine Design: The machine was suitable for grinding a crankpin having a diameter of 140 mm and a bearing width of only 62 mm. ● High Dimensional Accuracy: The grinding process is designed to achieve close dimensional tolerances, with ovality maintained within 0.01–0.02 mm, depending on the repair requirements. ● Special Undersize Bearings: RA Power Solutions maintains stocks of different undersize and special-size bearings to reduce waiting time after machining. ● Technicians for Worldwide Repairs: Experienced technicians holding valid Indian CDC documents can travel to international locations on short notice. ● Quick Equipment Transportation: Portable grinding machines can be carried by technicians as accompanied baggage, subject to airline regulations, avoiding delays associated with conventional cargo transportation. ● Onboard Repair Facilities: The compact machine design allows crankshaft grinding in restricted engine room spaces, including onboard vessels. Worldwide Yanmar Crankshaft Repair Services RA Power Solutions has carried out crankshaft grinding, crankpin machining, and repair services in several countries, including Laos, Lebanon, Malaysia, Maldives, Mongolia, Nepal, North Korea, Oman, Philippines, Qatar, Russia, Saudi Arabia, Singapore, South Korea, Sri Lanka, Syria, United Arab Emirates, and Yemen. This Yanmar S185L-ST repair is an example of how a severely damaged crankpin can be restored through proper inspection, accurate measurements, and specialised onsite machining. For technical information or assistance with Yanmar engine crankshaft inspection, grinding, and Crankpin Repair , you can contact RA Power Solutions. Email: rajshahani@rapowersolutions.com | info@rapowersolutions.com Phone: +91 9582647131 | +91 9810012383