On Site Machining and On Site Crankshaft Repair

RA Power Solutions was approached by a company based in Dubai for the serious accident in one of their auxiliary engine of MAN B&W having following major details:

Grinding of Crankshaft of 8L 27/38 (Auxiliary Engine)

Based on the photographs of crankpins of crankshaft received by us, we could make out that it’s a case of failure of bearing or a lubricating oil pump.

Repair of Crankshaft of MAN B&W

Team of two technicians was deputed on board a vessel which was sailing near Singapore. The preliminary inspection was conducted.

On Site Machining of MAN B&W

Following are the main observations:-

• All the eight crankpins were subject to dimensional inspection for taper and ovality. The ovality ranging from 0.16 mm to 0.99 mm was observed.
• Deep bearing line marks were observed on all crankpins.
• Hardness of crankpins was checked by the portable hardness tester. Hardness ranging from 244 to 256 was observed on HRC scale.
• All the crankpins were subject to magnetic particle examination and no cracks or abnormalities were observed on crankpin surface. This was of great relief as our technicians were assuming that with this nature of serious accident crankpins may have developed cracks.
• Crankshaft cold deflection was checked and it was observed to be within limits.

Crankshaft Grinding

On site machining and on site crankshaft repair

Based on the above inspection of all the crankpins conducted by our technicians, it was decided to undertake grinding of crankpins. It was also decided in consultation with owners and technical managers that we should remove the minimum stock from the crankpins based on the presence of taper and ovality of each crank pin.

The onsite machining was undertaken by portable, light-weight on site crankshaft grinding machine.

On site Crankshaft Repair

The following diameter was maintained after machining and grinding of crank pins.

• Crankpin no. 1, 3 and 6 were maintained 0.50 mm undersize having minimum and maximum dimensions of 249.48 and 249.50 respectively.
• Crankpin no. 2, 4, 5 and 7 were maintained 1 mm undersize i.e. 248.99 to 249.00.
• Crankpin no. 8 diameter was reduced by 1.50 mm and it was maintained as 248.48 to 248.50.

Final inspection after crankshaft machining:-

• It was observed that all the crankpins, taper and ovality has been maintained within 0.02 mm which is as per the tolerances stipulated by the manufacturer of engine in the maintainence manual.
• Radius fillet of both the ends, lubricating oil hole profile was maintained strictly as per the original profile.
• Surface finish was measured with mitutoyo surface tester and was observed to be less than 0.20 Ra value.
• As a matter of caution and a standard procedure followed by RA Power solutions technicians crankpin hardness was checked and crankpins were also subject to MPI test. Hardness was  within limits and no cracks were observed.

The satisfactory performance of engine was reported after commissioning.

Crankshaft Grinding Services

RA Power Solutions Pvt. Ltd. is a leading crankshaft machining company having qualified technicians who have experience of more than 30-40 years in repair of crankshafts. With the thoughtful planning and guidance we were able to undertake the repair of crankshaft successfully and by removing the minimum stock. We at RA Power Solutions always believe in removing the minimum stock from the crankshaft, crankpins and main journals in order to increase the life of crankshaft.

For more information related to on site machining and on site crankshaft repair, please email us at rajshahani@rapowersolutions.com, info@rapowersolutions.com, or call us at +91 9582647131 or +91 9810012383.