RA Power Solutions was advised about the damage to the crankshaft of MAN B&W 9L27/38 on board the vessel. The vessel was stranded at Lumut Port Malaysia due to non performance of the main engine of MAN.
We deputed a team of two technicians with necessary onsite crankshaft grinding equipment to undertake the inspection and repair of the crankshaft.
The details of Engine are mentioned below:
MAN Aux. Engine
Crankpin Diameter Standard
Crankpin Bearing Length
Place of execution of crankshaft repair
Lumut Port Malaysia
Following are the main observations of the crankshaft of MAN Aux. Engine Model No. 9L 27/38
i) On visual inspection by our technicians it was observed that crankpin no. 2 have a deep depression mark measuring about 40 x 25 mm.
ii) The minimum and maximum dimensions of crankpin no. 2 were observed as following:
a) Standard dimensions of crankpin: 250 mm
b) Minimum size observed : 247.80 mm
Thus the ovality of more than 2.2 mm was observed.
iii) Our technicians reported that damage to Crankpin is more as the micrometer is not able to take the reading due to the nature of damage. The crank pin was subject to crack detection by MPI and no cracks were observed.
iv) The hardness was taken off the crankpin. The hardness ranging between 260 to 300 on the HB scale was observed. On a few scattered areas the hardness was as high as 616 on the HB scale.
Planning for Repair of Crankshaft of MAN Engine Model No. 9L 27/38
i) During the discussions with the technical staff of the vessel it was informed that a crankshaft repaircompany from Singapore inspected the damage crankpin no. 2. They observed higher hardness and have undertaken local grinding of the hard spots by a hand grinder.The exact depth of hand grinded area cannot be measured.
The decision was taken br R A Power technicians to undertake grinding of crankpin.
ii) Our technicians checked the hardness of the crank pin at every step while undersizing it, to our surprise the hardness was coming down as the grinding was done.
iii) Our technicians have undertaken the grinding to the undersize of 4.0 mm and the maximum hardness observed is 328 mm.
iv) The damaged crank pin has been successfully repaired.
Damaged to the crankpin by Singapore based company
Due to the lack of knowledge and experience the hand grinder was used to check the hardness which in turn rather damaged the crankpin.
Crankshaft is the most expensive part of a diesel engine and it is important that experienced companies are engaged for repair.
It is our experience of forty two years that hardness increases whenever there is a seizure of the bearings and in the most of cases it is a skin hardness which reduces after grinding is done.