Repair of Threads in Engine Block

RA Power Solutions was informed about the serious accident of MAN diesel engine on board a vessel sailing near a port of China. On investigation, it was observed that the cam cover of the engine block was broken into pieces and all the threads, including the dowel pins, were damaged. It was not possible to assemble the new cam cover and operate the engine.

Following was observed by RA Power Solutions technicians on investigation of engine block:

1.   6 nos. Of threads were damaged, on which the cam cover is assembled.
2.   2 nos. Dowel pins (locating pins) were also badly damaged.

Following are the photographs that illustrate in detail the damage caused to engine block and cam cover.

Cracked Housing

Broken Bolt

Broken Bolt Inside the Threaded Hole

Damaged Upper Threads

Housing Base

The engineers of MAN were called, who advised that considering the extent of damage, it is not possible to undertake the repair of damaged threads on engine block, and it needs replacement. RA Power Solutions was called, and after investigation, it was decided to repair the damaged threads by using helicoil thread inserts and a new dowel pin. The job was executed by following this method:

1.   The bolts, which were stuck in the engine block housing cam cover thread, were removed by the drilling process.
2.   The thread-damaged area was metal-stitched and metal-locked with the use of special alloys and profile keys developed by RA Power Solutions.
3.   Fresh holes of 12 mm were drilled.
4.   Helicoil thread inserts were fitted.
5.   The damaged locating pin/dowel pin was removed.
6.   The damaged area on engine block was metal stitched and metal locked.
7.   A new hole was drilled, and a dowel pin was fitted.

Following are the pictures showing the process followed for repair of damaged threads.

Repair of Threads On Engine Block Under Process

Repair Of Thread Hole By Metal Stitching

Metal Stitching of Bottom Area of Threaded Hole to Give Extra Strength

Cam Cover Sitting Area of Engine Block After Repair

The engine block is saved from rejection, resulting in considerable savings for the shipowner. For more details, please email us at rajshahani@rapowersolutions.com or info@rapowersolutions.com, or call us at +91 9582647131 or +91 9810012383.