VASA 32 – 9 CYLINDERS
CYLINDER LINER SEAT RESURFACING – MULTIPLE BENEFITS
During a recent call out for ‘in situ’ crankshaft grinding repairs on the above engine, our technicians were tasked with investigating and eliminating the root cause of the accident. This engine was also due for 20,000 hours overhaul, therefore major components were removed for renewal at the same time. As the engine was now bare, this allowed our technicians to thoroughly inspect the engine block and all the parts that have been removed.
It was noted that on all cylinders, there was an uneven wear down on the piston rings. The wear position on the rings indicated that the clearance between the piston and cylinder liner was not even circumferentially. With that in mind, the pistons were inspected and it was discovered that on some of the units, there were scuffing marks. This meant that on these cylinders, the pistons were in contact with the cylinder liner during operation, prior to the engine failure.
The next item up for inspection was the cylinder liners, since we had an indication from the pistons that the problem was in this area. All cylinder liners were measured for wear and ovality, however no significant issues were found with the bore diameter, even at the corresponding position of the scuffing marks from the piston. The next course of action was to check the cylinder liner seating surface on the engine block and this is where we found the root cause of the engine failure.
This is a picture from Number 2 cylinder block, showing the damaged area of the cylinder liner seating surface. The cylinder liner should be resting from the inside of the bore up to the outer edge of the shiny surface seen in the above photograph. In the condition found, it is only resting on the area where the shiny metal can be seen. The dark watermark is where cylinder liner is not seated properly and where the cooling water was leaking out. All other cylinders were in similar condition.
With this information, we tested our theory and proved that, when the cylinder head and cylinder liner was tightened down to full torque, the uneven seating area caused an ovality on the inside bore of the cylinder liner. This ovality in the cylinder liner then led to the piston scuffing and eventual piston seizure.
Our equipment was precisely centred to the cylinder bore and the alignment was set to the original engine block level. The equipment was then set to cut exactly 1.0mm depth from the surface. This process was repeated for all 9 cylinders.
This is a photograph of the cylinder liner mating surface after the machining repairs. This is a new, smooth and level surface for which the cylinder liner can properly seat on. Because a new surface has been cut into the engine block, the cylinder liner will now sit lower. To compensate for this, 1.00 mm shim was installed onto the newly machined surface before installing the cylinder liner. All cylinders have been machined to 1.00mm depth. The entire repair of all the cylinder liner seating surfaces was completed in less than 5 days and the damaged crankpin journals were repaired at the same time. With our technicians that are cross trained across multiple disciplines, we are able to provide services that will put your engine back in operation as soon as possible.
The benefit of repairing the cylinder liner seating surface goes beyond the reduced possibility of piston seizures and engine failures. This engine has been in operation for over 1000 running hours since the repairs and we are happy to report that:
- Lube oil consumption has been reduced to 0.63 ml/KWh compared to well over 3.52 ml/KWh, prior to the engine failure. This results in lube oil savings of approximately 4000 Litres every month.
- The depth of sludge in the centrifugal separator is at 3mm thickness compared to over 19mm thickness, prior to the engine failure
- Cooling water consumption has been reduced
- Combustion chamber blow-by into the engine crankcase has been reduced due to the elimination of ovality in the cylinder liner and lessened wear on the piston rings
With all these immediate benefits, the service life of the engine lubricating oil can be extended back to the manufacturer’s specifications. As a result, the service life of all lubricated components has been extended back to manufacturer’s specifications as well.
Our on site machining services offer a very cost efficient method to carry out machining on castings and components that are too big (and therefore costly) to move. The solutions to your problems may be by way of turning, facing, milling, drilling and or boring – ALL CARRIED OUT ON SITE . We work on 24/7 basis at your site during scheduled shutdowns or on emergency breakdowns.
Call us today to find out more about the many benefits of ABC Grinding’s on site machining services.