Thanks to Peter Paine for supplying the information and photographs describing the removal and replacement of a cylinder liner on a Sulzer ZAL40S engine.
The oil mist detector had activated during a day at sea and the engine had shut down automatically due to high oil mist content in the crankcase. After a period of about 30 minutes the crankcase doors were removed and the crankcase partitions inspected. The reason for the activation was not an overheated bearing, but water vapour due to the failure of a cylinder liner lower “O” ring seal on one cylinder that was allowing cooling water from the jacket cooling space into the crankcase. This meant that the whole running gear for that cylinder was required to be removed for replacement of the liner.
The photograph above shows clearly the evidence of the leaking liner. The cooling water has evaporated leaving white deposits of the cooling water treatment chemical.
The engine was isolated from main cooling water systems and drained, the compressed air system was isolated, the pre-lubrication pump was stopped, and the turning gear engaged. The expansion tank levels were monitored during maintenance in case a valve was passing on the engine, and the engine refilling with water. The drain for the engine was kept open and monitored closely for signs of leakage.
The cylinder head and the piston were removed. The cylinder lubrication pipes at the bottom of the cylinder liner were disconnected by undoing and removing the banjo bolts. The bolt securing the centering piece which locates the liner in the correct position in the cylinder bore is removed.
The liner must be jacked off its seating using a hydraulic jack. In the case of the ZA40 the jacking device is bolted to the crankpin bearing. (Left in place when removing the con rod, which is normally bolted to the bearing by means of a marine palm see The 4 stroke engine conrod).
After attaching the jacking device to the bottom end bearing the bearing was turned through 90° and the crankpin turned to TDC. The hydraulic pump connected to the jacks was operated so that the jack locates in the bottom of the liner. The liner was then jacked upwards until the liner moved off its seat. (the jack has only a 54mm lift).
The new assemblies were inspected prior to fitting. While the liner was removed from the engine, the jacket cooling space around the liner was inspected for overall condition that can indicate the effectiveness of the cooling water treatment. The guiding bores in the entablature and O ring seatings were cleaned and examined for evidence of corrosion /erosion and the landing face for the cylinder liner was cleaned and examined.
Once the liner was in position the centering piece location bolt was fitted and the cylinder lubricators connected and checked by operating the pumps by hand and ensuring that oil issued from the lubrication points. The Liner was gauged and the readings recorded.
The running gear was reassembled, fitting new piston rings. Once the cylinder running gear was all in place, the engine was refilled with water, and the crankcase checked to ensure no leakage was occurring. The engine was then prepared for running. All equipment used was accounted for and the crankcase was checked clear of tools, rags and personnel. The cylinder lubricators were wound 15 times to ensure lubrication of the piston and liners, and the engine was turned a minimum of 2 revolutions with the turning gear to check for correct operation of the running gear, the running gear is observed through the crankcase doors and the rocker cover. The ammeter on the turning gear panel is monitored so that if a partial seizure was to occur, the current drawn by the motor would have increased, indicating a problem. The engine crankcase was monitored for water leakage from the liners during the warming through procedure. The lubricating oil, which had been circulating through the purifier was checked for water content, and the oil pumps switched on and oil flow through the bearings checked.
Once the engine was ready for starting the normal routine for checking the engine was followed: After a very short run (30 seconds) the engine was stopped and the bottom end bearing on the overhauled unit checked. The engine was then run for increasing intervals of time; 2, 10, 30 minutes, checking the bearing in between. Finally the load on the engine was slowly increased and the unit run in as per manufacturers instructions; reduced load and increased cylinder lubrication whilst the rings bedded into the liner.