|Vessel Type:||Cargo Container Vessel|
|Year of build:||2013|
|Time:||21 hours (April 2016)|
Manufacturer: Doosan MAN B&W
Model/Type: 9S90ME-C Mk8
The purpose of the repair was to replace piston crown with piston rings and stuffing box, due to micro seizures and sharp burrs on piston rings. Liner was out of wear limits and presented scratch marks on the liner walls.
Works started with the disconnection of all piping and instrumentation lines, sensors, air and exhaust gas duct from cylinder head, in order to be free to lift up from sitting position.
Once all pipes and sensors were disconnected from cylinder head, special tool with hydraulic jacks was putted in place.
Cylinder head is fixed on the engine block by eight tie rods with nuts, tighten up to 2200 bar.
To release these nuts you have to set up hydraulic jacks, connect an air driven hydraulic pump, raise the pressure up to 2200-2400 bar and unscrew them partially (approx. 1 round). Then released the pressure and unscrew them totally and remove them. Cylinder head was free to be lifted up.
The same procedure was used to remove piston and connecting rod. First you have to remove the four rods with nuts that are fixing the connecting road to the crosshead. After install the extracting rods for stuffing box and then piston is also free to be lifted up.
Special lifting tool had to be fixed on the adequate point in cylinder head to raise up and settle down on the structure.
Once cylinder head was secured, polishing and cleaning works were started on it.
At the same time, before lift up the piston, anti-polishing ring and metallic gasket have to be removed.
Then special lifting tool was fixed on piston head and piston lifted up until the rest position on ME platform.
Polishing and cleaning works started on cylinder liner to take proper measurements.
Measurements of liner were found out of wear limits, so decision was to change it.
Preparation works started at once. All lubricators were removed with relevant piping and liner securing bolts.
Then cylinder liner was lifted up and secured on ME platform, next to the new one.
New cylinder liner was full of protecting grease, so we cleaned and prepared with new O-rings for the water side in order to install it on the block.
Once new liner was placed on rest position, inside the engine, we started to mount again the tie rods and lubrication injectors.
Later on, new piston with new stuffing box and rings was maneuvered to unit number #1. Once piston was inside, stuffing box was fitted and fixed on under piston space.
Anti-polishing ring and metal gasket were installed back on upper part of the liner.
Next step was to screw and tight the hydraulic bolts to the crosshead.
At the same time, the maneuver to fit the cylinder head was started.
Once in position, bolts were tighten, first at 1000 bar and later on to 2200 bar.
When cylinder head was tighten, mounting of all pipes (air, water fuel, etc.) dismounted before had to take place.
When all pipes installed, water, fuel and lub oil systems were commissioned in order to prepare the engine for vessel departure. In the meantime, our engineers were checking for any leakages.
No any leakages was found, so, vessel was ready for departure.