Cylinder head overhauling of Auxiliary engine on board- YANMAR series 

CYLINDER HEAD OVERHAULING IS THE MOST BASIC OVERHAULING THAT IS CARRIED OUT ONBOARD. WHEN CYLINDER HEAD IS TAKEN OUT FROM THE AUXILIARY ENGINE IT IS TAKEN TO THE WORKSHOP. FOLLOWING PROCEDURE IS CARRIED OUT FOR CYLINDER HEAD OVERHAULING:
FIRST OF ALL, REMOVE THE SPLIT COTTER AND SPRINGS.
TAKE OUT THE INLET AND OUTLET VALVES.
CLEAN THE CYLINDER HEAD THOROUGHLY IN CHEMICAL TO REMOVED ALL CARBON. DRAIN THE CHEMICAL AND BLOW AIR.
WHEN CYLINDER HEAD IS DRY THEN INSPECT THE CYLINDER HEAD FOR ANY DAMAGED IN SEAT. DAMAGED SEAT TO BE REMOVED AND NEW SEAT TO BE INSTALLED.
INLET AND EXHAUST VALES ARE ALSO INSPECTED AFTER CLEANING FOR ANY CRACK AND PITTING AND SIGNS OF CUT MARK. IF CUT MARK IS THERE THAN NEW VALVE SHOULD BE USED.
THE VALVE GUIDE TO BE INSPECTED FOR CLEARANCE. IF CLEARANCE IS MORE THAN VALVE GUIDE TO BE REMOVED.
SPRINGS SHOULD BE INSPECTED FOR SPRIING ACTION.
VALVE ROTATOR TO BE OPENED. BALLS TO BE CHECKED FOR FLATNESS AND BELEVELLE WASHER TO BE CHECKED FOR DEEP BALL MARKING IN WASHER AS IT WILL RESTRICT THE MOTION OF THE VALVE ROTATOR. RENEW BALL AND WASHER FOR EFFICIENT OPERATION.
IN CASE PITTING IS PRESENCE IN SEAT AND VALVE THEN LAPPING IS CARRIED OUT. BUT CARE TO BE TAKEN THAT THE VALVE AND SEAT ANGLE DOESNOT EXCEED THE VALVE IN THE MANUAL AS IT WILL LEAD TO SHROUDING.
NEW SEAT AND VALVE GUIDE SHOULD BE FIRST COOLED IN REFRIGERATION ROOM AND THEN SHRUNK FIT ON ITS PLACE.
FUEL VALVE AREA TO BE THOROUGHLY CLEANED.
PRESSURE TESTING OF CYLINDER HEAD IS CARRIED OUT TO INSPECT THAT CYLINDER HEAD DOESNOT LEAK WATER WHEN FITTED IN PLACE.
PRESSURE TESTING OF CYLINDER HEAD :-
ALL THE OPENING UNDERSIDE OF HEAD IS BLANKED. ON THE TOP OF THE HEAD ALL OPENING EXCEPT ONE IS BLANKED. NOW POUR WATER INSIDE THE HEAD TILL IT FILLS UP COMPLETELY. NOW CONNECT THE HAND PUMP ON THE OPENING AND PUMP WATER INSIDE THE HEAD TILL PRESSURE IN PRESSURE GAUGE SHOWS 4-6 BAR PRESSURE. LET IT HOLD FOR 30 MINUTES. CHECK FOR SIGNS OF WATER LEAKAGE FROM ALL THE OPENING AND TIGHT IT IF LEAKAGE IS THERE, AGAIN RAISE THE PRESSURE IF PRESSURE HAD DROP DUE TO LEAKAGE FROM OPENINGS BLANKED. ALSO CHECK FOR LEAKAGE FROM ANY OTHER AREA SPECIALLY EXHAUST VALVE SEAT, FUEL VALVE AREA , SIDE COVERS OF JACKET AND UNDER SIDE OF JACKET. IF LEAKAGE FROM CYLINDER JACKET IS THERE THAN OPEN THE JACKET AND RENEW THE ORING. AGAIN DO PRESSURE TESTING TO CHECK THE LEAKAGE.

Наука