How To Check And Adjust The Valve Clearance Of Diesel Generator

For new diesel generators and diesel generators put into service after overhaul, the first valve clearance inspection shall be conducted during the first maintenance, so as to timely adjust and correct the initial changes of valve clearance. During subsequent normal operation, check and adjust according to the maintenance schedule.

Check the valve clearance after the diesel generator stops running and the coolant temperature drops below 60 ℃.

(1) Remove the cylinder head cover.

(2) Remove the observation window cover on the flywheel housing.

(3) Turn according to the rotation direction sign beside the flywheel housing observation window to make the piston of the first or sixth cylinder of the diesel engine at TDC. Observe the pointer position of the flywheel housing cover plate from the observation window. When the pointer is aligned with the "0" mark on the flywheel, it is the top dead center of the piston of the first or sixth cylinder.

Note: Turning gear

Turning of diesel generator for power station: unscrew the bolts on the fixing plate of the turning shaft behind the flywheel housing, remove the fixing plate, push the turning shaft inward to the end, and make the teeth on the turning shaft mesh with the flywheel gear ring. Insert the socket into the hexagonal hole of the turning shaft, and turn the turning shaft with a ratchet wrench.

Turning gear of marine diesel generator: the front pulley bolt of diesel generator is used for turning.

(4) Check whether the valve rocker arm of the first cylinder can swing. If it can, it means that the piston of the first cylinder is at TDC. If not, the piston of the 6th cylinder is at TDC.

(5) When the piston of the first cylinder is at TDC, use a micrometer (thickness gauge) to check the inlet valve clearance of cylinders 1, 2 and 4 and the exhaust valve clearance of cylinders 1, 3 and 5. When the piston of the sixth cylinder compresses TDC, use a micrometer (thickness gauge) to check the inlet valve clearance of the third, fifth and sixth cylinders and the exhaust valve clearance of the second, fourth and sixth cylinders.

Note: When checking the clearance with clearance plugs, if the plugs move between the top surface of the valve bridge and the rocker arm with a little resistance, it is the correct valve clearance.

(6) If the clearance does not meet the requirements, loosen the lock nut of the valve clearance adjusting screw on the rocker arm, adjust the valve clearance to the specified value, and then tighten the lock nut to 125 ± 6N · m. Recheck the valve clearance, and the clearance value shall not change.

Valve clearance:

The intake valve is 0.45mm.

Exhaust valve 0.40mm.

(7) Mark the vibration damper or crankshaft pulley, and then rotate the crankshaft for one circle (360 °) to adjust the remaining inlet and exhaust valve clearances in the same way.

(8) Install the cylinder head cover, check the cover seal ring and gasket, and replace them if damaged. Tighten the cylinder head cover bolts to a torque of 75~85N · m.

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