WÄRTSILÄ PAAE051728, Instruction Manual

Page: 205 / 394

5 Before grinding, check the valve stem clearance.
If
the clearance is too large, measure the stem and guide, and
change the worn part; the valve guide can be pressed out.
Check the bore in the cylinder head. When refitting, cooling in
with liquid nitrogen is recommended, but pressing in with oil
lubrication can also be accepted. After fitting in, check the
guide bore and calibrate, if necessary.
12.3.4 Lapping of inlet valves
If there are slight pits on the sealing faces they can be lapped by
hand:
Note! Lapping is not allowed for exhaust valves.
1 Fit the turning tool
to the valve.
2 Apply a thin layer of lapping compound
to the sealing
surface of the valve; No.1 for coarse lapping, No.3 for fine
lapping.
3 Rotate the valve to and fro
towards the seat with the
turning tool 800028. Lift the valve from the seat at intervals
while lapping.
4 Remove the smallest possible amount of material
because the sealing faces have hardened during operation and
are valuable. It is not necessary to grind off all pits.
5 Clean the valve and seat
carefully after lapping.
12.3.5 Machine grinding of exhaust and inlet valves
Note! The valve should be cooled by water during the grinding.
1 Seat face of the inlet valve:
The seat angle of the inlet
valve is 20° with a tolerance of 0°- +0.10°. Minimum allowable
inner diameter “X” of the seat face after grinding is 85 mm, see
Fig 12-6; after that, the valve must be replaced by a new one.
2 Seat face of the exhaust valve:
The seat angle of the ex-
haust valve is 40° with a tolerance of 0.10°- +0.20° to achieve
contact to the seat ring at the periphery of the valve. Minimum
allowable inner diameter “X” of the seat face after grinding is
82 mm, see Fig 12-6; after that, the valve must be replaced by a
new one.
32-200646-01 Cylinder Head with Valves 12
WÄRTSILÄ 32 12 - 9