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Baker Hughes
© 2020 Baker Hughes Company. All rights reserved.
The valve repair operation will depend upon the damage.
In some cases, it is easier to replace the part. In a
number of cases, only the nozzle and disc need to be
repaired. This can be done in the following manner:
1. If the disc is damaged by nicks, cuts, dents on the
soft seat, it is to be replaced by using any sharp
tool to pull out the retaining ring, then soft seat. See
Reassembly Procedure for installing new soft seat.
2. Lapping a flat seat is extremely simple. No special
skill is required and the technique is readily apparent
after a few minutes of actual lapping.
3. The following precautions and hints will enable
anyone to do a “Professional” job of lapping seats.
a. Keep the work clean.
b. Always use a fresh lap. If signs of wearing (out of
flatness) are evident, recondition the lap.
c. Apply a very thin layer of compound to the lap.
This will prevent rounding off the edges of the
seat.
d. Keep the lap squarely on the flat surface and
avoid any tendency to rock the lap which will
cause rounding of the seat.
e. When lapping the Base keep a firm grip on the
lap or part to prevent the possibility of dropping it
and damaging the seat.
f. Lap, using a reciprocating motion in all
directions, at the same time applying uniform
pressure and rotating the lap or the part slowly. If
reconditioning necessitates removing more than
.010” (0.03 mm), replace the base.
g. Replace the compound frequently after wiping off
the old compound, and apply more pressure to
speed the cutting action of the compound.
h. To check the seating surfaces, remove all
compound from the lap. Then, shine up the
seat with the same lap using the lapping motion
described above. Low sections on the seating
surface will show up as a shadow in contrast to
the shiny portion. If shadows are present, further
lapping is necessary, and only laps known to be
flat should now be used. Only a few minutes will
be required to remove the shadows.
i. When the lapping is completed, any lines
appearing as cross scratches can be removed by
rotating the lap which has been wiped clean of
compound on the seat about its own axis.
j. The seat should now be thoroughly cleaned with
kerosene, light oil, or carbon tetrachloride, using
a lint-free cloth or tissue paper.
XII. Inspection and Part Replacement
