XVIII. Part Inspection of Pilot Valve (Contd.)
12. Modulator Stop: Top seating surface for cuts
or deformities. The surface can be lapped if the
distance from the seat to the outside shoulder
does not reduce to less than .086” (2.18 mm).
13. O-Ring Retainer: Seating surface for cuts or
deformities. The surface can be lapped if the
overall height of the part does not reduce to less
than .160” (4.06 mm). Also, check the outside
diameter for any scratches that might prevent
the O-Ring (Modulator Seat) from sealing.
14. Modulator Piston Bottom: Galling or excessive
wear on the outside diameter that rubs against
the Modulator Base. Make sure that the lip holding
the O-Ring (Modulator Seat) is not deformed. Also,
check the outside diameter of the O-Ring groove for
scratches that might cause the O-Ring (Modulator
Seat) not to seal. Check for any corrosion or pitting.
15. Modulator Base: Galling or excessive wear on any
inside diameter. Any corrosion or pitting.
C. 39MV22/72
1. Main Piston: Galling or excessive wear on the
diameter where the Spring Seal (Main Piston)
engages or on the spherical bearing surface.
Any corrosion or pitting that appears detrimental
to the function of the valve. The part can be
polished as long as the outside diameter of the
where the Spring Seal (Main Piston) rides must be
.970 ± .001” (24.64 ± 0.03 mm) on 39MV22 model
or .812 ± .001” (20.63 ± 0.03 mm) on 39MV72. A
surface finish of 8 RMS must be maintained for
proper sealing on these surfaces.
2. Piston Nose: Galling or excessive wear on
the diameter where the spring seals engage.
Any corrosion or pitting that appears detrimental
to the function of the valve. The part can be
polished as long as the outside diameter of the
stem remains at .243 ± .001” (6.17 ± 0.03 mm). The
stem itself must have a T.I.R of .001” (0.03 mm)
along its length.
3. Insert Top: Galling or excessive wear on the
inside diameter that guides the Main Piston.
Check for any corrosion or pitting. Also, check for
galling of threads.
4. Insert Bottom: Galling or excessive wear on
the inside diameter that guides the Main Piston.
Check for any corrosion or pitting.
5. Adjuster Top: Galling or excessive wear on the
inside diameter that guides the Main Piston.
Check for any corrosion or pitting. Also, check
for galling of threads.
6. Adjuster Bottom: Galling or excessive wear on
the inside diameter that guides the Main Piston.
Check for any corrosion or pitting. Also, check for
galling of threads.
7. Vent Seal Adaptor: Check for any corrosion
or pitting.
8. Top Plate: Galling or excessive wear on the inside
diameter that guides the Main Piston. Check for any
corrosion or pitting. Also, check for galling
of threads.
9. Bonnet: Check for any corrosion or pitting. Also,
check for galling of threads for the compression
screw and where it attaches to the Pilot Base.
10. Compression Screw: Galling at the spherical
bearing surface or in the thread. Check for any
corrosion or pitting.
11. Spring Washer(s): Galling at the spherical bearing
surface. Check for any corrosion or pitting.
12. Pilot Base: Check for any corrosion or pitting.
Also, check for galling of threads.
13. Spring: Check for any corrosion or pitting.
If any damage listed above is present, the part should
be replaced or repaired per instruction. Other valve
parts may be acceptable with light corrosion, pitting,
or minor damage of other types if it can be determined
that it will not affect product performance. All O-Rings
and spring seals should be replaced each time the valve
is disassembled.
Refer to Tables 25 and 26 for O-Ring/Spring Seal repair
kits. Recommended spare parts are listed in Table 23.
60 | BHGE
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