Maintenance Instructions; General Information; O-Ring Seat; Re-Machining Nozzle Seats - Baker Hughes Consolidated 4900 Series Instruction Manual

XIII. Maintenance Instructions
A. General Information
After the valve has been disassembled, closely
inspect the seating surfaces. O-Ring seat seal valve
nozzles can only be reconditioned by machining, not
lapping.
(For specific information concerning the machining
of nozzle and disc seating surfaces, see the
Re-Machining Nozzle Seats and Bores and
Re-Machining the Disc Seat sections.)
B. O-Ring Seat
The nozzle must not have any defects to prohibit the
O-Ring from sealing properly, especially the O.D. of
the seat where the surface must maintain a minimum
of 32 RMS finish. See Figure 13 and Table 1 for
reworking O-Ring Nozzle.
The O-Ring Retainer must also maintain a flat
surface for it to sit on the Nozzle. Only polishing of
surface can be done since material removal from
this surface will cause the Nozzle to over engage
O-Ring. Polishing paper or some other light abrasive
can only be used since the part cannot function
properly if its overall dimensions are changed
significantly. If significant corrosion or damage has
occurred on O-Ring retainer, discard and replace.
ATTENTION!
Before assembly, grind the contact surfaces of the
nozzle and O-Ring retainer to provide metal-to-
metal seat tightness in the event of O-Ring failure.
A
R
Ø .004" (0.10 mm) Z
B
50˚
Z
Figure 13: Nozzle O-Ring Seat (DA)
© 2020 Baker Hughes Company. All rights reserved.
F
Ø .005" (0.13 mm) Z
G
.001" (0.03 mm)
C. Re-Machining Nozzle Seats
Remove the nozzle from the valve to be remachined.
If it cannot be removed from the base (1), re-machine
it inside the base.
Take the following steps to setup the lathe and
nozzle:
1. Grip the nozzle in a four-jaw independent chuck
(or collet, if appropriate), using a piece of soft
material such as copper or fiber between the
jaws and the nozzle as shown at A (Figure 14).
2. True up the nozzle so that the surfaces marked
B and C run true within .001" (0.03 mm) on
indicator (Figure 14).
D. Machining Procedure: O-Ring Seat
See Figure 13 and Table 1
1. Take light cuts across surface A (50°), until
the damaged areas are removed. Turn to the
smoothest possible finish.
2. Cut back the outside surface B, until dimension
H is obtained.
3. Machine radius R.
4. When the minimum dimension L is reached, the
nozzle should be discarded.
H
L
A
Z
Figure 14: Machining Nozzle Seats
Nozzle
B
C
Chuck Jaw
Consolidated 4900 MPV Series POSRV Manual
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