Baker Hughes Masoneilan 525, Instruction Manual

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Reserved.
Avoid over-lapping as this can cause damage to the
seating surface rather than improve leakage
performance.
10. After completion of the lapping operation,
remove bonnet and plug. The seating area of the
seat ring and the plug must be cleaned of all
lapping compound in preparation for
reassembly. Do not remove seat ring.
8.3.2 526 (Back Pressure Service)
1. CIean body gasket surface areas.
2. When seats have been removed, insure that the
sealing surfaces in the body bridge and the threads
are thoroughly cleaned.
NOTE: A sealant compatible with the process should be
applied sparingly to the seat ring threads and sealing
shoulder.
3. lnstall and tighten seat rings using fabricated wrench
used for removal.
Do not over-tighten. Do not strike seat ring lugs directly.
This could distort the seat ring resulting in seat leakage.
4. Apply lapping compound on the plugs at several
spots equally spaced around the seating area.
5. lnsert the stem and plug sub-assembly carefully into
the body until it is seated.
6. Place bonnet (8) on the body and fasten the bonnet to
the body using four body stud nuts (10) spaced
equally apart. Apply slight pressure and tighten
evenly.
Do not tighten nuts to final torque specifications at this
time. The bonnet is used temporarily for guiding purposes
only.
7. lnsert two or three pieces of packing (16) into the
packing box to assist in guiding the stem and plug
during lapping.
8. Screw a drilled and tapped rod with a T-handle onto
the plug stem and secure with a locknut (see Figure 3).
NOTE: As an alternative, drill a hole through a flat steel
plate and fasten to the plug stem using two locknuts.
9. Apply slight upward pressure on the stem to establish
seating contact, and rotate the stem in short
oscillating strokes (around 8 to 10 times). Repeat this
step as necessary.
NOTE: The plug should be lifted and turned 90° each time
before repeating Step (9). This intermittent lifting is
required to keep the plug and seat rings concentric during
lapping.
10. Avoid over-lapping as this can cause damage to the
seating surface rather than improve leakage
performance.
11. After completion of the lapping operation, remove
bonnet and plug. The seating area of the seat ring
and the plug must be cleaned of all lapping
compound in preparation for reassembly. Do not
remove seat ring.
8.4 Pinning
Valve plug and stem assemblies are normally furnished as
a complete assembly in which case the installation
involves no further assembly steps. It is only necessary to
lap the plug and seat ring and assemble the valve. If it is
necessary to replace the plug it is recommended that a
new stem be used. If the old stem must be used, it is
necessary to determine if the stem will be long enough
since the stem will require cutting. If the stem does not
engage the actuator stem by a minimum of one stem
diameter, the old stem should not be used. If it does
engage a minimum of one stem diameter, proceed as
follows.
Note: While pinning is being performed, care must be
taken not to damage the seating surface and plug guides.
A. Using a drift punch, drive out the old pin (8).
Note: If it is necessary to drill out the pin, a drill somewhat
smaller than the pin should be used and the remainder of
the pin driven out.
B. Unscrew the plug from the stem (counter clock-wise).
C. Measure threaded portion of the stem.
D. Cut off the stem directly above the existing pin hole.
E. Rethread the stem to the original amount.
Note: The area of the plug stem marked X in Figure 4
serves as a guide and must be checked to ensure a close
fit in the valve plug.
F. Screw the stem solidly into the plug.
Note: This can be checked by measuring the depth of the
pilot recess in the plug (X in Figure 4), and making a
reference mark on the stem the same distance from the
thread. When properly assembled, the reference mark
should be flush with the end of the guide section.
G. Place the plug guide on a V block and using a suitable
size drill, drill the stem using the hole in the plug as a
guide.
H. Remove any burrs from the plug guide by making a
slight counter bore.