Baker Hughes Masoneilan 525 Seris, Инструкция по эксплуатации

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Masoneilan Regulators Models 525 & 526 Manual | 4
Copyright 2020 Baker Hughes Company. All rights reserved.
7. Maintenance & Repair
The purpose of this section is to provide recommended
maintenance and repair procedures. These procedures assume
the availability of standard shop tools and equipment.
7.1 Failure to shut off
If there is excessive leakage through the valve when it is shut off,
the cause may be foreign matter holding the plug off the seat.
If so, disassemble and clean. If leakage is the result of normal
wear, regrind the seating surfaces or, if necessary, replace the
plug and/or seat rings.
7.2 Bushing Removal
The bushing (23) is press fit into the bonnet and blind head. This
part does not normally require replacement. If necessary, it may
be pulled or machined out. When machining the bushing out, care
must be taken to maintain proper dimensions and tolerances in
the bonnet or blind head. These will be furnished upon request.
7.3 Lapping Seats
Lapping Seats Lapping is the process of working the valve
plug against the seat ring with an abrasive to produce a close
fit. If valve leakage is excessive, lapping becomes necessary.
The plug and seat ring seating surfaces should be free of large
scratches or other defects, and the contact surfaces of the seats
should be as narrow as possible. This may require dressing
both parts in a lathe. A good grade of fine grinding compound is
required for the lapping operation.
The compound should be mixed with a small quantity of lubricant
such as graphite. This will slow the cutting rate and prevent
tearing of the seating surfaces. The amount of lapping required
depends on the materials, condition of seating surfaces, and
accuracy of machining. If a short period of lapping does not visibly
improve seating, there is usually no advantage in continuing as
excessive lapping may result in rough seats. The only remedy is
replacement or re-machining of one or both parts. When lapping
new plugs and seat rings, begin with a medium fine (240 grit) and
finish with a finer grade (600 grit).
Note: Lapping should produce a line contact area, not the
entire surface.
Before lapping, the plug and stem sub-assembly must
be concentric. (See pinning operation, section 8.4).
7.3.1 525 (Reducing 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 di-
rectly. 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.
Donottightennutstofinaltorquespecificationsat
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 pressure on the stem, 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.
Avoid over-lapping as this can cause damage to the
seating surface rather than improve leakage perfor-
mance.
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.
7.3.2 526 (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.