6 | Baker Hughes
Copyright 2021 Baker Hughes Company. All rights reserved.
7. Place an appropriate tool on the valve stem (5) threads to
allow for manual rotation. Options for creating a manual
resurfacing tool include using a T-handle secured with a
locknut, or using a flat piece of steel with a drilled hole and
two locknuts to fasten to the valve stem (5).
8. Lapping of the seat ring (3) is accomplished by rotating the
plug (5) in short oscillating strokes. After 8 to 10 strokes, lift
the plug (5) and repeat the operation three or more times in
increments of 90°, 180°, and 270°, from the original position.
Note: Performing the operation at various increments is
critical in maintaining concentricity between the parts
during lapping.
9. Lapping can be repeated, but should be limited as much as
possible so that the seat line remains sufficiently narrow to
guarantee tightness.
10. After lapping, disassemble the parts to clean them and then
reassemble, making sure the seating angles are within
tolerance as shown in Figure 2.
Gaskets
Gasket seating surfaces must be free of dents, scratches,
corrosion, or other types of damage. Clean mating surfaces as
required and replace any non-conforming parts. Spiral wound
gaskets (items 7, 8 and 34 for top entry designs) must always be
replaced after disassembly.
Valve Reassembly
After completing the recommended maintenance and repair
actions noted above, reassemble the valve using the following
procedure.
Make sure the valve body and all gasket surfaces are clean and
free of any damage
Make sure any recommended lubricants or sealing compounds
are compatible with the process fluid. Use acceptable substitutes
as required.
For Bottom Entry 77001 Series Designs follow disassembly
instructions 1-4:
1. Install the upper stem guide bushing (6) into the top end of
the body (1).
2. Install the seat ring (3) into the body and carefully lower the
plug stem (5) into the seat ring using caution to not damage
any surfaces.
Be careful not to damage the plug stem (5) or the
seat ring (3) while removing these parts from the
body. Scratches or damage to these parts can
result in leakage and premature wear.
3. Coat the upper spider gasket (8) lightly with gasket
compound and secure on top of spider (4). Insert spider into
the valve body over the plug (5) until it makes contact with
the seat ring (3). Install the lower spider gasket (7) over the
spider.
Note: Some designs may be equipped with an integral
spider as part of the bottom entry spool. For these
designs there will not be a lower spider gasket as it is a
one piece construction.
metal removal from both the plug and seat seating surfaces is
allowable for any valve size.
Seating Surfaces: Make sure the seating angles on the reworked
parts are within the specified tolerances as shown in Figure 2
below. Parts requiring more metal removal to restore should be
discarded and replaced.
5
3
Figure 1: Plug and Seat Surfaces
Ra 0.
4
32° 0'
31° 0'
.03[.001] A
Ra 0.
4
31° 0'
30° 0'
.03[.001]
A
Figure 2: Plug and Seat Ring
1. Clean body gasket surface areas.
2. If lapping is to be done outside of the body ensure the seat
ring (3) is set on a flat and stable surface and proceed to
step 5.
3. For lapping done with the trim installed inside the body, install
new gaskets into the valve to ensure the ideal geometric
characteristics in order to have the correct position of the
seat ring during lapping.
Note: The gaskets used during lapping must not be reused
for the body reassembly.
4. Loosen the packing flange nuts (16) to remove friction and
allow the plug (5) to rest against the seat ring (3) by its own
weight.
5. Spread a fine layer of high quality lapping compound (600
grit) on the seating surface of the seat ring. If lapping with
the trim installed inside the valve, insert the seat ring (3) into
the valve body (1).
Do not allow the lapping compound to get onto
plug or nonseating stages of the seat ring.
6. Insert the plug (5) carefully into the seat ring (3) until it is
seated.
Note: It is highly recommended to assemble the valve
completely including using new gaskets before lapping
the valve. Assembly with the top entry bonnet or bottom
spool aligns the trim parts and improves the integrity of
the surface geometric characteristics.
