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6 | Baker Hughes
Maintenance
If there is excessive leakage through the regulator when it is
shut off, the cause may be:
1.
Foreign matter holding valve off seat : disassemble and
clean.
2. Normal wear of seating surfaces : disassemble and replace
plug and/or seat ring.
3.
Seat ring gasket (2) damaging (except with trim for C
v
max.
3.8) : replace gasket.
Disassembly (Figure 3)
• Disconnect the control line(s) at the diaphragm case.
•
Remove the two packing flange nuts (8b). Raise packing
flange (10) up the plug stem and remove the two nuts (8a)
as well as the two mounting screws (16).
•
By means of two flat spanners, unlock the plug stem nuts
(27) and unscrew them to the threaded end of the plug stem
(12 or 183). Tighten nuts in this position.
•
Fasten the actuator to a hoisting gear and very slowly pull
out the actuator-plug S/A.
•
With a flat spanner applied on the nuts (27), unscrew the
plug stem from the actuator stem while pulling out vertically
and slowly the actuator. Carry on until plug stem is fully
unscrewed from actuator stem.
•
Separate actuator and packing flange (10) from the body
S/A.
• Remove two nuts (27) and packing follower (9) from the
plug stem.
• Using a packing hook, remove the largest number of
packing rings (6) from packing box. Remove safety pin (11)
and pull plug stem to remove packing spacer (5) and the
remainder of packing rings.
•
Using a 9/16” or 14 mm piece of hex stock and a wrench,
unlock and pull out seat ring retainer (4).
• Pull out seat ring (3) and gasket (2) using a hook made from
steel wire, diameter about 3 mm. Carefully fettle the hook
end.
Note:
The seat ring with Cv < 0.10 consists of two parts: The
seat ring proper (3e) and a spacer (3f). The small size of
orifice of these parts does not allow for their removal by means
of a hook. Therefore, it is necessary to remove the body from
the pipe, turn it over and, if needed, to hit the bottom with a
wooden mallet. Should the seat ring be jammed in its housing,
it is possible to move it using a screwdriver inserted through
the outlet orifice.
Reassembly and Plug Stem Adjustment
(Figures 3, 4, and 5)
Before reassembly, thoroughly clean the inside of the valve
body and parts. Mating surfaces must be thoroughly cleaned.
On reassembly, new seat ring gasket (2) and new packing (6)
must be used.
• Place a new seat ring gasket (2) in the valve body (13) and
install the seat ring (3) taking care to correctly center the
gasket on the seat ring shoulder. Orient it in such a manner
that one of its ports lines up with the body outlet orifice.
Note:
For a C
v smaller than 0.10, the seat ring (3e) shall
first be positioned on the new gasket (2) taking the same
precautions as shown above. Next, engage spacer (3f) and
orient one of its ports towards the body outlet orifice.
Regulator with Cv 3.8 does not feature any seat ring gasket (2).
•
Carefully apply Never Seez grease (or equivalent) to
threads and bottom of retainer (4). With a 9/16” or 14 mm
piece of hex stock and a wrench, torque the retainer to 59
ft-lbs (8 daN.m) if a graphite gasket st. st. reinforced, or to
40 ft-lbs (5,5 daN.m) if a glass filled PTFE gasket.
See Figure 4.
Note:
On regulator with Cv 3.8, torque the retainer to 15 ft-lb
(2 daN.m).
Regulator must be isolated and pressure vented
before disassembly.
Figure 4 - Tightening the seat ring retainer (4)
Carefully avoid that seating surface of the plug
contacts the seat ring during the plug unscrewing.
