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5. Maintenance – Repair
5.1 Packing Box
Tightness of the packing box is obtained by compression
of the packing (6). Compression must be achieved by
evenly tightening the packing flange nuts (3) on the
packing flange (4). Periodical retightening of the packing
flange nuts is required to maintain tightness.
Make sure that the packing is not over tightened as this
could prevent smooth operation of the valve. If a leak
persists after the packing has been compressed to a
maximum, the packing needs to be changed.
A packing spacer (5) is only mounted when the bonnet
has a side connection.
5.1.1 Carbon/PTFE and pure PTFE packing rings
Carbon/PTFE and pure PTFE packing rings are cut in
such a way that they can be replaced without having to
separate the valve plug stem from the actuator stem.
A. Unscrew and remove the packing flange nuts (3).
B. Lift the packing flange (4) and packing follower (23)
up along the valve stem.
C. By means of a puller, remove the packing (6) and
packing spacer (5), taking care not to damage the
sealing surface of the packing box lantern or the
valve plug stem.
D. Replace the packing rings, with the cut in each ring
placed about 120° from the next, pressing them
down one at a time and respecting the table below:
Carbon/PTFE and pure PTFE packing box
Number of rings
without side
N.D. mm (in.)
connection
50
6
(2")
80 – 100
8
(3" – 4")
150 to 600
7
(6" to 24")
E.
Put the follower (23) and the packing flange (4)
back on.
F.
Screw and tighten the packing flange nuts (3) without
cramming the packing rings.
10 | GE Oil & Gas
with side connection
on top of
under
packing
packing
spacer
spacer
2
3
2
Figure 3
G. Put the valve back into service and check for
tightness. Tighten packing flange nuts (3) as required.
5.1.2 Graphite packing ring
To carry out this operation, the valve plug stem must be
removed. See chapter on actuator disassembly.
A. Loosen and remove packing flange nuts (3).
B. Remove packing flange (4), and packing follower (23)
from the plug stem.
C. By means of a puller, remove packing rings (6),
insuring not to damage the sealing surface of
packing box or plug stem.
D. Replace new packing set (6); first one back-up ring
(Carbon/Graphite braided ring), then expanded
graphite rings (smooth rings), at last, one other
braided back-up ring; it is important to press the
rings down one at a time in the packing box.
Number of
packing set
N.D. mm (in.)
50 (2")
80 – 100
(3" – 4")
150 to 600
(6" to 24")
E.
Put the follower (23) and packing flange (4) back on.
F.
Screw and moderately tighten the packing flange
nuts (3).
G. Reassemble the valve plug stem (see chapter on
actuator re-assembly).
H. Open and close the valve several times then tighten
the packing.
4
I.
Put the valve back into service and check for
tightness. Tighten packing flange nuts (3) as required.
5
5.2 Repair of Parts
5
Before re-assembly, the parts must be carefully
examined in order to eliminate any scratched, worn or
damaged parts.
5.2.1 Guiding surfaces
The guiding surfaces of the cage and valve plug, the
guide bushing, and the guiding surfaces of the plug stem
and auxiliary pilot plug must be checked in particular. If
Number of rings
Braided
Graphite
1
4
1
6
1
5
Figure 4
© 2015 General Electric Company. All rights reserved.
Braided
1
1
1
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