Doc. #: A-718C, Rev. 1
Page 21 of 36
6.1.2
Stem
(item 2)
.
Roll the stem in “V” blocks or on a flat surface. It will be apparent if the stem is bowed. If
straightening is required, do not grip or deflect it on the ground surface of the packing zone, in the Acme
thread zone, in the 1/16"-20 thread area and below, where deformation of the metal would foul the threads
or damage stem straightness. All nicks, burrs, pits, scratches, etc., must be removed. Inspect for cracks in
the thread root area.
Figure 6-2 Valve Stem
6.1.3
Body
(item 4)
.
Inspect the part for corrosive degradation, particularly in areas where O-rings and flat gasket
seals are positioned. Clean off these areas to be sure they are free of pits, scratches, etc. that could form
leak paths. The threads are 3/8"-16 on top flange and 1/2"-13 on side flange. If any of the threads are
stripped or corroded, remove and replace the studs.
Figure 6-3 Valve Body
6.1.4
Bonnet
(item 5)
.
Since this is not a pressure containing part, a visual
evaluation of its general condition should be made. The Acme thread
is 3/4"-6. The thread for the packing screw 1-1/4"-12. If either thread is
stripped, crossed or pitted, the part should be discarded and replaced.
6.1.5
Packing Screw
(item 7)
.
The thread is 1-1/4"-12. It must be clean
without nicks, scratches, pits and other defects that would strip or gall
the bonnet thread when assembled.
6.1.6
Retainer Seal Washer
(item 27)
.
If this has been dished due to over-
torqueing the stem, flatten in a vise.
Figure 6-5 Retainer Washer
Figure 6-4 Valve Bonnet and
Packing Screw
