IOM-DA8
7
loosened and socket wrench is removed.
c. Remove upper diaphragm pressure plate
(8).
d. Remove diaphragm(s) (9, 9.1, 9.2, 9.9).
Examine diaphragm(s) to determine
wheth er failed; determine if operating
conditions are ex ceed ing pressure drop
or temperature limits.
e. Remove upper stem seal (14.1).
f. Remove lower diaphragm pusher plate
(10).
g. Remove middle stem seal (14.2).
h. Remove piston/guide bearing (13) with
dynamic side seal (27) in place.
i. Remove lower stem seal (14.3).
j.
Place socket wrench on upper end of plug
(20) as in Step b. above. Rotate plug (20)
CCW (viewed from above) to loosen seat
disc nut (30). Once nut (30) is loos ened,
re move partial as sem bly (20, 27, 28, 29,
30) from vise. Complete re mov al of seat
disc nut (30), seat disc washer (29) and
seat disc (28).
3. Examine the components (27.1, 27.2, 27.3,
27.4, 27.5, 27.6) of the dynamic side seal (27)
to determine if sig nif i cant leak age was oc cur-
ring. If the dynamic side seal (27) shows signs
of significant leakage, de ter mine if op er at ing
conditions are ex ceed ing pres sure, pres sure
drop, or temperature lim its.
Remove dynamic side seal (27) com po nents
from plug (20) for sizes 1/2" – 2", or from
piston/guide bearing (13) for sizes 2-1/2" –
4". Spe cial care should be taken when using
“tools” to remove the com po nents to ensure
that no scratches are im part ed to any portion
of the plug (20) or piston/guide bear ing (13)
groove.
4. Solvent clean all metal parts to be reused.
D. Inspection of Parts:
1. After inspection, remove from the work area
and dis card the old “soft goods” parts (i.e.
o-rings, di a phragms, seals, etc.). Met al
di a phragms should be replaced. These parts
MUST be re placed with fac to ry supplied new
parts.
2. Inspect the metal parts that will be reused. The
parts should be free of surface con tam i nants,
burrs, oxides, and scale. Rework and clean
the parts as necessary. Surface con di tions
that affect the regulator performance are stated
below; replace parts that can not be re worked
or cleaned.
3. QC Finish & Dimensional Re quire ments:
a. Valve plug (20);
1. No major defects on plug's (20) bot tom
guide spindle, or at guide area near
dynamic seal groove.
b. Cage
(19);
1. 16 rms finish on cylinder bore. No
“ledges” formed due to wear from
moving dynamic side seal (27).
2. 16 rms finish on its seating surface
for tight shutoff.
c. Lower guide bushing (24);
1. 16 rms finish on bore.
2. Max 0.015 inch (0.38 mm) clearance
be tween valve plug (20) spindle and
lower guide bushing (24).
d. Internal sensing drilled plug (32);
1. Ensure that bore is minimum 0.125
inch (3.20 mm). Drill out as required.
e. Piston/Guide Bearing (13)(2-1/2"-4" only);
1. No defects at guide area near dy nam ic
seal groove.
4. Staging Material for Reassembly.
a. Inspect and clean parts, as nec es sary,
from the spare parts kit. (See Article
VII.A.4. comments concerning cleaning
for ox y gen service.)
b. Lay out all the regulator parts and check
against the bill of material.
E. Reassembly of the ITA:
1. Position valve plug (20) with seat disc-end up-
wards. Place new seat disc (28) into recess of
lower end of valve plug (20) properly ori ent ed.
2. Position seat disc washer (29) next to seat
disc (28).
3. Engage seat disc nut (30) to secure washer
(29) and seat disc (28) to valve plug (20).
Firmly hand-tighten.
4. Body Sizes 1/2" through 2":
a. Using the two square-section metal bar-
stock pieces of VII.C.1.a., clamp the plug
(20) into a vise with the plug's (20) spindle
pointed upwards.
b. Using a torque wrench, tighten the seat
disc nut (30) to 20-35 ft-lbs. by rotating
CW.
c. Remove assembly (20, 28, 29, 30) from
vise and rotate end-for-end and resecure
in vise using same metal bars.
5. Body Sizes 2-1/2" through 4":
a. Orient plug (20) with threaded end up-
