Cashco DA8 Differential - Manual (Page 6)

IOM-DA8/9 6
1. Shut down the system in accordance with
Section
VI.
2. Disconnect the external sensing line, if
in
stalled.
3. The quick change trim allows for the disas-
sembly of the regulator while installed in the
pipeline. Alternatively the maintenance can
be done in a shop area. NOTE: It is easier to
repair the regulator when mounted upright in
a horizontal pipe run compared to a vertical
pipe run or a regulator mounted with spring
facing down. The description hereafter will
assume shop disassembly.
4. Place the valve unit in a vise with the spring
chamber (4) upwards.
5. Relax range spring (6) forces by turning ad-
justing screw (1) CCW for DA8 (viewed from
above) until spring relaxes. Turn the adjusting
screw CW for the DA9 to relax the extension
load of the spring assembly (item 6). The easi-
est way to check this, is to carefully loosen the
locknut (item 2). If the adjusting screw (item
1) sinks into the chamber as the locknuts are
loosened, then the spring assembly is still
in extension. Turn the adjusting screw CW
to remove the extension. Fully remove the
locknuts.
6. Loosen the diaphragm fl ange bolts (11) and
nuts (12) uniformly.
7. Place matchmarks on body (23) and spring
chamber (4) fl anges. Com plete ly remove bolt-
ing (11,12) Re move the spring cham ber (4).
8. Remove spring follower (5) and range
spring (6.1) on DA8. Unthread the range spring
assembly (6.2) from the valve plug on DA9.
9. Grasp opposite edges of diaphragm (9) and
withdraw the ITA from within the cage (19).
Set the ITA aside.
10. Evenly loosen the cage cap screws (18) in
single revolution increments until fully loos-
ened; remove cage cap screws (18).
11. Pull cage (19) up and out of body.
12. Remove o-ring cage seal (15).
13. Remove lower cage gasket (21).
14. For metal diaphragm constructions, remove
diaphragm gasket (37) from body (23) di a -
phragm fl ange.
15. Remove body (23) from vise. Solvent clean
all removed metal parts.
C. Disassembly of the ITA:
1. Body Sizes 1/2" – 2". (See Figures 2 thru 4):
a. Obtain two pieces of square-section
barstock with a 3/8"-7/16" dimension,
approximately 2 inches long.
b. Place plug (20) into a vise using the bars
of a. above positioned on "fl ats" located
on plug (20) to prevent vise jaw marks
from direct surface contact with the plug
(20). Orient with diaphragms on topside.
c. Sizes 1/2"-1": Remove diaphragm lock nut
(7) by rotating CCW.
Sizes 1-1/4"-2": Remove diaphragm cap-
screw (7) by rotating CCW.
d. Remove upper diaphragm pressure plate
(8).
e. Remove diaphragm(s) (9, 9.1, 9.2, 9.9).
Examine diaphragm(s) to determine
wheth er failed; determine if op er at ing
conditions are ex ceed ing pressure drop
or temperature lim its.
f. For composition diaphragm con struc tion,
remove upper stem seal (14.1).
g. For metal diaphragm con struc tion, re move
lower pusher plate gasket (14.4).
h. Remove lower diaphragm pusher plate
(10).
i. Remove middle stem seal (14.2).
j. Remove plug (20) from vise, ro tate end-
for-end, and resecure in vise using same
metal bars above.
k. Loosen seat disc nut (30) CCW (viewed
from above) ap prox i mate ly two (2) rev o -
lu tions.
l. Remove assembly (20, 27, 28, 29, 30)
from vise. Complete re mov al of seat disc
nut (30), seat disc washer (29), and seat
disc (28).
2. Body Sizes 2-1/2" – 4". (See Figure 6):
a. Place seat disc nut (30) into a vise with
the plug (20) oriented ver ti cal ly. Do NOT
over-tighten nut (30) in vise.
b. Place closed-end hex wrench onto
di a phragm locknut (7). Place sock et
CAUTION D
SYSTEM UNDER PRESSURE. Prior to per form ing
any maintenance, isolate the reg u la tor from the
sys tem and relieve all pressure. Fail ure to do so
could result in personal injury.
B. Main Valve Disassembly: