Cashco DA2 - Positive Differential - Manual (Page 6)

IOM-DA2 6
12. For composition diaphragm construction,
remove lower diaphragm pusher plate (10).
13. Evenly loosen the three cage cap screws (18)
in single revolution increments. If the reg u la tor
con tains a lower piston spring (22), the ITA
should rise as the cage cap screws (18) are
evenly backed out. A downwards holding force
should be ap plied to the top of the piston-guide
bearing (13) to pre vent the ITA from pop ping
up as the last threads of the cage cap screws
(18) are backed out.
14. Remove the ITA by pulling up on the valve
plug (20). Set ITA aside.
15. Remove the lower piston spring (22), as
applicable, from within the body (23). NOTE:
Com po si tion diaphragm constructions do not
nor mal ly include a lower piston spring (22); all
metal diaphragm constructions MUST in clude
a lower piston spring (22).
16. Remove o-ring cage seal (15).
17. Remove body (23) from vise. Clean all
reusable metal parts according to owner's
pro ce dures. (See Article VII.A.4. comments
concerning cleaning for ox y gen service.)
B. Main Valve Disassembly:
1. Shut down the system in accordance with
Section VI.
2. Disconnect the external sensing line, if
installed.
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. Remove regulator body (23) from pipeline.
Place the regulator in a vise with the spring
chamber (4) upwards.
5. Relax range spring (6) forces by turning ad-
justing screw (1) CCW (viewed from above)
until spring relaxes. The easiest 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 match marks on body (23) and spring
chamber (4) fl anges. Remove the spring
chamber (4).
8. Remove spring follower (5) and range
spring
(6.1).
9. For composition diaphragm construction, hold
the milled “fl ats” on top of the valve plug (20)
stationary with appropriate socket wrench.
Loosen and remove the diaphragm lock nut
(7). NOTE: Metal diaphragm constructions
do NOT have a diaphragm lock nut (7).
10. Remove upper diaphragm pressure plate (8).
11. Remove diaphragm(s) (9, 9.1, 9.2, 9.9) and
o-ring upper stem seal (14.1). Examine
diaphragm(s) to determine whether failed; de-
termine if op er at ing conditions are exceeding
pressure, pressure drop or temperature limits.
Figure 2: Assembled ITA,
Composition Di a phragm Construction
C. Disassembly of the ITA:
1. Removal of piston-guide bearing (13).
a. For a regulator with a composition
diaphragm(s) (see fi gure 2); pull the
valve plug (20) downwards and out
the piston-guide bearing (13) and out
of the lower end of the cage (19). Re-
move the piston-guide bearing (13)
from the upper end of the cage (19).
b. For a regulator with a metal diaphragm(s)
(see fi gure 3); hold the lower part of the
20
14.2
14.3
13
27
15
16
17
19
21
20