IOM-DA0
4
the "pressed-in-place" lower guide bushing
(24) and the surface can not be marred.
B. Main Valve Disassembly:
1. Shut down system in accordance Section VI.
2. Disconnect the external piping line(s) con-
necting pilot to main regulator.
3. Though it is possible to disassemble the main
unit while installed in a pipeline, it is rec om-
mend ed that maintenance be done in a shop
when possible. The descriptions hereafter will
assume shop disassembly. Remove regulator
from pipeline.
4. Place the body in a vise with the cover dome
(25) oriented upwards.
5. Loosen the flange bolts (11) and nuts (12)
uniformly and remove.
6. Place matchmarks on body (23) and cover
dome (25) flanges. Remove cover dome and
gasket (13).
7. Evenly loosen the three cage cap screws
(18) in single revolution increments.
NOTE:
Regulator con tains a lower spring (22); the
ITA should rise as the cage cap screws are
evenly backed out. A down wards 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
are backed out
.
8. Remove the ITA by pulling up on the plug
(20). Set ITA aside.
9.
Remove spring (22) from within the body (23).
10. Remove cage o-ring seal (15).
11. Remove body (23) from vise. Clean all re us able
metal parts according to owner's pro ce dures.
C. Disassembly of the ITA:
1. To disassemble the ITA, hold the lower part
of the plug (20) in a bench vise; Do not hold
on the machined sur face in the plug's (20)
spindle area.
NOTE:
The spin dle “slides” in
Figure 2:
Assembled ITA,
2. Rotate
di
a phragm lock nut (7) CCW and re-
move.
3. Remove stop plate (10). Remove ITA from
vise.
4. From below the cage (19) pull the plug (20)
downwards out of the piston-guide bearing
(13) and out thru the bottom of the cage.
5. Remove the piston-guide bearing (13) from
the upper end of cage (19).
6. Examine
the
dy
nam ic side seal (27) mecha-
nism to de ter mine if sig nif i cant leakage was
oc cur ring. If the dy nam ic side seal shows signs
of sig nif i cant leakage, de ter mine if operating
conditions are ex ceed ing pres sure, pres sure
drop, or tem per a ture lim its.
7. Remove top seal (14) and dynamic side seal
(27) and discard.
NOTE:
Special care should
be taken when using “tools” to remove the
components to ensure that no scratches are
imparted on to any portion of the piston-guide
bearing (13) groove.
8. Remove wiper seal (16)and wiper washer (17)
from within cage (19).
9. Remove lower stem seal (14) from plug (20).
10. Remove seat ring (21) from bottom of cage;
examine for signs of leakage. If seat ring
shows signs of significant leakage, determine
if op er at ing con di tions of pressure, pressure
drop, or temperature are ex ceed ing limits.
WARNING
SYSTEM UNDER PRESSURE. Prior to per form ing any
maintenance, isolate the reg u la tor from the system and
relieve all pressure. Failure to do so could result in
personal injury.
