Cashco 521 - Manual (Page 11)

IOM-521 11
15. For Direct Action ATC-FO Only: Release
all air pressure from actuator assembly (AA),
see step 9 previous and remove temporary
air supply.
16. Re-tighten packing gland nut (5).
VI. CALIBRATION
A. General:
1. This section only covers calibration of this
control valve with Actuator Models C27-C53.
2. Positioner, if installed, requires reference to
the spe cifi c positioner model IOM for proper
cal i bra tion pro ce dure.
3. All indicated Item Num bers that are with
re spect to IOM-C27-C53 will be in pa ren-
the sis and un der scored; i.e. (20). All Item
Num bers that are with respect to this IOM-
521 are not un der scored; i.e. (32).
B. Procedure – Reverse Ac tion, ATO-FC:
1. Reference the name plate (40) at tached to
the actuator yoke (3). De ter mine the bench
set ting of the installed range springs (10)
from the name plate (40).
2. Connect a temporary air supply with an in-
line ad just able airset reg u la tor and gauge
to the lower actuator con nec tion. DO NOT
LOAD with any air pressure at this point.
3. To determine when stem/plug (9) begins to
lift out of the seat, touch the stem below the
jam nut with one fi nger. (Stem will begin to
move when actuator pressure exceeds the
spring load.)
4. Slowly pressurize the ac tu a tor to a pres sure
equal to the lower pres sure level of the bench
setting; i.e. for 5-15 psig (.34–1.03 Barg)
range, set pressure at 5 psig (.34 Barg).
Take note of pressure reading when the
stem fi rst begins to move.
5. If the loading pressure for the start of stem
movement is below the lower end of the
desired bench setting, then the com bined
stem (9, 6) length is too short.
a. Rotate jam nut (20) down to base of
threads on stem (9).
SECTION VI
b. Increase pressure in the actuator to
approximately mid range of the bench
setting.
c. Rotate lower knuckle (44) CCW to in-
crease the combined stem length. DO
NOT allow actuator stem (6) to rotate
in the actuator.
d. Release all pressure from the actuator
and repeat Step 4 previous.
6. If the loading pressure for the start of stem
movement is above the lower end of the
desired bench setting, then the com bined
stem (9, 6) length is too long.
a. Rotate jam nut (20) down to base of
threads on stem (9).
b. Increase pressure in the actuator to
approximately mid range of the bench
setting.
c. Rotate lower knuckle (44) CW to shorten
the combined stem length. DO NOT
allow actuator stem (6) to rotate in the
actuator.
d. Release all pressure from the actuator
and repeat Step 4 previous.
7. Observe the location of the in di ca ting washer
(51) to the "C" mark on the in di ca tor plate
(23), mak ing sure to use the “top edge” of
the in di ca ting washer (51) as the ref er ence
point. Adjust indicator plate as needed.
8. Remove vented pipe plug (12) from the neck
of the bonnet (2).
9. Slowly increase the pressure in the actuator
until the indicating washer (51) is in align-
ment with the "O" mark on the indicator plate.
As pressure increases, thru the hole where
the vent ed pipe plug (12) was re moved,
watch for the anti-ro ta tion al "stop" (square
or fl at surface of the stem) to appear.
17. Tighten yoke nut (15) to 85 ft--# (115 N-M)
18. Calibrate actuator to valve per Section VI.