Cashco SCV-S - Manual (Page 7)

7 IOM-SCV-S
SECTION VI
VI. CALIBRATION
A. General:
1. This section only covers cal i bra tion of the
control valve with Actuator Model C27-C53.
2. Positioner, if in stalled, requires ref er ence to
the spe cifi c positioner mod el IOM for prop er
cal i bra tion pro ce dure.
3. All indicated items numbers that are with
re spect to IOM-C27-C53 will be in pa ren-
the sis and un der scored; i.e. (20); those that
reference the po si tion er IOM will be in double
paranthesis; i.e. ((AP)). All item numbers that
are with respect to this IOM-SCV-S are not
un der scored; i.e. (3).
B. Procedure - Reverse Action, 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 (3,10) begins
to lift out of the seat, touch the stem with one
fi nger. (Stem will begin to move when actua-
tor 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 (3,10 & 6) length is too short.
For Std Threaded Stem:
a. Rotate both jam nuts (17) down to base of
threads on stem (3) and tighten together.
b. Increase pressure in the actuator to
approximately mid range of the bench
setting.
c. Rotate upper jam nut CW to increase the
combined stem length. DO NOT allow
actuator stem (6) to rotate in the actuator.
d. Rotate upper jam nut CCW to hold indi-
cating washer (16) up against stem (6).
e. Release all pressure from the actuator and
repeat Step 4 previous.
For Opt-68 QDS Stem:
a. Rotate jam nuts (17) down to base of
threads on upper collar (42a).
b. Increase pressure in actuator to approxi-
mately mid range of the bench setting.
c. Rotate upper collar (42a) CCW to increase
the combined stem length. DO NOT allow
actuator stem (6) to rotate in the actuator.
d. Rotate upper jam nut CW to hold indicator
washer (16) up against stem (6).
e. 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 (10, 6) length is too long.
For Std Threaded Stem:
a. Rotate both jam nuts (17) down to base of
threads on stem (3) and tighten together.
b. Increase pressure in the actuator to ap-
proximately mid range of the bench set.
c. Rotate lower jam nut CCW to shorten the
combined stem length. DO NOT allow
actuator stem (6) to rotate in the actuator.
d. Rotate upper jam nut CCW to hold indi-
cating washer (16) up against stem (6).
e. Release all pressure from the actuator
and repeat Step 4 previous.
For Opt-68 QDS Stem:
a. Rotate jam nuts (17) down to base of
threads on upper collar (42a).
b. Increase pressure in actuator to approxi-
mately mid range of the bench setting.
c. Rotate upper collar (42a) CW to shorten
the combined stem length. DO NOT allow
actuator stem (6) to rotate in the actuator.
d. Rotate upper jam nut CW to hold indicator
washer (16) up against stem (6).
e. Release all pressure from the actuator
and repeat Step 4 previous.
7. After the opening set point pressure has been
established, rotate lower jam nut (17) CW up
tight under the upper jam nut.
8. Release all pressure from the actuator.
9. Observe the location of the in di ca ting washer