Cashco 964 - Manual (Page 13)

IOM-964 13
7. Observe the position of the in di ca tor disc (20)
and the in di ca tor plate (21), mak ing sure to use
the “top edge” of the in di ca tor disc (20) as the
ref er ence point. If the position in di cat ed is not
exactly at “S” (for “shut”), then the valve stem
(3)-to-ac tu a tor stem (19) com bined length is
in cor rect, and must be ad just ed.
8. a. If travel indicator stops above the “S”
position, combined stem (3, 19) length is
long. Loosen jam nut (18) hold ing in di ca-
tor disc (20) against ac tu a tor stem (19).
b. Release 6-8 psig (0.4-0.6 Barg) of pres-
sure from the actuator. This step will
ensure that when the com bined stem (3,
19) length is de creased, the plug will not
be mis tak en ly ro tat ed while seated.
c. Decrease combined stem (3,19) length by
ro tat ing valve stem (3) CW (viewed from
plug end) a distance equal to the amount
of undertravel. Retighten jam nut (18).
9. a. If travel indicator stops below the “S”
position, com bined stem (3,19) length is
short. Loos en jam nut (18) hold ing in di ca-
tor disc (20) against ac tu a tor stem (19).
b. Release 6-8 psig (0.4-0.6 Barg) of pres-
sure level in the actuator. This step will
ensure that when the combined stem (3,
19) length is in creased, the plug will not
be mis tak en ly ro tat ed while seated.
c. Increase combined stem (3, 19) length by
rotating tvalve stem (3) CCW (viewed from
plug end) a dis tance equal to the amount
of undertravel. Retighten jam nut (18).
10. Repressurize the actuator to the lev el of Step
6 above. If the “S” closed position is not cor-
rect, repeat Steps 8 and 9 until the com bined
stem (3, 19) length is correct.
11. Pressurize the actuator to a pres sure level
cor re spond ing to the level of Step 6. Do the
pres sur iza tion slowly while ob serv ing the
in di ca tor disc (20) and in di ca tor plate (21)
si mul ta neous ly.
12. The proper calibration of the ac tu a tor/valve unit
will occur when, at the upper pres sure level of
bench setting, the valve stem as sem bly’s (3)
plug will just begin to travel from the closed
po si tion.
Depressurize actuator slowly. If plug (3) be-
gins travel before reaching the upper pres sure
level of bench setting, release all air pres sure,
then de crease the ac tu a tor’s range spring (6)
com pres sion by wrench loos en ing spring ad-
jus tor (4) CCW (viewed from plug end) in 1/2
rev o lu tion in cre ments. Re peat this pro ce dure
until de sired bench set ting is reached.
Depressurize actuator slowly. If plug (3) be gins
travel after surpassing the upper pres sure
level of bench setting, release all air pres sure,
then in crease the actuator’s range spring (6)
com pres sion by wrench tight en ing spring
ad jus tor (4) CW (viewed from plug end) in 1/2
rev o lu tion in cre ments. Re peat this pro ce dure
until de sired bench set ting is reached.
13. Decrease pressure to ac tu a tor down to the
lower level of bench setting and ob serve valve
plug (3) position at the in di ca tor plate (21).
The valve plug (3) should be within ± 8% (of
full stroke) of the “O” (for “open”) po si tion of
the in di ca tor plate (21). “Stroke” length is
in di cat ed on the name plate (12), and is the
dis tance between the “S” and “O” points of
the in di ca tor plate (21).
14. Record here the theoretical and ac tu al pres-
sure levels of para graphs 12 and 13:
Theoretical ____________________ psig
Bench Setting
from Nameplate ____________________ Barg
____________________ psig
Setting at “S”
Position ____________________ Barg
____________________ psig
Setting at “O”
Position ____________________ Barg
15. Tighten second stem jam nut (18).
SECTION VI
VI. START-UP
A. General:
1. Ensure that the Model 964 unit has been
prop er ly adjusted and cal i brat ed, in clud ing
the po si tion er, if in stalled.
2. Recommend startup to be in a “man u al”
mode. This pro ce dure assumes dou ble
block (iso la tion) and bypass valves for the
“control valve station”. See Fig ure 1.