Cashco 521 - Manual (Page 4)

IOM-521 4
SECTION IV
IV. STARTUP
A. General:
1. Ensure that the Model 521 unit has been
properly adjusted and calibrated, including
the po si tion er, if in stalled.
2. Recommend startup to be in “manual”
mode. This procedure assumes double
block (iso la tion) and bypass valves for the
“control valve station" per Figure 1.
3. Start with either of the two block valves
closed, with the other open. The bypass
valve should be closed. Pres sur ize system
if possible/prac ti cal.
4. Back out the airset’s adjusting screw until
loose.
5. Turn on air supply pressure.
6. Adjust the air supply airset (fi lter-regulator) to
the proper level as indicated in the technical
bulletin 521-TB. DO NOT STROKE THE
CON TROL VALVE WITH AN AIR SUPPLY
PRESSURE SET TING GREATER THAN
REC OM MEND ED MAX I MUM PRESSURE!
7. Place loop controller into “manual” mode.
Vary setting from minimum – mid-range—
maximum SIG out put. Ob serve response of
control valve unit to these changes of input
SIG. The valve should fully stroke at the
variation from minimum SIG to maximum
SIG; the mid-range SIG should have the
valve stem travel at/near 1/2 open.
8. Confi rm that action of controller and po si-
tion er – direct or reverse – are producing
the desired response in the control unit.
Confi rm that the control valve “fail” position
is as re quired.
9. Hereafter, the procedure assumes that
actual fl uid fl ow may be established. This
may not be practical/pos si ble in all cases;
if so, vary pro ce dure as required.
Always “heat” or “cool” down the system
pip ing SLOW LY by opening the control valve
station bypass valve in small increments.
10. With one of the control valve station block
valves still closed, and the loop controller
still in “man u al” mode, open bypass valve
and vary fl ow rate manually to observe the
re sponse of the controller and control valve
unit to geth er.
11. Attempt to develop manual control of the
loop by opening/closing the manual bypass
as required, or by manually controlling
main stream fl ow as required.
12. When the control valve is partially open,
crack open, slowly, the closed block valve
while si mul ta neous ly clos ing the bypass
valve; it may be necessary/desirable to vary
the man u al output SIG from the controller
si mul ta neous ly also. Continue this proce-
dure until the by pass is closed and the block
valves are both fully open. The system is still
under “manual” mode control, but all fl ow is
passing thru the control valve.
C. Auxiliary Detection:
1. When a fl uid is known to permeate TFE over
a fi nite time period and the fl uid is lethal or
is subject to stringent limits of fugitive emis-
sions, the vented pipe plug (12) should be
removed and one of, or a com bi na tion of, the
following methods should be considered to
monitor the integrity of the internal primary
stem (9) seal – the bellows sub-assembly
(8):
a. gas detector with alarm
b. pressure indicating gauge
c. pressure switch with alarm
d. inert gas, constant fl ow purge.
CAUTION
DO NOT WALK AWAY AND LEAVE A MANUALLY
CONTROLLED CONTROL VALVE UNATTENDED!
13. Vary controller “manual” SIG output until
match ing the “automatic” SIG output, then
change the mode of the controller over to
“automatic”, and the loop will ex pe ri ence a
minimum of upset conditions, and will be in
automatic control.