Cashco SA4 - Manual (Page 2)

IOM-CA4/SA4 2
IV. PRINCIPLE OF OPERATION
1. When a loading pressure – P
Load
– is applied to
the top side of a diaphragm, the outlet controlled
pressure – P
2
– will balance at approximately
.90 – .98 of the loading pressure - P
L
. (NOTE:
Fluc tu a tions in P
1
– Inlet Pressure will cause a
deviation in P
2
– Outlet Pressure due to inverse
sym pa thet ic ratio effect.) See Section VIII.
2. Movement occurs as pressure variations register
on the diaphragm. The registering pressure is the
outlet, P
2
, or downstream pressure. The loading
V. STARTUP
1 Start with the block valves closed.
2. Adjust the loading system pressure control de vice
so that main regulator is trying to be con trolled at
0 psig pressure.
3. If it is a “hot” piping system, and equipped with
a bypass valve, slowly open the bypass valve
to preheat the system piping and to allow slow
ex pan sion of the piping. Closely monitor outlet
(down stream) pressure via gauge to ensure not
over-pressurizing. NOTE: If no bypass valve is
in stalled, extra caution should be used in start ing
up a cold system; i.e. do everything slowly.
SECTION VI
tor is fl owing. If not, slowly increase the loading
pressure into the cover dome until fl ow be gins.
6. Continue to slowly open the inlet (upstream) block
valve until fully open.
7. Continue to slowly open the outlet (downstream)
block valve, especially when the downstream pip-
ing system isn’t pressurized. If the outlet (down-
stream) pressure exceeds the desired pres sure,
close the inlet block valve and go to Step 2. Close
bypass valve approximately 25%, and re peat
pro ce dure.
8. When fl ow is established steady enough that the
outlet (downstream) block valve is fully open, begin
to slowly close the bypass valve if installed.
9. Develop system fl ow to a level near its expected
normal rate, and reset the regulator set point by
increasing the loading pressure to increase outlet
pressure, or decreasing the loading pressure to
reduce outlet pres sure.
10. Reduce system fl ow to a minimum level and ob-
serve pressure set point. Outlet pressure will rise
from the set point of Step 9. The maximum rise
in outlet pressure on decreasing fl ow should not
exceed the stated upper limit of the range spring
by greater than 10%. If it does, consult factory.
SECTION IV
SECTION V
pressure fl uid op pos es di a phragm move ment.
As outlet pres sure drops, the loading pressure
push es the di a phragm down, opening the port; as
outlet pres sure increases, the diaphragm pushes
up and the port opening closes.
3. A diaphragm failure will tend to cause the reg u la tor
to fall below setpoint. A loss of loading pres sure
while inlet pressure is imposed will cause the
regulator to fail close. A com plete diaphragm failure
will cause the inlet process fl uid to mix with the
loading fl uid.
4. Crack open the outlet (downstream) block valve
to approximately 10% full open.
5. Slowly open the inlet (upstream) block valve to
about 25% open, observing the outlet (down-
stream) pres sure gauge. Determine if the reg u la-
CAUTION
Do not walk away and leave a bypassed reg u -
la tor unattended!
VI. SHUTDOWN
1. Shutoff auxiliary loading pressure source. Close
inlet block valve.
2. Allow suffi cient time for the line pressure down-
stream of the inlet block valve to bleed down.