Cashco DA4 - Manual (Page 2)

IOM-DA4 2
Use 1/4" or 3/8" (DN8 or 10) outer di am e ter
tubing or 3/8" (DN10) pipe having an inner
di am e ter equiv a lent to Schedule 40 pipe.
d. For condensable vapors (i.e. steam) slope the
external sensing line downward 2 to 5 de grees
to outlet piping to prevent water pock ets, which
allows the diaphragm chamber to always be
self draining. The external sensing line may
be sloped upward for liquids or gas es.
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. Ensure proper steam
trap operation if installed. 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 starting
up a cold system; i.e. do everything slowly.
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. Adjust the loading system
pres sure control device setpoint pressure upwards
until the main valve is fl owing. Observe the outlet
pressure gauge to ensure not overpressurizing.
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.
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.
SECTION IV
SECTION V
CAUTION
DO NOT HYDROSTATIC TEST THROUGH AN IN STALLED
UNIT; ISOLATE REGULATOR FROM TEST. The "OUTLET
RATING" as printed on the name plate is the rec om mend ed
“upper op er at ing limit” for the sens ing di a phragm. Higher
pres sures could cause internal dam age. In ad di tion, note
on the nameplate that the Inlet and Outlet pres sure and
temperature ratings are at different levels.
CAUTION
Do not walk away and leave a bypassed reg u la tor unat-
tended!
CAUTION
Installation of adequate overpressure pro tec tion is recom-
mended to pro tect the reg u la tor from over pres sure and
all down stream equip ment from dam age in the event of
regulator failure.
Model DA4