Cashco 3381 - Manual (Page 2)

IOM-3381/4381 2
III. PRINCIPLE OF OPERATION
1. Movement occurs as pressure variations regis-
ter on the diaphragm. The registering pressure
is the outlet, P
2
, or downstream pressure. The
range spring opposes di a phragm movement. As
SECTION III
IV. STARTUP
SECTION IV
5. Slowly open the inlet (upstream) block valve ob-
serv ing the outlet (downstream) pressure gauge.
De ter mine if the regulator is fl owing. If not, slowly
rotate the regulator adjusting screw clockwise
(CW) until fl ow begins.
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 block valve and go to Step 2, then return
to Step 4.
8. When fl ow is established steady enough that the
outlet (downstream) block valve is fully open, be-
gin 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
turning the adjusting screw CW to increase outlet
pressure, or CCW to reduce outlet pressure.
10. Reduce system fl ow to a minimum level and
ob serve 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 up per limit of the range spring
by greater than 10%; i.e. 20-80 psig (1.38-5.52
Barg) range spring. (Example: at low fl ow the
outlet pressure should not exceed 88 psig (6.07
barg), if it does, con sult factory).
CAUTION
outlet pressure drops, the range spring pushes
the dia phragm down, opening the port; as outlet
pres sure in creas es, the diaphragm pushes up
and the port opening clos es.
2. A complete diaphragm failure will cause the reg u -
la tor to fail open.
10 A. Basic Regulator - (Refer to Figure 1, Model 3381
or 4381): Regulator may be rotated around the
pipe axis 360°. Recommended position is with
spring chamber vertical upwards. Orient such
that the spring chamber vent hole does not col-
lect rain wa ter.
10B. Cryogenic Regulator - Options 3381-5 and 4381-
36 (Refer to Figure 2, Model 3381 or 4381):
a. Recommended installation is with spring
cham ber hanging directly be low the body
in a ver ti cal down wards orientation. Allows
water to drain; etc.
b. Recommend inert purge gas be supplied to
spring cham ber through vent hole and be
discharged out drain hole.
11. Regulators are not to be buried un der ground.
12. For insulated piping systems, recommendation is
to not insulate regulator.
CAUTION
The maximum outlet pressure is list ed on the name plate
as the upper range spring pres sure level, and is the rec om -
mend ed "upper operative limit" for the sens ing diaphragm
(See Section IV. Startup, Step 7). Higher press ures could
dam age the di a phragm. (Field hydro static tests fre quent ly
de stroy dia phragms. DO NOT HYDRO STATIC TEST THRU
AN IN STALLED UNIT; ISO LATE FROM TEST.)
1. Start with the block valves closed. A by pass
valve may be used to maintain out let pres sure
in the down stream sys tem without changing the
fol low ing steps.
2. Relax the range spring by turning the adjusting
screw counter clockwise (CCW) a minimum of
three (3) full revolutions. This reduces the outlet
(down stream) pres sure set point.
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) pres sure 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.