Cashco 3171 User Manual

Page 2

IOM-3171

SECTION III

III. PRINCIPLE OF OPERATION

1. Movement occurs as pressure variations register

on the diaphragm. The registering pressure is
the inlet, P

, or upstream pressure. The range

spring opposes diaphragm movement. As inlet
pressure drops, the range spring pushes the dia-

IV. START-UP

1. Start with the block valves closed. A bypass

valve may be used to maintain inlet pressure
in the up stream system 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 inlet
(up stream) pres sure setpoint.

3. If it is a “hot” piping system, and equipped with

a bypass valve, slowly open the bypass valve
to pre-heat the system piping and to allow slow
ex pan sion of the piping. Closely monitor inlet
(up 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 inlet (upstream) block valve.

5. Slowly open the outlet (downstream) block

valve ob serv ing the inlet (upstream) pressure
gauge. De ter mine if the regulator is fl owing. If
not, slowly rotate the regulator adjusting screw
counter clock wise (CCW) until fl ow begins.

6. Continue to slowly open the outlet (down-

stream) block valve until fully open.

phragm down, closing the port; as inlet pres sure
in creas es, the diaphragm push es up and the port
opens.

2. A complete diaphragm failure will cause the reg u -

la tor to fail close and process fl uid will discharge
from the spring chamber vent hole.

SECTION IV

7. Observing the inlet (upstream) pressure gauge,

ro tate the adjusting screw clockwise (CW) slowly
until the inlet pres sure begins to rise. Rotate CW
until the desired setpoint is reached.

8. Continue to slowly open the inlet (upstream) block

valve. If the inlet (upstream) pressure exceeds
the desired setpoint pressure, rotate the ad just ing
screw CCW until the pres sure decreases.

9. When fl ow is established steady enough that

both the outlet and inlet block valves are fully
open, begin to slowly close the bypass valve, if
in stalled.

10. Develop

system

fl ow to a level near its expected

normal rate, and reset the regulator setpoint by
turn ing the ad just ing screw CW to increase inlet
pressure, or CCW to reduce inlet pressure.

11. Reduce system fl ow to a minimum level and

ob serve setpoint. Inlet pressure will rise from the
setpoint of Step 9. (Ensure that this rise does not
exceed the stated upper limit of the range spring
by greater than 20% i.e. 20-80 psig (1.38 - 5.52
Barg) range spring, at maximum fl ow the inlet
pressure should not exceed 1.2 x 80 psig (5.6
Barg), or 96 psig (6.6 Barg). If it does, consult
factory).

12. Increase

fl ow to maximum lev el, if possible. Inlet

(up stream or P

) pressure should fall off. Re ad just

setpoint as necessary at the normal fl ow rate.

V. SHUTDOWN

1. On systems with a bypass valve, and where

sys tem pressure is to be maintained as the
reg u la tor is shut down, slowly open the by pass
valve while closing the inlet (up stream) block
valve. Fully close the inlet (upstream) block
valve. (When on bypass, the system pressure
must be constantly ob served and manually
regulated. Close the outlet (down stream) block
valve.

2. If the regulator and system are to both be shut

down, slowly close the inlet (upstream) block
valve. Close the outlet (downstream) valve only
if reg u la tor re mov al is required.

SECTION V

CAUTION

Do not walk away and leave a bypassed reg u la tor
unattended.