Cashco 31-N User Manual
INSTALLATION, OPERATION & MAINTENANCE MANUAL (IOM)
IOM-31-N
05-14
MODEL 31-N
Pressure Reducing Service Regulator
SECTION I
I. DESCRIPTION AND SCOPE
The Model 31-N is a pressure reducing service regulator used to control downstream (outlet or P2) pressure to levels
between 2" – 16 “WC (50–400 mm H2O). Sizes are 1/2" 3/4”, 1", 1-1/2" and 2" (DN15, 20, 25, 40 and 50).
The unit is designed for gaseous service only.
Refer to Technical Bulletin 31-N-TB for sizing, application and selection recommendations.
WARNING
1. Model 31-N does not include an internal relief mech a nism. Overpressure protection requires use of a downstream
safety relief valve or rupture disc.
2. User to determine acceptance of non-relieving design by federal, state, and/or local codes.
3. IF GAS IS DETECTED BY SMELL, CONTACT YOUR GAS COMPANY IMMEDIATELY.
4.
User to comply with instructions, operating re quire ments and maintenance requirements located herein the “IOM-31-N”.
II. INSTALLATION
1. An inlet block valve should always be installed.
An outlet block valve is recommended.
2. If service application is continuous such that
shut down is not readily accomplished, it is
rec om mend ed that an outlet block valve and a
manual bypass valve be installed.
3. Pipe unions are recommended to be installed to
allow removal from piping. Trim can be changed
without removal from pipeline.
4. An outlet pressure gauge should be located
ap prox i mate ly 10 pipe diameters downstream,
and within sight.
5. All installations should include a downstream
re lief device if the inlet pressure could exceed the
pressure rating of any downstream equipment.
A downstream safety relief valve or a rupture
disc is absolutely required if the inlet P1
pres sure exceeds 100 psig (6.9 Barg) under
any normal or upset conditions.
SECTION II
CAUTION
Installation of adequate overpressure pro tec tion is recommended to pro tect the reg u la tor from overpressure and
all down stream equip ment from damage in the event of
regulator failure.
WARNING
The maximum outlet pressure listed on the name plate is
the “upper operative limit” for the sensing di a phragm.
Higher pressures could damage the internals. (Field hy dro stat ic or pneumatic pressure tests fre quent ly destroy
diaphragms. DO NOT HY DRO STAT IC OR PNEUMATIC
PRESSURE TEST THRU AN IN STALLED UNIT EX POS ING
THE OUTLET POR TION OF THE REGULATOR TO PRES SURES GREATER THAN 50 PSIG (3.45 BARG) FAIL URE
TO HEED MAY RESULT IN CAT A STROPH IC FAIL URE WITH
FLYING PARTS AND POSSIBILITY OF PER SON AL INJURY!
ISO LATE FROM TEST.)
CAUTION
For welded installations, all internal trim parts, seals and
diaphragm(s) must be removed from reg u la tor body prior to
welding into pipeline. The heat of fusion welding will dam age non-metallic parts if not re moved. NOTE: This does
not apply to units equipped with extended pipe nip ples.
6. Clean the piping of all foreign material including
chips, welding scale, oil, grease and dirt before
in stall ing the regulator. Strainers are rec om mend ed.
Figure 1
Recommended Piping Schematic For
Pressure Re duc ing Station
7. In placing thread sealant on pipe ends prior to
en gage ment, assure that excess material is
re moved and not allowed to enter the regulator
upon startup.
8. Flow Direction: Install so the fl ow direction match es
the arrow cast on the regulator body.
9. Refer to Figure 2. Regulator may be rotated
around the pipe axis 360°, and may be installed
in a horizontal or vertical pipeline. Four orientation/
arrangement assembly positions are standard. Orient to prevent the spring chamber vent hole from
collecting rainwater or debris. Reorient ac tu a tor
around the stem axis 360° if nec es sary.
10. Regulators are not to be direct buried un der ground.
11. For insulated piping systems, recommendation is
to not insulate regulator.
12. Cashco does not recommend fi eld welding on
the body of the regulator. If weld connections are
desired, specify Opt-32, extended plain end pipe
nipples.
FOR VERTICAL PIPING
Position 1
Position 1
Position 2
FOR HORIZONTAL PIPING
Position 2
III. PRINCIPLE OF OPERATION
1. Refer to internals drawings Figures 5 thru 8.
2. Internal trim movement occurs as pressure vari a tions register on the diaphragm. The registering
pressure is the controlled outlet pressure, P2, or
down stream pressure. The range spring opposes
Figure 2
SECTION III
Position 3
Position 3
up wards movement of the diaphragm due to the
P2 pressure. As outlet pressure drops, the range
spring pushes the diaphragm down, opening the
regulator’s port via the linkage lever travel. As
outlet pressure increases, the diaphragm pushes
up against the range spring and the port closes.
Position 4
Position 4
IOM-31-N2
3. Model 31-N includes a linkage lever in its mech a nism. The linkage lever allows the regulator to
operate fl ow-to-open (FTO) and provides plug
travel multiplication thru the lever length ratio.
5. Aspiration (jet) effect is developed by properly
locating the “windows” of the loading ring. When
properly po si tioned, a high velocity path is in tro duced. This causes a corresponding decrease in
IV. STARTUP
static pressure to be de vel oped at a location that
allows this decreased pressure to register into the
lower case and beneath the diaphragm. The net
result is to pull the diaphragm down and open the
valve port, providing higher unit capacity.
6. A complete diaphragm failure will cause the reg u la tor to fail open.
SECTION IV
1. Assure that the proper range spring is indicated
to be within the regulator by inspection of the
unit’s name plate. Apply setpoint pressures that
are only within the stated range.
2. When stating direction of rotation of the ad just ment
screw, the view is with respect to looking down
towards the closing cap or its normal lo ca tion.
3. Start with the block valves closed. A bypass
valve may be used to maintain outlet pressure
in the down stream system without changing the
fol low ing steps.
4. Remove closing cap on top of spring chamber.
Relax the range spring by turning the adjustment
screw CCW a minimum of three (3) full rev o lu tions.
This reduces the outlet (downstream) pres sure
setpoint.
5.
Crack open the outlet (downstream) block valve.
6. Slowly open the inlet (upstream) block valve ob serv ing the outlet (downstream) pressure gauge.
Partially close off the bypass valve, if open. De ter mine if the regulator is fl owing. If not, slowly
rotate the regulator adjustment screw CW until
fl ow begins.
7. Continue to slowly open the inlet (upstream) block
valve until fully open.
8. Continue to slowly open the outlet (downstream)
block valve, especially when the downstream piping system isn’t pressurized. If the outlet (down stream) pres sure exceeds the desired pressure,
close the inlet (up stream) block valve fi rst, then
the outlet (downstream) block valve, and go to
Step 4, then return to Step 6.
9. 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.
10. Develop system fl ow to a level near its expected
normal rate, and reset the regulator setpoint per
Section VII.
11. Reduce system fl ow to a minimum level and ob-
serve setpoint. Outlet pressure may rise from the
set point of Step 10. 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%; i.e. 5.5–8.0 “WC (140–200 mmH2O) range
spring, at low fl ow the outlet pressure should not
exceed 8.8 “WC (224 mmH2O). If it does, consult
factory.
V. SHUTDOWN
1. On systems with a bypass valve, and where system pressure is to be maintained as the reg u la tor
is shut down, slowly open the bypass valve while
closing the inlet (up stream) block valve. Fully
close the inlet (up stream) block valve. (When on
bypass, the system pres sure must be con stant ly
observed and manually reg u lat ed.) Close the outlet
(downstream) block valve.
IOM-31-N
SECTION V
WARNING
Do not walk away and leave a bypassed reg u la tor
un at tend ed.
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 regulator removal is required.
3
SECTION VI
VI. MAINTENANCE
A. General:
WARNING
SYSTEM UNDER PRESSURE. Prior to performing any
maintenance, isolate the regulator from the system and
relieve all pressure. (Including the External Sensing
line when specifi ed.) Failure to do so could result in
personal injury.
1. Maintenance procedures hereinafter are based
upon removal of the regulator from the pipeline
where installed.
2. Owner should refer to owner’s procedures for
re mov al, handling and cleaning of re us able
parts, the dis pos al of non-reusable parts, i.e.
gaskets, suitable sol vents, etc.
3. If desired, gaskets may be oiled, or coated with
gasket sealant or thread sealing com pound,
provided the sealant is compatible with the fl u-
id. (See below for “oxygen cleaned” valves.)
4. Valves originally supplied as “special cleaned”
(Opt-56) are assembled using special seal ant,
Fluorolube GR-3621, or equivalent. Cash co,
Inc., rec om mends fol low ing factory cleaning
specifi cation #S-1542, or equiv a lent. Contact
factory for details.
5. When directions such as upwards, down wards,
leftwards or rightwards are given, they are with
respect to Figures 5 and 6.
When counter clockwise (CCW) or clock wise
(CW) ro ta tions are indicated, they are with
respect to:
a. Spring Chamber – as viewed from above
looking down towards the closing cap or
its normal location.
b. Body – as viewed looking into the body
cavity with the upper case assembly re moved.
B. Diaphragm Replacement:
WARNING
SPRING UNDER COMPRESSION. Prior to re mov ing upper case, relieve spring compression by removing the
ad just ing screw. Failure to do so may result in fl ying parts
that could cause personal injury
1. Install the body (1) in a vise with the spring
chamber (4) directed upwards.
2. Remove closing cap (5). Relax range spring
(17) by turning adjustment screw (18) CCW
until removed from spring cham ber (4); count
number of full revolutions and record below.
No. of revolutions to remove ad just ment
screw (18) ____________________ .
3. Paint or embed a match mark between lower
case (3) and spring chamber (4) at fl ange
O.D.
4. Remove all diaphragm fl ange nuts (10) and
screws (9).
5. Remove spring chamber (4) and range spring
(17).
6. Pry up the edges of the diaphragm (12) from
around the pe rim e ter of the lower case (3)
diaphragm fl ange to assure that the diaphragm
(12) is not “sticking” to the lower case.
7. Grasp stop post (19) and with hand carefully
lift up wards and to the right to disengage linkage lever (21) from cir cu lar opening of lower
di a phragm plate (20). Fully remove diaphragm
sub-assembly (DSA) from lower case.
8. Place the “ear” of the lower diaphragm plate
(20) into a soft jawed vise and fully secure,
with stop post (19) pointed upwards. Place a
wrench on the hex surface of stop post (19)
and loosen by rotating CCW (viewed from
above).
.
1
Product of Fisher Scientifi c Company
9. Grasp upper diaphragm plate (13) with fi n gers
and continue to loosen stop post (19) until removal. Finger remove washer (16), and nylon
bushing (15). Lift upper diaphragm plate (13),
together with stuck-on diaphragm (12) away
from lower diaphragm plate (20), and place
on bench top.
IOM-31-N4
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