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Bulletin AY-770-F
Model GD-50
Pressure Reducing Valve
Installation and Maintenance Instructions
Steam Service
This bulletin should be used by
experienced personnel as a guide to
the installation of the Model GD-50
Pressure Reducing Valve. Selection
or installation of equipment should
always be accomplished by
competent technical assistance. You
are encouraged to contact
Armstrong-Yoshitake, Inc., or it’s
local sales representative for
additional information.
Figure 1-1
Installation Instructions
1. An Armstrong Inverted Bucket
Steam Trap is recommended to
drain condensate at the inlet of
the Pressure Reducing Valve
2. An Armstrong Y Strainer (20-100
mesh, depending on system dirt)
should be installed before the
PRV to reduce the chance of dirt
3. Pressure gauges should be
installed before and after the
4. If system cannot be turned
off to service PRV then piping
a by-pass line with a high quality
globe valve around the PRV will
allow manual system operation
while the PRV is being serviced.
5. Do not install quick opening or
closing valves downstream of
the PRV.
6. Install the PRV with the flow in
the direction of the arrow on the
Note: For air or gas service replace steam
trap with an Armstrong Liquid Drainer.
GD-50 Adjustment
Note: Improper adjustment of the
PRV may cause hunting, improper
control and possible damage to the
PRV. Damaged pressure gauges,
leaking by-pass valves, or clogged
inlet strainers may cause problems
similar to that of a malfunctioning
3. Loosen the jam nut on the
adjusting screw (See Figure 2-1)
to allow adjustment.
Start-up and
Adjustment Procedures
1. Open valve on drip leg to allow
inverted bucket steam trap to
drain condensate on PRV inlet.
Note: Downstream usage must be
present in order to set any pressure
reducing valve (40 - 60% is optimum).
2. Open the blowdown valve on the
inlet strainer and blow out the
condensate until only steam is
blowing to atmosphere. If a
blowdown valve is not installed
then close the gate valves before
and after after PRV. Open the bypass valve slowly in the by-pass
line and blow the system down.
Care should be taken not to open
the by-pass valve completely to
prevent the safety relief valve
from popping off (if one is
installed). After blowing down the
system, close the by-pass valve.
4. Slowly open the inlet side gate
valve to the fully open position,
and partially open the outlet side
valve so only a small amount of
steam can pass.
5. Using a 5/16” allen wrench on
the adjusting screw (See Figure
2-1) turn clockwise until the
pressure desired is achieved on
the down stream gauge.
6. Slowly open the outlet gate valve
to full open.
7. Adjust pressure again after
system stabilizes. Turning the
adjusting screw: - Clockwise
increases pressure, counterclockwise decreases pressure.
8. Tighten the adjusting screw jam
nut after adjustment is completed
and system pressure stabilized.
Troubleshooting Guide
C au ses
The inlet pressure is too low or too high.
The valve size is smaller than what is required.
Change the pressure to the appropriate level.
Change the valve size to the appropriate one.
The desired
Readjust according to the adjusting procedure.
pressure cannot The adjustment is not appropriate.
(See adjustment procedure).
be obtained
The inlet strainer is clogged by foreign matter. Disassemble and clean the screen.
The pressure gauge is out of order.
Replace the pressure gauge.
The valve and the valve seat are contaminated Disassemble and clean the valve and seat or
by foreign matter.
replace valve and seat.
The outlet
The sensing port of the outlet pressure is
Disassemble and clean the sensing orifice,
pressure rises
clogged with foreign matter.
valve and the valve seat.
higher than the
The by-pass valve is leaking.
Repair or replace the by-pass valve.
Disassemble and inspect bellows for cracks or
The bellows has been damaged.
The reducing ratio is larger than 10:1.
Reduce pressure in two stages.
Water hammer (for steam service).
Install a steam trap before the reducing valve.
Abnormal noise is
Provide as much distance as possible between
There is a quick-responding valve near the PRV.
the two valves.
The valve may be oversized.
Verify sizing and change out valve if needed.
Disassembly Procedures
1. Eliminate pressure from inside the valve. Make sure
the valve us completely free from pressure.
Figure 2-1
2. Turn the adjusting screw counterclockwise to make
the adjusting spring free (not loaded)
3. Remove the 4 bolts and take away the spring housing.
Take out the spring and bellows.
4. Unscrew (counterclockwise) the cap and take out the
spring, screen and valve from the body.
Armstrong-Yoshitake, Inc. / 221 Armstrong Blvd. / Three Rivers, MI 49093 / Ph: (269) 279-3600 / Fax: (269)273-8656
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