GD-45

GD-45
Bulletin No. AY-745-A
Model GD-45
Pressure Reducing Valve
Installation and Maintenance Instructions
This bulletin should be used by experienced personnel as a guide to the installation of the Model GD-45 Pressure
Reducing Valve. Selection or installation of equipment should always be accompanied by competent technical
assistance. You are encouraged to contact Armstrong International, Inc. or its local representative for additional
information.
Installation for Air Service
Installation Instructions
Globe
Valve
Minimum of 10 Outlet
Pipe Diameters from
Last Valve or Fitting
By-Pass
Safety Relief
Valve
Armstrong
Strainer
2. An Armstrong Y-Strainer (20-100
mesh, depending on system dirt)
should be installed before the PRV to
reduce the chance of dirt fouling.
GD-45
Minimum of 10 Inlet
Pipe Diameters from
PRV to First Turn
Minimum of 20 Outlet
Pipe Diameters from
PRV to First Turn
Note:
Safety Relief Valve to be set at
10 psi higher or 10% higher than
the downstream pressure, whichever
is greater.
Armstrong
Liquid Drainer
Trap
3. Pressure gauges should be installed
before and after the PRV.
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.
Installation for Steam Service
Globe
Valve
1. An Armstrong Inverted Bucket Steam
Trap is recommended to drain condensate at the inlet of the Pressure
Reducing Valve (PRV). A Liquid
Drainer is recommended for air service.
Minimum of 10 Outlet
Pipe Diameters from
Last Valve or Fitting
By-Pass
Safety Relief
Valve
GD-45
6. Install the PRV with the flow in the
direction of the arrow on the body.
Armstrong
Strainer
Minimum of 10 Inlet
Pipe Diameters from
PRV to First Turn
Armstrong
TVS Trap
5. Do not install quick opening or closing
valves downstream of the PRV.
Minimum of 20 Outlet
Pipe Diameters from
PRV to First Turn
Note:
Safety Relief Valve to be set at
10 psi higher or 10% higher than
the downstream pressure, whichever
is greater.
Start-Up and Adjustment Procedures
Improper adjustment of the pressure reducing valve may cause hunting, scale problems, water hammer, etc., and
damage to the valve itself. Damaged pressure gauges, leakage or opening of a bypass valve, or clogging of an inlet
strainer may cause problems similar to that of a malfunctioning reducing valve. Adjust the valve as follows:
1. Close the gate valves before and after the pressure
reducing valve. Open the globe valve slowly in the
bypass line and blow down the inlet piping. Adjust the
opening of the bypass valve so the safety valve does
not blow. After blowing the system down, close the
bypass valve.
2. Slowly open the inlet side gate valve to the fully open
position, and partially open the outlet valve so only a
small amount of steam or air can pass.
3. To increase the downstream pressure, turn the
adjusting screw clockwise until the desired pressure is
obtained on the downstream pressure gauge.
4. Slowly open the outlet valve to the fully open position.
Troubleshooting Guide
Problem
The desired pressure
cannot be obtained.
The outlet pressure rises
higher than the specified
pressure
Abnormal noise is heard.
Causes
The inlet pressure is too low or high.
The sensing port of the outlet pressure is clogged with
foreign matter.
The valve size is smaller than what is required.
The adjustment is not appropriate.
The inlet strainer is clogged by foreign substance.
The pressure gauge is not functioning properly.
The valve or valve seat is contaminated by foreign
substance.
The by-pass valve is leaking.
The reducing ratio is excessively large.
Water hammer (for steam service).
There is a fast closing valve near the PRV.
Solutions
Change the pressure to the appropriate level.
Disassemble and clean the sensing port.
Change the valve size to the appropriate one.
Readjust according to the adjustment procedure. (See
start-up procedure)
Disassemble and clean the strainer.
Replace the pressure gauge.
Disassemble and clean the valve or the seat.
Repair or replace the by-pass valve.
Reduce pressure by staging with second PRV.
Install a steam trap at the reducing valve inlet.
Provide as long a distance as possible between the two
valves.
Disassembly
(11) Adjusting Screw
1. Eliminate pressure from inside the valve. Make
sure the valve is completely free from pressure.
2. Turn the adjusting screw (11) counterclockwise
to make the spring (12) free (not loaded).
3. Remove the bolts (15) and take away the
spring housing (2) (the handle cannot be
disassembled). Take out the spring (12),
bellows (10) and valve rod (8).
4. Unscrew (counterclockwise) the cap (3) and
take out the spring (13), screen (9) and valve
(7) from the body (1).
(23) Nameplate
(15) Bolt
Body (1)
Valve Seat (6)
Valve (7)
(2) Spring Housing
Main Valve Spring (13)
(26) Spring Retainer
Screen (9)
(12) Adjusting Spring
Gasket (16)
Cap (3)
(10) Bellows
Reassembly
E-Ring (20)
(17) Gasket
1. Check all parts to make sure they are in good
condition before putting back together.
(8) Valve Rod
2. Lap valve (7) and valve seat (6) with 1000 grit
lapping compound if needed to ensure no
leakage.
3. Reassemble in reverse order as disassembly.
Note: Replace all gaskets where disassembly is required.
Armstrong Pressure/Temperature Controls Group, 221 Armstrong Blvd., Michigan 49093 - USA Ph: (269) 279-3600 Fax: (269) 273-8656
Bulletin AY-745-A
8/03
www.armstrong-intl.com
Printed in U.S.A.
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