Instructions–Parts List
STAINLESS STEEL, WATERBASE COMPATIBLE
308401E
ENG
Back Pressure Regulator
For use in circulating systems to provide regulated back pressure to spray
gun(s) and to maintain proper system pressure. Model 237503 is the back
pressure regulator only. Model 236770 includes the gauge, tube, inlet adapter
and outlet swivel union.
300 psi (21 bar, 2.1 MPa) Maximum Inbound Pressure
180 psi (12.4 bar, 1.24 MPa) Maximum Regulated Pressure
Model 236770, Series B
Model 237503, Series B
Important Safety Instructions
Read all warnings and instructions in this manual.
Save these instructions.
Model 237503
03963
Table of Contents
Warnings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Parts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Dimensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Technical Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Accessories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Warranty . . . . . . . . . . . . . . . . . . . . . . . . . . . . Back Cover
Model 236770
Graco Information . . . . . . . . . . . . . . . . . . . . Back Cover
03505
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Installation
KEY
A
B
C
D
E
Fluid Supply Line
Air Spray Gun
Fluid Pressure Regulator
Air Supply Line
Adjusting Screw
F
Back Pressure Regulator
(236770 shown)
Fluid Return Line
Ball Valve
G
H
A
B
C
D
G
E
H
F
03506
Fig. 1
Connect the line to the inlet and outlet. Make sure the
flow direction agrees with the IN and OUT markings on
the bottom of the regulator body.
Installing the Back Pressure Regulator
CAUTION
Handle the back pressure valve with care to avoid
damaging the diaphragm.
The back pressure regulator is adjustable to control
the fluid pressures in a circulating system from 5 to
180 psi (0.3 to 12.4 bar, .03 to 1.24 MPa).
If more than one spray station is used, install the back
pressure regulator in the fluid supply line after the last
station. This will help maintain proper circulating
pressures in the system.
Install the back pressure regulator in the spray gun
return line. See Fig. 1.
Operation
NOTE: The back pressure regulator controls pressure
ahead of its intake.
Flush the back pressure regulator with a compatible
solvent whenever the rest of the system or unit is
being flushed. Open the back pressure regulator
before flushing by turning the screw counterclockwise.
Turn the adjusting screw clockwise to increase pres-
sure and counterclockwise to decrease pressure.
Adjust the pump pressure and back pressure regulator
for the best spraying combination and for proper
circulation of fluid.
308401 3
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Service
3. Disassemble the regulator and clean it with a
Pressure Relief Procedure
suitable solvent. See the parts drawing, page 5.
4. Carefully inspect the diaphragm (14) for cracks or
WARNING
other damage. Replace if necessary.
PRESSURIZED EQUIPMENT HAZARD
The system pressure must be manually relieved to
prevent the system from starting or spraying acci-
dentally. To reduce the risk of an injury from acci-
dental spray from the gun, splashing fluid, or
moving parts, follow the Pressure Relief Proce-
dure whenever you:
5. Check for chips or dirt that could puncture the
diaphragm before assembling the regulator.
6. Reassemble the diaphragm and related parts.
Torque the cap nut (3) to 27 to 33 in-lb (3.1 to 3.7
NSm).
D are instructed to relieve the pressure,
D stop spraying,
D check or service any of the system equipment,
D or install or clean the spray nozzle.
7. Carefully inspect the seat (1) for damage, wear, or
dirt. These things could cause the regulated pres-
sure to creep. Replace the seat if necessary.
8. Replace the seat gasket (6) when replacing the
seat (1). Torque the seat to 70 to 80 in-lb (8 to 9
NSm).
1. Shut off the pump.
2. Open the dispensing valve, if used.
9. To remove or install the gauge on model 236770
(20), use the wrench on the square portion of the
gauge stud only.
3. Open the fluid drain valve to relieve all fluid pres-
sure, having a container ready to catch the drain-
age.
CAUTION
Use thread sealer sparingly on the gauge’s male
threads when installing it to avoid plugging the
gauge.
Service
NOTE: Regular cleaning and inspection of the regula-
tor, based upon the degree and kind of service, is
essential.
10. Lubricate the adjusting screw (15) threads.
11. Assemble the remaining parts.
1. Shut off the pump and open the back pressure
regulator by turning the adjusting screw (15)
counterclockwise until no spring pressure is felt.
Relieve all air and fluid pressures in the system.
12. Tighten the regulator cap (4) to 324 to 396 in-lb (37
to 45 NSm).
2. Remove the back pressure regulator from the fluid
13. Reinstall the back pressure regulator in the fluid
line.
line.
Troubleshooting
Checking the Ball and Seat
WARNING
To reduce the risk of serious injury whenever you
are instructed to relieve pressure, always follow the
Pressure Relief Procedure above.
The ball and seat may be checked for wear by closing
the ball valve directly upstream of the back pressure
regulator (Fig 1). When the ball valve is closed, the
gauge pressure should drop slightly. If the pressure
continues to drop, then the ball or seat is worn and
needs to be replaced. Follow the preceding Service
procedure to replace the worn ball or seat.
4 308401
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Parts
Stainless Steel Back Pressure Regulator –
Model 236770, Series B Includes items 1 to 20
Model 237503, Series B Includes items 1 to 15
Ref.
Ref.
Qty. No.
No.
Part No. Description
Part No. Description
Qty.
1n
2n
3
4
5
6n
7n
8
9
10
11
236893
236894
100529
189815
101976
189817
154789
16C761
157796
160180
100111
SEAT, valve
STEM, valve
1
1
1
1
1
1
1
1
1
1
1
12
13
189816
177432
PLATE, backup
PLATE, support, diaphragm
DIAPHRAGM
SCREW, adjusting, 1/2–20 x
1–5/8 long
UNION, adapter; 1/2–14 npt(m)
x 3/8–18 npsm(f) swivel
ADAPTER, inlet; 3/8–18
npsm(m), 3/8–18 npt(m), 1/4–18
npt(f)
1
1
1
1
NUT, hex, cap; 5/16–18
CAP, regulator, air
WRENCH, Allen; 3/8
GASKET, acetal
GASKET, copper
HOUSING, valve
SPRING, compression
PLATE, spring
14n 177431
15
17
18
112844
236892
16C760
1
1
NUT, lock; 1/2–20
19
187877
TUBE, fluid gauge
GAUGE, 0–300 psi
(0–21 bar, 0–2.1 MPa)
1
1
20n 187876
n Keep these spare parts on hand to reduce down
time.
12
20
5
15
11
3
2
7
13
14
1
4
19
18
2
1
3
10
9
6
8
1
Torque 324 to 396 in-lb (37 to 45 N.m)
Torque 27 to 33 in-lb (3.1 to 3.7 N.m)
2
3
17
Torque 70 to 80 in-lb (8 to 9 N.m)
03504
308401 5
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Notes
6 308401
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Dimensions
Technical Data
Maximum Inlet Pressure: . . . 300 psi (21 bar, 2.1 MPa)
Regulated Pressure Range . . . . . . . . . . . . . . 5–180 psi
(0.3–12.4 bar, .03–1.24 MPa)
236770 Inlet Size . . . . . . . . . . . . . . . . . . . . . 3/8 npsm(m)
236770 Outlet Size . . . . . . . . . . . . . . . . . . . . 3/8 npsm(f)
237503 Inlet . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3/8 npt(f)
237503 Outlet . . . . . . . . . . . . . . . . . . . . . . . . . . 1/2 npt(f)
236770 Weight: . . . . . . . . . . . . . . . . . . . . . 3.5 lb (1.6 kg)
237503 Weight: . . . . . . . . . . . . . . . . . . . . . 2.4 lb (1.1 kg)
Wetted Parts:
2.25 in. (57.2 mm
diameter
7.25 in.
(184 mm)
316 stainless steel, tungsten carbide (with nickel
binder), acetal and PTFE
3/8
npsm(m)
Inlet
Maximum flow chart for 180 psi (12.4 bar, 1.24 MPa)
inbound pressure and fluid viscosity of 65 cps
Regulated Pressure
50 psi (3.4 bar, 0.3 MPa) 4.7 gpm (17.8 lpm)
100 psi (7 bar, 0.7 MPa)
150 psi (10.3 bar,
1.0 MPa)
Maximum Flow Rate
3/8
npsm(f)
Outlet
4.3 gpm (16.3 lpm)
3.7 gpm (12.9 lpm)
Model 236770 shown
03505
Fig. 2
Manual
Change Summary
Assembly
Changed
Part
Status
Ref. Part No. Name
No.
Accessories
236770 and Old
237503, to
Series B
20
20
187873
187876
Gauge
Gauge
New
Air-Charge Conversion Kit 237448
Maximum inbound pressure is increased to 300 psi (21
bar, 2.1 MPa).
Includes necessary parts to convert back pressure
regulator from spring operated to air operated.
308401 7
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The Graco Warranty and Disclaimers
Graco warrants all equipment listed in this manual which is manufactured by Graco and bearing its name to be free from defects in
material and workmanship on the date of sale by an authorized Graco distributor to the original purchaser for use. With the exception of
any special extended or limited warranty published by Graco, Graco will, for a period of twelve months from the date of sale, repair or
replace any part of the equipment determined by Graco to be defective. This warranty applies only when the equipment is installed,
operated and maintained in accordance with Graco’s written recommendations.
This warranty does not cover, and Graco shall not be liable for general wear and tear, or any malfunction, damage or wear caused by
faulty installation, misapplication, abrasion, corrosion, inadequate or improper maintenance, negligence, accident, tampering, or
substitution of non-Graco component parts. Nor shall Graco be liable for malfunction, damage or wear caused by the incompatibility of
Graco equipment with structures, accessories, equipment or materials not supplied by Graco, or the improper design, manufacture,
installation, operation or maintenance or structures, accessories, equipment or materials not supplied by Graco.
This warranty is conditioned upon the prepaid return of the equipment claimed to be defective to an authorized Graco distributor for
verification of the claimed defect. If the claimed defect is verified, Graco will repair or replace free of charge any defective parts. The
equipment will be returned to the original purchaser transportation prepaid. If inspection of the equipment does not disclose any defect
in material or workmanship, repairs will be made at a reasonable charge, which charges may include the costs of parts, labor, and
transportation.
Graco’s sole obligation and buyer’s sole remedy for any breach of warranty shall be as set forth above. The buyer agrees that no other
remedy (including, but not limited to, incidental or consequential damages for lost profits, lost sales, injury to person or property, or any
other incidental or consequential loss) shall be available. Any action for breach of warranty must be brought within two (2) years of the
date of sale.
GRACO MAKES NO WARRANTY, AND DISCLAIMS ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
A PARTICULAR PURPOSE IN CONNECTION WITH ACCESSORIES, EQUIPMENT, MATERIALS OR COMPONENTS SOLD BUT
NOT MANUFACTURED BY GRACO. These items sold, but not manufactured by Graco (such as electric motors, gas engines,
switches, hose, etc.), are subject to the warranty, if any, of their manufacturer. Graco will provide purchaser with reasonable assistance
in making any claim for breach of these warranties.
In no event will Graco be liable for indirect, incidental, special or consequential damages resulting from Graco supplying equipment
hereunder, or the furnishing, performance, or use of any products or other goods sold hereto, whether due to a breach of contract,
breach of warranty, the negligence of Graco, or otherwise.
FOR GRACO CANADA CUSTOMERS
The parties acknowledge that they have required that the present document, as well as all documents, notices and legal proceedings
entered into, given or instituted pursuant hereto or relating directly or indirectly hereto, be drawn up in English. Les parties
reconnaissent avoir convenu que la rédaction du présente document sera en Anglais, ainsi que tous documents, avis et procédures
judiciaires exécutés, donnés ou intentés à la suite de ou en rapport, directement ou indirectement, avec les procédures concernées.
Graco Information
TO PLACE AN ORDER, contact your Graco distributor or call to identify the distributor closest to you:
Phone: 612–623–6921 or Toll Free: 1–800–328–0211 Fax: 612–378–3505
All written and visual data contained in this document reflects the latest product information available at the time of publication.
Graco reserves the right to make changes at any time without notice.
This manual contains English. MM 308401
Graco Headquarters: Minneapolis
International Offices: Belgium, China, Japan, Korea
GRACO INC. P.O. BOX 1441 MINNEAPOLIS, MN 55440–1441
Copyright 1994, Graco Inc. is registered to ISO 9001
Revised 11/2009
8 308401
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