INSTRUCTIONS-PARTS LIST

This manual contains important warnings and information.

READ AND KEEP FOR REFERENCE.

INSTRUCTIONS

STAINLESS STEEL, WATERBASE COMPATIBLE

Back Pressure Regulator

180 psi (12.4 bar) Maximum Inlet Pressure

Models 236–770 and 237–503

Used in circulating systems to provide regulated back pressure to the spray gun(s) and to maintain proper circulating pressure throughout the system. Model

237–503 is the back pressure regulator only. Model

236–770 includes the gauge, tube, inlet adapter and outlet swivel union.

Model 237–503

Table of Contents

Warnings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Parts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Dimensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Technical Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Accessories

Warranty

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . .

7

Back Cover

Graco Phone Numbers . . . . . . . . . . . . . . . Back Cover

Model 236–770

308–401

Rev. C

Supersedes B

GRACO INC. P.O. BOX 1441 MINNEAPOLIS, MN 55440–1441

COPYRIGHT 1994, GRACO INC.

Graco Inc. is registered to I.S. EN ISO 9001

WARNING

EQUIPMENT MISUSE HAZARD

Equipment misuse can cause the equipment to rupture or malfunction and result in serious injury.

INSTRUCTIONS

D This equipment is for professional use only.

D Read all instruction manuals, tags, and labels before operating the equipment.

D Use the equipment only for its intended purpose. If you are not sure, call Graco Technical Assistance at 1–800–543–0339.

D Do not alter or modify this equipment.

D Check equipment daily. Repair or replace worn or damaged parts immediately.

D Do not exceed the maximum working pressure of the lowest rated system component. The maximum working pressure of this equipment is 180 psi (12.4 bar).

D Follow the Pressure Relief Procedure on page 4 if the spray tip clogs and before cleaning, checking or servicing the equipment.

D Do not stop or deflect leaks with your hand, body, glove or rag.

D Be sure all equipment safety devices are operating properly before each use.

D Use fluids and solvents which are compatible with the equipment wetted parts. Refer to the Tech-

nical Data section of all equipment manuals. Read the fluid and solvent manufacturer’s warnings.

D Always wear protective eyewear, gloves, clothing and respirator as recommended by the fluid and solvent manufacturer.

D Wear hearing protection when operating this equipment.

D Comply with all applicable local, state, and national fire, electrical, and safety regulations.

Installation

KEY

A Fluid Supply Line

B Air Spray Gun

C Fluid Pressure Regulator

D Air Supply Line

E Adjusting Screw

B

F Back Pressure Regulator

(236–770 shown)

G Fluid Return Line

H Ball Valve

A

C

D

G

H

E

F

Fig. 1

Installing the Back Pressure Regulator

CAUTION

Handle the back pressure valve with care to avoid damaging the diaphragm.

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.

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).

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.

Turn the adjusting screw clockwise to increase pressure and counterclockwise to decrease pressure.

Adjust the pump pressure and back pressure regulator for the best spraying combination and for proper circulation of fluid.

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.

Service

Pressure Relief Procedure

3. Disassemble the regulator and clean it with a suitable solvent. See the parts drawing, page 5.

WARNING

PRESSURIZED EQUIPMENT HAZARD

The system pressure must be manually relieved to prevent the system from starting or spraying accidentally. To reduce the risk of an injury from accidental spray from the gun, splashing fluid, or moving parts, follow the Pressure Relief Proce-

dure whenever you:

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.

4. Carefully inspect the diaphragm (14) for cracks or other damage. Replace if necessary.

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 57 to 63 in-lb (6 to 7

N S m).

7. Carefully inspect the seat (1) for damage, wear, or dirt. These things could cause the regulated pressure to creep. Replace the seat if necessary.

1. Shut off the pump.

2. Open the dispensing valve, if used.

8. Replace the seat gasket (6) when replacing the seat (1). Torque the seat to 70 to 80 in-lb (8 to 9

N S m).

9. To remove or install the gauge on model 236–770

(20), use the wrench on the square portion of the gauge stud only.

3. Open the fluid drain valve to relieve all fluid pressure, having a container ready to catch the drainage.

Service

CAUTION

Use thread sealer sparingly on the gauge’s male threads when installing it to avoid plugging the gauge.

NOTE: Regular cleaning and inspection of the regulator, based upon the degree and kind of service, is essential.

10. Lubricate the adjusting screw (15) threads.

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.

WARNING

To reduce the risk of serious injury whenever you are instructed to relieve pressure, always follow the

Pressure Relief Procedure above.

11. Assemble the remaining parts.

12. Tighten the regulator cap (4) to 350 to 360 in-lb (40 to 41 N S m).

2. Remove the back pressure regulator from the fluid line.

13. Reinstall the back pressure regulator in the fluid line.

Troubleshooting

Checking the Ball and Seat

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.

20

Parts

Stainless Steel Back Pressure Regulator –

Model 236–770

Includes items 1 to 20

Model 237–503

Includes items 1 to 15

Ref.

No.

Part No.

Description Qty.

1 n 236–893 SEAT, valve

2 n 236–894 STEM, valve

3 100–529 NUT, hex, cap; 5/16–18

4 189–815 CAP, regulator, air

5 101–976 WRENCH, Allen; 3/8

6 n 189–817 GASKET, Delrin R

7 n 154–789 GASKET, copper

8 189–811 HOUSING, valve

9

10

11

157–796 SPRING, compression

160–180 PLATE, spring

100–111 NUT, lock; 1/2–20

1

1

1

1

1

1

1

1

1

1

1

Ref.

No.

Part No.

Description Qty.

12

13

189–816 PLATE, backup

177–432 PLATE, support, diaphragm

14 n 177–431 DIAPHRAGM

15 112–844 SCREW, adjusting, 1/2–20 x

17

1–5/8 long

236–892 UNION, adapter; 1/2–14 npt(m) 1 x 3/8–18 npsm(f) swivel

189–812 ADAPTER, inlet; 3/8–18 1 18

19 npsm(m),1/2–14 npt(m), 1/4–18 npt(f)

187–877 TUBE, fluid gauge

20 n 187–873 GAUGE, 0–200 psi/0–14 bar n Keep these spare parts on hand to reduce down time.

1

1

1

1

1

1

12

5

15

13

14

2

3

7

11

4 1

19

18

2

1

3

8

6

10

9

17

1 Torque 350 to 360 in-lb (40 to 41 N m)

2 Torque 57 to 63 in-lb (6–7 N m)

3 Torque 70 to 80 in-lb (8–9 N m)

03504

308-401 5

6 308-401

Notes

7.25 in.

(184 mm)

3/8 npsm(m)

Inlet

Dimensions

2.25 in. (57.2 mm) diameter

Technical Data

Maximum Inlet Pressure: . . . . . . . . . . 180 psi (12.4 bar)

Regulated Pressure Range . . 5–180 psi (0.3–12.4 bar)

236–770 Inlet Size

236–770 Outlet Size

. . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . .

3/8 npsm(m)

3/8 npsm(f)

237–503 Inlet and Outlet Size

236–770 Weight:

. . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . .

1/2 npt(f)

3.5 lb (1.6 kg )

237–503 Weight: . . . . . . . . . . . . . . . . . . . 2.4 lb (1.1 kg)

Wetted Parts:

316 stainless steel, tungsten carbide (with nickel binder), Delrin r and PTFE r

PTFE r and Delrin r are registered trademarks of the

Company

Maximum flow chart for 180 psi (12.4 bar) inbound pressure and fluid viscosity of 65 cps

Regulated Pressure

50 psi (3.4 bar)

100 psi (6.9 bar)

150 psi (10.3 bar)

Maximum Flow Rate

4.7 gpm (17.8 lpm)

4.3 gpm (16.3 lpm)

3.7 gpm (12.9 lpm)

Fig. 2

Model 236–770 shown

3/8 npsm(f)

Outlet

Accessories

Air-Charge Conversion Kit 237–448

Includes necessary parts to convert back pressure regulator from spring operated to air operated.

308-401 7

The Graco Warranty and Disclaimers

WARRANTY

Graco warrants all equipment manufactured by it 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. As purchaser’s sole remedy for breach of this warranty, Graco will, for a period of twelve months from the date of sale, repair or replace any part of the equipment proven 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, 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 with Graco equipment of structures, accessories, equipment or materials not supplied by Graco, or the improper design, manufacture, installation, operation or maintenance of 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 claim. 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.

DISCLAIMERS AND LIMITATIONS

The terms of this warranty constitute purchaser’s sole and exclusive remedy and are in lieu of any other warranties (express or implied), including warranty of merchantability or warranty of fitness for a particular purpose, and of any non–contractual liabilities, including product liabilities, based on negligence or strict liability. Every form of liability for direct, special or consequential damages or loss is expressly excluded and denied. In no case shall Graco’s liability exceed the amount of the purchase price.

Any action for breach of warranty must be brought within two (2) years of the date of sale.

EQUIPMENT NOT COVERED BY GRACO WARRANTY

Graco makes no warranty, and disclaims all implied warranties of merchantability and fitness for a particular purpose, with respect to accessories, equipment, materials, or components sold but not manufactured by Graco. These items sold, but not manufactured by Graco (such as electric motor, 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.

Graco Phone Numbers

TO PLACE AN ORDER, contact your Graco distributor, or call Graco: 1–800–367–4023 Toll Free

FOR TECHNICAL ASSISTANCE, service repair information or answers about the application of Graco equipment, call: 1–800–543–0339 Toll Free

Sales Offices: Atlanta, Chicago, Detroit, Los Angeles

Foreign Offices: Belgium, Canada, England, Korea, Switzerland, France, Germany, Hong Kong, Japan

GRACO INC. P.O. BOX 1441 MINNEAPOLIS, MN 55440–1441

PRINTED IN U.S.A. 308–401 July 1974, Revised October 1995