INSTRUCTIONS–PARTS LIST
306640
This manual contains important
warnings and information.
READ AND KEEP FOR REFERENCE.
INSTRUCTIONS
Back Pressure Valve
300 psi (21 bar, 2.1 MPa) Maximum Inbound Pressure
180 psi (12.4 bar, 1.24 MPa) Maximum Regulated Pressure
Model 205122, Series C
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.
Rev. F
Supersedes E
First choice when
quality counts.t
D Use the equipment only for its intended purpose. If you are uncertain about usage, call your Graco
distributor.
D Do not alter or modify this equipment. Use only genuine Graco parts and accessories.
D Check equipment daily. Repair or replace worn or damaged parts immediately.
D Do not exceed the maximum working pressure of the lowest rated component in your system. This
equipment has a 300 psi (21 bar, 2.1 MPa) maximum inbound pressure and a 180 psi (12.4 bar,
1.24 MPa) maximum regulated pressure.
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 Comply with all applicable local, state, and national fire, electrical, and safety regulations.
PRESSURIZED EQUIPMENT HAZARD
Spray from the gun, hose leaks, or ruptured components can splash fluid in the eyes or on the skin
and cause serious injury.
D Do not stop or deflect leaks with your hand, body, glove or rag.
D Tighten all fluid connections before operating the equipment.
D Follow the Pressure Relief Procedure on page 2 whenever you: are instructed to relieve pres-
sure; stop spraying; clean, check, or service the equipment; and install or clean the spray nozzle.
GRACO INC. P.O. BOX 1441 MINNEAPOLIS, MN 55440–1441
eCOPYRIGHT 1994, GRACO INC.
Graco Inc. is registered to ISO 9001
Pressure Relief Procedure.
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 Procedure 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.
1. Shut off the power to the pump. If you are using an air–
powered pump, open the bleed–type master air valve.
2. Trigger the gun.
3. Relieve the line pressure by turning the adjusting screw
(26) counterclockwise until there is no spring pressure.
Installation
This valve is used in a circulating system to regulate the back
pressure to spray guns and to maintain the proper circulating
pressure throughout the system.
22
Fig. 2
11
04520
Operation
The back–pressure valve controls pressure in the fluid
return–line. Adjust the pump pressure and the back–pressure
valve for the best combination of spraying pressure and fluid
circulation.
To adjust the back–pressure valve, loosen the locknut (27)
and insert the hex key wrench (7) into the socket on the
adjusting screw (26). Turn the screw clockwise to increase
pressure in the return line. Turn the screw counterclockwise
to decrease pressure in the return line. Lock in the adjustment by tightening the locknut (27).
The valve is adjustable to control fluid pressure in a circulating system from 0 to 180 psi (0 to 12.4 bar, 0 to 1.24 MPa).
CAUTION
To prevent damage to the diaphragm, the hard carbide seat
and stem, and other sensitive parts, handle the valve carefully.
Install the valve in the return line of the spray guns, downstream from the last gun. See Fig. 1. Connect the return line
to the 3/8 npsm(m) inlet (22) and the 3/8 npsm(f) outlet (11).
Be sure the connections match the direction of fluid flow in
the line. See Fig. 2.
C
B
A
D
E
NOTE: Always check and adjust the back pressure valve if
you make changes to the system such as a change of fluids,
the length of the lines, and the number of spray guns.
Flush the valve with a compatible solvent whenever the rest
of the system is being flushed. Fully open the valve before
flushing by turning the adjustment screw counterclockwise.
Always use the lowest possible pressure when flushing.
Service
NOTE: Clean and check the valve regularly to maintain it in
good working condition. Refer to the Parts drawing on page
3.
1. Remove the valve from the system.
2. Disassemble the pressure gauge (5) and the tube (16)
from the inlet adapter (22). Remove the inlet adapter and
the outlet union (11) from the housing (25).
3. Unscrew the cap (28) from the housing (25). Remove the
adjusting screw (26) and the locknut (27).
4. Remove the spring plate (15) and the spring (13).
5. Loosen the cap nut (4). Disassemble the diaphragm and
its related parts (2,10, 18, 19, 20, 21).
F
Fig. 1
CAUTION
04521
3066402
Be careful not to damage the valve seat (1) or stem (2)
which are made of hard carbide.
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