Graco 25T478 Parts list manual

3A7681A
EN
Instructions-Parts
Medium Pressure Back
Pressure Regulators
The back pressure regulator (BPR) controls fluid pressure and flow in circulation systems.
For professional use only.
See page 2 for model information, including maximum
working pressure and approvals.
Important Safety Instructions
Read all warnings and instructions in this
manualbeforeusingtheequipment.Save
these instructions.
Optional gauges are shown.

Related Manuals
23A7681A
Contents
Related Manuals . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Models. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Warnings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Installation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Install the Back Pressure Regulator. . . . . . . . . . . 5
Grounding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Operation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Pressure Relief Procedure. . . . . . . . . . . . . . . . . . 7
Adjusting the BPR . . . . . . . . . . . . . . . . . . . . . . . . 7
Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Flush the Equipment. . . . . . . . . . . . . . . . . . . . . . . 8
Cleaning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Parts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Accessories. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Dimensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Technical Specifications . . . . . . . . . . . . . . . . . . . . 14
California Proposition 65 . . . . . . . . . . . . . . . . . . . . 14
Notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Graco Standard Warranty . . . . . . . . . . . . . . . . . . . 16
Related Manuals
Models
* Regulated range is 250–1000 psi (1.7–7 MPa, 17–70 bar) above 3 gpm (11 lpm).
Manual in English Description
3A4030 Intelligent Paint Kitchen
3A7709 Pneumatic Pump Control Module
Part Description Flow
Range Regulated Fluid Pressure Max. Fluid Inlet Pressure
Max. Air
Working
Pressure Approvals
25T478
Back pressure
regulator (BPR),
low flow, medium
press, pneumatic 0–5 gpm,
0–19 lpm
100–1000 psi
(0.7–7MPa,7-70
bar)*
3000 psi
(20.7 MPa,
207 bar)
100 psi
(0.7 MPa, 7.0
bar)
25T477 250–2000 psi
(1.7–13.8 MPa,
17-138 bar)
25R490 250–3000 psi
(1.7–20.7 MPa,
17–207 bar)
25R491
Back pressure
regulator (BPR),
low flow, medium
pressure,
mechanical with
locking nut
250–3000 psi
(1.7–20.7 MPa,
17–207 bar) ------
Ex h IIB T6 Gb
0°C to 50°C
NOTE: Type of
Protection“h”applied
is constructional
safety “c.”

Warnings
3A7681A 3
Warnings
The following warnings are for the setup, use, grounding, maintenance, and repair of this equipment. The
exclamation point symbol alerts you to a general warning and the hazard symbols refer to procedure-specific risks.
When these symbols appear in the body of this manual or on warning labels, refer back to these Warnings.
Product-specific hazard symbols and warnings not covered in this section may appear throughout the body of this
manual where applicable.
WARNING
FIRE AND EXPLOSION HAZARD
Flammable fumes, such as solvent and paint fumes, in work area can ignite or explode. Paint or solvent
flowing through the equipment can cause static sparking. To help prevent fire and explosion:
• Use equipment only in well-ventilated area.
• Eliminate all ignition sources; such as pilot lights, cigarettes, portable electric lamps, and plastic drop
cloths (potential static sparking).
• Ground all equipment in the work area. See Grounding instructions.
• Keep work area free of debris, including solvent, rags and gasoline.
• Do not plug or unplug power cords, or turn power or light switches on or off when flammable fumes
are present.
•Stop operation immediately ifstaticsparkingoccursoryoufeelashock.Donotuseequipmentuntil
you identify and correct the problem.
• Keep a working fire extinguisher in the work area.
SKIN INJECTION HAZARD
High-pressure fluid from gun, hose leaks, or ruptured components will pierce skin. This may look like
just a cut, but it is a serious injury that can result in amputation. Get immediate surgical treatment.
• Do not spray without tip guard and trigger guard installed.
• Engage trigger lock when not spraying.
• Do not point gun at anyone or at any part of the body.
• Do not put your hand over the spray tip.
• Do not stop or deflect leaks with your hand, body, glove, or rag.
• Follow the Pressure Relief Procedure when you stop spraying and before cleaning, checking, or
servicing equipment.
• Tighten all fluid connections before operating the equipment.
• Check hoses and couplings daily. Replace worn or damaged parts immediately.

Warnings
43A7681A
WARNING
EQUIPMENT MISUSE HAZARD
Misuse can cause death or serious injury.
• Do not operate the unit when fatigued or under the influence of drugs or alcohol.
• Do not exceed the maximum working pressure or temperature rating of the lowest rated system
component. See Technical Specifications in all equipment manuals.
• Use fluids and solvents that are compatible with equipment wetted parts. See Technical
Specifications in all equipment manuals. Read fluid and solvent manufacturer’s warnings. For
complete information about your material, request Safety Data Sheets (SDSs) from distributor or
retailer.
• Turn off all equipment and follow the Pressure Relief Procedure when equipment is not in use.
• Check equipment daily. Repair or replace worn or damaged parts immediately with genuine
manufacturer’s replacement parts only.
• Do not alter ormodify equipment. Alterations or modifications may void agency approvals and create
safety hazards.
• Make sure all equipment is rated and approved for the environment in which you are using it.
• Use equipment only for its intended purpose. Call your distributor for information.
• Route hoses and cables away from traffic areas, sharp edges, moving parts, and hot surfaces.
• Do not kink or over bend hoses or use hoses to pull equipment.
• Keep children and animals away from work area.
• Comply with all applicable safety regulations.
TOXIC FLUID OR FUMES HAZARD
Toxic fluids or fumes can cause serious injury or death if splashed in the eyes or on skin, inhaled, or
swallowed.
• Read Safety Data Sheets (SDSs) to know the specific hazards of the fluids you are using.
• Store hazardous fluid in approved containers, and dispose of it according to applicable guidelines.
PERSONAL PROTECTIVE EQUIPMENT
Wear appropriate protective equipment when in the work area to help prevent serious injury, including
eye injury, hearing loss, inhalation of toxic fumes, and burns. Protective equipment includes but is not
limited to:
• Protective eyewear, and hearing protection.
• Respirators, protective clothing, and gloves as recommended by the fluid and solvent manufacturer.

Installation
3A7681A 5
Installation
The Typical Installation shown in Fig. 1 is only a guide to
design a system. For assistance in designing a system
to meet your needs, contact your Graco distributor.
Install the Back Pressure
Regulator
1. Install the back pressure regulator (BPR) (A) in the
Fluid Return Line (D) or circulation loop return line.
See FIG. 1. Verify that the BPR is securely installed
in a rigid piping system. If flexible fluid lines are
used, the two 1/4 - 20 tapped mounting holes on the
side of the regulator should be used to securely
mount the regulator.
2. The BPR (A) has one 3/8 inch inlet port and one 1/4
inch gauge port. (The gauge port can be used as an
optional inlet port for low flow applications.) The two
outlet ports are 3/8 inch npt.
Connect fluid lines to the inlet and outlet ports that
are convenient for your installation. Make sure the
fluid flow agrees with the IN and OUT markings on
the BPR housing.
3. Install an accessory gauge, if used, in the 1/4 inch
gauge port. Install plugs in the unused inlets and
outlets.
4. If more than one spray station is used, install the
BPR (A) in the Fluid Return Line (D) after the last
spray station to maintain proper system pressures.
5. Install an air line to the top fitting on the BPR (A) for
air piloted models. The Air Line (G) needs an Air
Regulator (H) and Air Filter (not shown) to allow for
the adjustment of the fluid pressure. The Air Filter is
required to remove harmful dirt and moisture from
theair supply.Installa BleedTypeShut OffValve (J)
upstream of the air regulator.
Grounding
Do not use PTFE tape on pipe threads. Such use
could cause a loss of grounded continuity, which
could lead to a fire or explosion caused by static. Also,
if pieces of the tape break off, the function of the BPR
could be affected.
The equipment must be grounded to reduce the risk
of static sparking. Static sparking can cause fumes to
ignite or explode. Install the BPR into piping that is
properly grounded. Grounding provides an escape
wire for the electric current.

Installation
63A7681A
Key:
A Back Pressure Regulator (BPR)
B Air Filter/Regulator
C Fluid Supply Line
D Fluid Return Line
E Fluid Regulator
F Air-Assisted Airless Spray Gun
G Air Line
H Air Regulator (Pilot Air) (Air Filter not shown)
J Bleed Type Shut Off Valve (Air)*
K Shut Off Valve (Fluid)
L Drain Valve (not shown)*
* Required in your system.
FIG. 1: Typical Installation: Single Circulating Spray Station
A
B
C
G
FE
D
H
J
K

Operation
3A7681A 7
Operation
Pressure Relief Procedure
Follow the Pressure Relief Procedure whenever
you see this symbol.
1. Engage trigger lock.
2. Follow the recommendedshut down procedure from
the respective pump manual.
3. Close the Bleed Type Shut Off Valve (J) on the Air
Regulator (H) to the pneumatic BPR to reduce fluid
pressure to zero. Turn the adjusting screw on the
mechanical BPR counterclockwise to reduce the
fluid pressure to zero.
4. Disengage trigger lock.
5. Hold a metal part of the gun firmly to the side of a
grounded metal pail, and trigger the gun to relieve
pressure.
6. Engage trigger lock.
7. Open the Drain Valve (L) (required in your system).
Have a container ready to catch the drainage.
8. Leave the drain valve open until you are ready to
spray again.
9. If you suspect the spray tip or hose is clogged or
that pressure has not been fully relieved:
a. VERY SLOWLY loosen the tip guard retaining
nut or the hose end coupling to relieve pressure
gradually.
b. Loosen the nut or the coupling completely.
c. Clear the obstruction in the hose or tip.
Adjusting the BPR
The BPR controls pressure upstream from the BPR.
Adjust the pump fluid pressure and the BPR for the best
spraying combination and proper circulation of the fluid.
• The pneumatic pilot operated BPR fluid pressure is
adjusted by increasing or decreasing the pilot air
pressure. The fluid to air pressure ratio ranges from
10:1 to 30:1 depending on the model chosen for the
application. See Technical Specifications, page
14.
• The mechanical operated BPR fluid pressure is
adjusted by rotating the adjusting screw clockwise
to increase fluid pressure and counterclockwise to
decrease fluid pressure.
This equipment stays pressurized until pressure is
manually relieved. To help prevent serious injury from
pressurized fluid, such as skin injection, splashing
fluid and moving parts, follow the Pressure Relief
Procedure when you stop spraying and before
cleaning, checking, or servicing the equipment.

Maintenance
83A7681A
Maintenance
Flush the Equipment
Flush the BPR whenever the rest of the system is
flushed. Before flushing, fully open the BPR by reducing
pilot air pressure to zero or turning the adjusting screw
counterclockwise to reduce pressure to zero.
NOTE: Do not allow paint or solvent to remain in the
system for a long time. Fluid could dry on the piston,
causing leakage at the piston packing. If leakage
occurs, disassemble and clean the BPR.
Cleaning
Regular cleaning and inspection, and lubrication of the
BPR are necessary to keep the BPR working properly.
1. Follow the Pressure Relief Procedure on page 7.
2. Remove the BPR from the system.
3. Disassemble the BPR, referring to the parts
drawings on pages 9 and 11. Clean and inspect all
parts.
To reduce the risk of serious bodily injury, including
fluid injection or splashing in the eyes or on the skin,
always follow the Pressure Relief Procedure before
adjusting, cleaning, repairing, or removing the BPR
from the system.
Never completely remove the adjusting screw when
system pressure is present.
NOTICE
Use special care when handling the hard carbide por-
tions of the piston (3) and seat (4). Damage causes
poor operation and leakage.

Parts
3A7681A 9
Parts
25R490, 25T477, 25T478 Lower Flow Medium Pressure BPR, Pneumatic
FIG. 2: Lower Flow Medium Pressure BPR, Pneumatic (25R490 shown)
3
1
4
4
7
6
10
1
2
12
8
1
5
9
13
4
14
1
11
1
6
1
1
7
5
6
Apply NLGI Grade 2 grease (Chevron SRI).
Torque to 175–200 in-lbs (20–23 N•m).
Apply metal assembly paste to threads
(Molykote®G-N paste).
1
6
4
7
Apply thread sealant.
Torque to 60–70 ft-lbs (81–95 N•m).
5

Parts
10 3A7681A
Ref. Part Description Qty.
1 19Y871 (25R490) CYLINDER,
REGULATOR, BP, MEDIUM
PRESS, 30:1
1
19B727 (25T477) CYLINDER,
REGULATOR, BP, MEDIUM
PRESS, 20:1
1
19B728 (25T478) CYLINDER,
REGULATOR, BP, MEDIUM
PRESS, 10:1
1
2 19Y873 HOUSING, REGULATOR, BP,
MEDIUM PRESS 1
3 238932 PISTON, VALVE 1
4 238933 SEAT, VALVE 1
5 113751 RING, RETAINING, INTERNAL 1
6 19Y810 (25R490) PISTON, AIR,
ACTUATOR, REGULATOR, BP 1
19B729 (25T477) PISTON, AIR,
ACTUATOR, REGULATOR, BP,
20:1
1
19B730 (25T478) PISTON, AIR,
ACTUATOR, REGULATOR, BP,
10:1
1
7 189817 GASKET 1
8 111796 SEAL, U-CUP 1
9 171885 WASHER 1
10 166985 PACKING, O-RING 1
11 19B484 (25R490) SEAL, U-CUP,
SYMETRIC, BEVEL, LITE 1
113249 (25T477) PACKING, U-CUP 1
112181 (25T478) SPACKING, U-CUP 1
12 101748 PLUG, PIPE SST 1
13 19Y872 (25R490)COVER,REGULATOR,
BP, AIR, UPPER, MP 1
19B731 (25T477, 25T478) COVER,
REGULATOR, BP, AIR, MED
PRESS
1
14 109458 (25R490) PACKING, O-RING 1
156594 (25T477, 25T478) PACKING,
O-RING 1
18 101970 PLUG, PIPE, HDLS, optional if
gauge is not used (not shown) 1
Ref. Part Description Qty.