SERVICING
CAUTION: Before commencing with service, shut off drive (electric motor,
gas or diesel engine) and turn off water supply to pump. Relieve all
discharge line pressure by triggering gun or opening valve in discharge
line.
Disassembly:
1. Disconnect by-pass, discharge and inlet plumbing from unloader.
2. Remove unloader from pump.
3. Secure lower body of unloader in a vise with pressure adjuster/
adjusting handle facing up.
4. Remove discharge fitting and o-ring, spring, check valve and o-ring.
5. Inspect check valve and discharge fitting for wear, spring for wear or
fatigue and o-rings for cuts or wear and replace as needed.
Note: While the discharge fitting is removed, inspect sealing area where
the check valve makes contact within the internal body of the unloader
for grooves, pitting and wear. If damage is found, stop the repair and
replace with complete new unloader. If not, proceed with disassembly.
6. Unscrew and remove pressure adjuster/adjusting handle, locking
nut, spacer (7592 only), spring retainer, upper spring retainer, spring,
lower spring retainer and ball. Inspect all parts for scale build up or
wear and replace as needed. Examine spring for fatigue or wear and
replace as needed.
7. Unscrew upper body from lower body.
8. Secure the valve on the flat surfaces and using an 8mm allen wrench
unthread the piston stem from the valve.
9. Remove piston retainer, o-rings and back-up-ring. Examine piston
retainer for wear. Examine o-rings and back-up-ring for cuts or wear
and replace as needed.
10. Examine the valve and piston stem for wear. Examine o-rings and
back-up-rings for cuts or wear and replace as needed.
11. Press the seat out of the lower body from the by-pass port. Examine
seat for grooves and o-ring for cuts or wear and replace as needed.
Reassembly:
1. Lubricate and install o-ring on outside diameter of seat and press seat
squarely into position in the lower body.
2. Lubricate and install o-ring and then back-up-ring onto piston stem.
Press piston stem with threads facing down into the top end of the
upper body.
3. Lubricate and install back-up-ring and then o-ring into inside
diameter of piston retainer. Insert piston retainer into the bottom of
the upper body.
4. Apply Loctite®242® to the threads of the piston stem and valve. Thread
valve onto piston stem and tighten with wrench.
5. Lubricate and install o-ring on to bottom of the upper body. Carefully
hand thread upper body into lower body and tighten with a wrench.
6. Replace the ball, lower spring retainer, spring, upper spring retainer,
spring retainer and spacer (7592 only) into top of upper body.
7. Thread in locking nut and pressure adjuster/adjusting handle.
8. Lubricate and install o-ring onto check valve. Place spring inside
check valve. Insert check valve with o-ring and spring into discharge
port of lower body.
9. Lubricate and install o-ring onto threaded end of discharge fitting.
Thread in discharge fitting to discharge port of lower body and
tighten with wrench.
10. Remove unloader from vise.
11. Re-install unloader onto pump.
12. Reconnect by-pass, discharge and inlet plumbing to unloader.
13. Proceed to PRESSURE ADJUSTMENT.
Loctite® 242® are registered trademarks of the Henkel Corporation.
TROUBLESHOOTING
Unloader cycles l Check for leak downstream of unloader.
l Worn O-ring or check valve.
l Air in system, poor connection.
l O-ring in gun worn.
l Insufficient flow through unloader.
Liquid leaking from l O-ring for fitting cut or worn.
bottom fitting l O-ring for seat cut or worn.
Liquid leaking from l O-ring for piston worn or cut.
middle l O-rings for piston stem worn or cut.
Unloader will not come l Not properly sized for system pressure.
up to pressure l Foreign material in unloader. Clean filter.
l Piston stem O-rings worn.
l Nozzle worn.
l Insufficient flow to pump.
Extreme pressure l Adjusting nut turned completely
spikes into unloader.
l Restricted by-pass or no by-pass.
l System flow exceeds unloader rating.
Filtration l Clean filter on regular schedule to
avoid cavitation.
Approximate Gauge Gauge
Pressure Reading Between Between
at Gauge Pump/Unloader Unloader/Gun-Nozzle-Valve
System in operation system pressure system pressure
(gun open)
System in by-pass low pressure system pressure
(all guns,valves closed) 0-150 PSI +200 PSI
PRESSURE READING
Read all CAUTIONS and WARNINGS before commencing
service or operation of any high-pressure system
