Disassembly
1. Disconnect by-pass, discharge and inlet plumbing from unloader.
2. Remove unloader from pump.
3. Secure body of unloader in a vise with adjusting handle facing up.
4. Remove discharge fitting and o-ring, spring, check valve and o-ring.
5. Examine check valve and discharge fitting for wear, spring for wear or
fatigue and o-rings for cuts or wear and replace as needed with check
valve kit.
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. Remove black nylon cap on top of adjusting handle.
7. Unscrew and remove hex nylock nut.
8. Unscrew and remove adjusting handle, flat washer and spring.
9. Examine all parts for scale build up or wear and replace as needed.
Examine spring for fatigue or wear and replace as needed.
10. Unscrew and remove two jam nuts from piston stem.
11. Unscrew piston retainer from body of unloader.
12. Grasp threaded end of piston stem and pull from body of unloader.
Piston retainer and all associated o-rings should come out upon
removal.
13. 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.
14. Examine piston stem for wear. Examine o-ring and back-up-rings for
cuts or wear and replace as needed.
15. Remove bottom inlet fitting and o-ring, spring, ball and seat w/o-ring
from bottom inlet connection. Examine seat for grooves and o-ring
for cuts or wear and replace as needed.
Reassembly
1. At bottom inlet port, lubricate and install o-ring on outside diameter
of seat and press seat squarely into position in the body.
Note: Polished chamfer towards the ball.
2. Install ball and then spring, thread in inlet fitting with o-ring.
3. Lubricate and install o-ring and then back-up-ring into groove near
piston stem tip end. Lubricate and install o-ring and then back-up
ring onto threaded end of piston stem.
4. Grasp threaded end of piston stem and press by hand into unloader
body.
5. Lubricate and install larger o-ring over threads of piston retainer
body. Slide piston retainer with threads facing downwards over
piston stem and thread into body.
6. Apply Loctite®242®to the last few threads of the piston stem. Hand
thread two jam nuts to bottom threads of piston stem.
7. Slide spring over piston stem. Install flat washer on top of spring.
8. Thread adjusting handle onto piston stem.
9. Install hex nylock nut onto piston stem.
10. At discharge side of unloader, 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 unloader body.
11. Lubricate and install o-ring onto threaded end of discharge fitting.
Thread in discharge fitting to discharge port of unloader body and
tighten with wrench.
12. Remove unloader from vise.
13. Re-install unloader onto pump.
14. Reconnect by-pass, discharge and inlet plumbing to unloader.
15. Proceed to PRESSURE ADJUSTMENT.
Loctite®and 242®are registered trademarks of the Henkel Corporation.
Read all CAUTIONS and WARNINGS before commencing
service or operation of any high-pressure system
TROUBLESHOOTING
Unloader cycles lWorn O-ring or check valve
lFitting leaking downstream
lO-ring in gun worn
Liquid leaking lO-ring for seat or inlet fitting cut or worn
from bottom
Liquid leaking lO-ring for piston worn or cut
from middle
Unloader will not lNot properly sized for system pressure
come up to pressure lForeign material in unloader
lPiston o-rings worn
lNozzle worn or too large.
lJam nuts not properly set
Extreme pressure lAdjusting handle turned completely into
spikes unloader
lRestricted by-pass or no by-pass
lSystem flow exceeds unloader rating
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
