Last update: 14/07/10
3
PROBLEM HANDLING: CAUSES AND SOLUTIONS
PROBLEMS
PROBABLE CAUSES
SOLUTIONS
Frequent unloader recycles
Damaged check valve O-Ring
Leaking connections
Restricted bypass
Replace
Check and renew
Clean or adapt
Unloader does not reach
pressure
Unloader not properly sized
Piston O rings worn out
Material matter between seat and shutter
Worn out nozzle
Change spring or type of valve
Replace
Clean the seat
Replace
Pressure peaks
Less than 5% of total flow in bypass
Excessive flow in bypass
Spring totally compressed
Reset
Change type of valve or adjust passages
Loosen knob and change nozzle
Unloader does not bypass at
low pressure
Jammed check valve
Check valve O ring worn out
Material matter on check valve
Clean or replace
Replace
Clean
Unloader causes oscillations to
the hydraulic system
Bypass system unfit
Bypass tube not properly sized
Bypass obstructed or throttled
Stick to the installation scheme represented at the
bottom of this page, with bypass directed into the
pump
Enlarge diameter
Clean or reset
REGULATIONS : see provisional manual
The accessory hereby described bears the CE mark in compliance with provisions and regulations
indicated on the Declaration of conformity.
For a correct utilization, follow the directions described in this manual and re-print them on the Use and maintenance manual of the
machine.
Make sure that you are given the Original Declaration of Conformity for the accessory chosen. The present manual is valid for all
unloader valves type VB 280 and VB 350.
MAINTENANCE
Maintenance has to be carried out by Specialized Technicians.
STANDARD: every 400 working hours (circa 10,000 cycles), control and lubricate the seals with water
resistant grease.
SPECIAL: every 800 working hours( circa 20,000 cycles), control the wear of the seals and internal parts and
if necessary, replace with original PA parts taking care during installation and to lubricate with water resistant
grease.
ATTENTION: reassemble the valve in the correct manner paying special attention to the Nut (pos 19) which must
always be in place.
The manufacturer is not to be considered responsible for damage as a result from incorrect fitting and
maintenance-
Technical data, descriptions and illustrations are indicative and liable to modification without notice
Fig 1
