Graco EnDure Instruction Manual page 12

Maintenance
Factors affecting valve life
The maintenance tables should be used as a guideline
for frequency of maintenance tasks. Additional factors
that affect valve life include the following:
• Process fluid - Abrasive or fiber filled fluids are
much harder on seals, shafts, and seats than
non-abrasive fluids such as oil.
• Pressure drop across the valve seat - As the
valve opens or closes, the fluid is accelerated to a
high velocity at the needle/seat contact area. The
rate of wear at the valve will be much greater at
3000 psi than at 1000 psi. Changing nozzle or tip
size can have a substantial affect on wear.
• Number of cycles - This has a much greater affect
on valve wear than number of gallons. If you can do
the same job with fewer on/off cycles, the valve will
last longer.
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• Speed of actuation - Snapping the valve open and
closed quickly will give longer needle and seat life.
Avoid long air tube runs after the solenoid, or use
quick exhaust valves (104661) on the dispense
valve.
• Air pressure - This is what provides the force to
hold the hardened SST needle against the carbide
seat to seal against fluid pressure. Any leakage on
these hard parts, at high pressure, will quickly
"worm-hole" the parts and cause the valve to fail.
This valve has been designed with two air pistons to
give it an exceptionally high, 68:1 advantage of air
pressure to fluid pressure. This means that you can
reliably operate at 60 psi of air, even with 4000 psi
of downstream pressure.
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