Troubleshooting
5-4
Part 104373
−
03
E
2015 Nordson Corporation
Corrective Action
Possible Cause
Problem
4. Pump strokes
irregularly or fluid
pressure fluctuates
(contd)
Solvent vapor in the hydraulic
system
During a siphon stroke, pressure
inside the hydraulic housing falls
below atmospheric pressure,
lowering the boiling point of the
solvents in the coating material. If
the fluid temperature is close to the
boiling point, the drop in pressure
may permit solvent to begin boiling
off, creating gas bubbles inside the
hydraulic housing.
The fluid temperature should be at
least 12
C (20
F) below the boiling
point of the most volatile solvent used
in the coating material. Lower the
temperature of the coating material or
pressure feed the coating material
into the pump.
NOTE:
Viscous coating materials,
long siphon systems, and blocked
siphon strainers may cause pressure
inside the hydraulic chamber to drop
to unusually low levels during the
siphon stroke, aggravating the
condition.
Leaks in the pneumatic system
Check the pneumatic system
schematic. Listen for continuous air
leaks from partially opened valves,
tubing connections, damaged tubing
or gaskets.
Ice in muffler or exhaust tubes
Formation of ice inside the muffler
boxes, exhaust tubes, or air valve
may restrict or prevent operation.
Heat and/or dry compressed air
supply.
Faulty air valve
If the pump continuously double
strokes and either plunger is taking
less than a 51-mm (2-in.) stroke and
then reversing, the air valve is faulty.
Rebuild or replace the air valve.
Continued...
