Dispense Valves - Graco PGM Instructions - Parts Manual

Troubleshooting
Dispense pattern too light
Measured flow does not match
command

Dispense Valves

Problem
Valve not opening
Valve not shutting off
Sluggish open/close
Material leaks from back of valve
Air leaks from dispense valve
30
Supply pressure too low
Flow rate too high for application
Supply pressure too low
Flow rate too high for application
Gear meter is not calibrated
Gear meter is worn or damaged
Cause
Air not getting to open port
No Dispense Trigger signal from
automation unit
Air not getting to close port (except
AutoPlus valve)
Dispense Trigger signal from auto-
mation unit is on
Air pressure low
Needle/seat worn
Pressurized material past the valve
shut-off is escaping
Shaft seal is worn
Loose air connections
Worn piston o-ring
Verify inlet pressure needed for flow
rate
Perform dispense weight verifica-
tion, see Calibration procedure on
page 24; Lower flow rate and repeat
Verify inlet pressure needed for flow
rate
Perform dispense weight verifica-
tion, see Calibration procedure on
page 24; Lower flow rate and repeat
Perform calibration; Perform weight
verification, see Calibration proce-
dure on page 24
Perform weight verification, see Cal-
ibration procedure on page 24; if
weights are not repeatable repair or
replace gear meter
Solution
Verify air pressure solenoid
Check input from automation unit
Verify air pressure to solenoid
Verify solenoid operation
Verify air line routing and connec-
tions
Check input from automation unit
Verify air pressure is above 60 psi
(0.4 MPa, 4 bar)
Rebuild valve; replace needle/seat
Reduce running pressure
Reduce nozzle length
Increase nozzle orifice size
Rebuild valve; replace seals
Check air connections; tighten if
necessary
Rebuild valve; replace piston o-ring
3A5185B