Graco Dispensit 792-20 [11/14] Troubleshooting

TROUBLESHOOTING

If operating difficulties are encountered, review the symptoms below. With each problem there are one or

more possible causes that should be investigated to resolve the situation.

NOTHING HAPPENS - If absolutely nothing happens when trying to cycle the Dispense Valve, check the

electric and pneumatic power. Check all control connections for proper installation.

VALVE CYCLES, NOTHING DISPENSED - First, try to purge the unit; this should fix most situations. If

nothing is dispensed, check to see that there is enough pressure to the material reservoir. Perhaps the

reservoir/material hose/needle path is clogged; examine and clear or replace as necessary. Consider

whether the material could have “set up” in the system. Refer to the Wet System Checkout and Periodic

Maintenance sections of this manual.

IRREGULAR VOLUME DISPENSED - Irregular dispensing can usually be attributed to faulty material.

The material must be a smooth (homogeneous) mixture, without any air trapped in it. A second cause

could possibly be that the material is not filling the material hose tube fully and in time. Check the

reservoir pressure -- it may be too low for the type of material being dispensed and/or the cycle time may

be set too fast. Cycle time is a function of the air supply controller. To adjust, follow the directions found in

the controller operating manual.

REDUCED VOLUMES DISPENSED Check to see if material hose requires replacement or whether

needle is partially clogged. (Refer to Periodic Maintenance Section).

TUBING LIFE VERY SHORT - Incorrect material hose (tube wall thickness too large).

VALVE DRIPS — Material hose needs replacing; wrong material hose used (wall thickness too small).

SLOW OR SLUGGISH CYCLE TIME - This may be due to inadequate lubrication of the piston walls.

Remove the pinch-off piston. Apply a very thin film of Krytox lubricant (part number 84/0200-K3/11) to the

outside diameter surfaces of the pistons and the U-seal and reassemble. This will restore smooth and

consistent operation.