Graco UniDrum C59784 Instructions And Parts List page 23

Preventing Pump Cavitation
NOTE: Cavitation occurs when the Pump cylinder did
not fully load with material on the upstroke, and a cavity
forms in the material after the Pump changes to the
downstroke. Perform step 20 when there is Pump
cavitation. If cavitation is not occurring, omit step 20
and proceed to step 21.
20. To prevent cavitation from occurring, perform the
following steps:
a. Lower the air motor air pressure until cavitation
stops.
b. Increase the ram down pressure.
Actuator
F . 7
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309169ZAF
Adjusting the Empty/Low Limit Switches
NOTE: When the low limit switch is activated, the
Pumps are normally turned off automatically by a
customer-supplied control, and a second set of Pumps
begin pumping.
21. Adjust the low limit switch as follows:
a. At the Pneumatic Logic Panel (G) (F
the RAM POSITION Switch (AJ) to LOWER,
allowing the Follower Plate to activate the low
limit switch.
b. Verify that the Follower Plate (D) lowers to the limit
set point: a level between 1 to 4 in. (25.4 to
101.6 mm) from the bottom of the drum.
c. Adjust the low limit switch to activate at the
level defined in step 21.b. See F
Limit switch
Operation
. 2), set
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. 7.
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