11.8.4 Rebuilding the Pumping Unit
The compact pumping unit depends on very close tolerances between all of its internal parts in
order to work properly. If any of these tolerances become to large due to wear, product will be
allowed to pass from the pressure side of the pumping unit to the suction side inside the pumping
unit itself (for instance product may pass between the idler and the pump body). If this leakage
is allowed to take place the speed of delivery will be slowed.
1
In order to check/correct these tolerances perform the following procedure:
2
Drain the product from the pumping unit.
3
Remove the screws securing the pump head assembly to the pump body.
4
Remove the pump head assembly together with the idler and the o-ring seal.
5
Check that the clearance, between the outside diameter of the idler gear teeth and the inner
surface of the relief valve assembly body crescent, is not more than 0.127 mm (.005 in).
6
Replace the idler and/or the by-pass assembly as necessary.
7
Check that the idler internal bore is a close fit with its pin, and that the pin is not damaged in
any way.
8
Replace the idler and/or the pump head assembly as necessary.
9
Check that the clearance between the outer diameter of the rotor and the bore within which
it revolves, is not more than 0.127 mm (.005 in).
10
Replace the rotor and/or the pumping unit body as necessary.
11
Check that the idler does not have more than 0.04 mm (.0015 in) end play when the pumping
unit is assembled. Plastigage can be used for this purpose. In the absence of plastigage make
sure that the rotor shaft cannot be pulled in and out of the pumping unit housing an excessive
amount.
12
Replace the idler and/or rotor to correct any problem with end play.
13
Check that the rotor shaft is not loose in its bearing bushings.
14
Replace the faulty or badly worn parts, reassemble the pumping unit and test the dispenser
for proper operation.
11.8.5 Replacing the Lip Seal
If the lip seal is worn, product will leak out of the pumping unit around the rotor shaft possibly
causing the pumping unit to not prime easily or deliver slowly.
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11 Suction Pumps
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