Vollrath 219-02 - Manual (Page 21)

13
SECTION 4
MAINTENANCE INSTRUCTIONS
4.1 OVER-RUN ADJUSTMENT
The product when served is a combination of air and
mix. Over-run is a measure of the amount of air blended
into the mix.
Over-run can be expressed in terms of the amount of
weight loss for a given volume. For example, if a pint of
liquid mix weighs 18 ounces and a pint of frozen product
with air added weighs 12 ounces, the over-run is said to
be 50 percent (18oz. – 12oz.= 6oz., (6÷ 12) x 100=
50%).
The over-run can be checked by placing a one pint
container on an ice cream scale and zeroing out the
scale. Then fill a one pint container with frozen product.
The container should be filled over the top and leveled
with a straightedge. The product should not contain any
air pockets. When weighed on an ice cream scale, one
pint of product should weigh 12 to 13 ounces.
The mix pump has been preset at the factory to produce
a product with approximately 40 percent over-run.
Because of differences in mix formulation, temperatures,
and barometric pressure, this figure may vary. A product
with the proper amount of over-run is firm and dispenses
at a smooth even rate. A product in which the over-run
is too low, is yellow, heavy, icy, hard or stiff, and
dispenses at a slow or pulsating rate. A product which
has small air pockets and dispenses smoothly, but with
an occasional popping as the product leaves the spigot,
has the over-run set too high. It will be necessary for
approximately two gallons of mix to be pumped thru the
freezer before changes in the product are noticeable
due to adjustments in over-run.
Over-run is controlled by the relative position of the
piston stroke within the pump cylinder. Raising the
stroke within the cylinder will increase over-run.
Conversely, lowering the stroke will decrease over-run.
To adjust the mix pump for a higher over-run, refer to
Figure 14, and follow the adjustment procedures below:
CAUTION
THE MIX PUMP SWITCH MUST BE IN THE OFF
POSITION WHEN SERVICING OR CLEANING
PUMP.
A. Remove two knobs and safety guard covering drive
mechanism.
B. The position of the stroke is adjusted by loosening
the jam nut (B) above the drive clevis (C) and then
turning the drive clevis up for a higher over-run.
CAUTION
THE DRIVE MECHANISM MUST BE
POSITIONED AT THE TOP OF THE STROKE.
THE TOP OF THE STROKE IS WHEN THE CAM
ROLLER IS IN ITS HIGHEST POSITION. PUMP
DAMAGE WOULD RESULT IF PISTON WERE
TO CONTACT CYLINDER TOP BEFORE
REACHING TOP OF STROKE. A 180 DEGREE
TURN OF THE CLEVIS IS APPROXIMATELY
AN OVER-RUN OF 2-1/2%.
Figure 14. Over-Run Adjustment
GUIDE RODS
PISTON
CYLINDER TOP
DRIVE PIN
A
C
B
CAM ROLLER