Blend Valve; Compact Pumping Unit; Priming The Compact Pumping Unit - Wayne Vista Series Service

5.4.

BLEND VALVE

The blend valve is used in blending dispensers to mix two different grades of product in
order to produce intermediate grades which have an octane rating somewhere between
the first two. The blend valve is designed in such a way that as it restricts the flow of one
product it permits increased flow of the other.
In order to accomplish this the valve has two separate chambers. Each of these chambers
has its own inlet and outlet. The outlets come together at some point after the blend valve
and this point is where the mixing actually takes place. Each of the outlets is covered, in
some part, by a "shoe". These "shoes" are attached to a drive shaft in such a way that as
one port is being uncovered the other is being covered, thus adjusting the flow of each
product. (see Figure 5-9.)
5.5.

COMPACT PUMPING UNIT

The Wayne compact pumping unit is a rotary-type gear pump. These pumps are called
"self-priming" because they will remove all air and vapor from the suction line without
assistance from an outside source. Rotary pumps operate with extremely close clearances
between the rotating member and the pump casing. This feature enables them to be good
"self-primers" and ideal pumps for gasoline dispensing systems.
The bypass valve in the compact pumping unit should be set at one of two pressures. If
the pumping unit is driven by a 1/3 horsepower motor the pressure should be 21-22 psi.
If the motor is 3/4 horsepower the bypass pressure should be 28-30 psi. To adjust the
bypass pressure remove the acorn nut on the bypass assembly, then loosen the locking nut
on the adjusting screw. Tightening the adjusting screw will raise the pressure; loosening
the screw will lower the pressure.
Also part of the compact pumping unit is the air eliminator. This is a fairly large holding
chamber with an outlet at the top. This outlet is attached to the sump assembly. As
product is delivered to the air eliminator the vapor, in the form of foam, rises to the top
and passes through the outlet to the sump assembly.
5.5.1.

Priming the Compact Pumping Unit

It is not advisable to run any type of pumping unit dry during the priming
process, therefore, it is recommended that a small quantity (1/2 pint or 1/4
liter) of motor oil be inserted through the priming port of the pumping unit
before commencing operation.
If difficulty is encountered using the priming port, the pumping unit should be
primed by removing the pressure relief valve seal cap complete with adjusting
screw, the valve spring and the valve poppet (for more detailed information on
the service and troubleshooting of the compact pumping unit see The Wayne
Compact Pumping Unit—Service; part number 917466)
November 1992 Part No. 917543 Rev. A
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