Bennett 111103, Operation, Service & Parts Manual

Page: 25 / 36

Bennett T140 Operation, Service, & Parts Manual Troubleshooting
20
B. It takes 1 inch of vacuum by the pump to overcome the restriction of
an angle check or foot valve. (Not part of the pump, but a necessary
part of the installation.) See Figure 24.
C. It takes 1 inch of vacuum by the pump to overcome the restriction of
60 feet of horizontal piping from the tank to the pump. See Figure 25.
To obtain the inches of vacuum to deliver product , simply add A, B and C.
6” of Suction - (A = 9 Feet of Lift)
1” of Suction - (B = Angle Check or Foot Valve)
+ 1” of Suction - (C = 60 Feet Horizontal Run)
TOTAL 8” of Suction
With 9.4” of suction to work with and only 8” of vacuum required, conditions
are normal and the pump delivers product without vapor locking.
Remember this condition exits when the product is at 60°F.
Using the same example as before, 8” of vacuum is still required to deliver
product.

With higher ambient temperatures , the vapor pressure of the product
changes. As mentioned above, the Vapor Pressure of today’s product is 10
PSI at 60°F. At temperatures of 90°F or higher, it can go as high as 12 PSI.
See figure 26.
60 feet of horizontal piping = 1” of vacuum.
60°
F
Figure 24
Figure 25
95°F
Vapor pressure of product may be
as high as 12 PSI.
Figure 26
1” of vacuum to overcome the restriction of angle
check valve or foot valve
Foot Valve
60°F
Angle Check Valve