Gasboy Gilbarco Global Pumping Unit Operation Manual - Manual (Page 38)

Reasons for Vapor Lock Vapor Lock Causes
Page 34 MDE-4447A Global Pumping Unit Operation and Service Manual · May 2008
Installation is the Key
The condition of installation dictates how much suction a pump must create to pump the
product.
It takes 1 inch of vacuum to lift gas 1.5 feet vertically.
To determine the inches of vacuum required to lift the gas in a system, proceed as follows:
1 Measure the distance from the top of the product in the tank to the center of the pumping unit.
See
Figure 6-6 . Divide the distance by 1.5 to obtain the inches of vacuum required by the
pump to lift the product.
For example: 9 feet of lift requires 6 inches of vacuum by the pump. See Figure 6-6 .
Figure 6-6: Amount of Vacuum Required for Pump Suction
It takes 1 inch of vacuum by the pump to overcome the restriction of an angle check valve or
foot valve (not part of the pump, but a necessary part of the installation). See
Figure 6-7 .
Figure 6-7: Compensating for Angle Check or Foot Valve
60º F
Lift
Amount of
Vacuum
Required
Angle Check Valve
Foot Valve
1 inch of vacuum to overcome the restriction
of an angle check valve or foot valve