Gasboy Gilbarco Global Pumping Unit Operation Manual - Manual (Page 37)

MDE-4447A Global Pumping Unit Operation and Service Manual · May 2008 Page 33
Vapor Lock Causes Reasons for Vapor Lock
Measuring Suction
To measure a pump’s suction, the Working Pressure must be converted to inches of vacuum.
To do this, multiply the Working Pressure by 2. The result is the number of inches of vacuum
that a pump can create before the product changes to a vapor. See
Figure 6-4 .
Figure 6-4: Converting Working Pressure to Inches of Vacuum
4.7 PSI Working Pressure = 9.4 inches of vacuum. See Figure 6-5 .
Figure 6-5: PSI and Vacuum Equivalents
14.7 PSI of Atmospheric
Pressure pushes down
on the bowl of mercury
and causes it to rise to 30
inches.
Atmospheric
Pressure (14.7 PSI)
equals 30 inches of
mercury
4.7 PSI = 9.4 inches of Vacuum
PSI Vacuum