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Vapor Lock Conditions Vapor Lock Causes

Page 36 MDE-4447A Global Pumping Unit Operation and Service Manual · May 2008

Vapor Lock Conditions

Using the same example as above, 8 inches of vacuum is still required to deliver the 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.

Figure 6-9: Vapor Pressure at 95º F

Using the same formulae in “Working Pressure” on page 32, the Working Pressure equals

Atmospheric Pressure less the Vapor Pressure. See Figure 6-10.

Figure 6-10: Working Pressure - Vapor Lock Conditions

14.7 PSI Atmospheric Pressure

- 12.0 PSI Vapor Pressure of the product

2.7 PSI Working Pressure

95º F

Vapor Pressure of Product

may be as high as 12 PSI

14.7 PSI

12.0 PSI

2.7 PSI

Atmospheric

Pressure

Less

Vapor Pressure

equals

Working Pressure

95º F

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Gasboy Gilbarco Global Pumping Unit Operation Manual Manual do Utilizador Página 40