Vapour locking and boiling
113. The main physical difference between kerosine and wide-cut fuels is their degree of volatility, the latter type of fuel having a higher volatility, thus increasing the problem of vapour locking and boiling. With kerosine-type fuels, the volatility is controlled by distil-lation and flash point, but with the wide-cut fuels it is controlled by distillation and the Reid Vapour Pressure (R.V.P.) test. In this test, the absolute pressure of the fuel is recorded by special apparatus with the fuel temperature at 37.8 deg. C. (100 deg. F.)
114. Kerosine has a low vapour pressure and will boil only at extremely high altitudes or high tempera-tures, whereas a wide-cut fuel wilt boil at a much lower altitude.
