[devil1711]

is the reid vapour pressure(RVP) and true vapour pressure is the same?

Why we need to fix the temperature (37.8C) when doin the experiment to measure the RVP?

Is it any converted from RVP to TVP?

PLs reply. thx.

[mbeychok]

devil1711:

No, Reid vapor pressure and true vapor pressure are not the same.  Reid Vapor Pressure (RVP) is a method of characterizing the vapor pressure of petroleum products. It is very widely used in the petroleum refining industry because it is a very simple and very quick test method. The test method is spelled out in ASTM method D323-06 which specifies that it be done at 100 deg F (37.8 deg C).

However, RVP differs somewhat from the True Vapor Pressure (TVP). You can find methods of converting RVP to TVP in the USA's Environmental Protection Agency (EPA) publication "AP-42, Compilation of Air Pollutant Emissions". Chapter 7, Section 1 of that publication deals with vapor emissions from storage tanks and is available online at:

www.epa.gov/ttn/chief/ap42/ch07/final/c07s01.pdf

Scroll down to pages 43 and 44 of that section and you will find a nomograph for converting RVP to TVP. You will also find equations for doing the conversion (obtained by linear regression of the nomograph).