3 replies to this topic

[Mohamed94]

Hi peeps,
I want to ask some questions about chemical storage:
1) In the MSDS, it mentions the vapor pressure at 20 degree C. Is it the RVP or TVP ?

2) should I determine the TVP at the storage temperature or which temperature?

3) how to determine if the chemical should be stored in fixed or floating roof ?

4) how to determine the material selection of the tank ?

I have done some research and found that TVP less than 1.5 psia (Fixed Roof), TVP 1.5 to 11.5 psia ( Floating Roof), and TVP above 11.5 psia (Pressurized Tank). As you can see the API does not specify TVP at which temperature.

[Pilesar]

Some answers:

1) Vapor pressure at 20 C is not the RVP or TVP.

2) TVP is measured according to ASTM D2879 (at 37.8 C)

3) In general, tank design should be selected according to suitability and economics.

4) Tank materials should be selected according to suitability and economics.

Edited by Pilesar, 24 October 2019 - 07:27 PM.

[Mohamed94]

Thank you Pilesar. I found website that provide the vapor pressure of chemicals at different temperature. If I interpolated to get the vapor pressure at 37.8 C, would it be the same as the TVP ?

[Pilesar]

For RVP between zero and 5 psi, the TVP and RVP should be very close to your interpolated vapor pressure results (within about 1 psi.) Real measurements are more accurate than literature data for any particular fluid. The lightest 5% in the composition greatly affect the vapor pressure.The RVP and TVP are lab results found after following explicit directions. TVP is a more complicated and expensive test, so the easier RVP is frequently used instead. I would assume vapor pressure at 37.8 C in literature would match the TVP in literature.