API 650 TANK: DIFFERENCE BETWEEN VAPOR PRESSURE AND INTERNAL DESIGN PRESSURE
API 650 TANK: DIFFERENCE BETWEEN VAPOR PRESSURE AND INTERNAL DESIGN PRESSURE
(OP)
HI,
What is difference between vapor pressure and design pressure. As per my knowledge design pressure will still be zero, even if there is vapor pressure given on data sheet.
I am working on a utility water tank. vapor pressure of 0.09 bar(abs) is mentioned, but there is no information regarding design pressure. API 650 has addressed product vapour pressure and tank design pressure differently.
Kindly eleborate
thanks,
Inam
What is difference between vapor pressure and design pressure. As per my knowledge design pressure will still be zero, even if there is vapor pressure given on data sheet.
I am working on a utility water tank. vapor pressure of 0.09 bar(abs) is mentioned, but there is no information regarding design pressure. API 650 has addressed product vapour pressure and tank design pressure differently.
Kindly eleborate
thanks,
Inam





RE: API 650 TANK: DIFFERENCE BETWEEN VAPOR PRESSURE AND INTERNAL DESIGN PRESSURE
RE: API 650 TANK: DIFFERENCE BETWEEN VAPOR PRESSURE AND INTERNAL DESIGN PRESSURE
For product stored in API 650 tanks, vapor pressure is typically a partial vapor pressure. The total pressure is still atmospheric. If the vapor pressure is over atmospheric, the liquid is boiling and would not be in an API 650 tank.
Vapor pressure - Wikipedia
https://en.wikipedia.org/wiki/Vapor_pressure
What is vapor pressure? definition and meaning - BusinessDictionary ...
www.businessdictionary.com/definition/vapor-pressu...
ChemTeam: Vapor Pressure - Chemteam.info
www.chemteam.info/GasLaw/VaporPressure.html
RE: API 650 TANK: DIFFERENCE BETWEEN VAPOR PRESSURE AND INTERNAL DESIGN PRESSURE
The design pressure of API 650 tanks is often stated as "atmospheric". At sea level this equates to 1 bara.
Vapour pressure is an indication of volatility of a liquid and varies with temperature. If the the vapour pressure exceeds the gas pressure above the liquid then vapour bubbles appear in the liquid and the liquid "boils".
Hence for your situation, the design pressure is 1 bara, but vapour pressure is 0.09 bara. Therefore all is good.
Even if the liquid boiled, so long as the venting system was big enough, the pressure in the tank would still be very low. max design pressure in an API 650 tank is 2.5 psig, but this is quite rare.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: API 650 TANK: DIFFERENCE BETWEEN VAPOR PRESSURE AND INTERNAL DESIGN PRESSURE
yes i am aware of difference between static head and design pressure :)
RE: API 650 TANK: DIFFERENCE BETWEEN VAPOR PRESSURE AND INTERNAL DESIGN PRESSURE
You would though have a LOT of vapour to deal with.
As said VP is variable by temperature so it's always important to say VP @ X C.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: API 650 TANK: DIFFERENCE BETWEEN VAPOR PRESSURE AND INTERNAL DESIGN PRESSURE