External Floating Roof Tank - Need for Circulation Vents

[Sriniva]

Dear Sirs,

As a rule we provide Circulation Vents in internal Floating Roof Tanks. Thus we could store liquids having Flash Point close to Storage Temperature without gas blanketing. Thread 1452-360717 discussed this aspect in detail.

My Query is:

Will API 650- Appendix H Circulation Vent considerations ( number, size , location) apply for External Floating roof Tank ?

What venting / blanketing considerations should be applied while storing Kerosene (Flash Point close to Storage Temperature) in External Floating Roof Tank?

Please reply

 

[LittleInch]

errr, You do actually realize the difference between an internal roof and an external roof do you?

External mean external - i.e. there is no other roof. It is therefore impossible to have vents in something which isn't there.

In general my understanding is that the effective limit on external roofs is that the vapour pressure of the fluid being stored (assuming sea level location) should not exceed 11 psia / 0.76 bara)

"Flash point" is not the issue here AFAIK

Vapour pressure of kerosene at normal storage temperatures is less than this limit, but depends on your mix.

Gasoline is commponly stored in EFR tanks and that's much more volatile, though volatility varies between seasons to partly allow for higher temperatures in the summer.

you can't vent or blanket an external Floating Roof tank.

https://en.wikipedia.org/wiki/External_floating_roof_tank

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Sriniva]

Dear Little Inch,

Thank you very much for the response and the ear bending.

Grateful for your consideration, time and expert advise.