Circulating Vents Vs Gas Blanketing

[gofish123]

Hi

I am new to the forum. As per Appendix H, Sec H.5.2.2 , API 650, 11th Edition, internal floating roof tanks require gas blanketing if there are no peripheral circulation vents on shell and a vent in the fixed roof.

For a greenfield project, what are the pros and cons of the both the cases. One when vents are provided and hence no gas blanketing. Other when vents are not provided but gas blanketing provided.

Thanks

 

[Duwe6]

With vents, and a hydrocarbon in the tank, an occasional time with the headspace air / hydrocarbon vapor mix in the Explosive/Deflagration Burn range is unavoidable. I REALLY don't like vents.

Look at an Argon blanket for the space above the floater. N2 blankets require a continous 'whisper' purge, and use a lot of N2 in a years time. Just dump 2 or 3 bottles of argon from the welding supply store on top of the roof. It is about twice as heavy as air/oxygen, and will form a 'fixed' blanket between the floater and the air. IIRC, there is 125 ft^3 in a single cylinder of Ar.