venting requirements for PVRV

[koshyeng]

I need to size a PVRV for an acetone tank( low pressure storage tank) in our facility which will have a weak roof to shell attachment. API 2000 doesn't show any equations for this case except inbreathing and outbreathing values.

My tank capacity will be 20,000 gal and since Acetone flash point is below 100 deg F, I came up with this numbers from API 2000.

Inbreathing = (5.6 + 500)SCFH of air. Liquid movement plus thermal effect.

Outbreathing = ( 12+ 500) SCFH of Air.

Emergency venting requirement is not required as it has weak roof to shell attachment.

Appreciate your comments on these values.

Thank You
Koshy

 

[zerosum]

I haven't looked at NFPA 30 for awhile but seems like it would be prudent to have an emergency relief function before blowing the roof off, say a venting manway.

 

[koshyeng]

Thank You Zerosum. I will consider your advice. NFPA code permits pressure relief by means of a "weak roof-to-shell seam".

If we want to consider PVRV for normal venting purpose, are those values good enough?

Thank You
Koshy

 

[zerosum]

I'll defer to a process engineer on the inbreathing/outbreathing. I don't have references needed.
I can tell you that all of our API 650 tanks here (perhaps ~15), have some provision for emergency venting in addition to the weak roof-to-compression-ring weld.

 

[lizking]

That's 5.6 & 12 SCFH per BPH of emptying or filling rate!

 

[koshyeng]

Thanks Lizking. Thats a big blunder.

Tank emptying rate in case of pipeline rupture or blast is 200GPM US Liquid(381 barrel US liquid per hour)and filling rate considering pump maximum output based on BHP and motor service factor is 152.4 barrel US liquid per hour.

Inbreathing = (5.6*381 + 500)SCFH of air. Liquid movement plus thermal effect.

Outbreathing = ( 12*152.4+ 500) SCFH of Air.

Are these calculations ok now? Appreciate your comments.

 

[lizking]

OK, except 200 GPM = 286 BPH.

 

[koshyeng]

Thank you Lizking. I considered Barrel US liquid instead of barrel US petroleum in unit cinversions.

Thank You
Koshy