sizing the vent line for hydrogen gas prv

[humboldtgreg]

Hi,
First time poster here and I'm not sure how much information to provide.

I am designing a vent line (to atmosphere) for a small compressed hydrogen fueling station. One of the only codes that addresses hydrogen stations (International Fire Code, Section 2209 Hydrogen Motor Fuel-Dispensing and Generation Facilities) states that the vent piping shall be designed for the maximum back pressure within the pipe..
and the vent pipe flow rate shall be sized IAW CGA 1.3 for a non-engulfing fire ...in this case...only 3 cfm (the electrolyzer and compressor are small).

Is the maximum back pressure in the pipe, essentially the storage pressure (MAWP of 6667 psig) minus the pressure drop across the RV
or
can the back pressure be calculated using Leq, f, Re and other parameters?
(the vent line is 15 ft long) (If so, what method/equations are appropriate?)

I plan on using a 1" SS pipe (same as PRV outlet), but I'm not sure what schedule is required.

Thanks for your help

 

[BigInch]

See these,

vent header design

http://www.chemengsoftware.com/ventheader/ventheaderdesign.htm

formula page

http://www.chemengsoftware.com/ventheader/formulas.htm

http://virtualpipeline.spaces.msn.com

 

[sailoday28]

Binginch Referring to formula page

http://www.chemengsoftware.com/ventheader/formulas.htm

The formula for "definitive pipe sizing" for G has a typo and for isothermal flow is messy to work with.
The radical should contain a "difference P1^2-p2^2

why calculate r2 and P2 since for isothermal flow r2/p2= R/T2 and T is presumably known.

I have not checked out the constant in that equation.

 

[JohnBreen]

Hello,

In addition to that you might look at the NASA Glenn RC Safety Manual to address other issues. Specifically, look at Chapter 6 regarding Hydrogen:

http://www.nfpa.org/assets/files/PDF/CodesStandards/HCGNASAHydrogenCh06.pdf

And specifically 6.5.8. for STV issues. NASA has much experience in handling hydrogen and "lessons learned" have found their way to the Safety Manuals.

ASME is currently working on a new B31 Code for Pressure Piping, B31.12, Hydrogen Piping. Watch for the first issuance.

Regards, John.

 

[sailoday28]

why calculate r2 and P2 since for isothermal flow r2/p2= R/T2 and T is presumably known.
CORRECTION TO ABOVE
r2/p2= 1/(RT)