# Calculate CFM on Hydrogen Vent Pipe

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1. Oct 30, 2015

I have a large hydrogen storage tank that vents when the pressure exceeds 150 PSI. I am trying to get a rough calculation of how much hydrogen we are losing. I know it is a 2 inch pipe and the pressure drops from 150 PSI to 120PSI. The venting lasts between 2 and 5 minutes. How do I calculate how much hydrogen I am losing?

2. Oct 30, 2015

### SteamKing

Staff Emeritus
1. How big is your storage tank?
2. What sort of ambient temperature is present when the tank vents?
3. How much 2-inch pipe is there from the tank to atmosphere? Are there any fittings (valves, filters, elbows, tees, etc.) in this vent line?
4. After the tank vents, how is the hydrogen replenished?
5. What is the set pressure point on the vent valve?
6. What's the pressure rating of the tank?

3. Oct 30, 2015

1. Tank holds 2 million cubic feet of hydrogen
2. Tank is outdoors so ambient can be any temperature in this area ( -10F to 100F )
3. 20 ft of pipe straight up with a 90 as it comes out of the tank and a vent valve.
4. Truck delivery
5. 150 PSI
6. Not sure of the pressure rating but approved for storage of liquid hydrogen.

4. Oct 30, 2015

### nasu

At what pressure are these 2 million cubic feet? Atmospheric?
And the tank can hold them at 150 PSI?

5. Oct 30, 2015

The hydrogen is stored as liquid similar to a liquid propane tank with vapor that builds on the top.
The vapor in the tank is allowed to reach 150 PSI before venting.
I am curious how many cubic feet we lose each time the tank vents.
2 inch vent line for 2-5 minutes.

6. Oct 30, 2015

### SteamKing

Staff Emeritus
I need some clarification on the tank capacity:

Is this 2 million ft3 of hydrogen measured at STP? Does the tank have an actual volume of 2 million ft3 or some other value?
If some other value, then please provide the actual interior volume of the tank.