5 replies to this topic

A contract requires a compressor casing lead test to be conducted using helium as the fas medium. The test pressure requirement is 4004 psig.

Helium can be supplied to the casing from an existing source to raise the casing pressure up to 1800 psig.
Bottles of helium must be purchased from an outside source to raise the casing pressure up to 4004 psig from 1800 psig. Given the following information, how many bottles of helium must be purchased to achieve the 4004 psig requirement?

Compressor Casing volume = 10.9 cubic feet

Helium bottle compacity - 500 standard cubic feet of helium at 6000 psig
(standard conditions - 60 def F, 14.7 psia)

Molecular weight of helium = 4.01
Ambient temperature = 70 deg. F.
Compressibility of helium - assume 1.0

144PQ=MRTZ

P -pressure, Psia
Q - volume, Ft3/min
M-mass, lbs/min
R- Gas Constant (1545/mol.wt
T- Temperature, R (absolute) deg F + 459.67 = deg R
Z - compressibility

Most are given in Standard conditions but we need acutal conditions so we need to calculate them first to plug them in.

[Art Montemayor]

You say you need help with the answer. What work have you done to get the answer (besides typing out the problem)? What, specifically, do you need help on?

What is "contract requires a compressor casing lead test to be conducted using helium as the fas medium" and what does it mean?

Are you saying that you have a fixed volume that you are filling with two sources of gas pressure?

Yes the volume is 10.9 cubic feet and I am filling with the exsisting source and also and outside sorece. I need to figure out how many bottles to buy.

[Art Montemayor]

Buy 4 cylinders of HP Helium.

Buy 4 cylinders of HP Helium.

Thank you for your reply. I would like to understand how you got it. I need more of the thinking process than the answer so I can understand. If you get a chance can you explain how you got it?

Thanks

[Art Montemayor]

I got the answer by using the gas law equation:

PV = ZN RT

N = Number of Mols
You know the rest of the symbology.

It took me about 7 minutes to do it; you can time it yourself when you work it (actually the answer was 3.2 cylinders).