Physics

not at 2000 psi!

Picky, picky

(P + an²/V²)(V-nb) = nRT

OK, NOW I'll give you a GA!

The original post was such a basic question and your answer such an obvious place to start for most of us here - basic answers for basic questions (as if you were saying "Well duh!") but being nice about it.

Mike

You made a good point, though. I was being overly terse because I smell a homework question. It does highlight a serious problem, though. The OP might be actually filling a pipeline with gas from high pressure cylinders without knowing about such things. If so, that scares the hell out of me - nitrogen is one of the more dangerous gases around since it doesn't trigger the breathing reflex. I hope the OP gets some mentoring.

Now that you mention it, it scares me too. If you have to ask such a basic question, you are likely not to have the experience required to know all the things to watch out for.

It's been a while since I was a chemical plant engineer - we used N2 to purge & blanket. There are volumes (sorry!) of things to be covered in N2 safety.

A non-airtight centrifuge (filtering a polymer from heptane) with insufficient N2 flow caused an explosion just as one of the operators was looking through the sight glass. Luckily, he lost the use of only one eye. The confined-space/asphyxiation issue is really scary too.

Mike

We used to use a lot of liquid helium in a fairly small room. We never worried much since you always knew when the helium was geeting bad - somebody would start talking like Donald Duck and we'd vent the room. One day an engineer from NASA Langley happened to be there and hit the roof. They had lost two guys not long before to nitrogen and he insisted we get a nitrogen monitor/alarm. We did and occasionally it went off.

I can see why he went through the roof. It seems to me that the amount of He required to talk like Donald Duck (although I don't know what that is), would put the O2 level considerably below 18%, the lower limit for supporting (human) life!

"he insisted we get a nitrogen monitor/alarm."

Did you mean oxygen monitor?

No, NASA, at least at that time, thought nitrogen level more of a problem than the oxygen level. If you go to low oxygen by way of CO₂, that's bad but you gasp and breathe faster. With N₂ you just go peacefully off to sleep.

I'm not sure about O₂ levels for life. The big criterion, I think, is the SaO₂ in your blood. That should normally be about 93-95%. Randall McCloy, the survivor of the Sago (WV) Mine explosion about three years ago had an SaO₂ level near 60% and required a lot of rehab to recover. Anyway, you can get low values from either bad air or from not breathing.

I'm some years out of gas safety, so I would today bow to your call and put in an O₂ monitor. Of course, today, I'd probably ventilate the area properly - it was stupid of us not to.

OK Thanks for Your Friendly Advise pal!

You are saying to much but not trying help to solve things or to figure out the solutions. Anyway thanks for the words.

Hi paulpangan,

I know I get sidetracked with what people are saying, many times focusing on what is not said. Many claim that I am just too intense and need to "lighten up". My apologies if you thought I was not being helpful - I could give you the answer and would be more than happy to do the exercise. However, would it help you in the long run? The next time a similar problem presented itself, would you be asking for help again, or be trying to figure it out on your own? Learning is admirable and learning requires effort.

Mike

Hmm since the basics in discussion I would have said P₁V₁T₂/P₂T₁=V₂

Sorry guys, but nitrogen will be a gas at 2000 psi. The critical temperature is 126 K, so it is a gas at any pressure above this temperature.

So P1V1/T1 =P2V2/T2 is the correct equation to use. No need to mess with weights or moles.

Tad

I know it will be a gas.

What I meant was, he cannot use the IDEAL gas law at that pressure, since that will make N₂ substantially non-ideal.

GA, but you need to lighten up a bit .

Mike

You must not be an old engineer yet. We all know you'll use up 5 cylinders (plus a little extra cause you forgot to tighten the regulator properly); we're just arguing about nit-picking details cause it's what engineers do to be happy. If you want to start a 1000 post thread, ask us which way to turn an adjustable wrench.

What's 15% between friends?

Is that how much it is? I thought 6%.

I failed to find the constants. However, tables (possibly not reliable) suggest 1.7% error for room-temperature nitrogen (between 1 atmosphere and 2000 psi). Oxygen would be about 6.2%.

[I was just being lazy - the density of liquid nitrogen suggests an inflated upper bound on the error of 20%.]

So your Nitrogen bottle holds ? litres of nitrogen @ 30 psi. ... 2000/30 x 50 = ? litres

Your pipes volume in litres is ? ( 3.14 x inside radius of pipe x inside radius of pipe ) x length of pipe .... all in the correct units = ? litres

I'm sure that you can now divide the two results to get the answer.

Nearly, but 30 psi (and 2000 psi) almost certainly means psig (if I'm wrong OP pls come back), so it should be..... So your Nitrogen bottle holds ? litres of nitrogen @ 30 psig = 45 psia ... 2015/45 x 50 = ? litres

Cheers......Codey

Apologies to you paulpangan

TVP45 is correct your cylinder / bottle will contain liquid nitrogen NOT just gas as I erroneously suggested!
You'll need to follow his good advice and find the weight of liquid contained in the cylinder and from this calculate the gas volume.

Regards A.Wood

Thanks very much pal....

You just gave me the best answer, although some people out there think its an easy or just a simple but this happened in a real job. I really appreciate of such a great help. God bless you and CR4.

Your welcome.

You might find this site useful .

http://encyclopedia.airliquide.com/encyclopedia.asp?LanguageID=11&CountryID=19&Formula=&GasID=5&UNNumber=&EquivGasID=26&PressionBox=&VolLiquideBox=&MasseLiquideBox=&VolGasBox=&MasseGasBox=&btnMSDS=0&MSDSLanguageBox=11&RD20=29&RD9=8&RD6=64&RD4=2&RD3=22&RD8=27&RD2=20&RD18=41&RD7=18&RD13=71&RD16=35&RD12=31&RD19=34&RD24=62&RD25=77&RD26=78&RD28=81&RD29=82

Before I go, for those who might want to calculate the various gas laws, here's a handy calculator. It works in a sort of RPN fashion, but it gives good comparisons.

http://antoine.frostburg.edu/chem/senese/javascript/realgas.shtml

6 should be enough

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