Precision pressure control of Oxygen and Nitrogen gas
Precision pressure control of Oxygen and Nitrogen gas
(OP)
Hello
I am trying to bring a pressure of Nitrogen or Oxygen gas from around the 300Bar relative (4351.1Psi) to just over the atmospheric pressures. To do this the first thing that came to mind was to use a needle valve. However I am not sure if this is the best way to go?
I am trying to keep the weight and size to minimum. Therefore I am trying to avoid using any intermediary pressures reducers if possible. I don’t know of any valves which will operate over such a large range, if you know of any please let me know.
Also if anyone knows any other ways of doing this please let me know.
Thank you
I am trying to bring a pressure of Nitrogen or Oxygen gas from around the 300Bar relative (4351.1Psi) to just over the atmospheric pressures. To do this the first thing that came to mind was to use a needle valve. However I am not sure if this is the best way to go?
I am trying to keep the weight and size to minimum. Therefore I am trying to avoid using any intermediary pressures reducers if possible. I don’t know of any valves which will operate over such a large range, if you know of any please let me know.
Also if anyone knows any other ways of doing this please let me know.
Thank you





RE: Precision pressure control of Oxygen and Nitrogen gas
RE: Precision pressure control of Oxygen and Nitrogen gas
RE: Precision pressure control of Oxygen and Nitrogen gas
The only thing good to say about trying to do it with needle valves is your capital is lower, but you need constant vigilance to maintain a constant downstream pressure.
David
David Simpson, PE
MuleShoe Engineering
www.muleshoe-eng.com
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.
The harder I work, the luckier I seem
RE: Precision pressure control of Oxygen and Nitrogen gas
Splitting hairs: The drop will be critical thus independent of P2. You'll still get a decaying flowrate with a fixed position of a needle valve when the tank pressure decays, just because the P1 decreases.
The regulators that come on compressed gas bottles do just the task that is being requested. AND they are certified oil-free if rated for use on oxygen.
RE: Precision pressure control of Oxygen and Nitrogen gas
RE: Precision pressure control of Oxygen and Nitrogen gas
From the research I have conducted (google and local dive shop) it looks like I have to design some thing my self if I need to bring the size and weight down to what I need. If anyone know any good references in the area let me know.
Thank you
RE: Precision pressure control of Oxygen and Nitrogen gas
If you seriously intend to design your own regulator, you will need to buy a book or two.
But even before doing that, search for free literature on safe handling of oxygen. It may contain some surprises.
Mike Halloran
Pembroke Pines, FL, USA
RE: Precision pressure control of Oxygen and Nitrogen gas
BigInch
-born in the trenches.
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RE: Precision pressure control of Oxygen and Nitrogen gas
Flow across a nearly closed needle-valve seat is considerably more complex than simply opening a hole between a high-pressure source and a low pressure sink. With the length of the seat you get a definate pressure gradient over the distance. The pressure gradient will often (some would say usually) cause the flow to never see enough dP at any given point to put you in critical flow at that point. I've seen very small upstream pressure changes have a significant impact on the volume flow rate out a needle valve when it is throttled very close to shut.
David
RE: Precision pressure control of Oxygen and Nitrogen gas
ht
RE: Precision pressure control of Oxygen and Nitrogen gas
I must caution as I know of two fatalities associated with supposedly off standard mixtures of these gases. Even though the mixing of these gases is straightforward there are several input variables that can complicate the calculations. A gas mixture computer is almost a necessity.
RE: Precision pressure control of Oxygen and Nitrogen gas
Unclesyd; I am not trying to mix diving gases but my application is similar to diving applications, hence my trip down to the local dive shops. If there are any guidelines regarding oxygen or nitrogen handling please let me know, web links will be fantastic.
Thanks you all as your input has been invaluable, especially with the links and suggestion of suppliers.
Happy New Year!
RE: Precision pressure control of Oxygen and Nitrogen gas
http://www.cisatlantic.com/trimix/tools.htm
h
RE: Precision pressure control of Oxygen and Nitrogen gas
http://www.northshorecompressor.com/nitrox.html
RE: Precision pressure control of Oxygen and Nitrogen gas
Thank you.
RE: Precision pressure control of Oxygen and Nitrogen gas
Can you comeback with a little more information about what you are trying to accomplish.
http:/
RE: Precision pressure control of Oxygen and Nitrogen gas
For information you need to contact the following company.
http://www.envirodive.com/nitroxinfo.php
RE: Precision pressure control of Oxygen and Nitrogen gas
RE: Precision pressure control of Oxygen and Nitrogen gas
I am not quite sure if such a thing as pressure reducing valve exist? A restriction which has a large pressure drop across it (200-250 bar)? If anyone know of such a device please let me know. Otherwise does anyone know how to build one? I can think of a few ways to achieve this but I will be experimenting.
Thank you and regards
RE: Precision pressure control of Oxygen and Nitrogen gas
RE: Precision pressure control of Oxygen and Nitrogen gas
I am not specifically looking for a primary stage pressure regulator as such and am trying to avoid primary stage regulator as size and weight are important, however what I was thinking about was orifice which will have a large pressure drop across it. However I am not sure if this is possible as I have not seen an orifice used in such an application before. I hope this clarifies my intent.
RE: Precision pressure control of Oxygen and Nitrogen gas
More detail about your application will make it easier to provide better suggestions.
RE: Precision pressure control of Oxygen and Nitrogen gas
As highlighted in the posting above I am trying to regulate the pressure from a gas cylinder to a tube for human consumption. I need a regulating system to bring the pressure down from the cylinder to a level where it is appropriate for human consumption. However size and weight is a factor therefore trying to avoid a secondary regulator if possible.
I think the orifice is appropriate because the primary pressure drop does not need to be accurate as long as it is with in the range of the input of the secondary regulator. Therefore the variance can be large coming out of the orifice.
The secondary stage regulator will regulate the pressure to the set value.
Let me know if my thinking is correct?
RE: Precision pressure control of Oxygen and Nitrogen gas
Is it your intention to just let the gas flow continuously, or do you need a demand flow regulator, like on a scuba pack? An orifice would not serve as a pre- regulator, unless you are prepared to dump the gas that's not being inhaled, continuously. This is because if you stop the flow, the pressure drop across the orifice goes to zero.
The demand flow regulator is less wasteful of expensive compressed gas.
Scuba systems used to have single- stage regulators, with a large diaphragm and mechanism attached to the air bottle, and large low pressure hoses to route the air to the diver.
For decades they have mostly used two-stage regulators, with a small pre-regulator on the bottle, and a demand flow regulator of modest proportions at the diver's mouth. Total volume of this mechanism is a bit smaller than the older system, and it doesn't suffer the problem of the large hoses getting full of nasty tasting gunk.
Mike Halloran
Pembroke Pines, FL, USA
RE: Precision pressure control of Oxygen and Nitrogen gas
You asked:
You can buy air in high pressure bottles. But you seem to be proposing separate oxygen and nitrogen bottles. Is it your intention to feed the human some odd or variable N/O mixture? If so, you need at least two regulators and a mixer, and probably a computer.
No this not my intention at all. My intention is to feed constant stream of the gas at constant flow and pressure (to the user).
Is it your intention to just let the gas flow continuously, or do you need a demand flow regulator, like on a scuba pack?
No I my intention is for a continuous flow of gas
An orifice would not serve as a pre- regulator, unless you are prepared to dump the gas that's not being inhaled, continuously. This is because if you stop the flow, the pressure drop across the orifice goes to zero.
I agree. Intend for the gas to flow through the orifice first then the regulator
The demand flow regulator is less wasteful of expensive compressed gas.
agree but in my situation; this is acceptable
Scuba systems used to have single- stage regulators, with a large diaphragm and mechanism attached to the air bottle, and large low pressure hoses to route the air to the diver.
I will be most interested to learn about the mechanism which was used and how it worked. Do you have any references or can you explain how it worked?
For decades they have mostly used two-stage regulators, with a small pre-regulator on the bottle, and a demand flow regulator of modest proportions at the diver's mouth. Total volume of this mechanism is a bit smaller than the older system, and it doesn't suffer the problem of the large hoses getting full of nasty tasting gunk.
I will be interested to learn how design changes influenced resolution of these situation!
I am new in this field and the only experience I have is in design of valves and regulators is in the natural gas and water and at lower pressures. Therefore any info in this area is most welcome and I thank you in advance.
RE: Precision pressure control of Oxygen and Nitrogen gas
http:
http://entertainment.howstuffworks.com/scuba.htm
Mike Halloran
Pembroke Pines, FL, USA
RE: Precision pressure control of Oxygen and Nitrogen gas
Thanks for the links.
If you have more information it will be fantastic. Especially if you know of any hand books which detail the deferent regulator designs and norms with in the industry.
RE: Precision pressure control of Oxygen and Nitrogen gas
Mike Halloran
Pembroke Pines, FL, USA
RE: Precision pressure control of Oxygen and Nitrogen gas
1. For constant output pressure, you do need a pressure regulator. Any other type of valve would require external feedback or adjustment to control pressure.
2. For this high of a pressure drop, you need to heed manufacturers pressure ratings.
3. Since you are working from cylinder gas (a variable source as the pressure decays as contents are used) you must use multiple stages of regulation or balanced valve design regulators. Not too many options with a balanced valve at those inlet pressures though...
4. Two stage regulators are available where the inlet pressure effect will be almost insignificant.
5. Make sure your regulators are compatible with oxygen. Typical oxygen regulators are free of contaminants, unapproved lubricants and are also typically brass construction.
Hope these guidelines help.