How much pressure before O2 clean?

[sunkmail]

This may be a silly question, but I'm having trouble finding a difinitive answer ....

At what pressure do you need to worry about an O2 clean environment when using 100% Oxygen??

I've heard many people say to clean everything that touches O2, and I've seen others that say only the High Pressure side of things ...

What about the IP?
Or even less - Would anyone feel you would need O2 cleaning with 2 ata? (~30psi)

If anyone has any written reports/standards/studies on this, a link or copy would be appreciated.

[captain]

With 100 % oxygen it needs to be oxygen clean at any pressure

[fdog]

Any pressure.

Even if a cylinder is only filled to, say, 200 psi, when you open the valve that oxygen will flow into the reg until it hits a dead end.

There the momentum will cause a pressure spike of several thousand psi, with an accompanying temperature spike. If the reg is contaminated, this elevates the chance of an internal fire.

There are a lot of opposing thoughts regarding oxygen clean requirements, and indeed, the bulk of problems can be negated with good technique (valve opening order, speed of fill, slow valve operation, etc). I know folks that don't bother to oxygen clean at all, and very pure technique has kept them from having problems.

Personally, I assume I will have a brain-damaged moment once in a while, and oxygen clean for anything that touches 50% or higher, and clean annually.


All the best, James

[wedivebc]

Hey Scott,
There are 3 aspects to oxygen service, O2 clean meaning removing flammable material including hydrocarbons, O2 compatible meaning the material you use in your product is suitable for use with oxygen mainly is not inflammable, and finally O2 design which means it is designed in such a way to reduce ignition sources such as adiabatic compression such as found in 90' corners and dead-end pipes. Every product in use in the scuba industry for use with oxygen tries to comply with some aspects of this standard but I can assure you the scuba industry falls far short in all departments of true oxygen service.
Your product (pressure pot I assume) should try to meet these specs but it is very difficult to make a product for use with oxygen service which will allow the user to remove and replace an item for testing without oxygen cleaning the pot between each use. I doubt you will find any hard and fast rules that can practically be applied to your product. It is better to focus on design aspects and material selection to make it as safe as possible.

[sunkmail]

This is getting closer to what I'm looking for - thanks Dave.

It is in regards to my pressure pot that this question came up. I'm not looking to market it, so it isn't so much an issue for that, but more of an academic question to further my understanding of the chemistry involved. Frankly, Chemistry was never a super strong area for me.

This may have been the wrong area to put it in, but I couldn't think of a better one, except for something overly general, like 'Advanced Diving' or something similar.

Anyway, 200 psi, using the example above, is far greater than I am thinking - I'm working in the 30 - 40 psi area.

I know, in theory, everything should be O2 clean, but fact is, it isn't. I work in a Hospital, we have O2 all over the place. Sure, the regulators are O2 clean, when installed, but the pipes aren't. (We recently did some renos and teh guys were not wearing cotton gloves, or any for that matter, or anythign else you would imagine for a 'clean' assembly.

We attach all sorts of stuff to the lines, sometimes 'contaminated' by surrounding items - I'm sure oil and other no-no materials have made there way to the connections too, but this is all at extremly low pressure. (If you have ever been in a trauma bay, you will understand what I mean) And above teh low pressure, we use relativily low flow.

In a few areas the current line pressures for the O2, Medical Air, and Vacuum are displayed in nice bright digital display - I believe the O2 line was somewhere in the 40-50 psi range.

So with all that in mind, using pure O2, at low pressure, and low flow rates:


Where would YOU draw the line in the real world, in regards to O2 clean at VERY low pressures? (Generic YOU, not meaning Dave in particular)

Would you not walk into a room filled with 100% O2 if you had some oil on your jeans?

Assuming nothing crazy like constrictions making 90 degree bends all over the place, or sparks in the area, Is O2 at 2 ata really more dangerous than air at 10 ata? (as an example)

Hey Scott,
There are 3 aspects to oxygen service, O2 clean meaning removing flammable material including hydrocarbons, O2 compatible meaning the material you use in your product is suitable for use with oxygen mainly is not inflammable, and finally O2 design which means it is designed in such a way to reduce ignition sources such as adiabatic compression such as found in 90' corners and dead-end pipes. Every product in use in the scuba industry for use with oxygen tries to comply with some aspects of this standard but I can assure you the scuba industry falls far short in all departments of true oxygen service.
Your product (pressure pot I assume) should try to meet these specs but it is very difficult to make a product for use with oxygen service which will allow the user to remove and replace an item for testing without oxygen cleaning the pot between each use. I doubt you will find any hard and fast rules that can practically be applied to your product. It is better to focus on design aspects and material selection to make it as safe as possible.

[mike_s]

This may be a silly question, but I'm having trouble finding a difinitive answer ....

At what pressure do you need to worry about an O2 clean environment when using 100% Oxygen??

I've heard many people say to clean everything that touches O2, and I've seen others that say only the High Pressure side of things ...

What about the IP?
Or even less - Would anyone feel you would need O2 cleaning with 2 ata? (~30psi)

If anyone has any written reports/standards/studies on this, a link or copy would be appreciated.

why would you only fill a tank with 30psi pure o2?


Get a copy of Oxygen Hackers Companion by Vince Harlow. Airspeed Press. It will be money well spent for you.

see Vance Harlow's OXYGEN HACKER'S COMPANION From AIrspeed Press

[wedivebc]

why would you only fill a tank with 30psi pure o2?

Because he is building a pressure pot for testing O2 sensors to 3 ATA.

[fppf]

Just use air for testing sensors.
You need to go to higher pressures but no O2 and you always know the FO2.
The last NEDU report I read this is how they tested sensors.

[Thalassamania]

Any pressure. Even well below 1 ata. Keep in mind that space suits are pressurized to about 0.2 ata with pure oxygen and they're kept oxygen clean.

[wedivebc]

Just use air for testing sensors.
You need to go to higher pressures but no O2 and you always know the FO2.
The last NEDU report I read this is how they tested sensors.

Yes but then he would need much higher pressure capability to achieve the same PO2. Oxygen is readily available to RB divers and the design is much simpler using 1/5 the pressure.