O2 Pipeline Velocity 4

[NGbri]

Hi guys,

I'm working on sizing an O2 pipe of about 300m. I was looking through the CGA standards and it suggests a limit of 30m/s for the pipe velocity due to impingement, but then later states that impingement is not an issue with high purity oxygen, or with long radius elbows, both of which apply to us. I still feel like I should be using this 30 m/s limit as my maximum for safetys sake, but any advice would be greatly appreciated.

Regards,
Brian, E.I.T

 

[BigInch]

Safety from what?

Going the Big Inch!

http://virtualpipeline.spaces.msn.com

 

[JLSeagull]

Read EIGA Doc 13 (CGA G4.4) carefully. Is this a long distance pipeline with no valves, flow elements, etc.? What pressure? If the installation includes valves, flow meters etc. it is more complex. 5.2.1 addresses impingement sites.

You might also check other standards such as NFPA Fire Protection Handbook Chapter 9, ASTM G88 and other G series standards.

 

[NGbri]

Safety from particle impact ignition primarily.

Thanks JL, I'll take a look over those. Its about a 1000ft pipe, low pressure (1 barg) with a couple of check and isolation valves, which would be potential impingement sites, so I think I am doing this right in keeping the velocity below 30m/s.

 

[25362]

The impingement refers, for example, to (carbon steel) rust particles picked up in the gas flow, or to the heat developed by a sudden closure of valves.

From an article by "Air Products" one can learn that reduced gas velocities are safer in the sense that lower impact energies reduce the chances of an ignition of elastomers in valves and regulator seats, or of some hydrocarbon remnants left over after air blowing the "new" already degreased pipe with not-so-pure shop air rather than with clean, dry nitrogen.

 

[BigInch]

Sorry, don't know about O2 lines. That's why I asked. I take it that the rust particles are going to ignite on impact and then set the rest of the inflamables going? I'd like to see the AP article. Know where I can get it?

Going the Big Inch!

http://virtualpipeline.spaces.msn.com

 

[NozzleTwister]

Back in the late '70s, I worked on project where we imported O2 vapor from an air separation plant, pure O2 to my knowledge. Our O2 transfer line had similar flow velocity limitations for the same reason. We had a high preformace butterfly valve as a block and it was alumninum bronze.

My understanding was that the impingement was not just impact, but also, slag or scale skidding done the inside wall of the pipe.

I think it's best to play it safe.

NozzleTwister
Houston, Texas

 

[BigInch]

O2 pressure with grease and oil, yes I believe. Impact, ya OK, but I'm not sure I'm buying the sliding and skidding bit. Seems like the O2 flow would cool it during the slidding process too... but I have no problems with being safe until we sort this thing out.

How hot do we have to get a bit of iron in a pure O2 atmos to ignite?

Going the Big Inch!

http://virtualpipeline.spaces.msn.com

 

[katmar]

Maximum velocity is an important consideration, but seeing that you are working at only 1 barg the pressure drop will be very important too. The relationship between maximum velocity and pressure drop varies with the pipe size. For example, if you try to use 30 m/s in a 2" pipe your supply pressure will not be enough to get the O₂ to flow at this rate. However, in a 10" pipe you could use 30 m/s and still get it to flow with 1 barg supply pressure.

It all depends on the capacity you require.

Katmar Software
Engineering & Risk Analysis Software

http://katmarsoftware.com

 

[insult2injury]

Chapter 5 deals with oxygen system design. It contains a small portion about velocity, but the whole document probably is worth a read if you are designing an oxygen system.

http://smad-ext.grc.nasa.gov/gso/manual/chapter_index.shtml

I2I

 

[insult2injury]

Another link about oxygen system design. Figures 1 and 2 on page 12 and 13 show velocity vs. pressure curves for impingement and non-impingement zones.

http://www.ecss.nl/forums/ecss/disp...d20060309173341/No/oxygen pipeline system.pdf

I2I

 

[25362]

BigInch, the Air Products' article appears on Google asking for Safetygram #33.

 

[NGbri]

Thanks guys. Some useful info. Basically at 30m/s this is going to be a 60" pipe. So its big stuff. However, we will have a long straight run on it, and it may be possible to increase the velocity in the line to 60m/s for non-impingment zones and decrease our pipe diameter to something like 42" (we'd have to increase our discharge pressure of course).

Brian, Mechanical E.I.T

 

[BigInch]

25362 I got the AP article, you got the *. Thx

Going the Big Inch!

http://virtualpipeline.spaces.msn.com