K or L type copper tube for LOX and LN facilities.

[jor1492]

Hello all,

I am in a piping Project about a facility of LOX and LN storage in cryogenic tanks and I want to know what kind of copper tube could be the better in this stage of the plant.
the design pressure and temperatura are 250 psi and -200 C. What kind of copper tube ? K or L?

 

[BigInch]

Never seen copper there.

 

[Gator]

For air separation plants we'd use 304L outside of the cold boxes for cryogenic liquid and gas lines but never copper. BUT, for customer installations such as hospitals, industrial N2 for blanketing, etc, often copper was used mainly because brazing is easier and cheaper than welding (a plumbing contractor can do it).

 

[BigInch]

But copper only after vaporization, right?

 

[Gator]

Customer centers would handle their own installations since they were numerous and fairly routine. The simple piping layouts were templated (so I wasn't daily specifying materials) but yeah, Cu from the liquid storage tank to the (usually) ambient vaporizer as I recall and then on to the regulating valve station. After that it was up to the client, based on some basic material and routing recommendations. This was all low pressure stuff.

 

[BigInch]

Surprising that there was copper in potentially liquid containing line. I didn't know that copper would tolerate those temperatures. OK.
All our piping was either LTCS or SS.

 

[Gator]

Then again, maybe I'm going senile and misremembering. I seem to recall the competition touting the use of stainless steel at customer installs but don't know how that worked out in the long run. On the production side (air separation and liquefaction plants) piping was all insulated, ducted or VJ SS with mostly aluminum equipment with explosion-fused Al/SS joints inside the cold boxes.

"Most LIN lines use type K copper pipe here in the US as opposed to XS 304L which will be much more expensive."

http://www.eng-tips.com/viewthread.cfm?qid=81664

(Of course, in the image above, the box interior is filled with perlite under operating conditions)

 

[jor1492]

Thanks Gator and Biginch,

Yes, I am working in a customer facility mainly for gas cylinder filling and other gas and liquid applications. Here in Latin america the lines for this kind of facilities are copper tube for liquid lines (up to 250 psi) to cryogenics temperature and SS and brass tube for higth pressure gas lines (up to 3000 psi).

Another question, do you recomend threaded joints for the liquid lines or those kind of joins is not a good practice?

thanks in advance

 

[BigInch]

I wouldn't want to use threaded joints on lines with large temperature changes.