Chromatography Forum

Hello everyone,

I'm researching into connecting multiple gas tanks (2 He, 2 N2, 2 H2, 2 Air) to our GC systems for the purpose of easily switching tanks without interrupting a running analysis. As I am less familiar with gas management than some of you are, I was wondering if I could pick your brain the subject.

There are some automatic swtichover regulators on the market, such as http://www.restek.com/catalog/view/1056sold by Restek, which will switch from a nearly depleted tank to a backup when the pressure drops below 170 psi. This sounds great, however, it is also about two thousand dollars. We are a small company so if a manual switchover system is more cost effective we would like to pursue that option.

My question to the community is, How would one properly install a manual gas switchover system which will not affect a running analysis? Avoiding pressure surges or drops, etc.

Using He as an example, I imagine that each tank would require a Two Stage Regulator and shut off valve, both flow lines would need to connect somewhere followed by another Two Stage Regulator? Does this sound like it is on the right track?

http://www.sigmaaldrich.com/content/dam ... 196898.pdf

This comprehensive article should answer your questions.

It doesn't need to be complicated - put a 2-stage regulator on each bottle with a 2-way valve on the downstream side to select which bottle feeds the line. When the active cylinder is nearly empty, switch to the other one. When you change a cylinder purge its regulator with backflow from the low pressure line.

Peter

Thank you dblux_ and Peter for your replies. The Supelco guide is very comprehensive and exactly what I was searching for. For our needs it pretty much recommends the set-up Peter suggested. You two have been a great help, thanks again!

LPC

If constant pressure is a must have on the system, then take the two regulators as Peter suggests and after the switching valve put another single stage regulator that operates at 10psi below what the two stage regulators are set to output. I have done this before with much success and it keeps the pressure on the system nice and steady.