Chromatography Forum

A 7890 GC (dual FID) is being relocated, and new gas lines will be installed. Currently air, nitrogen, and helium gas lines are 1/4" copper from the cylinder to the lab. Hydrogen is 1/4" stainless from the cylinder. Is there a reason for the stainless? As I recall from previous employers copper was used for all the gases without issue. There is a significant cost difference betwen materials. Any thoughts?

In one of the facilities I work with, copper for everything but the hydrogen. For my lab, copper for everything but the hydrogen (and plastic for the air.) (Part of the reason for that is to demonstrate that my helium ionization detector can run with copper lines and un-purged plumbing but that's a story for another day.) Could save a chunk of change by going 1/8" instead of quarter if you are only running a few GC's.

For what it's worth.

Best regards,

AICMM

Is there a reason not to use copper for hydrogen lines? Copper 1/8" tubing was used for hydrogen gas in both places I have worked. Am I missing something or am I in danger

skunked_once,

The Analytical Chemist at our company install hundreds of new GC's a year. Most of them are here this week so I walked downstairs and asked them their opinion. They said if you are going to use copper make sure it is new and clean. Hydrogen has a stripping effect, so if you use a copper line that was once used for helium carrier the hydrogen will strip the deposits left over time by the helium onto the FID. The same principle applies to filters, never use a used filter on a hydrogen line.

What was also mentioned is that Agilent does recommend using stainless steel lines on hydrogen carrier. They were not sure exactly why?

Jed Sullenger

I've used copper for more than 20 years without a problem.

We have copper for some or most or our hydrogen lines and haven't had a problem.
Agilent may be recommending the use of stainless steel because hydrogen may cause brittleness in copper. The potential consequences of failure may make their legal department nervous and it's not their money paying for the tubing..

We have copper for some or most or our hydrogen lines and haven't had a problem.
Agilent may be recommending the use of stainless steel because hydrogen may cause brittleness in copper. The potential consequences of failure may make their legal department nervous and it's not their money paying for the tubing..

I believe this is the best response. Stainless steel tubing is less likely to get bent, and eventually break, so liability reason more than "chemical".

Copper can age and turn brittle over time. Also I've heard Hydrogen can accelerate that. I use copper for everything except hydrogen as well where I use 1/8" stainless steel.

Reason is
1. After a few years, cooper tubing will become harder by oxidation. It will be easy to broken. Tubing will be leak, as you know, very dangerous
2. SS tubing, very stable up to many years!
3. Chemical matter do not exists here, just stable material only. I always install GC for my customer by copper tubing 1/8 inch without problem.

I am just reading this as they are putting in stainless steel tubing for our hydrogen GC supply - of course, it is not cleaned or inert, nor are the regulators. That said, while you are concerned about hydrogen and brittling in copper, may I throw in pit corrosion of hydrogen in steel? Has someone done the risk comparison?