Chromatography Forum

My lab is currently using helium as a carrier gas. The tanks are all in the basement and it is piped to 6 instruments (total) in 2 different rooms. We have recently begun losing gas pressure at about twice the normal rate and of course suspect a large leak. I have gone around testing every joint and fitting I can find with a handheld restek leak detector and plugged 2 seemingly small leaks however the problem is persisting. Does anyone have any advice on the best way to pinpoint the problem?

Thanks for your help,
Jon

Has anyone changed anything or done any maintenance that coincides with the higher gas consumption ? - that would be a good place to focus.

The leak is more likely to be at a place were connections and disconnections take place than in the piping runs. This is usually at the cylinder regulators and of course in the GCs. If you can isolate one GC at a time (you do have shut off valves at the back of each one ?) then close them all, shit the cylinder valve, the pressure shoul dstya up, if not you have a leak at the cylinder regulator or in the pipes. If the pressure stays up, connect the GCs one at a time and repeat. A systematic, step by step is the sure way to success.

Peter

If I were to connect a flowmeter right after the tanks and shut all of the gas valves to the gc's then the reading should drop to zero correct?

Which kind of injector do you have? I´ve had this kind of problem with CTC COMB-PAL systems, with the flush pipelines.
And, no, the flowmeter is not going to zero, once the pressure is being released through it.
As already said, better is try to trace back what has changed when the problem started.

Good luck!!

If I were to connect a flowmeter right after the tanks and shut all of the gas valves to the gc's then the reading should drop to zero correct?

Correct. but you have to make and break two connections and then couple the lines again, which is exactly the kind og thing that causes leaks !. Rather do the pressure test.

Peter

The description of cylinders in a basement and possible He leaks !!!!
When checking I'd also make sure you have adequate ventiliation and consider carrying and O2 monitor when entering the basement.