Help! Gas sampling valve clogged

[Jonathanz]

My Varian 450 GC's gas sampling loop is clogged with solids. Does anybody know how to clean the loop? We tried backflushing the loop with 40psi helium and observed some solids came out. Many thanks in advance.

JonathanZ

[Peter Apps]

If you have solids inside the valve you have probably scratched the rotor and its seals, so you will have to strip the valve anyway. To get solids out of a tube the best way is to put some pressue on it with a liquid and immerse it in an ultrasonic bath.

Peter

[larkl]

I guess you don't have a spare loop? They're not expensive and nice to have around. If you know what the solids might be, you could pick out a suitable solvent. We do quite a bit of ultrasonic in (don't laugh) Formula 409, followed by water and metanol or acetone rinse.

[Bricevan]

As Peter said, you likely have damage to the valve rotor and possibly the valve head as well.

Open up the valve and check the rotor for damage, it will have to be replaced if there is any.

Use a flashlight to inspect the inside of the valve head where the rotor was. Sometimes particulates that have not damaged the surface, looks like damage. Use a bit of solvent on a cotton swab to gently clean the inside of the valve head if you see anything. It should be bright and shiny with no scoring between ports. If there is any damage to the metal surface the valve head will need to be replaced.

[Ron]

I would never consider cleaning and reusing a sample loop that had been completely clogged by solid material. There is too much danger of residual material damaging the rotor and seals. I would suggest replacing the loop, then putting a frit in front of the valve to catch any solid material. You might want to consider taking the loop off once a month or so and flushing it out with solvent.

[tigerk2001]

I would suggest to install 10u particle filter at the sample inlet of the instrument.
Now, re-build your rotary valve and change the sampling loop. No chance to take in such case.
I'm normally using AFP(Analytical flow products) for rotary valve or diaphragm valve. Let me know if you need some more details about this great new products.