Chromatography Forum

I have been assigned the task of resurrecting a HP 5890 Series II for use. The instrument has spent the last 7 years idle, and I need to find what does not work and fix it.

The GC is equipped with a 10-port rotary valve for sampling gas mixtures. I suspect that the valve is faulty somehow for a couple reasons:
1. Regardless of the valve position, both the carrier gas and sample gas pass through the valve extremely slowly when pressures as high as 60 psi are applied. It seems as though the gas should flow through the valve relatively unhindered.
2. Changing the position of the valve requires a very significant amount of torque, so much so that the actuator used to do so scrapes the aluminum plate to which it is attached.

I suspect that the valve is faulty, perhaps clogged with something that a) inhibits the flow of gas and b) hinders the easy turning of the valve.

That being said, I have two questions.
1. Does it seem like the valve is indeed flawed, or is difficult flow and difficult turning to be expected?
2. If indeed the valve is flawed, how might I try to clean/fix it or would it be best to simply replace it?

Many thanks for any assistance.

Sincerely,

Aleksandr Gamble

yes the valve may be damaged.

remove from the actuator and remove the rotor. Has the rotor material melted?

If the valve itself is not scratched a new rotor will make it as good as new.

If it has been scratched it can be rebuilt but that will require a new and non original rotor. (See Valco (VICI.com) for details.

best wishes,

Rod

Thank you for the advice.

I removed the rotor. It was slightly dirty and had a very small chip. The valve did not appear to be scratched, but it did have two rings where the metal had lost its luster from wear. After cleaning and reinserting the rotor, the valve worked much better, but still not perfectly. I will probably buy a new rotor.

In the meantime, I have a few more questions.
1. Should the rotor have a thin coating of lubricant, and if so what type?
2. Does the wear observed on the valve seem to be normal, or does it seem to be damaged?
3. Are there any other periodical maintenance things I should do to the valve? It has been sitting for several years without use.

Many thanks again.

- Aleksandr Gamble

You do not use lubricant on this valve rotor.

Perform leak checks and pressure maintenance checks to determine if the valve is reliable.

Look for air peaks when injecting samples to see other possible leaks not seen by static tests.

The wear sounds extensive but it depends upon how well it is sealing.

It might be ok.

Replace the rotor when needed. Avoid sending samples through the valve that contains particles larger than 2 micron. Filters are available from Valco.

best wishes,

Rod