Replace Rotor/Stator

[Chris]

I am looking at preventative maintenance of HPLC autosamplers and would like to try and keep the cost down. Is it tru that the rotor is normally made of softer material than the stator? As I would like to replace the rotor every year and the stator every two rather than replacing both at the same time.

Any comments?

[skunked_once]

This query "Replace Rotor/Stator" could just as well be posted on the "650 Garage USA" forum. I have a Yamaha 650 twin motorcycle and these bikes often need the rotor or stator for the charging system replaced. You really had me confused for a moment.

I'm not sure that I would recommend replacing these items that often considering the cost. Both the rotor and stator in your autosampler should last for more than a couple of years if you have clean samples. However, if your samples or mobile phase contain abrasive particles, or if you run thousands of samples per year, these parts may need replacement. You could monitor the number of injections until the injector starts leaking and use that as your maintenance guideline. This is only my opinion and is subject to correction by others with more specific experience.

[Chromatocrat]

Chris:


There's no thumb rule for replacing the rotor & stator. It's true rotor seals are made up of softer materials. There are diffrent materials used for different pH, reverse phase or normal pahse. If you are using extreme pH solvents chances of rotor seal damage are more frequent than using it for moderate pH. This can only be guessed by keeping a track of injections, large variations in area counts etc.

The indications to replace a rotor seal could be,
- crossport leak: can be diagnosed by perfoming the pressure/leak test.
- If you observe a drop of mobile phase coming out of the needle tip.

Stator face materials are hard materials, they don't require much attention, only proper cleaning is essential. They don't require replacement unless and until any physical damage such as crack or permanent blockages are observed.

Precisely you can schedule maintenance based on your observation on the behavior of the instrument.

regards,

[Jackus]

It is not necessary to replace rotor and stator frequently. The best monitoring of any leakage is to perform pressure test. Block the output of sampler and pressurize system with isopropanol (Agilent uses 400 bars but you must have metal blank nut - plastic is not useable for such pressures).
Wait for approx. 2 minutes to eliminate influence of heat and then observe pressure drop. I think that system with pressure drop approx. 2bars per min. can be pronounced as leakproof. Check both possitions (bypas and mainpass too).

We change rotor seals only after bad result of mentioned pressure test (approximatelly once per 1-2years). We never changed stator. It is not reason for changing when you dont use abrasive material.

(sorry for my english, I'm writing in hurry )

[DR]

Other potential symptoms of leaks - poor RSD, carryover.

We change them out on an "as needed" basis.

[Mark Tracy]

If your autosampler is reasonably new, it has a counter for injections. The manual will suggest a service interval based on the number of injections. When you are changing the rotor seal, carefully inspect the stator, and only replace it if it is damaged. You may wish to open the valve up and inspect it while it is still new so you know what it ought to look like (take a picture).

[John]

We change both the rotors and stators every 3 years. There is a suggestion that stators be changed every 6 years because they are hard ceramic. We change both at the same time while the injector is apart. This also makes scheduling easier when you are dealing with 40 instruments.
J

[rnelson]

We actually replace the rotor seal every 6 months since we are mainly a high-throughput QC lab. It's replaced whether or not it really needs it. We would rather be pro-active about PM rather than reactive.

As far as the stator, on those same LC's, we've hardly ever replaced any of them. Some are probably 7-8 years old.

Because the rotor seal is a softer material, most of your normal wear will be here rather than on the stator.