HPLC Products

The injection valve is almost never made by the autosampler manufacturer, but sourced from a valve specialist such as Rheodyne or Valco. The valve manufacturer supplies the valve, its actuator (the motor which turns it), a control box, and a cable between the control box and the actuator.

So if there is a problem and the valve won’t turn, assuming the autosampler is sending the control box the signal, the problem must lie with one of these components, and generally it is not a user-serviceable problem. However it is worth removing the valve from the actuator and trying again. If the actuator turns, the problem lies with the valve, which is usually quite easy to remove and replace without paying £150 an hour for a service engineer to queue round the M25!

What causes a valve to jam? Either leaving it unused for ages so it dries out, or not flushing it out regularly. If a sample dries to leave a sticky material, then this can easily dry in a valve overnight and cause it to stick. It tends to build up, until the motor just can’t make it turn.

The danger is that by then the motor itself can burn out, or pull so much current that the cable fails. If it all goes, it will be expensive (possibly £2K or more) to fix. The secret is to keep the valve flushed out, not to use buffer in the wash solution, and to be very careful when using an autosampler for the first time after a prolonged period of disuse. If in doubt, please call us on the number below for free advice.

A common service repair is to replace the rotor seal. This is a relatively straightforward procedure, and you may like to see our guide to replacing a worn rotor seal in the Rheodyne Valve Rebuild notes. This should be replace in an annual maintenance service, but may need replacing if the valve begins to leak from mid way along the valve.

If you need to repalce a valve, it is not usually that complicated, and usually obvious how it is fitted to the autosampler chassis. Be careful with the tubing connections though. Some autosamplers us a 12 port valve, and it can be a bit hairy trying to remember what goes where. If in doubt, check the port numbers (very small etched numbers) and label the tubes. If you have a phone with a digital camera, you may find the photo invaluable when reconnecting the tubing.

If you have a six port Rheodyne valve, the port connections are usually:

1 and 4 Loop

2 Pump

3 Column

5 Inject

6 Waste

But please check. It isn't always like this.