Chromatography Forum

I have an Agilent binary pump (made around 2001) which gives a pressure reading of 13 bar with no flow and the drain valve open. As recommended by Agilent, I cleaned out the drain valve with hot water and replaced the purge inlet frit-but the pressure still reads 13 bar even with the purge valve removed.

Agilent say it could be the pulse damper (about $4000 to replace) or the main board in the pump ($2000).

Does anyone have experience of this problem? The pump works perfectly with the fault, although is displaying a higher pressure than it should.

But does this fault indicate an imminent breakdown of the pump? I don't have the money for these repairs, so I will have to make plans to cope with this system becoming inoperable.

With no flow, a constant reading of 13 bar can only be an electronic problem with the pressure transducer or the board. It might be something as simple as a dirty/corroded/marginal electrical connection, in which case the old trick up unplugging everything and reconnecting may solve the problem.

If it's a bad transducer and the transducer is built in to the pulse dampener, then the whole assembly may, in fact, have to be replaced. Ditto for an electronic problem.

Unfortunately, I don't know enough to tell you whether the pump will fail totally tomorrow or continue to limp along for years.

Don't worry, your pump is fine. This is normal fatigue of the transducer (strain gauge) over time and many Agilent 1100/1200-Series pumps show a 'high' reading with zero flow and no backpressure on the system (esp after several years of use). It is annoying, but I am not aware of any method to re-calibrate or adjust it besides replacement of the transducer. *The older HP 1050-series pump had a re-zero feature built-in to the system which could be accessed directly from the front panel. The 1100/1200-series did away with this useful feature.

Thank you very much for these helpful answers. I know there was a problem with rapid failure of the pulse dampener on some 1100 pumps of around this period.... but if it goes wrong, then 8 years of use is hardly a rapid failure.

I have a feeling that on newer designs of the pump that the pressure sensor is not an integral part of the pusle dampener, so if it goes wrong the repair is not so extensive?

If you have an independent (calibrated) gauge, you can measure the pressure signal of the pressure transducer versus the gauge. If it is a constant off-set, you just subtract this value from all your future pressure measurements.

The pressure sensor is separate in the 1200SL (RRLC) and the 1290.