Chromatography Forum

I have a 5890 series II with EPC. I struggled to get it working after long storage, and finally discovered some deposits in the split vent line that were blocking flow. After clearing them, everything worked fine for a week or so, but now I get no flow out the purge vent at all, with system pressure set to 30psi. I have verified flow all the way to the purge controller, and I have verified that the purge line from the controller to the purge outlet is clear, so it would seem that the purge controller is the culprit. However, it seems awfully strange that a purely mechanical controller would fail so quickly and completely.

The other symptom, is that the system pressure when set to zero does not reach zero. Instead it hovers about .6 or so.

Has anyone successfully disassembled/reassembled a purge controller?

Ok, fixed the problem, it was the purge controller. I swapped another one in and problem solved. As for the pressure sensor, there apparently is no zero calibration that I can find, so I swapped that sensor too, and now I get 0.1 psi when I turn the head pressure off. If I disconnect the pressure sensor from the purge controller, then the measured pressure goes to zero, so perhaps there is some other issue here.

The 5890 EPC uses and needle valve and solenoid that pulses to adjust the back pressure and flow, so it may be that the needle valve is not making a complete seal which is giving you a slight pressure when it is off. If you cap the column connection can you measure any small flow at the split vent or septum purge vent with the flow set to zero? If so you could have a very tiny leak at the needle valve on the EPC. Sounds like the other valve had become clogged, which can happen.

I remember our first instrument with the EPC and it went through several needle valves when we were injecting 2ul of MeCl extracts, it was just too much and would really dirty them up fast.