Chromatography Forum

My Agilent 2001-vintage G1946D/1100 system shuts down randomly during a sequence with a "S4 turn on requested with high foreline pressure" followed by a "difficulty with vacuum system gauges" and finally "S4 pressure below calibrated range". The MS module icon comes up "red" other modules' are all "green". The sequence stays in "run mode" (status icons blue) and hangs with the yellow "sequence stopping" messages when you manually intervene. I cannot get the system back to "ready" state through the Chemstation. After doing the reset procedure to get MS module communication back, it runs fine for awhile, then the error will return. I'm pumping at 0.2 ml/min using a narrow bore column, so it's not like I'm flooding the source. The foreline pressure reads about 2.8-2.9 torr on average, turbos are at 98-99% all the time. The Edwards pump has been rebuilt recently and this pressure is how it read when it came back, I've NEVER seen it run below 2 torr. Data looks really good when the system is "working", that is, before the error pops up. But I cannot reliably run a long sequence overnight! Any ideas on how to proceed? Is my foreline pressure on the "ragged edge"? Any help would be much appreciated.

No, your pump is fine. Your vacuum gauge, on the other hand, is flaky. I've have to replace several, and the foreline gauge gives me exactly that type of error. Unfortunately the G1946D is kind of like the 1999 Volvo I bought for my kids. One hell of a solid mechanical box with crappy, flaky sensors stuck all over it and it won't run without the stupid sensors.

The high vac gauge is even more fun!