-
- Posts: 45
- Joined: Mon Jun 13, 2011 6:36 pm
I finally got the seal adjustment to work out and tested the valves with pressures of 4000 +. The valve tests, as outlined by the Waters 717 Plus manual, passed. Valve test page 157 http://www.meadowshplc.com/pdfs/717plus.pdf
However, for test number four where the needle is in the seal, and valves 2 and 3 are open while 1 is closed (1-injection, 2-syringe, 3-waste) and pressure is ramped to 4500 psi, I noticed that while the pump pressure/system pressure didn't degrade, the pressure indicated by the tranducer on the other hand (as indicated on the autosampler display) increased from a negative value all the way up to 1000 psi. Now since injection valve was closed, this seems to indicate that some flow from the pump is entering through the seals and increasing the pressure on the transducer.
In addition to this the compression test did not pass "compressibility exceeds limit". I set the pressure parameter at 30 psi and then at 350 psi and on both instances the test did not pass.
I also set the system pressure at 1000 psi via methanol flow in normal mode and messed with the valves motion page a bit, I moved the injector between the different positions and observed no leaks (except when the injector was in the sample vial position). I did this because the seal calibration test numbers seemed a bit skewy
up seal-350
dow seal-70
seal width-20
So apparently it's sealing in liquid pretty well when the pump is on but not when the syringe is applying pressure on it by moving. I did an injection accuracy test with four injections of 30 uL and it's pulling in about half of the expected amount.
Anyways, does everyone here agree that the most likely issue here is a worn seal? Any other suggestions as to what I should investigate? Why is it sealing in the flow but not when the syringe is applied to the seal? Thanks to bulldog and nkg for their assistance so far.