Waters 2695: Sudden Pressure Drop upon Injection

[acgt838]

I have a question that may be very elementary. Since I am new to the Waters 2695, any help will be greatly appreciated.

Every time I do an injection, the system pressure drops by 600-700 psi (from about 1200 psi to 500 psi). This lasts only for a second or two and the pressure will slowly go back up. Is this normal for the Waters 2695? I have rebuilt the seal pack using Waters parts and replaced the syringe but the problem still persists. I think a couple of columns have already been ruined by this pressure fluctuation. Any suggestion as to how I can stop this? Thanks!

[tom jupille]

Do you see the same pressure drop in both directions (i.e. when the valve goes from "load" to "inject" and then again from "inject" to "load")?

[acgt838]

Actually, the pressure goes up (to 2000 psi) first and then drops down to 200-300 psi on injection.

[thohry]

Actually, the pressure goes up (to 2000 psi) first and then drops down to 200-300 psi on injection.

Probably the bypass channel of the valve is partly clogged