Back pressure while purging

[Hooman]

Dear All,
I'm using an Agilent 1100 HPLC with a binary pump. When I open the purge valve, I see a pressure of 9-11 bar in the system. I wonder if recognizing such a pressure residue during purging the pump is a common and normal thing or not.
Thank you.

[Consumer Products Guy]

Agilent 1100 binary pumps (like their 1100 isocratic and quaternary pumps) have a test where purge of an aqueous phase at 5ml/minute must be less than 10 bar. Of course a pre-mixed mobile phase of water and methanol (for example) would be higher than water, so purge each channel separately at 5ml/minute and note the pressure of an aqueous phase.

OK, yours reads high. You need to install a new PTFE purge frit in the purge valve. Pull off the waste tubing, unscrew the pump outles line using a 1/4 inch open end wrench, use the THIN 14mm open end wrench supplied by Agilent and unscrew the purge valve. Now you can see the gold seal, pull that off with your fingernail, then you see the PTFE frit in side the purge valve, and the slot faces you. Use a paper clip, pull out the frit (note it will not look as good as a new one), install a new PTFE frit, and replace in opposite order. Simple, and routine procedure; check for leaks.

Now you're also trained how to replace a leaky purge valve, when it leaks out the "waste" side when closed. Don't close these like a gorilla.