Chromatography Forum

I'm refurbing an HP 5890 for a personal project (i.e., no budget), and it's been working fine up until a few days ago. Now I get a low pressure alarm upon start up, unless I ramp the head pressure way down (0.5 or so). But once the instrument warms up (10-15 minutes), it'll accept any pressure requirement I give it, same as it always did.

Any recommendations as to what to look for?

I'm refurbing an HP 5890 for a personal project (i.e., no budget), and it's been working fine up until a few days ago. Now I get a low pressure alarm upon start up, unless I ramp the head pressure way down (0.5 or so). But once the instrument warms up (10-15 minutes), it'll accept any pressure requirement I give it, same as it always did.

Any recommendations as to what to look for?

Sounds as if something is sealing once it is up to temperature. If it depends on the injection port temperature I would be looking at the gold seal at the bottom of the injection port(providing it is a split/splitless port) or the column ferrule. Graphite/vespel ferrules will shrink when put through heat/cool cycles, if you are using that type on the column it could be the problem.

Liner O-ring, ferrules, septa. Start with those as the most likely problem and see if there are any leaks when it is cold.

Loose liner nut!

Of all the things to miss....

Thank you!

It's great when it's something easy!