Agilent 1290 Infinity G4220A Leak in Primary Pump Head

Hey Stacey, how does the pressure look during the primary leak rate test? Does it stay at zero (this would indicate a problem likely with the inlet valve) or it goes up and cannot reach 800 bar (this would indicate some leak inside the the chamber because of the piston or seals, or less likely a problem with the outlet valve)? I would recommend to replace the piston seal (0905-1719). Also, make sure the piston is not scratched. Also, make sure you have properly assembled the pump head. Not sure what you have, normally this will be written on the pump head for easy maintenance or longlife technology and blank for classic. Keep in mind that the older classic pumpheads require an alignment tool. Agilent 1290 Infinity Pump Head Maintenance Technical Note

It is quite unlikely that the seal wash leaks into the mobile phase because this is behind the chamber. 

Evaluation of pump leak rate test, see page 128: Agilent 1290 Infinity Binary Pump

Hello kbusch,

Thanks for your quick response and the suggestions! I'm not exactly sure which type of pump head we have (there doesn't seem to be any labeling on the pump), but all the parts look like the ones shown on pg. 203-205 of the second manual that you linked, which seems to be the longlife? For example, our seal wash holder has the tubing inlet/outlet in the V shape, rather than parallel.

For the leak rate test -- the pressure goes up a little bit (a few bar) but mostly stays at zero. Just to report all of what we've done:

- The problem was originally on the Channel A primary pump head, so we worked on Channel A following pg. 160-178 in the G4220A manual. Disassembled both the primary and secondary pump heads, cleaned the interior parts, replaced both primary/secondary wash seals (but not the piston seals), and reinstalled everything to proper torque using a torque wrench. Pistons were gently cleaned with IPA and 4000 grit paper (looked smooth and unscratched), we lubricated all parts with isopropanol when reassembling, and the piston felt snug with the seal wash holder. The secondary head that we worked on is mostly OK after reassembling (there's a slight leak, ~ 3 uL/min, but not like the primary head).

- Since we're mostly running isocratic operations (e.g. SEC), on Channel A only, we swapped the entire primary pump head for Channels A and B so that we can still run in between troubleshooting. We confirmed the problem moved to B. Here's the leak rate test:

I've just now tried swapping the inlet valve assembly between A and B (the part with the gold seal, and also swapped the tubing coming from the degasser), but the problem is still showing up on B. Here's the leak test after swapping inlet valves:

For the seal wash -- before attempting any of the maintenance, there was a time we were equilibrating the system with DI water and had 20% ethanol on the seal wash rinse. The seal wash was set to periodic, and we could see a peak on multiple detectors (UV, light scattering, RI, etc.) every time the seal wash pump turned on. When the seal wash was switched to DI water to match the mobile phase, the issue went away. So, I wasn't sure if the fluids were somehow mixing or if some other issue could cause that.

Sorry for the long post, but hope that might be helpful for any suggestions on the next part to troubleshoot? 

Hey Stacey, thanks for the information. Sounds likely that you have a LL pumphead or easy maintenance. The inlet valve does not have a gold seal. The inlet valve is located at the bottom of the primary chamber. Has this the part that has been swapped to check? I attached a picture where i colored the inlet valve red. If you have not yet done this part, I would still check this part first. However, I think this is likely what you have already done. FYI The part with the gold seal is the outlet ball valve located on top of the pump head. If the inlet valve has already been checked then I would start to suspect some issues with the primary pump seals. 

Thanks for the diagram! The inlet valve in red is indeed the one we've swapped. We have the piston seal on our list to replace, and are planning to swap the other pump parts to check as well. Hopefully I can update next week with which one is causing the issue.

Hi staceylouie please let us know how you went with the piston seal replacement in the primary pump chamber and if you tried anything else after this.

Hi, thanks for checking in. We tried swapping a few more parts (outlet valve, piston & seal wash holder), but fell behind in ordering the piston seals to replace. None of the other parts were causing the issue, so hopefully the seal replacement will resolve the leak.

Hello -- just an update, the piston seal replacement fixed the problem. All pump heads are now able to pressure up and are passing the leak rate test. Appreciate all the advice on this!

Hi staceylouie thank you for letting us know the outcome of the seal replacements, glad to hear that the issue is solved.

Hi staceylouie thank you for letting us know the outcome of the seal replacements, glad to hear that the issue is solved.