G7120A 1290 Infinity II High Speed Pump issues with leaking

Hi All,

For the last 1.5 years, the pump has been running fine even though the rear seal wash was blocked. Then in September, we were having issues with our pumps and found there was leaking in pump B. We did a maintenance, meaning cleaning the pumps and changing all of the seals for pump A and B, as they all looked extremely used and dirty. The system was running fine for about one month until now. We noticed some RT shifts in our samples and a higher baseline of noise, so we started checking our LC system. Both pumps failed the leak rate test, so we took apart both pumps, cleaned everything, checked the seals (which looked fine as they are quite new), and put it back together. At first the pumps could not get to pressure, so we opened the rear seal wash, and the pumps could get to pressure. However, both pump A and B kept having secondary leaks, or not being able to get to the required pressures for the pump leak rate test (but got quite close, like 750 instead of 800 bars). We have taken apart, cleaned, and put back the pumps multiple times, hoping that once it will do the trick, always getting a step closer. Now, after a very long purge of the rear seal wash, we got pump A to pass the pump leak rate test, but then after going for lunch and coming back an hour later, it failed the test again. For both pumps, we typically notice that the leak comes from where the heat capillary meets the gold seal between the primary and secondary pumps. Does anyone have any suggestions of what to test, what could be the issues, or how to know if the heat capillary or the gold seal need to be changed? It´s strange that is happening to both pumps and that it occurs right after a maintenance.

  • Hello,

    Can you tell us what pump model this is? That would be a good start.

    Also, when you change seals, you should be doing seal wear-in procedure. That procedure is included in the user manuals of the pumps. 

    Not sure what is the heat capillary, but have you looked into the check valves of the pump heads?


  • Hi,

    Thanks for your answer.

    The model of the pump is G7120A, and the piece is actually called a Heat Exchanger and not heat capillary, it is the part that connects the primary and the secondary pump heads. I have also checked all the inlet and outlet valves of the pumps, and they seem fine.

    Regarding the seal wear-in procedure, the manual that I have simply explains how to take apart the pumps, remove the seals, then to add the new seals that should be lubricated with isopropanol, put everything back together, and after installing the pumps, simply doing a leak rate test. I haven´t found any part mentioning the seal wear-in procedure.


  • I do not think there is a procedure for that particular model, you are correct.

    Now if you have changed the check valves and it is still not working, then you might be correct. It might be something about the heat exchange, although I have not seen issues with that particular part other then it being broken.

    If it fails on both sides, maybe the issue is after the solvent is mixed all the way to the automatic purge valve. Might want to look into the rotor seal of the purge valve.

  • Do you know if there is a way to check if the heat exchanger is broken?

    And good idea, I will check now the purge valve, as it would be strange for both heat exchangers to break at the same time.

  • Did you use a torque wrench when assembling the pumpheads back together?
    And if the heat exchanger is leaking..I would consider to change the outlet valve as well.

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