Failed Dynamic Leak test

DGJL
DGJL
in Instrumentation and Mass Spectrometry
<p>Hi,</p><p></p><p>We have been having sensitivity issues with a degradation analytical run which is believed to be related to BSM. I have changed the seals and the check valves.</p><p></p><p>When a dynamic leak test was carried out at 500bar, primary A failed. All other pump heads passed. The message was 'the leak rate was above acceptable limit', but a possible cause or solution was not given. The pressure plot gave a stable reading but the highest pressue only went up to 430bar and remained at this point until the end of the test. The question is why does the pump not reach the set limit, but still remain at a constant pressure? I did the test at ~960bar, but the highest pressure it got to was ~800bar and therefore failed.</p><p></p><p>Any suggestion would be gratefully revceived.</p><p></p><p>Darren</p>

Comments

  • MarcNoble
    MarcNoble

    Darren,

    The pressures that you describe for the primary pump heads are normal.  The pressure that you set on the diagnostic page for the leak test is used for the Accumulator pump head (the one on the right that is tested first).  The software then sets a lower pressure for the primary pump head.  This is to ensure that the Accumulator check valve is not forced open during testing of the primary head (so that it is isolated for the test.)  Further, if the utility can not reach the setpoint, you get a different failure message, "Unable to compress...

    As for your sensitivity issue, although not impossible, the pump is generally not the cause of sensitivity issues.  The common mode of failure for the pump is eratic or drifting retention times.  Are the retention times for the peaks of interest correct?

    Marc

  • UPLCMD
    UPLCMD

    Hi,

    Did the pump pass the static leak tests?

    Regards,

    Michael

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