Leak Test Failure -

Question

The slope of the second plateau in the leak test for the quat pump of our Agilent 1100 fails. We are getting a negative slope of -2.18. Pressure and slope for the first plateau passed. Pressure for second plateau passed but the slope was negative giving a failure. The pressure value passed at 389 and the final pressure drop passed at 1.5. Any ideas of the source of failure or causes of negative slope for our leak test evaluation? Thank you.

ankugler · Answer

The slope of the second plateau is produces by the piston the chamber one. This means that the system pressure is between active inlet valve and blank nut. As all other values passed it seems that the leak would be with the inlet valve. 
 In case you are able to identify some amount of leaking solvent it would be an external leak, typically between one of the gold surfaces of the AIV cartridge and its counterpart (pump head or AIV) 
 Without external solvent the leakage would be internally, meaning the ball and seat of the cartridge. 
 You could try to gently re-tighten the AIV while the system is not under pressure and retry the test. 
 But beware of overtightening as the gold surface quickly gets compressed and flows away or internal parts could crack.