Agilent 8453 Dissolution Testing System Installing and Operating Manual 89
Using the Valve Unit and Valve-pump Controller 4
Troubleshooting Your Valve System
If the valve drive assembly does not operate, call Agilent Technologies.
If the valve drive assembly operates, the valve has stuck. Clean the valve,
see “Cleaning Tubing and Valve” on page 91.
Leaking Tubing Connectors at Valve
This may be solvent leaks or air leaks causing bubbles in the tubing.
1 Check the connectors at the valve are tightened fully.
2 Check the connectors at the valve are not damaged. If the connectors are
damaged replace them, see “Replacing Fittings” on page 94.
Leaking Valve
Solvent is leaking and you can see solvent at the recess on the underside of the
valve, or air is being drawn in and also causing air bubbles in the valve tubing.
1 Check there is no restriction before the valve causing reduced pressure in
the tubings.
2 If there is no flow in all eight inlet tubings, either the outlet tubing is
blocked (see step 4) or the valve is blocked and needs cleaning, see
“Cleaning Tubing and Valve” on page 91.
3 If there is no flow in some of the inlet tubings, either these tubings are
blocked (see step 4) or the valve is blocked at these positions and needs
cleaning, see “Cleaning Tubing and Valve” on page 91.
4 To check if a tubing is blocked, connect the tubing directly to the pump and
observe the liquid meniscus while pumping solvent. If the tubing is blocked,
replace it.
Some earlier models of the valve drive assembly turn continuously when the valve is not
fitted. Place and hold a screwdriver in the slot on the rotor drive to provide mechanical
resistance. Do not turn the screwdriver.
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