ThermoFisher Scientific Wellwash 4, Service Manual

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Chapter 7: Maintenance
Thermo Scientific Wellwash
®
4 Mk 2 User Manual Rev.2.3, Cat. no. 1507340 42
7.1.8 Pinch valve
Occasionally the tube passing through the pinch valve becomes permanently
closed, i.e., it will not return to its normal shape when the valve opens while in
use. This tends to occur after extended periods of non-operation.
Release the pressure in the tubing by opening the wash bottle cap slightly. To
unpinch, locate the valve under the wash arm assembly. Press the black top of
the valve to release the tube, and pull the tube gently through the pinch valve a
few millimeters; the valve will now pinch into a new position. See Fig. 7.6.
Warning: Never press the black top of the pinch valve without first releasing the
pressure by slightly opening the wash bottle cap. Let the hissing sound
end prior to pushing the valve top.
Fig. 7.6 Unpinching the tube
If the washer is run now, the liquid will flow normally.
It may be necessary to replace the tube after extended periods of use due to
fatigue. Use the spare tubes supplied with the instrument (Fig. 5.2, item 3).
1.
Switch OFF the instrument and make sure there is no pressure in the wash
bottle by opening the wash bottle cap slightly.
2. Press the black top of the valve to release the tube and slide the tube gently
out of the pinch valve through the slit on the side.
3. Disconnect the tube from both ends and replace with a new one.
4. Press the black top of the valve and slide the new tube back into the valve
through the slit. Make sure the tube is properly in place through the valve
and is not pinched especially on the rear side of the valve.