Preventive Maintenance

Nitrogen-phosphorus detector (NPD)

4. Remove the collector from the collector assembly as follows:

Loosen the 1.5•mmscrew holding the transformer secondary wire to the top of the collector and disconnect the wire. The hex key wrench required is a 1.5•mmsize and was provided with the instrument.

Loosen the 1.5 hex key screw holding the brass connector to the collector top and remove the brass connector.

Remove the Teflon spacer and the stainless steel spacer/spring from the top of the collector body.

Loosen the 1.5•mmhex key screw holding the collector into the collector body and pull the collector out the top of the collector body. Grasp only the top portion of the collector to avoid contamination. If you plan to reinstall the collector, lay it aside on a clean surface until ready for reassembly. See below for cleaning instructions.

5.The jet can be removed for cleaning or replacement (if the jet is very dirty it should be replaced) with the 1/4•in.nutdriver supplied with the instrument. Using the nutdriver, unscrew (turn jet counterclockwise) and remove the jet from the detector base.

The jet exists in two sizes: 0.018•in.and 0.011•in.id. A cleaning wire may be used to help remove deposits from the bore of the jet (jet cleaning wire, Part No. 18765•20070is 12 inches of 0.016 od wire that can be used for this purpose).

Wash both the bore and the exterior of the jet with a 1:1 (V/V) solution of methanol and acetone. The jet may also be cleaned in an ultrasonic bath in the same solution. It is best to dry the jet and bake it out in an oven (70 to 150 C) before replacing it in the detector. After cleaning, apply a small amount of lubricant to the threads of the jet. The lubricant is necessary to prevent galling of the threads in the detector base.

The detector base may be cleaned using solvents (such as used for the jet), a cleaning swab, or wire brush, and dried with low•pressure compressed air.

Caution The detector should be cold and the instrument unplugged to avoid the danger of the flammable solvents flashing and possibly igniting the fumes.

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