Model MicroCEM

Instruction Manual

748467-A January 2002

5-5 CHEMILUMINESCENSE DETECTOR ASSEMBLY

Refer to Figure 5-4and Figure 5-5.

a.Reaction Chamber

Removal

Disconnect the stainless steel tubing lines at the Gyrolok fittings. Remove the (4) nuts holding the Detector Assembly to the chassis. Disconnect the plug from connector J1 on the Signal Board and remove the assembly from the chassis.

NOTE

Heatsink Compound. Care should be taken to avoid getting heatsink compound on optical surfaces. If this substance is removed during the disassembly process, a zinc oxide -filled, silicone grease (e.g., Dow Corning 340 or EG&G Wakefield Engi- neering's Series 120 Thermal Joint Compound) be reapplied in the reassembly of this component.

Although the heater and thermostat can be removed to facilitate handling, contact with the white heatsink compound can be minimized by leaving these items in place. Remove the (2) screws holding the top plate of the Detector , and move the plate along the wires and away from the Detector .

Remove the (2) screws holding the tube assembly in place. Hold the tubing with one hand while inverting the Detector Housing with the other, allowing the Reaction Chamber O-ring and window to be removed from below.

Installation

To reinstall, hold the housing in the inverted position while sliding the Reaction Chamber O-ring and window into position and the tubing into the slot in the housing. Hold the Reaction Chamber in place while rotating the housing upright. Replace the hold-down screws.

NOTE

Component Positioning. The procedure described above is for the purpose of maintaining the relative positions of windows and O-ring to the Reaction Chamber during installation.

Replace the top cap and screws. Reverse the removal procedure to reinstall the Detector Assembly into the Analyzer Module.

b.Photodiode

Removal

Remove the Detector Assembly as de- scribed above. Invert the housing to ac- cess the mounting bracket. Remove the

(3) screws and shoulder washers from the bracket. Remove the bracket, insulating disk and bottom plate as a unit to mini- mize the spread of the heatsink com- pound.

Remove the (2) screws holding the lower section of the Detector Housing, then slide the section along the cable and re- move.

Remove the (2) screws holding the socket, thermistor and photodiode in place, being careful not to lose the washers that are used as shims.

Grasp the socket and photodiode base while slowly rotating to separate the photodiode from the housing. Some friction will be felt as an O-ring is used around the photodiode as a seal.

Installation

To replace the photodiode, carefully remove the diode from the green socket, and replace with a new one. Before mounting the new diode, the top cap of the enclosure should be temporarily removed and the (2) screws holding the Reaction Chamber loosened about two turns. This allows air which is trapped between the O-ring seals to escape when the diode is inserted. It also maintains the

Rosemount Analytical Inc. A Division of Emerson Process Management

Maintenance and Service

5-5