Instruction manual

11.0 INSPECTION and MAINTENANCE SM425 INSTRUCTION MANUAL
11.0 INSPECTION and MAINTENANCE
This section describes the inspection and maintenance procedures for the SM425 Zirconia Oxygen
Analyzer.
Carefully observe the following when working on the detector:
- The sensor at the tip of the probe operates at temperatures approaching 750 °C. To avoid possible skin
burns allow the sensor and probe to cool sufficiently before touching.
- Do not subject the probe to strong mechanical vibration, mechanical shock, or cool it rapidly.The sensor
is made of ceramic (zirconia). If the detector is dropped or bumped, the sensor may be damaged.
- Do not reuse the metal O-ring between the sensor cell assembly and the probe. Process gas leakage
may cause corrosive damage to the heater, thermocouple, or cell. Always replace the metal O-ring.
- Handle the probe with care. The dust-filter mounting screws on the tip of the probe may cause injury.
- Remove dust and other debris from the terminal box cover prior to opening or closing the terminal box.
11.1 Inspection and Maintenance of the Detector
11.1.1 Cleaning the Calibration Gas Tube
Calibration gas is supplied to the detector through tubing in the probe and ejected at the tip of the probe.
Over time this tubing may become clogged by exposure to process gas and require a higher calibration
gas pressure to achieve the specified flow rate. Clean the calibration gas tube if clogging is suspected.
To clean the tube, follow these steps:
1. Remove the detector from the mounting flange.
2. Remove the four bolts (and associated spring washers) that tighten the sensor assembly to the
tip of the probe, the pipe support and the U-shaped pipe following Section 1.59.2
3. Use a rod 2 to 2.5 mm in diameter to clean the calibration gas tube inside the probe while
keeping air flowing from the calibration gas inlet at about 600 ml/min. Insert the rod into the tube
(3-mm inside diameter) no deeper than than 40 cm for a general-purpose detector or 15 cm for a
high-temperature detector.
4. Clean the U-shaped pipe. The pipe can be rinsed with water. Dry thoroughly before reassembly.
5. Reassemble all components removed for cleaning following Section 1.59.2. Replace the O-ring(s)
with new ones.
Figure 11-1 Cleaning the Calibration Gas Tube
42500001 REV A 175