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10.3 INSPECTING AND CLEANING THE SENSOR
CAUTION!
(1) Do not allow moisture to penetrate the units.
(2) Wipe the outside of the enclosures with a dry or damp (but not wet) cloth only.
(3) Do NOT use solvents or oil-based cleaners to remove contamination or accumulations of dirt as these can
damage the surfaces, and the seals and insulator on the sensor.
(4) An abrasive, such as wire wool, or wire brushes may be used on the sensor metal parts only.
The nature of many processes is such that a build-up of particulate may develop on the sensor rod. This build-up will
normally have no effect on the performance of the instrument, but it is recommended that the build-up is removed
periodically.
If the probe rod requires cleaning, remove the sensor from the duct and thoroughly clean the entire rod, paying particular
attention to the area of the non-metallic insulator and about 25 mm (1") of the metal parts either side of the insulator
(the aim is to prevent shorting across the insulator). The cleaning may be performed using wire wool. For sticky or
stubborn deposits, a cleaning agent may be used (use a fast-drying solvent cleaner –not water). Always ensure that
the probe rod is thoroughly dried before refitting the sensor.
The instructions below cover the standard sensor. All sensor parts should be cleaned as outlined in this section.
Always refer to the Safety Information at the start of this section before commencing cleaning procedures.
IMPORTANT NOTES:
(i) Where an air purge is attached to the sensor, this must remain switched ON, until the sensor has been fully removed
from the stack/duct.
(ii) The purge air section must be fitted to the sensor and purge air must be connected and switched ON before the
sensor is re-inserted into the duct.
(iii) Do not disconnect the grounding strap. The grounding strap (or wire) should be long enough to remove the sensor from
the stack/duct and place it on the ground or platform without disconnecting the sensor.
1. Switch OFF and isolate mains power.
2. Referring to the installation diagram (see Figure 1 on page 11), fully loosen the lock nut.
3. If the thread behind the lock nut is very dirty, this should be cleaned before loosening the nuts.
4. Undo the floating nut and carefully remove the sensor from the process.
5. Fully release the floating nut, then move both the floating and lock nuts back from their positions.
6. Check that the lock nut and floating nut move freely.
7. Apply a small amount of copper slip or grease to the mounting thread. This prevents binding and helps ensure a good
grounding is maintained with the stack.
8. Using a damp cloth or stiff brush remove any contamination from the probe rod, insulator, and the back of the sensor
enclosure.
NOTE: Clean the sensor parts using a rotational cleaning action to prevent scratches, particularly along the sensor
probe (especially when using wire wool).
9. Ensure the sealed connectors are secure and undamaged.
10. Inspect the connecting cables (where possible) to ensure they are not damaged or stressed.
11. Check that no moisture or foreign bodies have entered the sensor enclosure, then refit the cover lid and secure with
the 4 off screws.
12. Reconnect the grounding strap (earth wire) between sensor and stack.
13. Replace the sensor in the stack. Tighten the floating nut, then fully tighten the lock nut to secure the sensor in
position.
14. Restore power to return the sensor to normal operation.
15. Run the sensor self-checks to ascertain the correct functioning of the sensor (refer to section 9.1 on page 25 for
details).
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INSTALLATION AND OPERATION MANUAL – OWNER'S RECORD PEM MANUAL – PARTICULATE EMISSION MONITOR
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