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< 11. Inspection and Maintenance >
11-4
IM 11M12D01-01E
11.3 Inspection and Maintenance of the Detector
11.3.1 Cleaning the Filter in Sensor Assembly
If the filter in the tip of the sensor assembly gets blocked by dirt or the like, this will affect measurement
accuracy. If it cannot be cleaned satisfactorily by blowing compressed air through it, use a brush to
clean it.
11.3.2 Cleaning the Calibration Gas Tube
The calibration gas, supplied through the calibration gas inlet of the terminal box into the detector,
flows through the tube and comes out at the tip of the probe. The tube might become clogged with
dust from the sample gas. If you become aware of clogging, such as when a higher pressure is
required to achieve a specified flow rate (600 ± 60 ml/min), clean the calibration gas tube.
To clean the tube, follow these steps:
(1) Remove the detector from the installation assembly.
(2) Following Subsection 11.3.3, later in this manual, remove the four bolts (and associated spring
washers) that tighten the sensor assembly, and the pipe support as well as the U-shaped pipe.
(3) Use a rod 2 to 2.5 mm in diameter to clean the calibration gas tube inside the probe.
In doing this, keep air flowing from the calibration gas inlet at about 600 ml/min and insert the rod
into the tube (3-mm inside diameter). However, be careful not to insert the rod deeper 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. However, it should be dried out
thoroughly before reassembly.
(5) Restore all components you removed for cleaning. Follow Subsection 11.3.3 to restore all
components in their original positions. Be sure to replace the O-ring(s) with new ones.
F11-4E.ai
Calibration gas tube
Exploded view of components
Rod
(with outside diameter
of 2 to 2.5 mm)
Figure 11.4 Cleaning the Calibration Gas Tube
11.3.3 Replacing the Sensor Assembly
The performance of the sensor (cell) deteriorates as its surface becomes soiled during operation.
Therefore, you have to replace the sensor when its life expectancy expires, for example, when it
can no longer satisfy a zero correction ratio of 100 ± 30 % or a span correction ratio of 0 ± 18 %. In
addition, the sensor assembly is to be replaced if it becomes damaged and can no longer operate
during measurement.
If the sensor becomes no longer operable (for example, due to breakage), investigate the cause and
remedy the problem as much as possible to prevent recurrence.