Yokogawa Integral Oxygen Analyzer ZR202 - Manual (Page 161)

<11. Inspection and Maintenance>
11-1
IM 11M12A01-02E 8th Edition : Jan.13,2012-00
11. Inspection and Maintenance
This chapter describes the inspection and maintenance procedures for the EXAxt ZR Zirconia
Oxygen Analyzer to maintain its measuring performance and normal operating conditions.
CAUTION
When checking the detector, carefully observe the following:
(1) Do not touch the probe if it has been in operation immediately just before being checked.
(The sensor at the tip of the probe heats up to 750 °C during operation. If you touch it, you
will get burned.)
(2) Do not subject the probe to shock or cool it rapidly.
The sensor is made of ceramic (zirconia). If the detector is dropped or bumped into
something, the sensor may be damaged and no longer work.
(3) Do not reuse a metal O-ring to seal the cell assembly. If you replace the cell or remove it
from the probe for checking, be sure to replace the metal O-ring. Otherwise, the furnace gas
may leak, and then the leaking corrosive gas will cause the built-in heater or thermocouple
to go open circuit, or the detector may corrode.
(4) Handle the probe with care so that the dust-filter mounted screws on the tip of the probe do
not hurt your finger(s).
(5) Before opening or closing the terminal box, first remove dust, sand, or the like from the
terminal box cover.
11.1 Inspection and Maintenance of the Detector
11.1.1 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 Section 11.1.2, later in this manual, remove the four bolts (and associated
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 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 Section 11.1.2 to restore all
components in their original positions. Be sure to replace the O-ring(s) with new ones.