YOKOGAWA DT450G Series, Руководство пользователя, Страница: 23 / 41

<3. Piping and Wiring>
3-2
IM 11K01C01-01E
3.1 Connecting the Pipe for Air Purge
As a rule, the insulated part of the sensor probe should be air-purged before the DT450G is put
into use. Air purge is mandatory if any of the following cases apply:
• The concentration of dust in a gas is extremely high and the resistance of the insulated part
of the sensor probe is likely to decrease due to dust accumulation.
• The gas temperature at the probe inlet is likely to drop, resulting in condensation.
Note that clean air, such as air specified for instruments, must be used for air purge. (If air is not
available, use gas such as nitrogen instead.)
Note: For reasons of the measurement principle, any dust accumulating on the insulated part of the sensor probe can cause
malfunction. The purpose of air purge is to prevent such dust accumulation. Care must be taken since an air purge with air
containing moisture or oil mist causes the same phenomenon as dust accumulation.
Air purge is normally carried out by continuously supplying air to the DT450G with a pressure
of approximately 50 kPa higher than that of the gas being measured. If the effect of air purge
is inadequate, due to the presence of moisture in the gas being measured, the DT450G may
require air purge at a higher pressure. For air purge, use an air source with a sufficiently large
capacity. (The normal rate of air consumption is approx. 50 Nl/min under the pressure of 50 kPa).
When connecting the pipe to the DT450G for air purge, note the following.
• The DT450G may be removed during inspection or maintenance. When connecting the pipe
to the DT450G, use a one touch connector and/or a pipe made of flexible material to ensure
easy maintenance.
• Install a stop valve or pressure reducing valve in a position as close as possible to the
DT450G.
• Connect a pipe with an inside diameter of 6 to 8 mm to the DT450G. Note that the pipe
connection of the DT450G is Rc1/4 threaded.
F0301.ai
Pressure
control valve
Stop valve
Pressure of gas under measurement
plus approximately 50 kPa
Coupling thread
Rc1/4
Piping material
with 6- to 8-mm
inside diameter
Air source
Note: The rate of air consumption is approximate 50 Nl/min.
In some cases, the pressure of air supply may
need to set higher than the specified.
Figure 3.1 Method of Piping for Air Purge
If air purge need not be carried out, attach a blind plug to the pipe connection.