YOKOGAWA ZO21DW, User Manual, Page: 19 / 39

<3. PIPING>
3-6
IM 11M03A02-00E
3.2.3 Piping for the Reference Gas
Reference gas piping is required between the air source (instrument air) and the flow setting unit,
and between the flow setting unit and the detector.
Insert the air set next to the flow setting unit in the piping between the air source and the flow
setting unit.
Use a ø6 × ø4 mm (or nominal size 1/4 inch) stainless steel pipe between the flow setting unit
and the detector.
3.2.4 Valve Operation of Reference Gas Outlet
1. For safety, stop the furnace that the detector is to be installed in. If furnace internal pressure
is high, this is especially dangerous.
2. Before starting instrument air flow, completely shut the stop valve in front of the reference
gas outlet.
3. Check that the reference gas outlet is not blocked by a flange gasket or the like.
4. Set the instrument air pressure higher than furnace internal pressure.
5. Completely open the stop valve in front of the reference gas outlet and, after turning on
instrument air flow, start furnace operation. As furnace internal pressure rises, confirm
that instrument air continues to flow and adjust the valve or increase supply pressure if
necessary.
6. After furnace internal pressure stabilizes, adjust flow.
7. If furnace operation is stopped, stop instrument air flow and completely shut the stop valve
in front of the reference gas outlet. You may leave reference gas flowing if you wish.
3.3 Piping for System 3
Piping in System 3 is illustrated in Figure 3.5. In System 3, calibration is automated but the piping
is basically the same as that of System 2. See section 3.2.
Instrument air
Calibration gas pressure regulator
Air Set
Needle
valve
flowmeter
Reference gas
Calibration gas
Check valve
~
Zero gas cylinder
Model ZR40H Auto Calibration unit
ZO21DW Zirconia Oxygen
Analyzer, Detector
Model ZR402G Converter
Calibration gas
unit case F4.9E.EPS
EXA ZR402G
100 to 240 V AC
Contact input
Analog output, contact output
Digital output (HART)
Signal
(6-core shield cable)
Heater (2-core cable)
Figure 3.5 Piping for System 3