Yokogawa GD40 Gas Density Detector - Manual (Page 33)

<2. Installation, Wiring and Piping>
2-10
IM 11T3E1-01E
2.3 Piping
CAUTION
In the case of replacement range, H
2
in CO
2
or Air in CO
2
, the output happen to be fluctuated by
pressure loading to detector. In order to reduce the effect, flowmeter is to be set upper side of
detector so that the pressure loading to the detector is going to be about atmospheric pressure.
The piping connected to the analyzer comprises a line that feeds the gas under measurement to
the detector, a line that returns (or releases to the atmosphere) the gas exhausted after meas-
urement, and lines that carry the zero and span calibration gases. The type of piping chosen
depends on the composition of the gas under measurement, its pressure, the amount of dust
mixed, and the response (dead time). It is advisable however to use stainless steel piping of sizes
from 6 mm and 4 mm in outer and inner diameters up to JIS 15 A (21.7mm in outer dia.).
Refer to the following instructions when connecting the analyzer piping.
l Figure 2.10, "System Configuration," shows an example of piping. Connect the lines secure-
ly to ensure that there is no gas leakage in the system.
l Make sure the pressure of the sample gas is no greater than 0.5 MPa when measured at
the detector inlet. If the pressure is too high, use a pressure reducing valve to regulate the
pressure to a normal level. If the pressure is too low, it must be raised using a pump.
l If the gas under measurement contains dust, mist or moisture, such impurities must be
removed. Install a filter, mist separator or dehumidifier to remove these impurities from the
gas.
l In order to return the gas exhausted after measurement, the difference in pressure between
the detector inlet and the point of returning the gas must be 0.5 kPa minimum. Choose pip-
ing with a large inner diameter to minimize pressure loss in the return gas line.
l ALWAYS install a stop valve at the point where the gas is sampled (or returned).
l The pressure transmitter for compensating pressure is designed to detect the pressure
inside the detector; install a pressure lead pipe as close to the detector as possible (prefer-
ably, no more than 0.5 m away).