Environnement AF22e, Technical Manual, Page: 78 / 118

Environnement
S.A
AF22e
Duplication prohibited
APRIL 2016
3–44
3.5.4. MULTI-POINT CALIBRATION
3.5.4.1. Overview
An appropriate device consists of a diluter (MGC101 type), a certified span cylinder (SO
2
) (2 %
accuracy), and a zero air generator. Certified span cylinder calibration may be associated to reference
materials of the National Institute of Standards and Technology (NIST) for calibration in the US EPA
measurement field. Refer to Figure 3–4.
Gases will be applied at atmospheric pressure to the analyzer sample gas inlet.
Analyzer calibration requires gas generation of 7 points including zero (example: 0, 15, 30, 45, 60, 75
and 90% of the full scale of the measurement range used). The dilution carrier gas must be the same
as for zero measurement.
Flow controler
Double-
pressure
reducing
valve
Flow rate measurement
Dilution air
cylinder or
zero air
generator
Mixing chamber
Flow controler Flow rate measurement
Gas
cylinder
Vent Manifold
To monitor
Figure 3–4 – Typical calibration device diagram
3.5.4.2. Equipment Required
−
Diluter:
•
Flow controllers: should regulate flow rates to
±
1 %.
•
Flow meters: should allow flow measurement and recording to
±
2 %.
•
Mixing chamber: shape and size should allow homogeneous mixing of span gas and dilution
air.
−
Manifold:
The manifold includes at least one excess flow outlet and one “analyzer” outlet. This “analyzer”
outlet has a sufficient diameter to avoid load losses at the analyzer inlet. The excess flow outlet (at
least 20 % of the total flow rate) is designed so the manifold pressure will be close to atmospheric
pressure (no overpressure) and ambient air should not cause back pressure.