Environnement AF22e, Technical Manual, Page: 74 / 118

Environnement
S.A
AF22e
Duplication prohibited
JUNE 2016
3–40
3.5.1.2. Span gas generation (SO
2
)
NOTE : The span gas cylinders used should be certified following the user’s quality assurance plan.
The zero air used for the standard gas dilution and for the analyzer zeroing should be the
same. It should contain less than 0.5 ppb of SO
2
.
When a permeation device is used, the appropriate warm-up duration is 24 hours.
The devices used for span gas generation will deliver 25 L/h minimum and 60 L/h maximum.
All fittings, valves, pneumatic lines and other elements in contact with the span gas have to
be made of highly SO
2
-inert materials (i.e. PTFE, glass or stainless steel).
–
Scale point check :

SO
2
cylinder (
≤
2 % accuracy) with a concentration of approximately 80 % of the full scale of
the measurement range used.

Dynamic generation of one scale point using a cylinder and a diluter to generate approximately
80 % of the full range scale.

Optional built-in permeation oven with SO
2
tube. The concentration generated by this device is
recorded on the test report (for span check only).

External permeation device equipped with SO
2
permeation tube to generate approximately 80
% of the full range scale.
– 2-point calibration :

SO
2
cylinder (
≤
2 % accuracy) with a concentration of approximately 80 % of the full scale of
the measurement range used.

Dynamic generation of one scale point using a cylinder and a diluter to generate approximately
80 % of the full range scale.

External permeation device equipped with SO
2
permeation tube to generate approximately 80
% of the full range scale.
–
Multi-point calibration :

A cylinder of SO
2
span gas in nitrogen (N
2
) or air, and a dilution in zero air must be provided to
obtain the various required concentrations. It is advised to use a zero air dilution system
providing a 100-time higher flow than SO
2
-in-nitrogen cylinder flow. Many certified cylinders at
the required concentrations can also be used.
NOTE : The span gas cylinders used should be certified following the user’s quality assurance plan.
3.5.1.3. Internal solenoid valves
When performing a multipoint calibration, the user should connect the zero and span gas sources to the
sample inlet port. After this calibration, the zero and span sources should be connected to the
corresponding analyzer inlet ports. The AF22e should give identical responses whether the sources are
connected to the sample or the zero and span inlets ports. If not, then internal valves should be serviced.
The various gas inlet ports can be used for zero and span checks and two-point calibrations.