Ultramat 7; Requirements For Reference Gas From The Gas Cylinder; Introducing Reference Gas - Siemens SIPROCESS GA700 Operating Instructions Manual

Commissioning
9.4 OXYMAT 7 / ULTRAMAT 7: Introduction of reference gas
The following example with four measuring ranges illustrates this:
Table 9-2
Measuring range
17 to 22% O
15 to 25% O
0 to 25% O
0 to 100 % O
Exception: If the smallest measuring span is ≥ 5% O
amounts to no more than 16 % O
range. The purity of the reference gas has to be appropriate for the measuring task.
9.4.1.2

ULTRAMAT 7

In an analyzer module without physically suppressed zero point, meaning with characteristic
initial value of zero, use nitrogen as the reference gas (purity 4.6).
In an analyzer module with a physically suppressed zero point, use an appropriate reference gas.
The concentration of the reference gas generally corresponds to the characteristic initial value
or, in special cases, the full-scale value or intermediate values.
In order to compensate for interference, the reference gas compartment can be subjected to the
purified sample gas of the measured component (absorber mode) or gas out of the cylinder,
which corresponds to the average interference gas composition.
9.4.2

Requirements for reference gas from the gas cylinder

The reference gas pressure must be 2 000 hPa above the sample gas pressure for sufficient
measuring ability.
1. Use a reference gas line with the following characteristics at measuring spans of < 2% oxygen:
– Small cross-section, e.g. pipe diameter 2 mm
– Made of metal, e.g., stainless steel
2. Flush the reference gas line thoroughly with reference gas before commissioning.
9.4.3

Introducing reference gas

• Set the flow of sample gas and reference gas to the same level.
• Always introduce the reference gas before introducing the sample gas.
92
Selection of the reference gas
Criterion for selection of the reference gas
The span of 17 to 22% O
2
may lie within this range. Air (20.95 % O
2
2
2
2
is part of all measuring ranges. The physical zero point
2
and the distance to the reference gas
2
, the physical zero point can also lie outside the measuring
%) is suitable as the reference gas.
2
Rack-mounted device
Operating Instructions, A5E31874006-12