ABB AO2000-LS25 User Manual

80 AO2000-LS25 LASER ANALYZERS | OI/AO2000-LS25-EN REV. D
… 13 Maintenance
Validation
The AO2000-LS25 analyzer may be fitted with different options
to carry out span and zero checks for validation on the process.
The following options are available:
• Span check for non-corrosive gases (e.g. O
2
, NO, CO, CO
2
)
with internal flow through cell inside receiver unit.
• Span check for corrosive gases
(e.g. HCl, NH
3
, H
2
S) with additional span flow through cell
mounted between receiver unit and process
• Span and zero check with internal sealed span cell.
Contact your local distributor for more information about these
options.
Span check with flow through cell
Span checks to validate analyzer performance may be carried out
with the instrument installed on the process.
For non-corrosive gases the internal 100 mm volume between
receiver window and receiver lens is used to this end.
For corrosive gases a dedicated span cell (accessory available
from ABB) mounted between receiver unit and process applies.
The span gas is measured in parallel with the process gas;
therefore it is important that during normal operation this
internal or span cell is empty for span gas.
The span mode is initiated by input through digital
communication, see Mode on page 53.
The instrument calculates and stores the absorption signal for
the gas concentration measured in normal mode just before the
span check.
The absorption signal is continuously subtracted from the
measured signal during span check operation. The resulting
signal, therefore, corresponds to the signal from the internal cell
(or span cell) providing that the signal from the process remains
stable.
The ambient temperature and pressure recorded with the
internal temperature and pressure sensors located inside the
receiver unit is used to calculate the concentration of the span
gas.
The default concentration relates to a optical path length of 1 m.
This means that for an span gas concentration of e.g. 1 %, the
span is 0.1 vol.%.
(The span can be scaled to a different optical path length.
Contact ABB for details.)
Span check procedure:
1. Initiate span check through one of the channels described
above. The device is forced to span check operation. After
few seconds the message “SPAN” appears on the
transmitter LCD. The measured concentration should
come to zero, which indicates that the process
absorption signal is properly subtracted.
2. Start flushing the internal cell with the span gas. Use
moderate flow rates (approximately 1 to 2 l/min) to avoid
pressure build-up in the cell.
3. Measure span concentration.
4. Remove any residual span gas from the flow through
span cell by flushing it with Nitrogen or air.
5. Set the device back to normal.

ABB AO2000-LS25 Specifications

General

Brand	ABB
Model	AO2000-LS25
Category	Measuring Instruments
Language	English