COSA Xentaur COSA 9610 - Manual (Page 19)

INSTALLATION, OPERATION AND MAINTENANCE MANUAL – COSA 9610™
Page 19 of 44
Relationship of pressure differential (gas/air) versus Wobbe-Index with different air
orifices and a fixed residual oxygen concentration of 5% (theoretically determined).
It is therefore recommended that a residual oxygen concentration of 2.5% is chosen
corresponding to the reference point. Possible fine-tuning of the reference point, (for the
purpose of attaining the correct O
2
%); can be carried out by giving the booster relay a
positive or negative offset.
3.1.3. Opening of shut-off valves
Open the shut-off valve with identification plate "instrument air supply".
3.1.4. Setting of gas pressure reducer
Turning the adjusting cap clockwise can raise the pressure of the gas pressure reducer.
The set outlet pressure can be read immediately from the pressure indicator mounted on
the reducer.
Set the output gas pressure to 30 PSIG.
3.1.5. Adjusting flow with flow meters
Unscrew the needle valve of bypass flow regulator completely (turn counter clockwise).
Use the "By-pass flow meter" needle valve; throttle back the flow so that the "Analyzer
flow meter" shows a flow of 50Nl/hr.
After this throttle back the output of the analyzer flow to 40Nl/hr using the needle valve
on flow meter tagged "Analyzer flow".
3.1.6. Adjusting booster relays
Set the chosen residual O
2
set point with help of the booster relay. With the booster
relay it is possible to give a small negative (i.e. the gas pressure is higher than the air
pressure) or positive offset of max 0.5 bar, as set point correction or as pressure drop
compensation over the air- and gas tubes in the heat exchanger.
In order to achieve the necessary offset pressure, the insert with internal hexagon at the
top of the booster relay must be removed. By doing this, the slotted adjusting screw is
accessible by means of a small rotation counter clockwise, a bigger negative offset is
reached. In other words, the air pressure is lowered in comparison with the gas
pressure. The correct choice of a negative rather than a positive offset needs to be used
for proper analyzer operation. The chosen residual oxygen concentration, combined with
the average of the chosen range of measurement, gives according to these curves the
selection of the air nozzle and an indication for the booster offset.