Siemens LMV5 Quick Start Manual page 179

Step by Step Commissioning of the O2 Trim System 6-2 continued...
3) Allow time for the QGO20 (O2 sensor) to heat up to temperature. The QGO20 will heat
the entire time the LMV52 and PLL52 are powered. For the initial heat-up, allow O2 sensor
to heat-soak for about 2 hours. This ensures the most accurate Actual O2 Value during
commissioning. The QGO Sensor Temp as well as other PLL52 related values can be
read under O2 Module > Displayed Values. The QGO Sensor Temp should heat up to a
minimum of 1290
Temp drops below about 1202
4) Turn the burner on. Verify that the Actual O2 Value is reading 20.9% O2 (+/- 0.6%) by the
end of pre-purge. If not, extend the prepurge time. The burner should light off and proceed
to Phase 60, which is normal operation.
Note : There should be at least 10 points in the Fuel-Air Ratio Control curves from low to high
fire, and these should be tuned at least 1.0% O2 leaner than normal. If this is not done,
please redo the Fuel-Air Ratio control curves before attempting to set up the O2 curves.
Verify that the load percentage on each Fuel-Air Ratio control point accurately
represents the fuel flow into the burner. This is critical to the O2 trim function. A fuel flow
meter or a manometer to measure burner pressure will be required to do this.
Three O2 curves must be set: O2 Monitor , O2 Ratio Control , and O2 Control
Set the O2 Monitor curve
1) This is found under: Parameters & Display > O2 Contr/Guard > Gas/Oil Settings >
O2 Monitor. This value must be set at every point that was defined in the
Fuel-Air Ratio control (combustion) curves from low to high fire.
There are two methods for setting this curve.
a. If the minimum safe O2 values are known across the firing rate, then values
for this curve can be input directly as a %O2. When this is done, the LMV52
will not actually drive the actuators to the point in question.
b. If the minimum safe O2 values are not known, the burner can be driven to the
point in question by displaying the point, pressing enter, and then scrolling
down to P air man.
When the P air man value is increased, the air influenced actuators will be slowly
driven back down their curves (closed) and the minimum safe %O2 value can be
effectively "probed". Increasing the P Air Man value will start closing the air
influenced actuators and should decrease the O2 measured in the stack.
At some point, smoke or a dramatic spike in the CO production will occur as the
air influenced actuators are closed. When this is found, the value of P Air Man
should be reduced slightly (opening the actuators, more air) until a somewhat
rich but safe combustion is achieved. After this, enter can then be pressed
moving the cursor to the left of P Air Man and saving the point. Next, press
escape to exit the point. After this, arrow over to the next point, or press escape
once more to exit O2 Monitor altogether.
Note : Point 1 on the O2 Monitor curve must be entered using method a. A safe % O2 can
be found (probed) at point 2, and then entered in for Point 1 using method a.
2) Repeat this process using Method a or b for every point that was defined in the
Fuel-Air Ratio control curves. A curve resembling the O2 Monitor curve shown in
Figure 6-1.1 should result.
The O2 Monitor curve is now complete.
LMV5 QSG Rev 4
o
F. The O2 sensor will no longer read O2 values if the QGO Sensor
o o
F (650
Sec 6 Pg 5
C). Readings will return at around 1290
www.scccombustion.com
o
F.