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19.11 Commissioning the O2 trim control system
19.11.1 Setting fuel-air ratio control
Caution!
First, adjust the ratio control curves the same way as with the LMV51 The
excess O2 rate must be selected high enough, ensuring that at all possible
ambient conditions (combustion chamber and fuel pressure, temperature and
pressure of the combustion air), the O2 level will not fall below the O2 setpoint of
O2 trim control.
Parameterize the loads at the curvepoints proportional to the effective fuel rate (amount
of fuel). For that purpose, ascertain the load with the help of the fuel meter.
The curvepoint identifies the smallest load where O2 trim control is still possible.
In normal situations, this is the low-fire position.
Typically, this curvepoint 2 is defined as the low-fire position by setting the MinLoadGas
or the MinLoadOil parameter to the load of the second curvepoint.
Point 1 defines the curve for reducing the air rate below point 2.
The O2 ratio value between the curvepoints should be linear. When O2 trim control is
activated, precontrol will transfer any nonlinearity to the actual O2 value. When
adjusting the load, the actual O2 value fluctuates about the O2 setpoint. Check the
linearity of the O2 progression by approaching the loads between the curvepoints. If the
O2 ratio value has such nonlinearities, they can be corrected by setting intermediate
curvepoints.
The more thoroughly the ratio control curve is set, the easier the subsequent
adjustment of O2 trim control, and the more accurate O2 trim control will be.
Note!
If the ratio control curves are changed later, the O2 trim controller must also be
readjusted.
19.11.2 Setting the O2 alarm
Next, the O2 alarm must be adjusted. When making the adjustment for the first time,
the O2 alarm should remain deactivated to avoid undesired responses. When changing
settings later, it can stay activated.
Set the O2 min. value as low as possible to ensure a high level of availability. The O2
min. value marks the boundary between the permanently non-hazardous range and the
potentially hazardous range.
Caution!
Above or at the O2 min. value, hazardous conditions must not constantly occur.
Guide values (for Europe): CO = 2,000 ppm, soot number 3.
The values vary, depending on the type of plant. They need to be checked.
After setting all O2 min. values, the O2 alarm can be activated.
The setting can be made in 2 different ways.
Basic Documentation LMV5...
19 O2 trim control with LMV52 and PLL52
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CC1P7550en
22.05.2018
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