Stager States; Add Stage Methods - CleaverBrooks CFC Operation, Service & Parts Manual

CB FALCON LEAD/LAG
STAGERSTATE = IDLE WITH SLAVES ACTIVE
If the stager runs and its state is Idle, it checks the status of
all slaves. If any of these have SlaveState=AddStage, Sus-
pendStage, or Firing then these are set to Available (this
will cause the Rate Allocator to turn them all off).

Stager States

The stager's operation is defined for each of its states:
STAGERSTATE = IDLE
Burner demand means that a demand source is calling for
heat and there is also setpoint demand.
When there is no burner demand the stager is forced to be
Idle.
When burner demand becomes true (Call for Heat) the
stager checks the sequencer to identify the lead boiler.
That boiler is given a command to start.
The stager resets (to verify it is at 0) and starts its Stager-
Timer, and sets the StagerTimeLimit to the value of the
slave's Demand-to-firing delay time.
If the Stager fails to get even one boiler from the
Sequencer, it issues an alert and suspends until it runs
again.
STAGERSTATE = ADDSTAGERESPONSE
During this state the stager is waiting for slave to transition
to Firing.
If the identified boiler has a SlaveState=Firing then the
stager:
Resets and starts it's StagerTimer, sets the StagerTime-
Limit to Add-stage interstage delay, and changes the
StagerState to InterstageDelay.
If the boiler's SlaveState is still AddStage then:
The stager checks to see if the StagerTimer has reached
the StagerTimeLimit.
If so then the stager: Changes the SlaveState to Suspend-
Stage, resets and starts its StagerTimer, sets the
StagerTimeLimit to T_StagerSuspend. This allows addi-
tional time for the slave to reach its firing condition.
STAGERSTATE = ADDSTAGESUSPEND
During this state the stager is waiting to see if the slave has
transitioned to Firing or Available.
If the identified boiler has a SlaveState=Firing then the
stager:
Resets and starts its StagerTimer, sets the StagerTime-
Limit to Add-stage interstage delay, it changes the
StagerState to InterstageDelay.
The stager checks to see if the StagerTimer has reached
the StagerTimeLimit.
If so then:
If the boiler's SlaveState is set to Available.
If any slave boiler is firing then StagerState = Active
Otherwise StagerState = Idle
STAGERSTATE = ACTIVE
During this state the stager is ready to manage add-stage
and drop-stage requests.
If AddStageRequest is true
The Stager ask the Sequencer for an available slave.
When an available slave is found the stager repeats the
above steps to bring this stage to Active.
If DropStageRequest is true and more than 1 slave burner
is firing, the stager:
Invokes SetRecovering for the stage identified by
DropStageRequest. This will turn the stage off and put
it into the recovering state until it has finished its post-
purge (if any).
Resets and starts its StagerTimer, sets StagerTime-
Limit to Drop-stage interstage delay, changes the
StagerState to InterstageDelay, invokes an action to
reset the Add/Drop detection timers.
When the Interstage time has elapsed, the Stager can
execute an AddStage or DropStage request.

Add Stage Methods

Various methods can be used to determine when a new stage
should be added. The internal algorithms that generate
AddStageRequests are called Add-stage methods.
All methods work by observing various criteria such as the
Firing stages, the commanded rate, or setpoint error.
Adding Stages Parameters:
ADD-STAGE DETECTION TIME1: MM:SS
This provides time thresholds.
In the descriptions below, the relevant parameter is
referred to as Add-Stage detection timeN.
Add-Stage method1:
Disable,
Error threshold,
Rate threshold,
dError/dt and threshold,
dRate/dt and threshold }
In the descriptions below, the relevant AddStageDetect-
Timer is referred to as
AddStageDetectTimerN.
ADD-STAGE ERROR THRESHOLD: DEGREES
This provides the error threshold as defined by the
methods below.
ADD-STAGE RATE OFFSET: -100% TO +100%
This provides the rate offset threshold as defined by the
methods below.
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