Flame Scanners Optimization

26/05/2010 Prepared By :- Mustafa Ali Lead Metering & Instrument Tech.

Flame Scanners

Optimization In Heaters Operation


Introduction

Flame whose UV radiation is absorbed by dust, water vapor or other material , may be monitored by these highly sensitive semiconductor UV photo elements,

These Flame monitors have also proven themselves in monitoring gas & oil combustion systems employing NOx reduction techniques ,

Flame scanners are used in burner applications with the widest variety of fuels,


Flame Scanners Installation at Heaters (Sawan CPP)

6 Scanners 6 Scanners 6 Scanners

6 Scanners 6 Scanners 6 Scanners

2 Scanners

2 Scanners


The photo elements used in the integrated optical flame scanner evaluate different spectral ranges of the flame.

The pulses generated by the integrated flame scanners, which offer a measure of the flame intensity, are transmitted to the microprocessor system and will trigger a flame ON or OFF signal, depending on the flame recognition threshold programmed in.

Three features of the flame scanner:

1) A fail-safe relay contact, K2,

2) A green LED on the front panel,

3) 4 – 20 mA O/P for display of the flame intensity.

Functional Description


Flame Scanners Malfunction Background / HistoryFlame Scanners failure often occurs during Heaters Startup

Pilot Flame Lit , but couldn’t recognized by Flame Scanner

Several attempts to be made to run a Heater , Specially after S/D or Cold Startup

Causing production delays, Causing excessive maintenance work hours utilization

The Flame Threshold have adjustable Range of“0” Low Sensitivity to “ 9 “ High Sensitivity in Flame Scanners,

These Flame Scanners since Sawan Commissioning always set to “ 9 ” Very low Pulse Frequency Threshold (High Sensitivity) to exposed Pilot Flame,That is to say, Very Narrow Flame Recognition Limit

Therefore If the flame image is very intense or deteriorates too much the flame signal (pulse frequency) dips below or go over the shut-off threshold. The safety time programmed into the scanner will then begin to run. After the safety time expires, the flame OFF signal is given and the green LED goes out , fail-safe relay output to the external flame ON signal is open & Flame Failure occurred

Flame Scanners Malfunction Cause


Threshold Rocker Switch Setting Graph


Threshold Settings Graph ( Conventional Practice Setting @ 9 )Flame Scanners Rocker Switch set at “ 9 “ at All Sawan Heaters


4-20 mA Flame Intensity Feature not Utilized 4 – 20 mA Flame intensity signal wires were cut from cable & kept isolated in JB

Every time a malfunction occurs, Flame Scanner cover removes to excess the Flame Scanner & we couldn’t get the problem rectified without it,


Threshold Settings Graph ( Setting Optimized Recently @ 6 )Methodology deployed & verified recently at Incinerator Train #1 & Train # 2


4-20mA Flame Intensity Feature Utilized Recently4 – 20 mA Flame intensity signal wires were identified , Tagged & kept in JB for measuring Flame Intensity at Incinerator Train # 1 & Train # 2


Action Taken

Discuss the observation among Instrument Team & prepare plan for implementation

Performed job on Train # 2 Incinerator during S/D on 20 / 05 / 2010

Flame Scanner mA used for Flame Intensity has verified

Flame Scanner Threshold Setting Change From “9” to “6”

Trouble Free Functionality checked Twice on startup of Incinerator Train # 2

Performed job on Train # 1 Incinerator during S/D on 23 / 05 / 2010

Flame Scanner mA used for Flame Intensity has verified

Flame Scanner Threshold Setting Change From “9” to “6”

Trouble Free Functionality checked Twice on startup of Incinerator Train # 1


Way Forward

Rocker Switch Threshold Adjustment at all theremaining Flame Scanners i,e “ 6 “

4 – 20 mA Flame intensity measurement at all the remaining Flame Scanners ,

Verify the Operation / Functionality of Flame Scanners


Flame must be visible to the flame scanner at all times, regardless of the load range of the burner. The 6° angle of view should always be oriented toward the root of the flame, that is, the bottom third of the flame.

The flame scanner’s purge air connection is responsible for keeping the sighting tube and optics free of particles from the combustion chamber.

Installation


The flame scanner is equipped with a push button switch for adjusting the flame recognition threshold .This threshold may be set to one of ten levels.

Programming the Flame Scanner

Flame OFF Setting:When burner is shut down, Threshold switch must be set high enough that the flame scanner does not see any ambient light and reliably signals ”Flame OFF”:• the green”Flame” LED is not illuminated,• the current in the flame intensity measurement circuit is less than 8 mA,• the fail-safe relay output to the external flame ON signal is open.

Flame ON Setting:If the burner is operating, Scanner must reliably exceed the flame recognition (shut-off) threshold and signal”Flame ON”:• the green”Flame” LED is illuminated,• the current in the flame intensity measurement circuit is greater than 12 mA• the fail-safe relay output to the external flame ON signal is closed.


If the internal self-check recognizes an error in the safety-related software and hardware components,

An error shutdown and internal lockout triggered. The relays for the flame, operational readiness and fault signals are released, and the red LED on the front panel will begin blinking.

The contact from K1 signals the present fault.

The red LED blinks 5 times by itself. After that, the yellow LED will also begin blinking with the red.

Fault RecognitionIf the cause of the error is a defect in the integrated flame scanner, the red and green LED’s will blink alternately.

The number of times that the yellow LED blinks corresponds to the type of error, which allows the operator to precisely analyze the source of the fault.


Flame Scanners

Optimization In Heaters Operation

ThanksForKind Attention

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Flame Scanners Optimization