Dear ParticipantsWELCOMETo a discussion onFSSS/ Boiler Protection SystemBasic Conceptsand Standards

CONTENTBasic concept Function of BMSFurnace purge procedureSTANDARDS / NFPA

Main Functions

Furnace purge before boiler light-upOil firing: Permissives, Sequences and ProtectionsCoal firing: Permissives, Sequences and ProtectionsMaster Fuel Trip (MFT) or Boiler TripPost-Trip Purge Fans TripRunback: Graded Mill TrippingRunback: Graded Mill Tripping

SG (Steam Generator) CONTROLSBACKBURNER MANAGEMENT SYSTEM

BOILER PROTECTIONS

MILLING SYSTEM

FUEL OIL SYSTEM

UNIT PURGESEC. AIR DAMPER CONTROL

SOOT BLOWER CONTROL

AUX. PRDS CONTROL

HP-BYPASS CONTROL

Some Definitions

Boiler Control System: Deals with Regulating ControlBurner Management System (BMS):Deals with Furnace Safety and Start/Stop of Fuel Preparation and Burning EquipmentBMS Logic:Deals with Control System which would give output based on external inputs and internal logic

Burner management systemBurner management system is designed to ensure the execution of a safe ,orderly operating sequence in the startup and shutdown of fuel firing equipments and to prevent errors of omission safe operating procedure.

Function of BMS TO PROVIDE SAFETY TO BOILER. TO PROVIDE ORDERLY SEQUENCE IN THE S/U & S/D OF FUEL FIRING EQUIPMENTS. PREVENT S/U OF FUEL FIRING EQUIPMENTS UNLESS CERTAIN PERMISSIVE INTERLOCKS HAVE BEEN SATISFIED. CONTINUOUS FLAME MONITORING. FAULT DETECTION AND ASSOCIATE S/D. INITIATE MFT UNDER CERTAIN CONDITION OF LOAD COMBINATION.

Basic Concepts of BMSBMS is an independent and discreet logic system specially designed for safety and protection during starting , shutdown, low load and emergency conditions.BMS system has been designed to provide increased safety, reliability, flexibility and over all performance of the boiler.The system is intended to protect against malfunction of fuel firing equipment and associated systems. In some phases of operation, the BMS shall provide permissive interlocks only to ensure safe startup of equipment.

The Burner Management system monitors the presence or absence of the forced draft fan running and verifies air flow is being produced, ensures the water level in the boiler drum is satisfactory, and verifies that there is at least one flame in the furnace. The Burner Management alarm system provides for a first out cause of trip allowing operators to readily identify the reason for an unexpected boiler trip condition.The Burner Management System controls the air registers, igniters and fuel oil valves for each burner, as well as monitoring of the flame signals for each burner in service.

If the flame quality degrades to 60% of maximum signal strength a poor flame alarm is issued to the alarm system. When a flame quality signal is below 40% for 4 seconds the burner will trip.The Burner Management System lights off the initial burner and cuts out burners automatically based on an operator selected sequence. It determines when burners need to be cutout based on the steam pressure signal from the ACC (Automatic Combustion Control) system.It also provides an interface to the ACC system to tell it when there is a state of change that can affect how the ACC will respond or perform.

Function of BMSControls boiler purge, fuel headers, and burner field devices, allowing sequential control of the start-up and shutdown of any burners.Continuous monitoring of supervisory interlocks, fuel valve positions, flame status and field devices.The control strategy normally utilize de energize to trip method. Smart alarms provide fail to open, fail to start, fail to close, and fail to stop information.Flame monitoring equipment provides the logic controller with flame status of burners and/or igniters. Prevent firing unless a satisfactory furnace purge has first been completed.

Prohibit start-up of the equipment unless certain permissive interlocks have first been completed.Monitor and control the correct component sequencing during start-up and shut-down of the equipment.Conditionally allow the continued operation of the equipment only while certain safety interlocks remaining satisfied. Provide automatic supervision when the equipment is in service and provide means to make a Master Fuel Trip (MFT) should certain unacceptable firing conditions occur.

SIMPLIFIED BLOCK DIAGRAM OF BURNER MANAGEMENT SYSTEM.LOCAL CONTROL BOX AIR DAMPERBMSFUELV/VFLAMEDETECTORIGNITERABCDASMILLCONTROLC.C.RBOILER PLANTIGNITION CONTROL PANEL

BURNER GROUP-EACH STEAM GENERATOR HAS FOUR BURNER GROUPS.EACH GROUP COMPRISES FOUR OIL BURNER WITH ASSOCIATE PF BURNER LOCATED ABOVE AND BELOW.

MILL GROUP- THERE ARE EIGHT MILL GROUPS PER STEAM GENERATOR EACH GROUP COMPRISES A MILL ,ITS ASSOCIATED COAL FEEDER AND A SEAL AIR FAN.

AIR DAMPER-AIR DAMPER ARE DIVIDED AS FOLLOWS-1-FIVE ELEVATION OF FOUR SECONDARY AIR.2- 4 ELEVATION OF 4 AIR TO OIL/S.A.D3-8 ELEVATION OF 4 AIR TO P.F. BURNER.4-TWO ELEVATION OF FOUR OVERFIRE AIR.

RELATIONSHIP OF MILL GROUP, ELEVATION NUMBERS & GROUP NUMBERS.BURNER NOZZLE NOZZLE MILL GROUPGROUP ELEVATION TYPE GROUPNUMBER NUMBER 4 13---------------------------SECONDARY AIR 12---------------------------COAL--------------------------- -F 11---------------------------OIL AND S/A3 10 --------------------------COAL-----------------------------E 9 --------------------------SECONDARY AIR 8---------------------------COAL------------------------------D2 7-------------------------- OIL AND S/A 6---------------------------COAL------------------------------C 5---------------------------SECONDARY AIR 4---------------------------COAL------------------------------B1 3---------------------------OIL AND S/A 2---------------------------COAL------------------------------A 1-------------------------- SECONDARY AIR

STANDARDS AND CODES

Prescriptive standards such as NFPA have done well at identifying what interlocks should be implemented based upon lessons learned from previous incidents and near misses.In todays microprocessor-based world, it is more important to know how to properly implement the prescriptive based interlocks. The logic solver was comprised of relays with simple and well-defined failure modes, it was very easy to understand what level of risk reduction the BMS provided.

NFPA Burner Management Systems (BMS) associated with fired devices in the power boilers are defined as Safety Instrumented Systems (SIS) if they contain sensors, a logic solver and a final control element according to NFPA. By actively embracing the concept that a BMS may in fact be a SIS, companies can ensure that these systems are designed, maintained, inspected and tested per both the applicable prescriptive standards (API, NFPA, etc.).A BMS can be designed that meets all requirements of the prescriptive standards such as NFPA.

Standard FollowedNational Fire Protection Authority (NFPA) of USA

Code 85 of 2001

This code is an amalgamation of earlier codes 8501 to 8506 applicable for various types of boilers and combustion

IBR RequirementsFuel supply should be shut off when:Flame failure occursFailure to ignite fuel within a pre-determined timeAbnormal drum levelTrip of Draft fansIncrease in Boiler Pressure

BMS Logic HardwareNo specific stipulation regarding type of hardwareNFPA stipulations are not retroactiveExisting system if giving trouble free operation can continue to work even if not PLC/DCS based

Some Requirements of NFPABurner Management System (BMS) Logic shall:be such that single failure does not prevent shutdownevaluate and address failure of componentsdiagnose improper logic functionshave a direct operable device for MFT which would work irrespective of BMS logicbe protected from unauthorised logic changesbe provided with independent logic, I/O, power supply and hardware etc for each boiler separately

Interesting Insights to NFPANFPA recognises that:It is not possible to encompass all specific hardware applicationsThe code should not be considered a cook bookNo standard can guarantee elimination of Furnace explosion or implosionBasic cause of Furnace Explosion is ignition of accumulated combustibles in the furnace

Certification, VDE, TRD, SIL LevelContinuance of existing system is purely a judgment/confidence of the owner