48628822 01 fsss basic concept and std

7/29/2019 48628822 01 FSSS Basic Concept and Std

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1 March 2013 PMI Revision 00 1

Dear Participants

WELCOMETo a discussion on

FSSS/ Boiler Protection SystemBasic ConceptsandStandards


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CONTENT Basic concept

Function ofBMS

Furnace purge procedure

STANDARDS / NFPA


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MainFunctions

Furnace purge before boiler light-up

Oil firing: Permissives, Sequences and Protections

Coal firing: Permissives, Sequences and ProtectionsMaster Fuel Trip (MFT) or Boiler Trip

Post-Trip Purge Fans Trip

Runback: Graded Mill TrippingRunback: Graded Mill Tripping


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SG (Steam Generator)CONTROLS

BACK

BURNER

MANAGEMENT

SYSTEM

BOILERPROTECTIONS

MILLING

SYSTEM

FUEL OILSYSTEM

UNIT PURGE

SEC. AIR DAMPER

CONTROL

SOOT BLOWERCONTROL

AUX. PRDS

CONTROL

HP-BYPASSCONTROL


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Some DefinitionsBoiler Control System:

Deals with Regulating Control

Burner Management System (BMS):

Deals with Furnace Safety and Start/Stop of Fuel

Preparation and Burning Equipment

BMS Logic:Deals with Control System which would give

output based on external inputs and internal logic


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Burner management system

Burner management system is

designed to ensure the execution

of a safe ,orderly operatingsequence in the startup and

shutdown of fuel firing

equipments and to prevent errors

of omission safe operating

procedure.


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Function of BMSTO 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 INTERLOCKSHAVE BEEN SATISFIED.

CONTINUOUS FLAME MONITORING.

FAULT DETECTION AND ASSOCIATE S/D. INITIATE MFT UNDER CERTAIN CONDITION OF

LOAD COMBINATION.


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Basic Concepts of BMS

BMS is an independent and discreet logic systemspecially designed for safety and protection duringstarting , shutdown, low load and emergencyconditions.

BMS system has been designed to provide increasedsafety, reliability, flexibility and over all performance ofthe 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 ofequipment.


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The Burner Management system monitors the presenceor absence of the forced draft fan running and verifies air

flow is being produced, ensures the water level in theboiler drum is satisfactory, and verifies that there is atleast one flame in the furnace.

The Burner Management alarm system provides for afirst out cause of trip allowing operators to readily

identify the reason for an unexpected boiler tripcondition.

The Burner Management System controls the airregisters, igniters and fuel oil valves for each burner, as

well as monitoring of the flame signals for each burner inservice.


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If the flame quality degrades to 60% of maximum signal

strength a poor flame alarm is issued to the alarmsystem. When a flame quality signal is below 40% for 4seconds the burner will trip.

The Burner Management System lights off the initialburner 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 (AutomaticCombustion Control) system.

It also provides an interface to the ACC system to tell itwhen there is a state of change that can affect how the

ACC will respond or perform.


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Function of BMS Controls boiler purge, fuel headers, and burner field devices,

allowing sequential control of the start-up and shutdown of anyburners.

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, andfail to stop information.

Flame monitoring equipment provides the logic controller with flamestatus of burners and/or igniters.

Prevent firing unless a satisfactory furnace purge has first been

completed.


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Prohibit start-up of the equipmentunless certain permissive interlockshave first been completed.

Monitor and control the correctcomponent sequencing during start-

up and shut-down of the equipment. Conditionally allow the continued

operation of the equipment onlywhile certain safety interlocksremaining satisfied.

Provide automatic supervision whenthe equipment is in service and

provide means to make a MasterFuel Trip (MFT) should certainunacceptable firing conditions occur.


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SIMPLIFIED BLOCK DIAGRAM OFBURNER MANAGEMENT SYSTEM.

LOCALCONTROL

BOXAIR

DAMPER

B

M

S

FUEL

V/V

FLAMEDETECTOR

IGNITER

ABC

DAS

MILLCONTROL

C.C.R

BOILER

PLANT

IGNITION

CONTROL

PANEL


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BURNER GROUP-EACH STEAM GENERATOR HAS FOUR BURNERGROUPS.EACH GROUP COMPRISES FOUR OIL BURNER WITH

ASSOCIATE PF BURNER LOCATED ABOVE AND BELOW.

MILL GROUP- THERE ARE EIGHT MILL GROUPS PER STEAMGENERATOR 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.


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RELATIONSHIP OF MILL GROUP,ELEVATION NUMBERS & GROUPNUMBERS.BURNER NOZZLE NOZZLE MILL GROUPGROUP ELEVATION TYPE GROUP

NUMBER NUMBER4 13---------------------------SECONDARY AIR

12---------------------------COAL--------------------------- -F

11---------------------------OIL AND S/A

3 10 --------------------------COAL-----------------------------E9 --------------------------SECONDARY AIR

8---------------------------COAL------------------------------D

2 7-------------------------- OIL AND S/A

6---------------------------COAL------------------------------C

5---------------------------SECONDARY AIR

4---------------------------COAL------------------------------B

1 3---------------------------OIL AND S/A2---------------------------COAL------------------------------A

1-------------------------- SECONDARY AIR


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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.


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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.


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Standard FollowedNational Fire ProtectionAuthority (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


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IBR RequirementsFuel supply should be shut off when:

Flame failure occurs

Failure to ignite fuel within a pre-determinedtime

Abnormal drum level

Trip of Draft fansIncrease in Boiler Pressure


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BMS Logic HardwareNo specific stipulation regarding type of

hardwareNFPA stipulations are not retroactive

Existing system if giving trouble free operation

can continue to work even if not PLC/DCSbased


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Some Requirements ofNFPABurner Management System (BMS) Logic shall:

be such that single failure does not prevent shutdown

evaluate and address failure of components

diagnose improper logic functionshave a direct operable device for MFT which would work

irrespective of BMS logic

be protected from unauthorised logic changes

be provided with independent logic, I/O, power supplyand hardware etc for each boiler separately


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Interesting Insights toNFPANFPA recognises that:It is not possible to encompass all specific

hardware applications

The code should not be considered a cookbook

No standard can guarantee elimination ofFurnace explosion or implosion

Basic cause of Furnace Explosion is ignition ofaccumulated combustibles in the furnace


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48628822 01 fsss basic concept and std

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