This document describes the logic and sequences for starting up and operating a boiler system. It discusses the furnace purge sequence that must be completed before any fuel firing. It then explains the logic for starting individual oil and coal elevations, including sequences for opening valves and sensing flame. Master fuel trip logic is also summarized, which ensures safe shutdown of the boiler under various abnormal conditions by closing fuel valves and tripping fans.
This document describes the logic and sequences for starting up and operating a boiler system. It discusses the furnace purge sequence that must be completed before any fuel firing. It then explains the logic for starting individual oil and coal elevations, including sequences for opening valves and sensing flame. Master fuel trip logic is also summarized, which ensures safe shutdown of the boiler under various abnormal conditions by closing fuel valves and tripping fans.
This document describes the logic and sequences for starting up and operating a boiler system. It discusses the furnace purge sequence that must be completed before any fuel firing. It then explains the logic for starting individual oil and coal elevations, including sequences for opening valves and sensing flame. Master fuel trip logic is also summarized, which ensures safe shutdown of the boiler under various abnormal conditions by closing fuel valves and tripping fans.
This document describes the logic and sequences for starting up and operating a boiler system. It discusses the furnace purge sequence that must be completed before any fuel firing. It then explains the logic for starting individual oil and coal elevations, including sequences for opening valves and sensing flame. Master fuel trip logic is also summarized, which ensures safe shutdown of the boiler under various abnormal conditions by closing fuel valves and tripping fans.
24 May 2012 PMI Revision 00 2 Furnace Safeguard Supervisory System Satisfactory Boiler start up Start up of individual oil system AB/CD/EF Operation of fuel firing subject to certain conditions A/B/C/D/F Protection and interlock of oil /Coal System 24 May 2012 PMI Revision 00 3 Typical Graphic Display of fuel firing 244 subscriptions (requests) for data from the DPU.
75 maxSCRIPTS
30 Buttons
29 List Controls
3 Bar Charts
14 Text State controls
45 objects have dynamic borders 200K of various static bitmaps 24 May 2012 PMI Revision 00 4 BOILER START- UP SEQUENCE The boiler can be placed in service, initially or after a Master Fuel Trip, in the following sequence through FSSS. Furnace Purge
Before any fuel firing can takes place, initially or following a boiler trip, a satisfactory Purge Cycle must be completed. 24 May 2012 PMI Revision 00 5 Initially, the Heavy Oil must be recirculated and heated to obtain the proper temperature and viscosity for efficient combustion. After this is accomplished, the Heavy Oil Trip Valve (HOTV) can be closed and then the furnace purge cycle can be started. 24 May 2012 PMI Revision 00 6 After the furnace purge cycle is completed, the heavy oil elevation (AB, CD, EF, & GH) can be taken into service. An oil elevation is said to be In Service, when at least three out of four heavy oil nozzle valves are open and the flame is sensed by the scanners.
After the heavy oil elevation is in service, either of the adjacent coal elevation can be taken into service because Ignition Permit is now available for starting the pulverizer. 24 May 2012 PMI Revision 00 7
A Coal elevation is said to be In Service after the Pulverizer is ON, its Hot Air Gate (HAG) is open and the associated Feeder is proven (i.e., feeder ON for more than 50 seconds). A fireball signal is established when the associated fireball flame scanner senses flame and ELEVATION FLAME indicator is illuminated on the FSSS console in control room. 24 May 2012 PMI Revision 00 8 Unit start up sequence Boiler purge operation Start up of oil firing(AB,CD,FH & GH) Adequate Ignition permit Firing of coal elevation(A,B,C,D,E,F,G & H) Flame sensing by scanners. 24 May 2012 PMI Revision 00 9 FSSS LOGIC FSSS logics can be broadly divided into 3 sections. Unit Logic. Oil Elevation Logic. Coal Elevation Logic 24 May 2012 PMI Revision 00 10 Unit logic
Boiler purge logic Master fuel trip logic Oil trip valve operation logic PA Fans logic Scanner air Fans logic Seal air Fan logic 24 May 2012 PMI Revision 00 11 FURNACE PURGE
Purpose: : Complete Removal of unburnt fuel from entire furnace
Procedure: Ensure that all fuel to furnace is cut off and all flame is out Provide adequate air flow through furnace (30 to 40%) Initiate a MANDATORY purge time cycle (9 min)
Consequence: Master Fuel Trip Relays are reset Firing of fuel into the furnace is allowed
24 May 2012 PMI Revision 00 12 A. Unit Logic Boiler purge logic, which ensures a five minutes purge cycle is completed before any fuel firing can take place.
A Purge Ready signal at control room will be available when all the following conditions are satisfied: 24 May 2012 PMI Revision 00 13 Boiler Purge Logic
All HFO nozzle valves are closed All Pulverizers are off No MFT condition present All feeders are off All scanners sensing no flame. All auxiliary air dampers modulating Both PA fans off All HAGs closed Air flow more than 30% and less than 50% HFO trip valve is closed Wind box to furnace DP is adequate. 24 May 2012 PMI Revision 00 14 PURGE PERMISSIVES TO FSSS All HFO nozzle valves closed All pulverisers OFF All feeders OFF No MFT condition present All scanners senses no flame All Auxiliary Air dampers modulating Both PA fans OFF All Mill HAGs closed Air flow more than 30% and less than 50% HFO trip valve is closed Wind box to furnace DP is adequate 24 May 2012 PMI Revision 00 15 MASTER FUEL TRIP (MFT) MFT or Boiler Trip means: Complete isolation of all fuel to furnace under certain conditions Automatic Procedure: All oil valves are given closing command All mills and feeders are given trip command All Primary Air (PA) Fans are given trip command All Hot Air Gates (to mills) are given closing command Further Consequences: Turbine protection is initiated (to trip turbine) All SH and RH spray valves are given closing command All elevation SADC are given full open command Furnace pressure & Air flow controls are set to manual 24 May 2012 PMI Revision 00 16 Master Fuel Trip Logic This ensures a safe shut down of the boiler in case of any abnormal conditions in boiler/ furnace. If some abnormal condition occurs, Master Fuel Trip Relay acts and ensures the closure of Heavy Oil Trip valve (HOTV) and all Oil Nozzle Valves (ONV), thus cutting off total oil supply. It also ensures the stopping of all pulverizer systems and Primary Air (PA) fans, cutting off total coal supply to boiler. The various abnormal operating conditions under which Master Fuel Trip occurs are as follows:- 24 May 2012 PMI Revision 00 17
Both FD fans OFF Both ID fans OFF. Inadequate water wall circulation for more than 5 seconds. Loss of Reheat Protection for greater than 10 seconds. All BFPs tripped. Drum level very high for more than 10 seconds (2/3 logic) Drum level very low for more than 10 seconds (2/3 logic) Furnace pressure very high (2/3 logic) Furnace pressure very low (2/3 logic) Loss of all fuel. All feeders OFF and loss of AC Supply to the elevation in service. Unit flame failure. Loss of Unit Critical Power for more than 2 seconds Both Secondary APHs OFF. Loss of 220 V DC Supply for more than 2 seconds. Air flow less than 30% and boiler load not greater than 30%. Manual Emergency trip.
24 May 2012 PMI Revision 00 18 Both FD fans OFF Both ID fans OFF MFT RELAY Air flow less than 30% and boiler load not greater than 30% Loss of 220 V DC Supply for more than 2 seconds Manual Emergency PB trip Both Secondary APHs OFF Loss of Unit Critical Power for more than 2 seconds Unit flame failure All feeders OFF and loss of AC Supply to the elevation in service Loss of all fuel Furnace pressure very low (2/3 logic) Furnace pressure very high (2/3 logic) Drum level very low for more than 10 seconds (2/3 logic) Drum level very high for more than 10 seconds (2/3 logic) All BFPs tripped Loss of Reheat Protection for greater than 10 seconds Inadequate water wall circulation for more than 5 seconds 24 May 2012 PMI Revision 00 19 Unit Logic MFT consequences Trips all mills Trips all feeders Trips PA fans Closes HFO trip valve Closes all elevation nozzle valves Close all HAGs 24 May 2012 PMI Revision 00 20
This logic ensures that oil trip valve can be opened after the purge cycle is completed and no MFT condition is present, if the following conditions are also satisfied. All nozzle valves are closed. HFO supply pressure is satisfactory. HFO header temperature is satisfactory. Similarly, this logic ensures the closure of oil trip valve in case of MFT. 24 May 2012 PMI Revision 00 22 Scanner air fans logic It monitors the scanner air duct to furnace DP and ensures starting of scanner air fan - A or in case it fails to start, scanner air fan - B. This logic gives an open command to scanner fan outlet damper after starting the fan.
Also, in case of both FD fans not running, it ensures the scanner air emergency damper is open. 24 May 2012 PMI Revision 00 23 Seal air fans logic
Monitors seal air header to cold air duct DP and ensures the starting of seal air fan - A or B ( in case A does not start), provided at least one PA fan is running.
Gives an open command to seal air fan discharge damper once fan starts. 24 May 2012 PMI Revision 00 24 Oil Elevation Logic AB/CD/EF/HJ* 24 May 2012 PMI Revision 00 25
24 May 2012 PMI Revision 00 26
24 May 2012 PMI Revision 00 27 Oil elevation logic Start of oil elevations AB,CD,EF and GH Sequential operation with start command Corner1,corner3,corner2 and corner4 Gun advance,igniter advance Spark,atomizing valve open,oil valve open Sensing of discriminatory flame Retract of igniter 24 May 2012 PMI Revision 00 28 Oil elevation logic Stop of oil elevation Closure of oil valve,opening of scavenge valve Igniter advance and sparking Closure of atomizing valve and scavenge valve Retract of igniter and gun 24 May 2012 PMI Revision 00 29
OIL ELEVATION LOGIC There are four heavy oil elevations AB, CD, EF & GH. For all these elevations, logics are same. Oil elevation can be placed in service auto/manual. For a particular elevation, only one command is given for all the four corners together. (e.g. One common start command for elevation AB-1, 2, 3 and 4 guns). But start command goes to corners 1 to 4 sequentially. First command goes to corner 1; after 15 seconds start commend goes to corner 3; again after a lapse of 15 seconds start commend goes to corner 2; and again after a gap of 15 seconds start command goes to corner 4. 24 May 2012 PMI Revision 00 30 A particular corner takes the start command only if the following conditions are satisfied:-
The particular corner oil gun engaged feedback is available. The steam scavenge valve is closed for the particular corner. 24 May 2012 PMI Revision 00 31
The sequence of operation taking place for a particular oil gun once the command is given is as follows:- First the oil gun is advanced. Once gun advanced feedback is available the HEA igniter is advanced. Then atomizing steam valve is opened for the particular corner. Then HFO nozzle valve gets open command. Spark command is given to igniter transformer, thus producing a spark at the spark tip. Then for this particular corner HFO flow satisfactory feedback comes from the flow switch in the oil line. The corner oil gun proves when the DISCR FLAME SCANNER senses FLAME. When 25 seconds elapses after oil valve open, igniter spark signal is removed and spark rod is retracted. If the corner oil gun did not prove FLAME by this time, Oil nozzle valve and atomizing steam valve closes. Gun and igniter are retracted. 24 May 2012 PMI Revision 00 32 OIL FIRING PERMISSIVE-
1- PURGE COMPLETE/MFT RESET AND NO FIRST UP FAULT. 2- HFO PR. OK >25 KSC. 3- HFO TEMP OK >95C 4- IGNITOR AIR PR. >200 MMWG. 5- IGNITOR OIL PR. >10 KSC. 6- NO LIGHT UP IN PROGRESS. 7- NO BURNER START INHIBIT. 8-PERMISSIVE TO FIRE OIL. 24 May 2012 PMI Revision 00 33 OIL BURNER START LOGIC *OIL BURNER START PUSH BUTTON (NO OTHER OIL BURNER START IN PROGRESS).
OIL BURNER START SEQUENCE-
1-OIL BURNER SEC. AIR DAMPER OPENED. 2-OPEN IGNITER OIL MASTER TRIP VALVE. 3-NO FLAME SENSED IN LAST 5 SEC. 4-ENERGISE IGNITOR TRANSFORMER. 5- OPEN IGNITOR OIL SOLENOID V/V. 6- DETECT IGNITION OIL FLAME. 7- 4 WAY V/V TO FIRING POSITION. 8- OIL FLAME DETECTED. 9-CLOSE IOTV/SOL. V/V. 24 May 2012 PMI Revision 00 34 Coal Elevation Logic A/B/C/D/F 24 May 2012 PMI Revision 00 35
24 May 2012 PMI Revision 00 36
24 May 2012 PMI Revision 00 37 Coal elevation logic Pulverizer start logic Availability of PA permit Availability of ignition permit Seal air /bowl differential pressure No MFT Lube oil pressure adequate Pulverizer stop logic 24 May 2012 PMI Revision 00 38 Coal elevation logic Feeder start logic Pulverizer on Outlet temperature adequate Speed demand minimum No MFT Feeder stop logic Had/cad logic
24 May 2012 PMI Revision 00 39
COAL ELEVATION LOGIC
PULVERISER LOGIC This logic takes the count of total no. of pulverisers in service at any point of time, the no. of FD Fans and PA fans in service. With PA Fan ON and PA Header Pressure adequate (>560 mmwcl), it gives PA permit to start the Pulverizer. In case of PA Header Pressure going low-low or PA/ FD fans trips, it ensures the shut down of Pulverizers from top elevation to bottom elevation in a timed sequence. 24 May 2012 PMI Revision 00 40
Each mill can be taken in to service manually or automatically. Auto manual selection push button is available on FSSS console for each mill. Initially, Pulverizer Ignition Permit signal must be established for the mill to start. Other condition required to be established for starting the mill are as follows:- 24 May 2012 41 INTERMEDIATE OIL BURNER ELEVATION FIRING OR 30% BOILER LOAD ADJACENT MILL FIRING PA FAN IN SERVICE AND AND 24 May 2012 PMI Revision 00 42
Mill lub oil pressure adequate. Start permit from FSSS. Mill Discharge valve open. Mill outlet temp. > 93 O C.(200 O F) Cold Air Gate (CAG) open. Tramp iron vale (Top Reject Gate) open. Feeder inlet gate open. Seal air DP adequate (200 mmwcl). Feeder local switch in remote. Once the mill is ON, associated HAG can be opened and feeder can be placed in service. 24 May 2012 PMI Revision 00 43 OIL BURNER FIRING ON MILL BEING BROUGHT INTO SERVICE-
FOR ANY MILLS(A,B,C,D,E,F,G,H) 1-AT LEAST THREE OIL BURNER S FIRING IN SELECTED ELEVATION. 2- (A) BOILER LOAD > 30% BCMR AND (B) UPPER OR LOWER ADJACENT COAL BURNER IN OPERATION
EXAMPLE: FOR MILL A START PERMISSIVE: 1- ELEVATION AB 3/4 OIL BURNER FIRING. OR 2- MILL B FIRING AND BOILER LOAD >30% BCMR. 24 May 2012 PMI Revision 00 44 FOR B,D,F MILL (A) AT LEAST 3 OIL BURNERS FIRING IN THE BURNER GROUP ABOVE AND (B) ADJACENT COAL BURNER ABOVE IN OPERATION AND (C) THIS ELEVATION IS HIGHEST IN THE BURNER GROUP.
EXAMPLE- FOR MILL B START PERMISSIVE- (1) ELEVATION AB 3 / 4 OIL BURNER ARE I/ S . OR (2) MILL A FIRING OR MILL C FIRING AND BOILER LOAD > 30% OF BCMR. OR (3) MILL C FIRING AND ELEVATION CD 3 / 4 OIL BURNER ARE I/S. * NOTE THAT B ELEVATION IS HIGHEST IN THE BURNER GROUP AB. 24 May 2012 PMI Revision 00 45 FOR MILL C,E,G (A) AT LEAST 3 OIL BURNER FIRING IN THE BURNER GROUP BELOW. AND (B) ADJACENT COAL BURNER BELOW IN OPERATION. AND (C) THIS ELEVATION IS LOWEST IN THE BURNER GROUP.
EXAMPLE- FOR MILL C START PERMISSIVE (1) ELEVATION CD 3 / 4 OIL BURNER I/S. OR (2) MILL B FIRING OR MILL D FIRING AND LOAD > 30% OF BCMR. OR (3) MILL B FIRING AND ELEVATION AB 3 / 4 OIL BURNER ARE I/S. * NOTE THAT C ELEVATION IS LOWEST IN THE BURNER GROUP CD 24 May 2012 46 30% BOILER LOAD ADJACENT MILL FIRING PA FAN IN SERVICE INTERMEDIATE OIL BURNER ELEVATION FIRING AND OR AND 24 May 2012 47 PARTIAL FLAME FAILURE IT WILL NEVER OCCUR FOR THE FOLLOWING CONDITION- (1) IF THREE OR MORE MILLS FIRING THEN PARTIAL FLAME FAILURE WILL NEVER EXISTS. (2) IF LESS THAN THREE MILLS ARE FIRING THEN PARTIAL FLAME FAILURE DOES NOT EXISTS IF MILL WHICH IS FIRING HAVE THE MILL PERMISSIVE FOR FIRING. IT WILL OCCUR WHEN THIS LOGIC SATISFY- <3 MILLS FIRING ANY MILL GROUP TRIP MILL FIRING WITHOUT PERMISSIVE AND 24 May 2012 PMI Revision 00 48 VOTING OF ELEVATION
VOTING IN AB ELEVATION WILL BE AVAILABLE (1) MILL A FEEDER OR MILL B FEEDER I/S. AND ELEVATION AB 2 / 4 FLAMES IN. INTRLOCKED WITH ( ALL BURNER IN AB ELEVATION SATISFACTORY S/D OR 3 / 4 OIL BURNER IN THAT ELEVATION ARE I/S.) (2) VOTING IN BC ELEVATION WILL BE AVAILABLE- MILL B FEEDER OR MILL C FEEDER I/S. AND ELEVATION B 2 / 4 FLAMES IN. VOTING WIL NOT BE AVAILABLE (1) BOTH FEEDERS ON BURNER ELEVATION ARE NOT I/S. OR (2) 2/4 FLAME ARE NOT SENSED INTERLOCKED WITH 3 / 4 OIL BURNER ARE NOT FIRING. OR (3) OIL GUN IN THAT ELEVATION NOT SATISFACTORLY SHUTDOWN INTROLOCKED WITH 3 / 4 OIL BURNER IN THAT ELEVATION NOT FIRING. 24 May 2012 PMI Revision 00 49 Feeder start Logic
Feeder start command is given from FSSS Elevation Logic only. This command is continuously required to keep the feeder in service. Feeder speed demand minimum, Pulverizer ON, pulverizer outlet temp > 130 O F, HAG open and no MFT are the important conditions required to give the feeder start command from FSSS. 24 May 2012 PMI Revision 00 50 In case of pulveriser power high, bowl DP High or feeder OFF command, feeder speed demand is driven to minimum.
Release feeder to Auto Signal is also coming from FSSS. All of the above conditions are present and feeder is not ON for more than 50 seconds, release signal for auto is available. 24 May 2012 PMI Revision 00 51