Aseem Ramteke

J.E. Khaparkheda TPS K-53

FURNACE SAFEGUARD SUPERVISORY SYSTEMy Furnace safeguard supervisory system popularly

called FSSS continuously monitors the operations related to fuel admission and some other vital parameters to ensure safety of the Boiler.y Generally furnace oil or any kind of fuel is

susceptible to explosion hazards.y Majority of explosion occurs during start up, shut

down and low load operations.

FURNACE SAFEGUARD SUPERVISORY SYSTEMy There are many steps that must be followed by the operator to

admit a fuel in to the furnace safely and properly.y In high capacity boilers, where fuel input rate is very high

major furnace explosions can result from the ignition of unburnt fuel accumulated in the first one or two seconds.y Human reaction time to such situations is inadequate. So

there is a need for proper burner management system called as FSSS is installed in the Boilers. Every operation related to fuel admission is accomplished through FSSS.

FSSS HARDWAREy Pushbutton switches for initiating operations related to Fuel Oil and Coal admission, y Alarm windows on desk and panels for indicating current status of coal mills, oil elevations and flame scanner at every corner. y Relay Panels in the Relay room y Oil admission valves at every corner y Oil trip valves and re-circulation valves controlling the oil to headers

FSSS HARDWAREy Limit switches sensing status of the valves in y y y y

oil admission Flame scanners Pressure and Temperature switches Electro- pneumatic Solenoid valves Relay panels consisting of Relays, Timers and Memory Units.

Logics in FSSS1)Unit Logic 2) Elevation Logic 3) Corner Logic

UNIT LOGICy It supervises the overall furnace conditions by

monitoring all critical parameters of fuel firing systemy Supervises furnace purge. y If there is a likelihood of dangerous condition, it trips

the boiler.

ELEVATION LOGICy Startup and stopping actions for the elevation

are carried out through the elevation logic.y Input to this logic is from operators for start

and stop commands of the elevation also trip commands from Unit logic.y It also provides essential trip commands for

corner logic.

CORNER LOGICy It controls and supervises the corner valves i.e. Oil

Valves. Atomizing Valves and Scavenge valves.y Trip signals from unit logic or elevation logic overrides

the commands from corner logic.

LOGIC GATES USED IN FSSSy AND GATE y OR GATE y NOT GATE & y DELAY TIMER

AND GATE

OR GATE

NOT GATE

DELAY TIMER

FUNCTIONS OF FSSSy Furnace Purge Supervision y Igniter Control y Warm up fuel control y Pulveriser Control y Secondary Air damper Control y Flame scanner intelligence y Boiler Tripping

FURNACE PURGEy Purpose of this control is to ensure that furnace is always purged prior to Boiler Light up. y When boiler trips on protection or otherwise, there is a possibility of accumulation of unburnt fuel in the furnace. This unburnt fuel need to be driven out prior to readmission of oil for lighting up the boiler. y Purging is achieved by establishing a sufficient airflow by running one air cycle for predetermined time 5 minutes for 210 MW and 9 minutes for 500 MW Boilers. y This is the first operation that has to be carried out for lighting up the boiler.

Furnace Purge Conditions1. All igniters retraced in case of HEA igniters/All igniter valve closed incase of HSD Igniters 2. All heavy oil valves closed 3. All Light oil valves 4. All pulverisers off 5. All Coal feeders Off 6. All flame scanners sense no flame

Furnace Purge Conditions7.All hot air gates closed and cold air dampers open 5%. 8. All auxiliary air dampers modulating 9. Igniters trip valves closed 10. Heavy oil trip valves closed 11. Light Oil Trip valves are closed 12. No Boiler trip

Furnace Purge Control

LOTV Open/Closey Before Boiler light up with Light Diesel oil, LOTV must

be opened by giving open command the desk.y Other conditions to be satisfied are

1. No Boiler Trip 2. All Corner Valves closed 3. LDO Pressure adequate 4. LOTV Close command not persisting

LOTV Open/CloseLOTV closes when 1. Close command through push button switch is initiated OR 2. Boiler trips. OR 3. After a delay of 3 seconds when any warm up oil elevation s Corner valve is NOT CLOSED

LOTV Open/CloseLOTV closes when 1. Close command through push button switch is initiated OR 2. Boiler trips. OR 3. After a delay of 3 seconds when any warm up oil elevation s Corner valve is NOT CLOSED AND a. If LDO Pressure drops to LOW value OR b. If dP between atomizing air and LDO is low

LOTV ON/OFF

Pulveriser Ready Permissive1. Pulveriser outlet temperature NOT HIGH 2. Tramp Iron Hopper Valve Open 3. Feeder Inlet gate Open 4. No Primary Air Fan Trip 5. Pulveriser Discharge Valve open 6. No Pulveriser trip

Pulveriser Ready Permissive7. No Pulveriser stop command existing from Local or control desk 8. Seal air valve open 9. Cold air gate open 10. No Boiler trip AND a. Any Feeder is ON OR b. Burner tilt horizontal AND Air Flow less than 40%.

Pulv ris r ea y Permissive

Pulveriser Ignition PermissiveFor Pulveriser Ay Pulveriser B is running with 50% loading AND Boiler

Load is More than 30% ORy Elevation AB in service with 3 out of 4 Guns

established.

Pulveriser Ignition PermissivePulveriser B Ignition Permissive:y Pulveriser A or C running at 50% loading AND Boiler

Load is more than 30% ORy Oil Elevation AB in service with 3 out of 4 guns

established

WIND BOX DAMPERSAuxiliary Air Dampers:y During furnace purge and when load is less than 30%. FSSS

modulates the auxiliary air dampers to maintain a low wind box Pressure.y When load increases beyond 30% the modulation is for a higher

wind box pressure, which is achieved by closing dampers near elevation not in service.

WIND BOX DAMPERSy When warm up oil is in service, the auxiliary air damper of AB elevation opens to a predetermined position. y When heavy oil is in service, the auxiliary air is allowed to be controlled by opening depending on oil pressure. y When one FD fan trips, then all auxiliary and fuel air damper open wide.

Fuel air dampers:y All the air dampers are shut on elevations where there

are no feeders in service.y After starting of feeder, the fuel air damper of that

elevation is allowed to be controlled with feeder speed.

BOILER PROTECTIONS

BOILER PROTECTIONS

OBJECTIVES ACHIEVED BY FSSSy Safe Furnace Operations. y Smooth Light up of Furnace. y Withdrawing of Boiler safely as and when required. y Protective system for Boiler.

THANK YOU