April 28, 2023 1

Presentation outline

Boiler Emergencies

Turbine Emergencies

Generator Emergencies

Grid Failure

April 28, 2023 2

BOILER

April 28, 2023 3

HIGH FURNACE PRESSURE

• One I.D. Fan tripped or Mal-operation of control vanes of I.D./F.D./P.A. Fans or

closing of damper • Unstable furnace flame conditions. Sudden

starting of coal mill. • Furnace water seal broken, E.P. or flue gas

path manhole opened.• Water wall tube rupture/leakage.

April 28, 2023 4

ID FAN LUB. OIL PRESSURE / BEARING TEMP TROUBLE

• Lub. oil pressure may be inadequate.• Lub. oil filters may be choked.• Greasing long overdue in fan bearings.• Corresponding alarm will indicate the problem

area.

April 28, 2023 5

ID FAN TRIP

• Motor over-loaded.• Corresponding FD Fan has tripped.• Spurious electrical fault.• Lub. Oil pressure problem.• Bearing temperature problem. • Corresponding APH may have tripped.

April 28, 2023 6

FURNACE PRESSURE LOW

• I.D. Fan auto control Failure.• I.D. Fan vane control mechanism Failure

causing vanes to open wide.• Sudden decrease in air input or tripping of one

F. D. fan.• Sudden tripping of one or more mills or

choking of mill/raw coal Feeder pipe.

April 28, 2023 7

FD FAN TRIPPED

• Motor over-loaded• Lub oil pressure trouble.• Bearing temperature trouble.• ID fan has tripped.• FD lub. Oil pressure low.

April 28, 2023 8

PA FAN TRIPPED

• tripping is due to high bearing temp.• Boiler has tripped.• Lub. Oil pressure may be very low.• It will lead to tripping of some mills in service.

April 28, 2023 9

AIR PRE-HEATER

• AIR PRE HEATER BEARING TEMPERATURE VERY HIGH.

• AIR PRE-HEATER ELECTRIC MOTOR TRIPPED.• APH ELECTRIC DRIVE TRIPPED AND AIR

MOTOR FAILS TO START.• AIR PRE-HEATER ON FIRE.

April 28, 2023 10

DRUM LEVEL LOW• Mal-operation of Feed Auto Control or Feed

Regulator or scoop auto.• Tripping of one of working feed pump (standby

pump does not start)• Sudden increase of load.• Sudden increase in firing rate, e.g.• starting of mills having sufficient coal left before

previous stopping.• Tube rapture/puncture of low point drain valves or

Emergency drum drain Valve • Inadvertant opening of low point drain valves or

Emergency drum drain valve.

April 28, 2023 11

HIGH DRUM LEVEL

• Mal-operation of feed water control.• Sudden decrease in firing rate e.g. tripping of

the running mills.• B.F.P. Scoop tube position suddenly increased.

April 28, 2023 12

FLAME FAILURE AT AN ELEVATION• Closing of trip valves on H.O. (Causing loss of ignition

support energy) Where F.O. is being used as support fuel or when only oil is being used

• Sudden decrease of mill feeder speeds to minimum.• Too low or too high wind box pressure causing

unstable combustion.• Water wall tube failure• Malfunction of flame scanners due to supply failure

or scanner air failure, • slag or soot on scanner lenses etc.• Burner tilt mechanism negative extreme due to air

failure to power cylinders.

April 28, 2023 13

ONE FEEDER TRIPS

• Support energy is removed within 3 minutes of feeder starting.

• No coal flow alarm comes & low current relay picks up simultaneously.

• (Feeder shear pin given way)• Mill trips,• Feeder motor supply fails

April 28, 2023 14

ONE MILL TRIPS

• Mill discharge valves are closed• Loss of elevation D.C. supply for more than 2

secs.• Support ignition energy is removed Within 3

minutes of feeder starting.• Motor protection operates.• One P.A. Fan trips (mill in excess of 3 will trip

starting from bottom).

April 28, 2023 15

WATER MILL TUBE LEAKAGE• Starved water walls due to very low drum level.• Sustained flame impingement on water wall

tubes.• Blocked tube, scaling of tube, resulting in

overheating of tube metal, pitting, corrosion of tubes.

• Soot blower steam impingement (wet steam impingement or direct impingement of steam).

• Circulation affected due to opening of low point drains.

April 28, 2023 16

REHEATER/SUPFRHEATER/ ECONOMISER TUBE FAILURE

• Sustained high metal temperatures due to water wall Slagging or forcing boiler at the time of hot restart.

• Erosion on tubes due to high excess air, high ash content in coal dislocated tubes, soot blowing.

• Blocked tubes causing overheating.• Salt deposition due to high water level in

drum, poor quality of water.• Inadequate flow due to open superheater,

reheater drain.

April 28, 2023 17

Problem in Bottom Ash System

• Continuous watch on ash build up• Reduce load• Stopping of unit