A boiler trip command stops all fuel inputs and closes all heavy oil nozzle valves. There are two separate boiler trip commands that must both be reset before a furnace purge can begin. A boiler trip establishes a master fuel trip memory signal, indicated by red and green lights, and triggers various safety events like tripping pulverizers and fans. Boiler explosions can occur if unburned fuel accumulates in the furnace, while implosions result from rapid decreases in furnace pressure. Preventive measures include maintaining minimum air flows and slowly reducing fuel and fan speeds after a trip.

1. BOILER TRIP
A “boiler trip’ command stops all fuel inputs by tripping all of the
pulverizers and feeders and closing all heavy oil nozzle valves on all
elevations.
There are two separate “boiler trip” commands in this unit. Both “no
boiler trip” command signals must be established before a furnace
purge cycle can be initiated.
A “boiler trip” command will establish a “master fuel trip” memory
signal. This is indicated by the (red) “ MFT TRIP” light being on and
the (green) “MFT RESET” light being off.
When a “master fuel trip” memory signals established (red, “MFT
TRIP” light is on),
The following events occur:
1. The (red) “MFT A TRIP” and MFT B TRIP” lights come on and the
associated (green) “MFTA RESET” and “MFT B RESET” lights go off.
2. The Data Logger receives a “MFT A TRIPPED” AND MFT B TRIPPED”
SIGNALS.

2. 3. The “boiler load greater than 30 %” memory signal is removed.
When the “master fuel trip” memory signal is established (red, “MFT
A TRIP” or MFT B TRIP” LIGHT IS ON), the following events occur:
4. Both of the (red ) “BOILER TRIP” light come on and the “PUSH TO
PURGE” AND “PURGING” light are “armed”.
5. The PULV MODE (green) “MANUAL” light comes on, if it was off.
6. All pulverizers are tripped as indicated by the PULV START PERMITS
(white) “NO PULV TRIP” lights going off.
7. A five minute counting period is started. Five minutes latter, all cold
air dampers are opened to the “100 % pulverizer air flow position”.
8.The “permit to start P.A. fans” signal is removed.
9. The “oil elevation trip” memory signal is established at all oil
elevations.
10. If all heavy fuel oil nozzle valves are not closed, the heavy fuel oil
trip valve is closed. The heavy fuel oil trip valve can then be reopened
after all heavy fuel oil nozzle valves are closed and the heavy fuel oil
recirculation valve is opened.

3. 11. A five second counting period is started. Five seconds later, the
“loss of fuel trip arming” signal is removed.
12. The CAUSE OF TRIP memories cannot be reset.
13. All feeders are shutdown.
14. The upper and lower fuel air dampers are opened.
15. The auxiliary air control is transferred to MANUAL control and all
auxiliary air dampers are opened.
16. The primary air (P.A.) fans are tripped.
17. The “feed forward to furnace draft control” signal is established
for thirty seconds if the following conditions are satisfied:
A. The unit critical power is available for more than six seconds AND
B. The “loss of fuel trip arming” signal is established.
When this signal is established, item “B” is no longer required to keep
this signal established.
Thirty seconds later, the “feed forward to furnace draft control” signal
is removed.
18. The furnace pressure recorder changes to a higher speed for
thirty seconds.

4. When the thirty second counting period expires, the furnace pressure
Recorder will remain at the higher speed if a “high furnace pressure
alarm” or a “low furnace pressure alarm” signal is established. When
both of these signals do not exist for more than thirty seconds, the
furnace pressure recorder reverts to its original speed. The recorder
will revert to the higher speed if either of these signals are
established.
A “boiler trip signal is established if any of the following conditions
exist:
19. Loss of ACS power for more than two seconds.
20 Loss of customer’s 220 VDC Battery power for more than 2 )
seconds.
21. Loss of unit critical power for more than two seconds.
22. A “simulator trip” signal exists.
23. The water drum level is “low” for more than ten seconds.
24. The water drum level is high” for more than ten seconds.
25 All boiler feed pumps are off.
26. “Inadequate water wall circulation” signal exists.

5. 27. All I.D. (Induced Draft) fans are off.
28. ALL F.D. (Forced Draft) fans are off.
29. The air flow is less than 30 % before the boiler load exceeds 30 %.
30. The deaerator level is “low-low”.
31. At least two of the three pressure switches indicate a “high furnace
pressure trip” condition.
32. At least two of the three pressure switches indicate a “low furnace
pressure trip” condition.
33. Both BOILER TRIP (emergency) push buttons are depressed
simultaneously.
34. All feeders are off and loss of power exists at the elevation that is in
service.
35. A loss of reheat protection occurs.
36 A “loss of fuel trip” signal is established (see Note below).
Note : The “loss of fuel trip” signal becomes “armed” when the first oil
elevation that is placed in service has at least three of the four heavy
oil nozzle valves proven fully open (OIL VALVE COR (green) “CLOSED”
lights are off).

6. After the “loss of fuel trip” signal is “armed”, a “loss of fuel trip” signal
will be established if all of the following conditions occur
simultaneously:
A. At all coal elevation, the feeder is off or loss of elevation power
exists. This condition exists for more than two seconds
AND
At all four oil elevations all oil nozzle valves are closed or an
“elevation trip” signal is established at the associated oil elevation.
The “loss of fuel trip” signal is proven established when the Data
Logger receives a “LOSS OF ALL FUEL TRIP” signal.
B. At all coal elevations, the feeder is off or loss of elevation power
exists. This condition exists for more than two seconds.
AND
The heavy fuel oil trip valve is not fully open
AND
At all four oil elevations, all oil nozzle valves are closed.
When the “master fuel trip” memory signal exists for more than five
seconds the “loss of fuel trip arming” memory signal is removed.

7. The Data Logger’s “LOSS OF ALL FUEL TRIP” signal will remain
established if item B above is satisfied. When the heavy oil trip valve
is proven fully open (for oil recalculation), this signal is removed.
37. A “unit flame failure” signal is established (see Note below).
NOTE : During light off and before any feeder is “proven” for more
than two seconds, the “fireball” flame scanners do not take part in
the overall flame failure protection systems. When any feeder is
“proven” for more than two seconds, the system automatically
changes from flame failure protection of an individual fuel nozzle to a
“FIREBALL” supervision of the furnace. The system is designed to
initiate a “boiler trip” when any feeder is “proven for more than two
seconds and all five fireball flame scanner elevations vote “no flame”
simultaneously.
After any feeder is “proven” for more than two seconds, the UNIT
FLAME FAILURE (amber) “ARMED” light comes on. After this light is
on, a “unit flame failure “signal is established when all five UNIT
FLAME FAILURE (amber) “GH” and “FG” and “DF” and
“BC” and “AB” lights are all on simultaneously.

8. This is indicated when the Data Logger receives a “FLAME FAILURE
TRIP” signal. This signal causes a “master fuel trip” memory signal to
be established (both (red) “BOILER TRIP” lights come on).
When each fireball flame scanner elevation votes “no flame”, the
associated UNIT FLAME FAILURE (amber) light comes on at the
associated fireball flame scanner elevation. Listed below are the
conditions that will cause this (amber)light to be illuminated for the
various fireball flame scanner elevations.
Elevation “AB”:
1. Feeder A is off or loss of elevation A power and Feeder B is off or
loss of elevation B power. This condition exists for more than two
seconds. OR
2. At elevation AB, less than three of the four heavy fuel oil nozzle
valves are fully open or fuel flow is not adequate at the associated oil
nozzle valve or elevation AB power is not available for more than two
seconds and less than two of the four “fireball” flame scanners
indicate flame on elevation “AB” OR

9. 3.At elevation AB, less than three of the four heavy fuel oil nozzle
valves are fully open or fuel flow is not adequate at the associated oil
nozzle valve or elevation AB power is not available for more than two
seconds and any elevation AB heavy fuel oil nozzle valve is not closed
or elevation AB power is not available for more than 2 seconds.
Elevation BC:
1. Feeder B is off or loss of elevation B power and Feeder C is off or
loss of elevation C power. This condition exists for more than two
seconds.
2. Less than two of the four “fireball” flame scanners indicate flame
on elevation “BC”.
Elevation “DE”:
1. Feeder D is off or loss of elevation D power and Feeder E is off or
loss of elevation E power. This condition exists for more than two
seconds.
2. Less than two of the four “fireball” flame scanners indicate flame
on elevation “DE”.

10. Elevation “FG”:
1. Feeder F is off or loss of elevation F power and Feeder G is off or
loss of elevation G power. This condition exists for more than two
seconds.
2. Less than two of the four “fireball” flame scanners indicate flame
on elevation “FG”.
3. One elevation GH, any heavy fuel oil nozzle valve is not closed or
elevation GH power is not available for more than two seconds.
Elevation “GH”:
1. Feeder G is off or loss of elevation G power and Feeder H is off or
loss of elevation H power. This condition exists for more than two
seconds. OR
2. At elevation GH, less than three of the four heavy fuel oil nozzle
valves are fully open or fuel flow is not adequate at the associated oil
nozzle valve or elevation GH power is not available for more than two
seconds and less than two of the four “fireball” flame scanners
indicate flame on elevation “GH” OR

11. 3. At elevation GH, less than three of the four heavy fuel oil nozzle
valves are fully open or fuel flow is not adequate at the associated oil
nozzle valve or elevation GH power is not available for more than two
seconds and any elevation GH heavy fuel oil nozzle valve is not closed
or elevation GH power is not available for more than
2 seconds.
CAUSE OF TRIP SYSTEM
A “Cause of Trip” system has been incorporated which allows the
Operator to determine the cause of a master fuel trip which was
initiated by a boiler trip command. The boiler trip commands that can
cause a “master fuel trip” memory signal to be established .
The first boiler trip command that causes a master fuel trip (both (red)
“BOILER TRIP” lights come on), will illuminate the appropriate indicator
in the CAUSE OF TRIP section on the console insert. The Data Logger
will also receive a corresponding signal.
Any successive boiler trip commands to the other indicators are
blocked. There will be only one indicator that is illuminated.

12. When the furnace purge cycle is successfully completed (PURGE
CYCLE (yellow) “PURGE COMPLETE” light is on) and a “ no master fuel
trip” memory signal is established (both (red) “BOILER TRIP” lights are
off), all CAUSE OF TRIP memories are reset and there are no
illuminated indicators.
POST PURGE EXCURSION PROTECTION
A post purge excursion circuit has been designed into the Furnace
Safeguard Supervisory System. It operates as described below:
1. During the Furnace Purge Cycle, the following conditions are
satisfied:
A. The mode permit is satisfied
B. All heavy fuel oil nozzle valves are closed
C. The heavy fuel oil trip valve is closed,
D. All pulverizers are off
E. All feeders are off
F. All flame scanners (discriminating and fireball) indicate no flame
G. Air flow is greater than 30 %

13. 2. When all of these conditions are satisfied simultaneously, a five
minute counting period is started. After the five minute counting period
expires, the following events will occur:
A. A “post purge time expired” memory signal is established and a “post
purge fan trip” signal is established if a “high or low furnace pressure
trip” signal is established.
This is indicated when the Data Logger receives a “FURNACE PRESSURE
HIGH” or a “FURNACE PRESSURE LOW” signal.
The “post purge fan trip” signal is proven established if the Data Logger
receives “POST PURGE FAN TRIP” signal. If this signal is established, the
I.D. and F.D. fans are tripped.
B. The “open upper fuel air dampers” memory signal is removed, closing
the upper fuel air dampers. Simultaneously, a thirty second counting
period is started.
When the thirty second counting period expires, the “open lower fuel
air dampers” memory signal is removed, closing the lower fuel air
dampers.
Simultaneously, a five second counting period is started.

14. When the five second counting period expires, the auxiliary air
dampers are now released from manual to the auxiliary air control
system and the “open auxiliary air dampers” signal is removed.
When any heavy fuel oil elevation has at least three of the four oil
nozzle valves fully open, the “post purge time expired” memory signal
is removed which will now prevent the “post purge fan trip” signal
from being established. When the heavy oil trip valve is moved form
the closed position (for oil recalculation), the five minute counting
period is reset.

15. Boiler Emergencies
Procedures during the following emergency conditions
1. Boiler Explosions
2. Boiler Implosions
3. Low Water Level
4. High Water Level
5. Boiler Tube Leaks
6. Master Fuel Trip
7. Reheater Protection Trip

16. Boiler Emergencies
Emergency boiler procedures :
A) Boiler explosions
a. Causes
1. Furnace explosions can be caused by an accumulation of unburned
fuel in the furnace due to incomplete combustion, loss of ignition, or
fuel valve leakage.
2. With a mixture of unburned fuel with air in explosive proportions,
and the application of heat sufficient enough to raise the
temperature of the mixture to the ignition point, explosions can
occur.
3. The accumulated fuel is ignited resulting in a greater than normal
pressure increase.
4. The fuel may enter the furnace in the unburned state in a number of
ways, for instance:
a) Through leaky main fuel or ignition fuel inlet valves on idle wind
box/burner compartments.

17. Boiler Emergencies
b) If the fires are extinguished and the if the fuel is not shutoff promptly.
c) If the fuel is not burning as rapidly as rapidly as it is entering the
furnace.
d) In starting up, if difficulty is experienced in establishing ignition.
b. Prevention
1) During start-ups maintain a high air flow (up to 30% of full load air
flow) to ensure an air rich furnace atmosphere and prevent accumulation of
explosive mixtures.
2) Be sure that the main fuel and ignition fuel inlet valves on idle fuel
compartments or burners are closed tightly and do not leak. It is advisable
to remove idle oil guns from the guide pipes, to avoid dripping.
3) Watch the fires so that the fuel may be shut off without delay if
extinguished unexpectedly. If the fires are lost, trip all main and ignition
fuel immediately. Close all trip and fuel shut off valves. Purge the furnace
at least for 5 minutes after shut down with 30% (minimum) air flow.

18. Boiler Emergencies
4) When a boiler has been idle, purge the furnace before putting igniters
in service. Be sure that the warm up fuel firing rate is high enough to
produce a flame not easily extinguished.
5)Always use an associated igniter to light off a main oil or gas nozzle.
6) Regularly check proper function of FSSS or BMS (interlocks, trips)
B) Boiler Implosions : Destructive negative pressure.
a. Causes
1) Tripping or sudden loss of fuel results in mass temperature reduction
resulting in rapid decrease in furnace pressure.
2) Rapid evacuation of heated gases by ID fans.
3) Failure of fan controls.
b. Prevention
1) The air flow to the furnace must be maintained at its pre trip value
and must not be prevented from increasing by following natural fan
curves; but positive control action to increase air flow is not allowed.

19. Boiler Emergencies – water levels
2) The flow of combustion products from a furnace must be reduced as
quickly as possible following a unit trip.
3) If the removal of fuel from the furnace can be over a 5 to 10 seconds
period (rather than instantaneously) there will be a reduction in the
magnitude of a furnace pressure excursion that follows a unit trip.
4) Further prevention of implosion can be accomplished by keeping
protective control systems in proper working order and well tuned.
C. Low Water Level
a. Causes
1. Control failure
2. BFP failure
3. Tube leaks
b. Action
1) Compare indication.

20. Boiler Emergencies- water levels
2) If the water level falls out of sight in the water gauge, due to failure of
the feed water supply or neglect of the operator, except in cases of
momentary fluctuations that might occur with extraordinary changes in
load, appropriate action should be taken at once to trip the fuel. Any
decision to continue to operate, even if only for a short time at a
reduced rating, would have to be made by someone in authority who is
thoroughly familiar with the circumstances that led to the emergency
and positively certain that the water level can be restored immediately
without damaging the boiler. In the absence of such a decision :
a) Trip all fuel immediately.
b) Shut off all steam discharged from the unit( trip turbine, steam
driven auxiliaries etc.)
c) Simultaneously, if feed water has become available and the operator
is assured that no pressure parts have been damaged, gradually
reduce the flow of feed water to the boiler by manual regulation.
This will avoid quenching of hot pressure parts with relatively cold
water. The feed water regulating valve should be closed completely
when all the steam flow from the unit has ceased.

21. Boiler Emergencies-water levels
d) Maintain a high air flow at first to hasten the cooling process.
e) If pressure parts damage is suspected, reduce the main steam
pressure gradually by opening the super heater startup drain. Open the
drum vents when the pressure drops below 1.75 bar. As the boiler cools,
reduce the air flow. Shut down the fans as soon as the unit is cool
enough for a man to enter. Drain the boiler when the drum metal
temperature is 93C. Determine the cause of low water and examine the
boiler for the effects of possible overheating such as leaks and
distortion of pressure parts.
D. High Water Level :Water impingement may cause turbine damage.
a. Causes
1) Feedwater control malfunction
2) Operator error
b. Action
1) Abnormally high water level should be avoided as it may lead to
carryover and even priming. If the water level rises above rises
above the recommended normal operating range proceed as follows

22. Boiler Emergencies-water levels
a) Reduce the water level immediately by opening the intermittent
blowdown valves.
b) Reduce the steam rate, if necessary, and place feedwater control on
manual.
2) If priming should occur, as indicated by rapid fluctuations in outlet
steam temperatures in outlet steam temperature, proceed as follows:
a) Reduce the steaming rate.
b) If the water level is abnormally high, reduce the level by opening the
intermittent blowdown valves and place feedwater control on
manual.
c) Investigate the water condition (alkalinity and solids)
d) Investigate the condition of the drum internals as soon as an
opportunity is afforded.

23. Boiler Emergency-Tube failure
Boiler tube failures : Operating a boiler with a known tube leak is not
recommended. Steam or water escaping from a small leak can cut other
tubes by impingement and set up a chain reaction of tube failures. By
the loss of water or steam, a tube failure can alter boiler circulation or
flow and result in other circuits being overheated. A tube leak can also
cause loss of ignition and, if reignition occurs, a furnace explosion. An
investigation of tube failure is very important so that the conditions
causing the tube failure can be eliminated and future failures prevented.
The investigation should include a visual inspection of the failed tube. In
some cases a laboratory analysis or consideration of background
information leading up to the tube failure is required. This information
should include the location of the failure, the length of time the unit has
been in operation, load conditions, start up and shutdown conditions,
and feed water treatment.

24. Boiler Emergencies-tube leaks
5. Tube Leaks
a. Indications of the tube leaks are
1) Feedwater flow greater than steam flow
2) Excessive desuperheater flow
3) Wetted insulation of water running down casing with no apparent
cause.
4) Excessive make up.
5) Noise from the boiler (Acoustic noise level indicators)
b. Action
1) Furnace tube leaks
a) The action taken is dependant on the size and location of the tube
leak
1) A large leak may extinguish fire or cause loss of drum level.
2) A medium size leak may force an immediate shut down.

25. Boiler Emergencies-tube leaks
3) A small leak may allow continued operation after considering its
consequences on continued operation.
b) If at all possible locate the leak
c) In the vent of failure of one or more water carrying tubes, the best
method of shutting down the unit will be dictated by the size of the
failure, the ability to maintain normal water level and the demands for
the service of the unit.
d) The following instructions regarding tube failures are of general
nature. It must be understood that conditions may arise which will
require exercise of judgment by the operators.
e) In case of a leak or tube failure which does not involve a serious drain
on the feedwater supply, the water level should be maintained and the
unit taken out of service in the normal manner.
f) If the tube failure results in a loss of water so great that the water
level cannot be maintained with the feedwater supply available, use the
method outlined below.
1) Trip all fuel

26. Boiler Emergencies-tube leaks
2) Shut off feedwater to the boiler.
3) Maintain only enough air flow to carry the escaping steam up the
stack.
4) Leave the fans in service until pressure is off the unit.
g) After the unit has cooled enough to permit a man enter it, make a
thorough inspection of pressure parts for any indication of damage
resulting from loss of water level. After the necessary repairs have been
made, apply a hydrostatic test and obtain the approval of the proper
authorities before putting the unit back in service.
2) Economizer Tubes
a) An economizer tube leak can be detected by sound and/ or
increased make up water requirements. The leak should be
detected at the earliest possible time and the unit shutdown in the
normal manner.
b) Water leaks in the economizer can cause considerable erosion
damage to the adjacent tubes. Water carried over from economizer
tube leak may cause plugging of hoppers and airheaters.

27. Boiler Emergencies-tube leaks
3) Super heater Tubes
a) A small leak in a superheater element should be investigated at the
earliest possible time, and the unit should be shut down in a normal
manner. Steam leaks in the superheater can cause considerable erosion
damage to the adjacent tubes. Any decision to continue operation with
leaks should be made this in mind.
b) A major superheater tube failure may require an emergency unit
shutdown.
6. Master Fuel Trip
a) Under conditions requiring a master fuel trip through normal
interlocks or operators action (manual trip), all fuel should be
tripped instantaneously.
b) The following steps should be taken immediately following an
emergency fuel trip.
1) Maintain the unit air flow at the pre-trip value for at least 5 minutes
to purge the system.
2) Check to ensure that all the fuel nozzles shut off valves are closed.

28. Boiler Emergencies-tube leaks
3) If all auxiliary power sources are lost during a trip, upon restoration of
power, start the ID and FD fans and purge the furnace for five minutes.
Other boiler emergencies
Air preheater fires/tripping of APH ( one fan operation)
Coal mill explosions ( may lead to boiler trip)
Loss of furnace seal
Loss of scan supply of any elevation
Loss of instrument air
Loss of cooling water to scaffold door
Bending of long retractable soot blower / furnace probe

29. Reheater Protection
Boiler will trip when any one or more of the following conditions
occur :
1. Turbine Tripped or Gen CB open and HP or LP Bypass valves
opening < 2% then after 5 sec of Time delay.
2. Turbine working (control valves >2 %) and Load shedding relay
actuated and if HP or LP Bypass opening is < 2 %,
Reheat protection will act after 10 sec. delay.
3. If Turbine is not working (HP or IP control valves < 2%) and boiler
working (No. contact of loss all fuel arming relay from FSSS) and HP
or LP Bypass valves < 2 % with a time delay of 5 Sec.
Reheat Protection will act.
Arming of Reheat Protection -Once HP & LP Bypass are open 2 %
and steam flow increases beyond 200T/hr Reheater protection will
be armed .

30. BOILER TRIP Causes
With the exception of the operator push button trip, following conditions will
automatically generate Master Fuel Trip (MFT)
• Loss Of All ID Fans
•Loss Of All FD Fans
•Less Than Two Circulating Pumps Running
•Circulating Δp Less Than 0.6 Bar
•Drum Level Low-low (-330 mm).
•Furnace Pressure More Than 330 Mmwc Or Less Than -250 Mmwc
•Loss Of All Fuel
•Air Flow Less Than 30%
•Turbine Trip
•Reheater Protection Trip
•Unit Flame Failure
•Loss Of Unit Logic Power
•Emergency Push Button.
Cause of trip system : The first boiler trip command that causes a MFT will
illuminate the appropriate indicator in the cause of trip section on the console
insert. Any successive boiler trip commands to the other indicators are
blocked. There will be only one indicator that will be glowing

31. Turbine protections
1. LOW VACUUM
( Hyd trip > 0.3 bar, electrical trip > 0.3bar)
2. HIGH AXIAL SHIFT
( 1.0 mm)
3. OVERSPEEDING OF TURBINE
( Mechanical Trip3330 rpm, electrical trip >3330 rpm)
4. MAIN OIL TANK LEVEL LL( fire protection 2)
( 1030 mm from top)
5. C. F. TANK LEVEL LL( fire protection 1)
( -115 mm )
6. LOW LUBE PRESSURE( A 4.8 bar,T 2.2 bar)
7. CONTROL OIL PRESSURE( T 3.5 bar)
8.TURBINE REMOTE PUSH BUTTON TRIP
9.FIRE PROTECTION 1 & 2(PUSH BUTTON)
10.BOILER TRIP LEADING TO TURBINE TRIP
11.GENERATOR TRIP LEADING TO TURBINE TRIP

32. Turbine protections
TURBINE ADVISORY TRIP
1. HIGH SHAFT VIBRATION / ECCENTRICITY
( A 120mic,T 200 mic)
2. HIGH BEARING VIBRATION
( A 35 mic,T 45mic)
3. HIGH BEARING METAL TEMPERATURE
( A 90C,T 120C)
4. HIGH DIFFERENTIAL EXPANSION
(HP -3/5mm,IP -2/7mm,LP -3/30mm)
5. HIGH/LOW MAIN STEAM TEMPERATURE
6.HIGH DRUM LEVEL