Garry Gill

8/19/2019 Garry Gill

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INTRODUCTION

Guru Nanak Dev Thermal Power Plant is a coal-based plant. The requirement of coal for

four units based on specific fuel consumption of 0.60 k ! k"h. The conve#in and crushin

s#stem will have the same capacit# as that of the unloadin s#stem. The coal comes in as lare

pieces. This coal is fed to primar# crushers$ which reduce the si%e of coal pieces from &00mm to

'(0mm. Then the coal is sent to secondar# crusher throuh forward conve#ors where it is

crushed from '(0mm to )00mm as required at the mills. Then the coal is sent to boilers with the

help of primar# fans. The coal is burnt in the boiler. *oiler includes the pipes carr#in water

throuh them+ heat produced from the combustion of coal is used to convert water in pipes into

steam. This steam enerated is used to run the turbine. "hen turbine rotates$ the shaft of

enerator$ which is mechanicall# coupled to the shaft of turbine$ ets rotated so$ three phase

electric suppl# is produced.

The basic requirements are,-

uel /coal

*oiler

1team turbine

Generator

2sh handlin s#stem

3nit au4iliaries


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*57 81T95: 9 T87 P;2NT

Due to hih rate of increasin population da# b# da#$ widenin ap between power demand and

its availabilit# was one the basic reason for envisain the G.N.D.T.P. for the state of Puni.

The historic town of bathinda was selected for this first and prestiious thermal pro


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2vailabilit# of fuel

2sh disposal facilities

1pace requirement

Nature of land

2vailabilit# of labour

Transport facilities

Public societ# problems

Development of *ackward 2rea

P;2NT 12;7NT 72T3571

PROJECT AREA:-

Power plant )CA acres

2sh disposal A&(

;ake 'A0

5esidential colon# )A(

?arshallin #ard )(6

Total area 'A0&

T9T2; B91T, - 5s. ''( crores

1T2T9N B2P2BT:, - four units of ''0?".each


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BOILER:-

?anufacturers *.8.7.;.

?a4imum continuous ratin /?.B.5. C@( T!hr.

1uperheater outlet pressure 'C= k!cm

5eheater outlet pressure CC.A k!cm

inal superheater!reheater temperature (&0°B

eed water temperature )&0°B

7fficienc# A6E

Boal consumption per da# per unit '&00 tones /2ppro4imate

STEAM TURBINE:-


5ated output ''0 ?".

5ated speed C000 r.p.m.

Number of c#linders three

5ated pressure 'C0 k!cm

5ated temperature (C(°B

Bondenser vacuum 0.= k!cm


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GENERATOR:-


5ated output

/3nit- ' F ) ')(000H2

/3nit -C F & 'C@000H2

Generator voltae ''000 volts

5ated phase current

/unit I' F ) 6(60 2mps.

/unit IC F & @))0 2mps.

Generator coolin h#droen

BOILER FEED PUMPS:-

Number per unit two of '00E dut# each

T#pe centrifual

5ated dischare &&( T!hr.

Dischare head '=60 ?"B.

1peed &(00 r.p.m.

CIRCULATING WATER PUMPS:-

Numbers for two units five of (0E dut# each


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T#pe mi4ed flow

5ated dischare A600 T!hr.

Dischare head )& ?"B.

COOLING TOWERS:-

Numbers four

"ater cooled 'A000 T!hr.

Boolin rane '0°B

8eiht ')0!') metres

COAL PULVERISING MILLS:-

Numbers three per unit

T#pe drum-ball

5ated output )@ T!hr.

Boal bunkers '6 per unit

RATING OF 6.6 KV AUXILLIARY MOTORS:-

Boal mill 6C0 "

Hapour fan C)0 "


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B.". an A00!@&6 "

Boal crusher ()0 "

Primar# air fan C)0 "

orced drauht fan C)0 "

*oiler feed pump C(00 "

nduced drauht fan =00!'000 "

Bondensate pump '@( "

"95NG 9 T87 T875?2; 57P95T

Coal received from collieries in the rail wagon is mechanically unloaded by

Wagon Tippler and carried by belt Conveyor ystem !oiler Raw Coal !un"ers after

crushing in the coal crusher# The crushed coal when not re$uired for Raw Coal

!un"er is carried to the coal storage area through belt conveyor# The raw coal

feeder regulates the $uantity of coal from coal bun"er to the coal mill% where the

coal is pulveri&ed to a 'ne powder# The pulveri&ed coal is then suc"ed by the vapour

fan and 'nally stored in pulveri&ed coal bun"ers# The pulveri&ed coal is then pushed

to boiler furnace with the help of hot air steam supplied by primary air fan# The coal

being in pulveri&ed state gets burnt immediately in the boiler furnace% which is

comprised of water tube wall all around through which water circulates# The water

gets converted into steam by heat released by the combustion of fuel in the

furnace# The air re$uired for the combustion if coal is supplied by forced draught


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fan# This air is however heated by the outgoing (ue gases in the air heaters before

entering the furnace#

The products of combustion in the furnace are the flue ases and the ash. 2bout )0E of

the ash falls in the bottom ash hopper of the boiler and is periodicall# removed mechanicall#.

The remainin ash carried b# the flue ases$ is separated in the electrostatic precipitators and

further disposed off in the ash dampin area. The cleaner flue ases are let off to atmosphere

throuh the chimne# b# induced drauht fan.

The chemicall# treated water runnin throuh the water walls of boiler furnace ets

evaporated at hih temperature into steam b# absorption of furnace heat. The steam is further

heated in the super heater. The dr# steam at hih temperature is then led to the turbine

comprisin of three c#linders. The thermal ener# of this steam is utili%ed in turbine for rotatin

its shaft at hih speed. The steam dischared from hih pressure /8.P. turbine is returned to

boiler reheater for heatin it once aain before passin it into the medium pressure /?.P.

turbine. The steam is then let to the coupled to turbine shaft is the rotor of the enerator$ which

produces electricit#. The power from the enerator is pumped into power rid s#stem throuh the

enerator transformer b# steppin up the voltae.


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The steam after doin the useful work in turbine is condensed to water in the condenser for

rec#clin in the boiler. The water is pumped to deaerator from the condenser b# the condensate

e4traction pumps after bein heated in the low pressure heater /;.P.8 from the deaerator$ a hot

water storae tank. The boiler feed pump dischare feed water to boiler at the economi%er b# the

hot flue ases leavin the boiler$ before enterin the boiler drum to which the water walls and

super heater of boiler are connected.

The condenser is havin a lare number of brass tubes throuh which the cold water is

circulated continuousl# for condensin the steam passin out sides the surface of the brass tubes$

which has dischared down b# circulatin it throuh the coolin tower shell. The natural drauht

of cold air is created in the coolin tower$ cools the water fall in the sump and is then recirculated

b# circulatin water pumps to the condenser.

G7N752; D71B5PT9N

BOILER FEED PUMP:-

2s the heart is to human bod#$ so is the boiler feed pump to the steam power plant. t is used

for rec#clin feed water into the boiler at a hih pressure for reconversion into steam. Two nos.

'00E dut#$ barrel desin$ hori%ontal$ centrifual multistae feed pumps with h#draulic couplin


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are provided for each unit. This is the larest au4iliar# of the power plant driven b# C(00 "

electric motor. The capacit# of each boiler at GURU NANAK DEV THERMAL PLANT is C@(

tones!hr. The pump which supplies feed water to the boiler is named as boiler feed pump. This is

the larest au4iliar# in the unit with '00E capacit# which takes suction of feed water from feed

water tank and supplies to the boiler drum after preheatin the same in 8P-'$ 8P-) and

economi%er. The deliver# capacit# of each boiler feed pump is &&( tones!hr. to meet better

requirements correspondin to the various loads$ to control steam temperature$ boiler make up

water etc. The detailed particulars checkin of protections and inter locks$ startin permission

etc. are as below,-

Particulars of BFP and its main motor :-

BOILER FEED PUMP: - The ''0 ?" turbo set is provided with two boiler feed pumps$ each of '00E of total quantit#. t is of barrel desin and is of hori%ontal

arranement$ driven b# an electric motor throuh a h#draulic couplin.

T#pe )00 8

No. of staes 6

Deliver# capacit# &&( t!hr.

eed water temperature '(A°

B

1peed &(00 rpm

Pressure at suction A.C0 k!cm

1tuffin bo4 mechanical seal

;ubrication of pump b# oil under pressure

2nd motor bearin supplied b# h#draulic couplin

Bonsumption of coolin water )C0 ;!min.

WATER TREATMENT PLANT:-

The water before it can be used in the boiler has to be chemicall# treated$ since untreated water

results in scale formation in the boiler tubes especiall# at hih pressure and temperatures. The


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water is demineralised b# on 74chane Process. The water treatment plant has production

capacit# of 'A00 Tonnes per da# for meetin the make-up water requirement of the power

station.

COAL MILL:-

Boal ?ill pulveri%es the raw coal into a fine powder before it is burnt in the boiler furnace. The

pulveri%in of coal is achieved with the impact of fallin steel balls$ weihin ().( tonnes$

contained in the mill drum rotatin at a slow speed of '@.( r.p.m. The raw coal is dried$ before

pulveri%in$ with inert hot flue ases tapped from the boiler. Three coal mills each with a

pulveri%in capacit# of )@ T!hr. are provided for one unit.

INDUC)D DR*U+,T -*N./

Two nos. a4ial flow nduced Drauht ans are provided for each unit to e4haust ash laden flue

ases from boiler furnace throuh dust e4traction equipment and to chimne#. The fan is driven

b# an electric motor throuh a fle4ible couplin and is equipped with remote controlled

reulatin vanes to balance drauht conditions in the furnace. The fan is desined to handle hot

flue ases with a small percentae of abrasive particles in suspension.

CONTRO0 ROO1./

The control room is the operational nerve center of the power plant. The performance of all the

equipments of the plant is constantl# monitored here with the help of sophisticated

instrumentation and controllers. 2n# adverse deviation in the parameters of various s#stems is

immediatel# indicated b# visual and audio warnin and suitable corrective action is taken$

accordinl#. The control room is air conditioned to maintain the desired temperature for proper

functionin of the instruments.

W*+ON TI220)R./

The coal received from the collieries$ in more than '00 rail waons a da#$ is unloaded

mechanicall# b# two nos. waon tipplers out of which one serves as a standb#. 7ach loaded

waon is emptied b# tipplin it in the underround coal hopper from where the coal is carried b#

conve#or to the crusher house. 2rranements have been provided for weihin each rail waon


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before and after tipplin. 7ach tippler is capable of unloadin 6-A rail waons of (( tonnes

capacit# in an hour.

CRU,)R ,OU)./

Boal unloaded b# the waon tippler is carried to crusher house throuh conve#ors for crushin.

Two nos. hammer t#pe coal crushers are provided$ which can crush coal to a si%e of '0 mm. The

crushed coal is then supplied to *oiler 5aw Boal *unkers. The surplus coal is carried to coal

storae area b# series of conve#ors. Brushin of coal is an essential requirement for its optimum

pulveri%in and safe storae.

COOLING TOWERS:-

Boolin Towers of the power plant are the land mark of the *athindaBit# even for a far distance

of A-'0 kilometers. 9ne coolin tower is provided for each unit for coolin 'A000 tones of water

per hour b# '0°B. coolin towers are massive erro-concrete structure havin h#perbolic profile

creatin natural drauht of air responsible for achievin the coolin effect. Boolin tower is as

hih as &0 store# buildin.

BOILER:-

t is a sinle drum$ balanced drauht$ natural circulation$ reheat t#pe$ vertical combustion

chamber consists of seamless steel tubes on all its sides throuh which water circulates and is

converted into steam with the combustion of fuel. The temperature inside the furnace where the

fuel is burnt is of the order of '(00°B. The entire boiler structure is of &)meter heiht.


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BOILER CHIMNEY:-

The flue from the boiler$ after removal of ash in the precipitators$ are let off to atmosphere

throuh boiler chimne#$ a tall ferro-concrete structure standin as hih as the historic

Jutab?inar. our chimne#s$ one for each unit$ are installed. The chimne# is lined with fire

bricks for protection of ferro-concrete aainst hot flue ases. 2 protective coatin of acid

resistant paint is applied outside on its top '0 meters.

CIRCULATING WATER PUMP:-

Two nos. of circulatin water pumps provided for each unit$ circulate water at the rate of '@)00

T!hr. in a closed c#cle comprisin of Turbine Bondenser and BoolinTower. 2n additional

Birculatin "ater Pump provided serves b# for two units. The water requirement for bearin

coolin of all the plant au4iliaries is also catered b# these pumps.

B92; ?;NG P;2NT

1ince G.N.D.T.P. units are primaril# coal fired units so each boiler is provided with closed

millin circuits to pulveri%e the raw coal which is received from coal conve#in s#stem after

coal crushes before it is fired in the furnace. The necessit# of pulveri%in the coal is to be

ensurin its ma4imum possible combustion in the furnace. The coal data for units are, -

COAL DATA UNITS 1 & 2 UNITS 3 & 4

T#pe of Boal

Net Balorific Halue

?oisture

*ituminous

&C00 cal!k

'0 E

*ituminous

&@)@ cal!

@.( E


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2sh Bontent

Holatile ?atter ncombustible

nlet of Boal

C0 E

)& E

'0 mm

C) E

)@ E

)0 mm

5aw coal of pulveri%ed in the millin circuit and the output fromthe mill is fine coal. ma4imum

si%e '0 mm I )0 mm is

COAL MILL:-

These are mainl# of two t#pes,-

i *all ?ills

ii *owl ?ills

Ball Mll!: -n *all ?ills there are steel balls which are revolvin in hori%ontal c#lindrical

drum. These balls are free from an# shaft and balls are touchin with each other and with internal

bod# of drum. These t#pes of mills are at *athinda Thermal Plant. 9n the other hand$ bowl mills

part of the mill contain drive s#stem i.e. it contains 6.6 kH electric motor and ear s#stem whichtranslates the revolution about hori%ontal a4is to revolve about vertical a4is. The revolvin

vertical a4is contains a bowl about the drivin s#stem. This bowl is fi4ed with drivin and

revolvin with shaft. There are also three rollers which are suspended at some inclination$ so that

there is a ap of few mm between roller surface. These rollers are free to rotate about the a4is.


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Bowl Mills: The coal is rinded and then fed into the mill at the center or near of revolvin

bowl. t passes between the rindin rin in revolvin bowl and rolls as centrifual force causes

the material to travel towards the out perimeter of bowl. The sprins$ which load the rolls$ impart

the necessar# force for rindin. The partiall# pulveri%ed coal continue oin up and down and

over the ede of bowl.

!AGON TIPPLER

The tippler is desined to work on the followin c#cle of operation,-

Tippin =0 seconds

Pause (-') seconds

5eturn =0 second1

"eihin C0 seconds

Total )'(-))) seconds

2llowin A( seconds for waon chanin it will be seen that ') eiht-wheel waons or )& four-wheel waons per hours can be tipped. 8owever since the coal carr#in capacit# is (00 tones per

hour load of ') waons comes to A to = per hour.

CRUSHER HOUSE:

The crusher house accommodates the dischare ends of the conve#or &2$ &* receivin ends of

conve#or (2$ (* and conve#or @2 and @*$ two crushers$ vibratin feeders and necessar# chute

work. There are two crushers each driven b# @008.P. electric motor$ C phase$ (0 c#cles and 6.6


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kH suppl#. The ma4imum si%e of the crushed coal is '0mm. The capacit# of each crusher is (00

tones!hr. one crusher works at a time and the other is standb#. rom the crusher the coal can be

fed either to the conve#ors (2$ (* or @2$ @* b# ad


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t is main part of 1T72? G7N52T95K it is an assembl# of a lare no. of vertical riser tubes

embedded in refractor# walls. There are two boilers one for each unit. The t#pe of the boiler is

N2T352; B5B3;2T9N 52D7NT 1NG;7 57872T boiler. The four refector# walls

make a closed bo4 called 352NB7 .The walls are iven special names. These are+

' 5G8T "2;; consistin 'C0 T3*71.

) ;7T "2;; consistin 'C0 T3*71.

C 59NT "2;; consistin 'A' T3*71.& 5725 "2;; consistin 'A' T3*71.

9n the riht and left wall$ the "ND *9L71 are installed. Thus there are our urnace

Boroners.

The water tubes cool the walls b# absorbin the heat and transferrin it to the water runnin in

them. The tubes are embedded in refector# walls ver# close /the Gap between two tubes is '0

mm. The inner diameter of the tubes is 6C.(mm.

>31TB2T9N 9 T87 *9;75 T:P7+

The t#pe of boiler is "2T75 T3*7$ N2T352; B5B3;2T9N$ 52D7NT 1NG;7

57872T boiler. The meanin of each word has been e4plained below+

"2T75 T3*7+ t mean the water runs in the tubes and the fire is outside the tubes.


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N2T352; B5B3;2T9N+ The B5B3;2T9N word mean how the water is raised in the

walls. "e know that the water upwards we have to suppl# some e4ternal power e..$ some pump

s#stemK *ut here a law dose this work naturall#. The saturated water collected at the bottom

known as 5NG 872D75. The water rises from it in riser pipes naturall#. There is a T"9

P8217 ?LT357 of "2T75 and 1T72? in risers. There is a D757NB7 *7T"77N the

D7N1T71 of the ?LT357 and 12T352T7D "2T75 in 5in 8eader. 2lso there is a

1T2TB 872D. Due to the result of both factors there is N2T352; B5B3;2T9N operates

in boiler.

52D7NT T:P7, 2s the name implies$ the heat is transferred from combustion as to the water

b# 52D2T9N. The heat is then B9D3BT7D to water tubes and throuh the thickness of tubes. There is B9NH7BT7D to the T"9 P8217D ?LT357.

1NG;7 57872T+ t implies that the s#stem is reheated onl# once . "hen the steam oes to 8

Turbine its temperature decreases from (&0 de to C&C de. t is then send to reheater to increase

the temp to aain (&0 de.

' t should be absolutel# reliable and capable of raisin ma4imum amount of steam for

minimum fuel consumption$ attention$ initial cost and maintenance chares.

) t should be liht in weiht and should occup# small space

C The refractor# s#stem should be as little as possible$ but sufficient to secure eas# inition

and smokeless combustion of fuel on reduced load.

?anufacturers *.8.7.;

?a4imum continuous ratin C@( T! hr

1uperheater outlet Pressure 'C= !cm)

inal 1uperheater Temp. (&00B

eed "ater Temp. )&00B7fficienc# A6E

Boal Bonsumption Per da# '&00 tones /appro4.


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;2?7 1B2NN75

2 "l#$% %'%('o) is a sensor desined to detect and respond to the presence of a flame or fire.

5esponses to a detected flame depend on the installation$ but can include soundin an alarm$

deactivatin a fuel line /such as a propane or a natural as line$ and activatin a fire suppression

s#stem. "hen used in applications such as industrial furnaces$ their role is to provide

confirmation that the furnace is properl# lit+ in these cases the# take no direct action be#ond

notif#in the operator or control s#stem. 2 flame detector can often respond faster and more

accuratel# than a smoke or heat detector due to the mechanisms it uses to detect the flame.

https://en.wikipedia.org/wiki/Sensorhttps://en.wikipedia.org/wiki/Sensorhttps://en.wikipedia.org/wiki/Flamehttps://en.wikipedia.org/wiki/Firehttps://en.wikipedia.org/wiki/Firehttps://en.wikipedia.org/wiki/Propanehttps://en.wikipedia.org/wiki/Propanehttps://en.wikipedia.org/wiki/Propanehttps://en.wikipedia.org/wiki/Natural_gashttps://en.wikipedia.org/wiki/Flamehttps://en.wikipedia.org/wiki/Firehttps://en.wikipedia.org/wiki/Propanehttps://en.wikipedia.org/wiki/Natural_gashttps://en.wikipedia.org/wiki/Sensor


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9PTB2; ;2?7 D7T7BT951


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lame detector t#pe reions

Ul')#*iol%'3ltraviolet /3H detectors work b# detectin the 3H radiation emitted at the instant of inition.

"hile capable of detectin fires and e4plosions within CI& milliseconds$ a time dela# of )IC

seconds is often included to minimi%e false alarms which can be triered b# other 3H sources

such as lihtnin$ arc weldin$ radiation$ and sunliht. 3H detectors t#picall# operate

with wavelenths shorter than C00 nm. The solar blind 3H wavelenth band is also easil#

blinded b# oil# contaminants.

N%#) IR #))#+ Near infrared /5 arra# flame detectors$ also known as visual flame detectors$

emplo# flame reconition technolo# to confirm fire b# anal#%in near 5 radiation usina chare-coupled device

I,")#)%nfrared /5 flame detectors monitor the infrared spectral band for specific patterns iven off b#

hot ases. These are sensed usin a speciali%ed fire-fihtin thermal imain camera /TB$ a

t#pe of thermo raphic camera. alse alarms can be caused b# other hot surfaces and

backround thermal radiation in the area. "ater on the detectorMs lens will reatl# reduce the

accurac# of the detector$ as will e4posure to direct sunliht. 2 sinle-frequenc# 5 flame detector

is t#picall# sensitive to wavelenths around &.& micrometers$ which is a spectral characteristic

peak of hot carbon dio4ide as is produced in a fire. The usual response time of an 5 detector is

CI( seconds.

UV-IR

https://en.wikipedia.org/wiki/Ultraviolethttps://en.wikipedia.org/wiki/Lightninghttps://en.wikipedia.org/wiki/Arc_weldinghttps://en.wikipedia.org/wiki/Arc_weldinghttps://en.wikipedia.org/wiki/Radiationhttps://en.wikipedia.org/wiki/Sunlighthttps://en.wikipedia.org/wiki/Sunlighthttps://en.wikipedia.org/wiki/Wavelengthhttps://en.wikipedia.org/wiki/Wavelengthhttps://en.wikipedia.org/wiki/Nanometrehttps://en.wikipedia.org/wiki/Infraredhttps://en.wikipedia.org/wiki/Infraredhttps://en.wikipedia.org/wiki/Charge-coupled_devicehttps://en.wikipedia.org/wiki/Charge-coupled_devicehttps://en.wikipedia.org/wiki/Infraredhttps://en.wikipedia.org/wiki/Thermal_imaging_camera_(firefighting)https://en.wikipedia.org/wiki/Thermographic_camerahttps://en.wikipedia.org/wiki/Thermographic_camerahttps://en.wikipedia.org/wiki/Thermal_radiationhttps://en.wikipedia.org/wiki/Carbon_dioxidehttps://en.wikipedia.org/wiki/Ultraviolethttps://en.wikipedia.org/wiki/Lightninghttps://en.wikipedia.org/wiki/Arc_weldinghttps://en.wikipedia.org/wiki/Radiationhttps://en.wikipedia.org/wiki/Sunlighthttps://en.wikipedia.org/wiki/Wavelengthhttps://en.wikipedia.org/wiki/Nanometrehttps://en.wikipedia.org/wiki/Infraredhttps://en.wikipedia.org/wiki/Charge-coupled_devicehttps://en.wikipedia.org/wiki/Infraredhttps://en.wikipedia.org/wiki/Thermal_imaging_camera_(firefighting)https://en.wikipedia.org/wiki/Thermographic_camerahttps://en.wikipedia.org/wiki/Thermal_radiationhttps://en.wikipedia.org/wiki/Carbon_dioxide


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These detectors are sensitive to both 3H and 5 wavelenths$ and detect flame b# comparin the

threshhold sinal of both ranes. This helps minimi%e false alarms.

IR-IR "l#$% %'%('io,

Dual 5 /5!5 flame detectors compare the threshold sinal in two infrared ranes. 9ften one

sensor looks at the &.& micrometer carbon dio4ide /B9) emission$ while the other sensor looks

at a reference frequenc#. 1ensin is B9) emission is appropriate for h#drocarbon fuels+ for

non-carbon based fuels$ e..$ h#droen$ the broadband water bands are sensed.

IR3 "l#$% %'%('io,

Triple-5 flame detectors compare three specific wavelenth bands within the 5 spectral reion

and their ratio to each other. n this case one sensor looks at the &.& micrometer rane while the

other sensors look at reference wavelenths both above and below &.&. This allows the detector

to distinuish between non-flame 5 sources and actual flames which emit hot B9) in the

combustion process. 2s a result$ both detection rane and immunit# to false alarms can be

sinificantl# increased. 5C detectors can detect a 0.'m)/' ft) asoline pan fire at up to 6( m

/)'( ft in less than ( seconds. Triple 5s$ like other 5 detector t#pes$ are susceptible to blindin

b# a la#er of water on the detectorMs .?ost 5 detectors are desined to inore constant

backround 5 radiation$ which is present in all environments. nstead the# are desined to

detect suddenl# chanin or increasin sources of the radiation. "hen e4posed to chanin

patterns of non-flame 5 radiation$ 5 and 3H!5 detectors become more prone to false alarms$

while 5C detectors become somewhat less sensitive but are more immune to false alarms.

Visi.l% s%,so)s

n some detectors$ a sensor for visible radiation /liht is added to the desin in order to better

discriminate aainst false alarms or to improve the detection rane.

Vi%o

Blosed-circuit television or a web camera can be used for visual detection of

/wavelenths between 0.& and 0.@ m. 1moke or fo can limit the effective rane of these$ since

the# operate solel# in the visible spectrum.

Io,i/#'io, (0))%,' "l#$% %'%('io,

The intense ioni%ation within the bod# of a flame can be measured b# means of a current that

flows when a voltae is applied b# the phenomena of lame 5ectification. This current can be

https://en.wikipedia.org/wiki/Closed-circuit_televisionhttps://en.wikipedia.org/wiki/Web_camerahttps://en.wikipedia.org/wiki/Web_camerahttps://en.wikipedia.org/wiki/Web_camerahttps://en.wikipedia.org/wiki/Wavelengthhttps://en.wikipedia.org/wiki/Smokehttps://en.wikipedia.org/wiki/Smokehttps://en.wikipedia.org/wiki/Foghttps://en.wikipedia.org/wiki/Foghttps://en.wikipedia.org/wiki/Flame_rectificationhttps://en.wikipedia.org/wiki/Flame_rectificationhttps://en.wikipedia.org/wiki/Closed-circuit_televisionhttps://en.wikipedia.org/wiki/Web_camerahttps://en.wikipedia.org/wiki/Wavelengthhttps://en.wikipedia.org/wiki/Smokehttps://en.wikipedia.org/wiki/Foghttps://en.wikipedia.org/wiki/Flame_rectification


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used to verif# flame presence and qualit#. 1uch detectors are used in lare industrial process as

heaters and are connected to the flame control s#stem. The# usuall# act as both flame qualit#

monitors and for flame failure detection.

These t#pes of sensors are also common in a variet# of household as furnaces.

T%)$o(o0l% "l#$% %'%('io,

Thermocouples are used e4tensivel# for monitorin flame presence in combustion heatin

s#stems and as cookers. 2 common use in these installations is to cut off the suppl# of fuel if

the flame fails$ in order to prevent unburned fuel from accumulatin. These sensors measure heat

and therefore are commonl# used to determine the absence of a flame. This can be used to verif#

the presence of a Pilot flame.

Types of pressure measurements

1ilicon resistive pressure sensors

Pressure sensors can be classified in terms of pressure ranes the# measure$ temperature ranes

of operation$ and most importantl# the t#pe of pressure the# measure. Pressure sensors are

variousl# named accordin to their purpose$ but the same technolo# ma# be used under

different names.

• A.sol0'% )%ss0)% s%,so)

This sensor measures the pressure relative to perfect vacuum.

• G#0% )%ss0)% s%,so)

This sensor measures the pressure relative to atmospheric pressure. 2 tire pressure aue is an

e4ample of aue pressure measurement+ when it indicates %ero$ then the pressure it is measurin

is the same as the ambient pressure.

• V#(00$ )%ss0)% s%,so)

This term can cause confusion. t ma# be used to describe a sensor that measures pressures

below atmospheric pressure$ showin the difference between that low pressure and atmospheric

pressure /i.e. neative aue pressure$ but it ma# also be used to describe a sensor that measures

low pressure relative to perfect vacuum /i.e. absolute pressure.

• Di""%)%,'i#l )%ss0)% s%,so)

https://en.wikipedia.org/wiki/Furnacehttps://en.wikipedia.org/wiki/Furnacehttps://en.wikipedia.org/wiki/Furnacehttps://en.wikipedia.org/wiki/Thermocouplehttps://en.wikipedia.org/wiki/Pilot_lighthttps://en.wikipedia.org/wiki/Vacuumhttps://en.wikipedia.org/wiki/Vacuumhttps://en.wikipedia.org/wiki/Atmospheric_pressurehttps://en.wikipedia.org/wiki/Furnacehttps://en.wikipedia.org/wiki/Thermocouplehttps://en.wikipedia.org/wiki/Pilot_lighthttps://en.wikipedia.org/wiki/Vacuumhttps://en.wikipedia.org/wiki/Atmospheric_pressure


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This sensor measures the difference between two pressures$ one connected to each side of the

sensor. Differential pressure sensors are used to measure man# properties$ such as pressure drops

across oil filters or air filters$ fluid levels /b# comparin the pressure above and below the liquid

or flow rates /b# measurin the chane in pressure across a restriction. Technicall# speakin$

most pressure sensors are reall# differential pressure sensors+ for e4ample a aue pressure

sensor is merel# a differential pressure sensor in which one side is open to the ambientatmosphere.

• S%#l% )%ss0)% s%,so)

This sensor is similar to a aue pressure sensor e4cept that it measures pressure relative to some

fi4ed pressure rather than the ambient atmospheric pressure /which varies accordin to the

location and the weather.

a Gaue Pressure b 2bsolute Pressure

c Differential Pressure

*ut the# are all related to each other

# G#0% P)%ss0)% is $%#s0)% wi' )%"%)%,(% 'o #'$os%)i( )%ss0)% 5l%#s% s%% 6737

n our e4ample above we e4plained that we had to remove atmospheric pressure to measure the

weiht of the fi%%# drink and because it was on the outside of the bottle we could measure it. n

da# to da# practice$ pressure measurement that uses atmospheric pressure as its referece iscalled G#0% P)%ss0)%. To indicate that this is what has been done$ 3nits of measurement are

noted with the OO Pascals Gaue /Pa or Pound per 1quare nch Gaue /Psi abbreviationsare used.

2ll pressure aues$ sensors$ transducers and transmitters that measure aue pressure actuall#measure the difference between atmospheric pressure and the pressure to be measured as shown

in fiC.

. A.sol0'% P)%ss0)% is $%#s0)% wi' )%"%)%,(% 'o V#(00$7

n some applications the variation in atmospheric pressure ma# affect our calculation. 2s ane4ample the as in our fi%%# drink chanes in si%e with atmospheric pressure$ so to ensure we are

consistant with the riht amount of as$ we in


26/32

To measure absolute pressure it is possible to meaure both aue pressure and atmospheric

pressure. *ut in realit# most absolute pressure aues$ sensors$ transducers and transmitters that

measure absolute pressure do so b# measurin the difference between a reference vacuum andthe pressure to be measured as shown in fi).

( Di""%)%,'i#l P)%ss0)% is ,o' $%#s0)% wi' )%"%)%,(% 'o # s%(i"i( )%"%)%,(% )%ss0)% 5s%%

6747

3nlike Gaue or 2bsolute pressure transmitters$ Differential Pressure Transmitters do not

attempt to fi4 the reference. mportantl# an increase in differential can be the result of increasinone of the pressures or decreasin the other.

2n increase in differential pressure would occur if P' became smaller OR if P) became larer. na similare wa#$ a decrease in differential pressure would occur if P' became larer 95 if P)

became smaller. The differential pressure measurement is not concerned whether the lower of the

two pressures is at a vacuum$ atmospheric or some other pressure. t is onl# interested in thedifference between the two pressures bein measured.

The fundamental of differential pressure measurement is established.

Not all aues$ sensors$ transducers and transmitters that measure differential pressure actuall#measure the difference between two pressure as shown in fi&. 1ome devices attempt to measure

two atmospheric or aue pressures and then mathematicall# calculate the difference. Thismethod in our opinion is flawed$ as it multiplies uncertainl# with the number of measurements

made. f #ou would like to know more about this sub


27/32

R)IT*NC) T)12)R*TUR) D)T)CTOR 3RTD4 / 2RINCI20) O- O2)R*TION

2n 5TD /resistance temperature detector is a temperature sensor that operates on the

measurement principle that a materialKs electrical resistance chanes with temperature. The

relationship between an 5TDKs resistance and the surroundin temperature is hihl# predictable$allowin for accurate and consistent temperature measurement. *# suppl#in an 5TD with a

constant current and measurin the resultin voltae drop across the resistor$ the

5TDKs resistance can be calculated$ and the temperature can be determined.

RTD 1aterials

Different materials used in the construction of 5TDs offer a different relationship between

resistance and temperature. Temperature sensitive materials used in the construction of 5TDinclude platinum$ nickel$ and copper+ platinum bein the most commonl# used. mportantcharacteristics of an 5TD include the temperature coefficient of resistance /TB5$ the nominal

resistance at 0 derees Belsius$ and the tolerance classes. The TB5 determines the relationship

between the resistance and the temperature. There are no limits to the TB5 that is achievable$ but

the most common industr# standard is the platinum CA(0 ppm!. This means that the resistanceof the sensor will increase 0.CA( ohms per one deree Belsius increase in temperature. The

nominal resistance of the sensor is the resistance that the sensor will have at 0 derees Belsius.

2lthouh almost an# value can be achieved for nominal resistance$ the most common is the platinum '00 ohm /pt'00. inall#$ the tolerance class determines the accurac# of the sensor$

usuall# specified at the nominal point of 0 derees Belsius. There are different industr# standards

that have been set for accurac# includin the 21T? and the 7uropean DN. 3sin the values of TB5$ nominal resistance$ and tolerance$ the functional characteristics of the sensor are defined.

RTD Con'gurations

n addition to different materials$ 5TDs are also offered in two ma


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dimensions that lead to better response times and packain capabilities. or a lon time wire

wound sensors featured much better accurac#. Thanks to recent developments$ however$ there is

now thin film technolo# capable of achievin the same level of accurac#.

Operations of RTD

2n 5TD takes a measurement when a small DB current is supplied to the sensor. The current

e4periences the impedance of the resistor$ and a voltae drop is e4perienced over the resistor.Dependin on the nominal resistance of the 5TD$ different suppl# currents can be used. To

reduce self-heatin on the sensor the suppl# current should be kept low. n eneral$ around 'm2

or less of current is used.

2n 5TD can be connected in a two$ three$ or four-wire confiuration. The two-wireconfiuration is the simplest and also the most error prone. n this setup$ the 5TD is connected

b# two wires to a "heatstone bride circuit and the output voltae is measured. Thedisadvantae of this circuit is that the two connectin lead wire resistances add directl# twothe 5TDKs resistance and an error is incurred.

5/Wire Con'guration

The four-wire confiuration consists of two current leads and two potential leads that measurethe voltae drop across the 5TD. The two potential leads are hih resistance to neate the effect

of the voltae drop due to current flowin durin the measurement. This confiuration is ideal

for cancelin the lead wire resistances in the circuit as well as eliminatin the effects of different

lead resistances$ which was a possible problem with the three-wire confiuration. The four-wireconfiuration is commonl# used when a hihl# accurate measurement is required for the

application.

6/Wire Con'guration

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The four-wire confiuration consists of two current leads and two potential leads that measure

the voltae drop across the 5TD. The two potential leads are hih resistance to neate the effect

of the voltae drop due to current flowin durin the measurement. This confiuration is idealfor cancelin the lead wire resistances in the circuit as well as eliminatin the effects of different

lead resistances$ which was a possible problem with three-wire confiuration. The four-wire

confiuration is commonl# used when a hihl# accurate measurement is required for theapplication.

7/Wire Con'guration

n combination with the wirin diarams shown$ a more comple4 circuit is often emplo#ed.There are man# different options for circuits when workin with an 5TD. The two most

important features of this circuit are current eneration and sinal conditionin. or purposes of

linearit#$ it is important that the current eneration circuit supplies a stable e4citation to the 5TD.

9nce a stable e4citation current is applied to the 5TD$ the sinal conditionin path of the circuitcancels lead resistances$ ains the sinal and converts the sinal to diital usin an 2DB$ which

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can then be read b# a controller.

Temperature 1witch

Temperature switches /also called thermostats$ aquastats or free%estats dependin on application

are commonl# used in DDB control s#stems to provide a diital input when a process medium

temperature rises or falls to a set temperature. 1witches with a number of different operatin

principles are manufactured. 1ome of the common t#pes include bimetallic$ fluid thermal

e4pansion$ free%estat and electronic.

*imetallic temperature switches use a bonded ObimetalO strip consistin of two dissimilar metals

with different thermal coefficients of e4pansion. "hen the temperature chanes$ the metals

e4pand or contract at different rates causin the strip to bend. Harious confiurations such as

coiled elements are used to increase the thermal movement to cause two contacts to come

toether or separate. 1ome confiurations use the bimetallic principle to chane the orientation

of a bulb containin liquid mercur# so that the mercur# flows into contact with two electrodes$

completin the circuit.

luid thermal e4pansion temperature switches use the principle of thermal e4pansion of a fluid to

cause displacement of a bellows$ diaphram$ bourdon tube$ or piston to open or close a set of

contacts. luid s#stem based temperature switches can be connected to a remote fluid containin

bulb b# a capillar# tube$ allowin the switch element to be remote from the sensin bulb.

iure ).6- 5emote *ulb Thermostat

The free%estat is commonl# used to prevent water or steam coils in air handlin units from

free%in. ree%estats use a fluid that is a saturated vapor at the switch set point temperature. This


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P)%ss0)% swi'(

?urph# oil pressure aues with switches that activate on low pressure

2 )%ss0)% swi'( is a form of switch that closes an electrical contact when a certain

set pressure has been reached on its input. The switch ma# be desined to make contact either on

pressure rise or on pressure fall.

2nother t#pe of pressure switch detects mechanical force+ for e4ample$ a pressure-sensitive mat

is used to automaticall# open doors on commercial buildins.

2ressure switch

2 pressure switch for sensin fluid pressure contains a capsule$ bellows$ *ourdon tube$

diaphram or piston element that deforms or displaces proportionall# to the applied pressure.

The resultin motion is applied$ either directl# or throuh amplif#in levers$ to a set of switch

contacts. 1ince pressure ma# be chanin slowl# and contacts should operate quickl#$ some kind

of over-center mechanism such as a miniature snap-action switch is used to ensure quick

operation of the contacts. 9ne sensitive t#pe of pressure switch uses mercur# switches mounted

on a *ourdon tube+ the shiftin weiht of the mercur# provides a useful over-center

characteristic.

The pressure switch ma# be ad


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The pressure-sensin element of a pressure switch ma# be arraned to respond to the difference

of two pressures. 1uch switches are useful when the difference is sinificant$ for e4ample$ to

detect a cloed filter in a water suppl# s#stem. The switches must be desined to respond onl#

to the difference and not to false-operate for chanes in the common mode pressure.

The contacts of the pressure switch ma# be rated a few tenths of an ampere to around '(

amperes$ with smaller ratins found on more sensitive switches. 9ften a pressure switch will

operate a rela# or other control device$ but some t#pes can directl# control small electric motors

or other loads.

1ince the internal parts of the switch are e4posed to the process fluid$ the# must be chosen to

balance strenth and life e4pectanc# aainst compatibilit# with process fluids. or e4ample$

rubber diaphrams are commonl# used in contact with water$ but would quickl# derade if used

in a s#stem containin mineral oil.

1witches desined for use in ha%ardous areas with flammable as have enclosure to prevent

an arc at the contacts from initin the surroundin as. 1witch enclosures ma# also be required

to be weatherproof$ corrosion resistant$ or submersible.

2n electronic pressure switch incorporates some variet# of pressure transducer /strain aue$

capacitive element$ or other and an internal circuit to compare the measured pressure to a set

point. 1uch devices ma# provide improved repeatabilit#$ accurac# and precision over a

mechanical switch.

T%$%)#'0)% Swi'(%s

T%$%)#'0)% swi'(%s are the mechanisms used to measure temperature. The workin of a

temperature switch is based upon the temperature variations takin place in an enclosed space$ or

in an open area ad

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