Pressure Control Flare Stack

8/13/2019 Pressure Control Flare Stack

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BACK GROUND OF VISAKHAPATNAM

STEEL PLANT

Vizag Steel! also known as Visakhapatnam Steel Plant"Telugu0 #! is a steel companyased in the outskirts of 1isakhapatnam! &ndia. &ts main plant is located 23 kilometers from

1isakhapatnam! (ndhra Pradesh! it is among &ndia4s premier steel mills. &t has also een conferred the

Mini Ratnastatus. &ts ,ision 5 &nfrastructuring &ndia.

6ith a ,iew to gi,e impetus to industrial growth and to meet the inspirations of thepeople from South &ndia! Go,ernment of &ndia decided to estalish integrated Steel plant in pulic sector

at 1SP "(P# and $ospet "7arnataka# esides a special steel plant at Salem "Tamilnadu#. The prime

minister of &ndia Late Smt. &ndira Gandhi made the announcement in the parliament on 8/th(pril 89/:.

Smt.&ndira Gandhi laid the Foundation Stone for the plant on 2:5:8589/8. Seeds were thus sownfor the construction of a modern and sophisticated steel plant ha,ing ;.3million tons annual capacity. (n

arrangement was signed etween Go,ernment of &ndia and the erstwhile 'SS(+ on Company. ( comprehensi,e re,ised =P+ jointly recei,ed

so,iets and =r.m.n.=astur > Company was sumitted in )o,emer 89?: to Go,ernment of &ndia.


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The construction of the plant started on 8st Fe 89?2. Go,ernment of &ndia on 8?thFe 89?2

formed a new company called +astria &spat )igam Ltd.!"+&)L# and transferred the responsiility of

constructing! commissioning and operating the plant at 1isakhapatnam from Steel (uthority of &ndiaLtd.! to +&)L.

The plant was formally dedicated to the nation on 8st

(ugust 8992 y The Prime %inisterof &ndia Sri.P.1.)arasimha +ao. Since Commissioning 1SP has already crossed many milestones in the

field of production! producti,ity and e-ports. Coke +ate of order of the @A; kgton of hot metal! a,eragecon,erter life of 3A9 heats an a,erage of 88.@ heats per seuencing in continuous loom caster. Specific

energy consumption of /.@8 Gkalton of luide steel! a specific refractor consumption of [email protected] and a

laor producti,ity of 892 ton man here are some of the peaks achie,ed"during the year 899952:::#inper suit of e-cellence.

Process of Steel making ; 1SP has the distinction to e the 8 stintegrated Steel Plant in &ndia to

ecome an &SD59::8 &SD58A::8 > D$S(S58?::8 certified company. These certificates co,er uality

systems of all operational! maintenance! ser,ices units esides purchase systems! *n,ironmental

management systems! Dccupational health safety measures.

1iag Steel agged the first prie in *nergy Conser,ation constituted y %inistry Df Power!

Go,ernment Df &ndia! consecuti,ely for the last two years primarily due to its focus on energy

conser,ation! cost reduction and waste utiliation. 1iag Steel Plant today is among the lowest cost steelproducers in the world. The 1isakhapatnam Steel Plant has een awarded the Safety &nno,ation (ward 5

2::3 y the &nstitution Df *ngineers for its Eoutstanding contriutions in the field and adoption of the

est and the most inno,ati,e safety practicesE. The plant was awarded the Prime %inister4s trophy forthe est steel plant in the country! for the year 2::252::;.

1SP added another feather to its cap y agging si- Go,ernment of &ndia! 1ishwakarma +ashtriya

Puraskar "1+P# (wards at national le,el out of total numer of 2? awards announced y %inistry ofLaour! Go,ernment of &ndia.

Functional histo!"

The 1isakhapatnam Steel Plant was designed way ack in late 893:s ut y the time its chief

Consultants 5 %) =astur > Company4s 5 report and re,ised reports were accepted in 89?A to startconstruction! it had ecome the most e-pensi,e steel plant e,er to e constructed! deisigned to produce

aout ; million tonnes "%t# of processed steel per year.

A#out th$ %lant"

The plant is spread across a sprawling 89!::: acres "// km# of which only @!::: acres "2: km# are

used so far. The rest is still pristine shru forest land.

The company also has a last furnace grade limestone capti,e mine at


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the satellite ,illage of Gajuwaka! and the newer gate that opens to the Township and straight onto the

)$@.

Coke ovens & Raw Material Handling Plant (COBPP and RMHP)

The Coke D,ens of 1SP are engineering feats y themsel,es. They are the tallest o,ens constructed thusreducing pollution consideraly. Besides a io5chemical plant separately undertakes the treatment of

effluents. By5products like enene! toluene! -ylene! naphthalene! coal tar! creosote oil! pitch!

ammonium sulphate and enol products are also reco,ered from the coke o,ens gas. Benene andtoluene are produced through hydro refining and e-tracti,e distillation process! a uniue technology.

The enene produced is of ,ery high purity "99.9;H#. 1SP produces! among other y5products!

pushkala a prime fertilier ased on ammonium sulphate.

M!"OR SO#RC$ %OR R! M!'$R!

&ron ore lumpus and fines Bailadilla! %.P

BF lime stone


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last furnace. The sinter plant comprises two sinter machines each ha,ing ;82 suar8e metres of grate

area with a total production capacity of @.2@3 million tonnes per annum.

Blast +,rna-es

1SP has two last furnaces EGoda,ariE and E7rishnaE with an effecti,e ,olume of ;2:: mI each ofwhich are the largest in the country. The last furnace is charged with coke! iron ore and sinter from the

top and produces aout 3::: tonnes of molten iron per day. &ts no,el circular cast house with four tap

holes ensures continuous tapping of hot metal. The annual production capacity of these Blast Furnaces is;.A million tonnes of liuid iron. &n +ussia they produce ?::: tonnes of molten metal"iron#per day with

the same last furnace which ha,e een used in our 1SP"Goda,ari > 7rishna#.They are the est in

&ndia.Blast Furnace: An Overview-

(t present 1SP is ha,ing 2 )o Blast Furnace "BFJ8! BFJ2# of ;2:: m; each with A)o of Taphole > ;A)o of Tuyers and is operating at 82:H of rated capacity. These furnaces are ha,ing =oule Bin Bell

Less Top with con,eyor charging system! A )o of Sto,es! Slag Granulation with (ir lift system. The

cast house is euipped with motoried Clay gun > =rilling machine. The slag is e,acuated to Slag Kard,ia series of con,eyors. The (nnual production capacity of the e-isting furnaces is around A.2 %T of

$ot metal.

Steel melt shop & Contin,o,s -asting

Three top5lown L= con,erters! each of 8;; mI ,olume! produce a total of ;.3 million tonnes of liuid

steel per annum. This liuid steel thus produced is cast in si-! A strand loom casters. ( special featurein energy conser,ation is the collection of con,erter gas to e used as a fuel in the plant. The entire

molten steel at 1SP is continuously cast at the radial type continuous casting machines resulting insignificant energy conser,ation and etter uality steel. 8::H continuous casting on such a large scale

has een concei,ed for the first time in &ndia.

Technology for Caster has een otained from erstwhile 'SS+ while Technology in L= shop is a mi-

of 'SS+ for mechanical euipment! (nsaldo &taly for *lectric =C dri,es! Brown Bo,eri 7ent 5'7! for

=istriuted control systems and Clecim 5 France for Gas cleaning plant.

Secondary facilities like &njection +efining 5 'P Temperature "&+'T#and Ladle furnace ha,e eenadded suseuently.


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Rolling mills

The cast looms from continuous casting department are heated and rolled in the three high speed and

fully automated rolling mills namely

Light > %edium %erchant %ill "L%%%#! 6ire +od %ill "6+% & > &! and

%edium %erchant > Structural %ill "%%S%#

to produce ,arious long products like reinforcement ars! rounds! suares! flats! angles! channels! illets!

wire rods etc. Technologies adopted at rolling mills include world5class Stelmor and Tempcore

processes.

HOW A BLAST FURNACE WORKS:

Into&uction

The purpose of a last furnace is to chemically reduce and physically con,ert iron o-ides into

liuid iron called Ehot metalE. The last furnace is a huge! steel stack lined with refractory rick! where

iron ore! coke and limestone are dumped into the top! and preheated air is lown into the ottom. The


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raw materials reuire 3 to ? hours to descend to the ottom of the furnace where they ecome the final

product of liuid slag and liuid iron. These liuid products are drained from the furnace at regular

inter,als. The hot air that was lown into the ottom of the furnace ascends to the top in 3 to ? secondsafter going through numerous chemical reactions. Dnce a last furnace is started it will continuously run

for four to ten years with only short stops to perform planned maintenance.

'he Pro-ess

&ron o-ides can come to the last furnace plant in the form of raw ore! pellets or sinter. The raw

ore is remo,ed from the earth and sied into pieces that range from :.@ to 8.@ inches. This ore is either

$ematite "Fe2D;# or %agnetite "Fe;DA# and the iron content ranges from @:H to /:H. This iron rich orecan e charged directly into a last furnace without any further processing. &ron ore that contains a lower

iron content must e processed or eneficiated to increase its iron content. Pellets are produced from this

lower iron content ore. This ore is crushed and ground into a powder so the waste material called gangue

can e remo,ed.


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The remaining iron5rich powder is rolled into alls and fired in a furnace to produce strong!

marle5sied pellets that contain 3:H to 3@H iron. Sinter is produced from fine raw ore! small coke!

sand5sied limestone and numerous other steel plant waste materials that contain some iron. These finematerials are proportioned to otain a desired product chemistry then mi-ed together. This raw material

mi- is then placed on a sintering strand! which is similar to a steel con,eyor elt! where it is ignited y

gas fired furnace and fused y the heat from the coke fines into larger sie pieces that are from :.@ to 2.:inches. The iron ore! pellets and sinter then ecome the liuid iron produced in the last furnace with

any of their remaining impurities going to the liuid slag.

The coke is produced from a mi-ture of coals. The coal is crushed and ground into a powder and

then charged into an o,en. (s the o,en is heated the coal is cooked so most of the ,olatile matter such asoil and tar are remo,ed. The cooked coal! called coke! is remo,ed from the o,en after 8? to 2A hours of

reaction time. The coke is cooled and screened into pieces ranging from one inch to four inches. The

coke contains 9: to 9;H caron! some ash and sulfur ut compared to raw coal is ,ery strong. Thestrong pieces of coke with a high energy ,alue pro,ide permeaility! heat and gases which are reuired

to reduce and melt the iron ore! pellets and sinter.

The final raw material in the iron making process in limestone. The limestone is remo,ed from the

earth y lasting with e-plosi,es. &t is then crushed and screened to a sie that ranges from :.@ inch to8.@ inch to ecome last furnace flu- . This flu- can e pure high calcium limestone! dolomite limestone

containing magnesia or a lend of the two types of limestone. Since the limestone is melted to ecome

the slag which remo,es sulfur and other impurities! the last furnace operator may lend the differentstones to produce the desired slag chemistry and create optimum slag properties such as a low melting

point and a high fluidity.

(ll of the raw materials are stored in an ore field and transferred to the stock house efore

charging. Dnce these materials are charged into the furnace top! they go through numerous chemical and

physical reactions while descending to the ottom of the furnace.

The iron ore! pellets and sinter are reduced which simply means the o-ygen in the iron o-ides is

remo,ed y a series of chemical reactions. These reactions occur as follows0

8# ; Fe2D; CD M CD2 2 Fe;DA Begins at ?@:N F

2# Fe;DA CD M CD2 ; FeD Begins at 88::N F

;# FeD CD M CD2 Fe Begins at 8;::N F

(t the same time the iron o-ides are going through these purifying reactions! they are also

eginning to soften then melt and finally trickle as liuid iron through the coke to the ottom of the

furnace. The coke descends to the ottom of the furnace to the le,el where the preheated air or hot lastenters the last furnace. The coke is ignited y this hot last and immediately reacts to generate heat as

follows0

C D2M CD2 $eat


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Since the reaction takes place in the presence of e-cess caron at a high temperature the caron

dio-ide is reduced to caron mono-ide as follows0 CD2 C M 2CD

The product of this reaction! caron mono-ide! is necessary to reduce the iron ore as seen in thepre,ious iron o-ide reactions. The limestone descends in the last furnace and remains a solid while

going through its first reaction as follows0

CaCD;M CaD CD2

This reaction reuires energy and starts at aout 83::NF. The CaD formed from this reaction is

used to remo,e sulfur from the iron which is necessary efore the hot metal ecomes steel. This sulfur

remo,ing reaction is0

FeS CaD C M CaS FeD CD

The CaS ecomes part of the slag. The slag is also formed from any remaining Silica "SiD2#!

(lumina "(l2D;#! %agnesia "%gD# or Calcia "CaD# that entered with the iron ore! pellets! sinter or coke.The liuid slag then trickles through the coke ed to the ottom of the furnace where it floats on top of

the liuid iron since it is less dense.

(nother product of the iron making process! in addition to molten iron and slag! is hot dirty

gases. These gases e-it the top of the last furnace and proceed through gas cleaning euipment whereparticulate matter is remo,ed from the gas and the gas is cooled. This gas has a considerale energy

,alue so it is urned as a fuel in the Ehot last sto,esE which are used to preheat the air entering the last

furnace to ecome Ehot lastE. (ny of the gas not urned in the sto,es is sent to the oiler house and is

used to generate steam which turns a turo lower that generates the compressed air known as EcoldlastE that comes to the sto,es.

&n summary! the last furnace is a counter5current realtor where solids descend and gases ascend. &n this

reactor there are numerous chemical and physical reactions that produce the desired final product whichis hot metal. ( typical hot metal chemistry follows0

&ron "Fe# M 9;.@ 5 9@.:H

Silicon "Si# M :.;: 5 :.9:H

Sulfur "S# M :.:2@ 5 :.:@:H

%anganese "%n# M :.@@ 5 :./@H

Phosphorus "P# M :.:; 5 :.:9H

Titanium "Ti# M :.:2 5 :.:3H


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Caron "C# M A.8 5 A.AH

Th$ Blast Funac$ Plant

)ow that we ha,e completed a description of the iron making process! let s re,iew the physicaleuipment comprising the last furnace plant.


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main that is euipped with a ,al,e used to control the last temperature and keep it constant. The hot

last main enters into a doughnut shaped pipe that encircles the furnace! called the Eustle pipeE "8;#.

From the ustle pipe! the hot last is directed into the furnace through noles called EtuyeresE ";:#"pronounced EtweersE#. These tuyeres are eually spaced around the circumference of the furnace. There

may e fourteen tuyeres on a small last furnace and forty tuyeres on a large last furnace. These

tuyeres are made of copper and are water cooled since the temperature directly in front of the them maye ;3::NF to A2::NF. Dil! tar! natural gas! powdered coal and o-ygen can also e injected into the

furnace at tuyere le,el to comine with the coke to release additional energy which is necessary to

increase producti,ity. The molten iron and slag drip past the tuyeres on the way to the furnace hearthwhich starts immediately elow tuyere le,el.

(round the ottom half of the last furnace the EcasthouseE "8# encloses the ustle pipe! tuyeres

and the euipment for EcastingE the liuid iron and slag. The opening in the furnace hearth for casting or

draining the furnace is called the Eiron notchE "22#. ( large drill mounted on a pi,oting ase called theEtaphole drillE "2;# swings up to the iron notch and drills a hole through the refractory clay plug into the

liuid iron. (nother opening on the furnace called the Ecinder notchE "28# is used to draw off slag or iron

in emergency situations. Dnce the taphole is drilled open! liuid iron and slag flow down a deep trenchcalled a EtroughE "2?#. Set across and into the trough is a lock of refractory! called a EskimmerE! which

has a small opening underneath it.

The hot metal flows through this skimmer opening! o,er the Eiron damE and down the Eiron

runnersE "2/#. Since the slag is less dense than iron! it floats on top of the iron! down the trough! hits theskimmer and is di,erted into the Eslag runnersE "2A#. The liuid slag flows into Eslag potsE "2@# or into

slag pits "not shown# and the liuid iron flows into refractory lined EladlesE "23# known as torpedo cars

or su cars due to their shape. 6hen the liuids in the furnace are drained down to taphole le,el! some

of the last from the tuyeres causes the taphole to spit. This signals the end of the cast! so the EmudgunE"29# is swung into the iron notch. The mudgun cylinder! which was pre,iously filled with a refractory

clay! is actuated and the cylinder ram pushes clay into the iron notch stopping the flow of liuids. 6henthe cast is complete! the iron ladles are taken to the steel shops for processing into steel and the slag istaken to the slag dump where it is processed into roadfill or railroad allast.

The casthouse is then cleaned and readied for the ne-t cast which may occur in A@ minutes to 2

hours. %odern! larger last furnaces may ha,e as many as four tapholes and two casthouses. &t is

important to cast the furnace at the same rate that raw materials are charged and ironslag produced soliuid le,els can e maintained in the hearth and elow the tuyeres. Liuid le,els ao,e the tuyeres can

urn the copper casting and damage the furnace lining.


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The gases emerging from a high5pressure gas furnace are suject to coarse particle separation and then

to washing and scruing with water efore dri,ing an e-pansion turine which has a gas ypass so that

the turine can e cut off. The scruing water recycled to the scruer when the turine is cut off! ispermitted to tra,erse a cooler of the washing5water reco,ery unit ut! when the turine is operati,e! the


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scruing water ypasses the cooler. The water introduced into the scruer can thus ha,e a temperature

of aout 2@N C. when the turine is ypassed and aout @:N C. when it is effecti,e.


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PRESSURE MEASURMENT"

OPressure in industry is used in a wide range from ,acuums to super high pressures "3:::: atm.#

reuired for the synthesis of diamond. $owe,er! pressures familiar to us are! for e-ample! atmospheric

pressure or water pressure. Figure 8 shows the kinds of pressure. Gage pressure is pressure ased on

atmospheric pressure! while pressure ased on an asolute ,acuum or asolute ero pressure is calledasolute pressure. (ccordingly! the following e-pression holds0

"Gage pressure# M "(solute pressure# 5 "(tmospheric pressure#&n order to distinguish asolute and gage pressures! asolute pressure is written with Oas.

There are also many units of pressure! such as Pa! kgfcm2! mm$2D! mm$g! ar! or atm. These units

ha,e now een unified as Pa y changing to the &nternational System of 'nits. The con,ersion ,alues ofPa to other units are shown in Tale 8. The representation of atmospheres in weather forecasting has

also changed to hector Pascals "hPa# from milli5ars "mar#.

Tale 8 shows the con,ersions etween pressure units freuentlyused for general purposes.

.eed o+ %!R$ S'!C/


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( gas +lareor +lare sta-kis an ele,ated ,ertical stack or chimney found on oil wells or oil rigs! and in

refineries! chemical plants and landfills used for urning off unwanted gas or flammale gas and liuids

released y pressure relief ,al,es during unplanned o,er5pressuring of plant euipment. &n landfills! the

primary purpose of this de,ice is to ,ent andor urn waste gas which results from the decomposition of

materials in the dump.

Dn oil production rigs! in refineries and chemical plants! its primary purpose is to act as a safety de,ice

to protect ,essels or pipes from o,er5pressuring due to unplanned upsets. This acts just like the spout on

a tea kettle when it starts whistling as the water in it starts oiling. 6hene,er plant euipment items are

o,er5pressured! the pressure relief ,al,es on the euipment automatically release gases "and sometimes

liuids as well# which are routed through large piping runs called +lare headersto the flare stacks. The

released gases andor liuids are urned as they e-it the flare stacks. The sie and rightness of the

resulting flame depends upon how much flammale material was released. Steam can e injected intothe flame to reduce the formation of lack smoke. The injected steam does howe,er make the urning of

gas sound louder! which can cause complaints from neary residents. Compared to the emission of lack

smoke! it can e seen as a ,alid trade off. &n more ad,anced flare tip designs! if the steam used is too wet

it can freee just elow the tip! disrupting operations and causing the formation of large icicles. &n order

to keep the flare system functional! a small amount of gas is continuously urned! like a pilot light! so

that the system is always ready for its primary purpose as an o,er5pressure safety system. The
http://en.wikipedia.org/wiki/File:PTT_flame_1.jpghttp://en.wikipedia.org/wiki/File:PTT_flame_1.jpg


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continuous gas source also helps diluted mi-tures achie,e complete comustion. Some flares ha,e een

used to urn flammale EwasteE gases or y5products that are not economical to retain. D,er time! the

industry is mo,ing to flare5gas reco,ery systems to decrease waste and reduce emissions.

Instu'$ntation"

nstr,mentationis the ranch of science that deals with measurement and control in order to increase

efficiency and safety in the workplace.

(n instrument is a de,ice placed in the field! or in the control room! to measure or manipulate

flow! temperature! pressure and other ,ariales in a process. &nstruments include ut are not limited to

,al,es! transmitters! transducers! flame detectors and analyers. &nstruments send either pneumatic or

electronic signals to controllers which manipulate final control elements "a ,al,e# in order to get the

process to a set point! usually decided y an operator.

Control instrumentation includes de,ices such as solenoids! *lectrically Dperated 1al,es!

reakers! relays! etc. These de,ices are ale to change a field parameter! and pro,ide remote control

capailities.

Transmitters are de,ices which produce an analog signal! usually in the form of a A52:m(

electrical current signal! although many other options are possile using ,oltage! freuency!orpressure.

This signal can e used to directly control other instruments! or sent to a PLC! =CS! SC(=(system or

other type of computeried controller! where it can e interpreted into readale ,alues! or used to control

other de,ices and processes in the system.

&nstrumentation plays a significant role in oth gathering information from the field and

changing the field parameters! and as such are a key part ofcontrol loops.

%!R$ S'!C/
http://en.wikipedia.org/wiki/Circuit_breakerhttp://en.wikipedia.org/wiki/Relayhttp://en.wikipedia.org/wiki/Analog_signalhttp://en.wikipedia.org/wiki/4-20http://en.wikipedia.org/wiki/Ampereshttp://en.wikipedia.org/wiki/Current_(electrical)http://en.wikipedia.org/wiki/Voltagehttp://en.wikipedia.org/wiki/Frequencyhttp://en.wikipedia.org/wiki/Frequencyhttp://en.wikipedia.org/wiki/Pressurehttp://en.wikipedia.org/wiki/PLChttp://en.wikipedia.org/wiki/DCShttp://en.wikipedia.org/wiki/SCADAhttp://en.wikipedia.org/wiki/Control_loophttp://en.wikipedia.org/wiki/Control_loophttp://en.wikipedia.org/wiki/Relayhttp://en.wikipedia.org/wiki/Analog_signalhttp://en.wikipedia.org/wiki/4-20http://en.wikipedia.org/wiki/Ampereshttp://en.wikipedia.org/wiki/Current_(electrical)http://en.wikipedia.org/wiki/Voltagehttp://en.wikipedia.org/wiki/Frequencyhttp://en.wikipedia.org/wiki/Pressurehttp://en.wikipedia.org/wiki/PLChttp://en.wikipedia.org/wiki/DCShttp://en.wikipedia.org/wiki/SCADAhttp://en.wikipedia.org/wiki/Control_loophttp://en.wikipedia.org/wiki/Circuit_breaker


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0es-ription o+ the B% 1!S .$'OR/ PR$SS#R$ S*S'$M

Pressure of B.F.Gas network is sensed y pressure transmitter PT2:8 efore 2::: dia gate ,al,e > sends

signal to Pressure indicating controller "P&C2:2#. 6hen the pressure in the BF gas network increases

eyond the set point "adjustale etween 82:: to 8A:: mm6C#! P&C2:2 gi,es signal to actuator %2:2 toopen PC12:2 control ,al,e accordingly. Thus e-cess gas is released to flare stack and BFG network

pressure reduces to set pressure.Control ,al,e PC12:2 is pro,ided with a standy actuator " % 2:;#! pressure transmitter "PT 2:2# and controller

"P&C 2:;#. %anual inter,ention is reuired for changing the linking rod from one actuator to other. (fter opening

PC12:2 ,al,e! flare stack pressure raises. The flare stack pressure is sensed y a pressure transmitter which gi,es

signal to Pressure &ndicating controllers mounted at GCP8 Control room as mentioned elow.


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Pressure &ndicating Controller

a# P&C8::2 55 To control PC18::2 at set pressure of ;@ %%6C.

# P&C8::; 55 To control PC18::; at set pressure of A@ %%6C.

c# P&C8::A 55 To control PC18::A at set pressure of @@ %%6C.

d# P&C8::@ 55 To control PC18::@ at set pressure of 3@ %%6C.

6hen pressure of flare stack goes ao,e ;@";:# mmwcl! P&C8::2 starts opening first control ,al,e

PC18::2 to meet pressure conditions. &f stack pressure reduces to ;@ "5;:# mmwc! ,al,e PC18::2 starts

closing. &f decrease in pressure continues! PC18::2 closes completely.

Similarly PC18::;! PC18::A > PC18::@ operate at their corresponding set ,alues.

&n case there is sudden rise of pressure more than 3@ ";:# mmwc! all four ,al,es i.e.! PC18::2! PC18::;

PC18::A! PC18::@ start opening and open fully in a duration of 8 minute "actuator operating time for Full

open position#.

(n orifice plate is installed at downstream of 2::: dia gate ,al,e with flow transmitter . Flow transmitter

senses flow and gi,es feedack to recorder on instrument panel at BFGCP2 control room. This recorder

records following0

B.F Gas flow to flare stack.

B.F. Gas Pressure at Flare stack.

B.F Gas network pressure "upstream of 2::: dia ,al,e#.


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PO' 1.'O. S*S'$M

To ensure ignition of e-cess BF gases leed through BF gas flare stack! continuous CD gas pilots

are pro,ided for all BFG urners. Pilot urners are lighted y means of remote ignition system

"Flame front type #. Pilot igniter controls are located in the electrical room of BFG flare stack! which

are closed5loop type! taking feed ack ,ia the thermocouple sensor mounted on the flare tip of thepilot.

There are four BF gas urners pro,ided with four pilots each "Two are lanked and two are

working#. Dne FFG panel is used for igniting each of total 83 nos. of pilots one after another.

*ach pilot is pro,ided with separate ignition line "&L#. *nclosure of FFG panel is di,ided into A

compartments one each for one BFG urner and located inside the electrical room. &gnition cycle for

all 83 )os. pilots can e initiated from enclosure58 only. $owe,er! indication of pilot D)DFF arepro,ided independently on each enclosure for corresponding BFG urner.

CDG and air are mi-ed together after passing through separate indi,idual orifices "+


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0$SCRP'O. O% 'H$ OOP 0!1R!M.

The )etwork pressure control loop is ha,ing three Transmitters . Two are located at BF Flare stack and

one is located at Gas Cleaning Plant.

(t BF Gas flare stack two transmitters are there. Dne is for CD)T+DL and another is for%*(S'+*%*)T.

The control transmitter " PT 2:8 # con,erts the )etwork pressure into A Q 2: m( signal and gi,es to the

PLC ! located at GCP58 Control room! and also to the P&= Stand alone Controllers through isolator. The

range of the transmitter is :52@:: mm6C. &n PLC two controllers are programmed to control the %2:2and %2:; actuators which are located at BF G(S FL(+*ST(C7. &n these two controllers one is

working and another is standy. The working controller set point is set y operator i.e.R SP. 6hen

process ,ariale " P1 # is more than SP! controller issues the DP*) command to the actuator then ,al,ewill open and ,ent the waste BF gas or )etwork gas. 6hen P1 is less than the SP controller issues the

CLDS* command to the actuator and ,al,e will close and maintains the network pressure at set le,el.

Dut of two actuators "%2:2 %2:;# one is working and another is standy. The feedack signal of theactuator is gi,en to the ,al,e position indicators located in GCP58 control room for knowing the control

,al,e position.

The second transmitter "PT 2:2# is ment for measurement and gi,es the output "A52:m(# to the

SC(=( system and also to the PLC of GCP58 control room for recording purpose. The transmitterrange is :5@::: mm6c.

The third transmitter "PT 3a# is located at GCP is standy transmitter for )etwork control loop and gi,es

the output to the PLC and then retransmitted to the Stand alone controllers and also to the SC(=(

system. The transmitter range is :52@:: mm6c.

The entire loop is ha,ing two power supplies one is from Flare stack 'PS and another is from GCP58

'PS. These can e selectale through selector switches.

The stand alone controllers are also ha,ing two analog inputs either from BF Flare stack or GCP58

transmitters. These are programmale and ha,ing the diagnosis facility for knowing the error codes.

The motoried actuators are working under ;5phase power supply. These are B*+)('+= make.Theao,e mentioned transmitters work on the strain gauge principle.


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PR.CP$ OF STRAIN 1!#1$

( Strain Gauge is used as the transducer in an electrical pressure transducer when attached directly to a

mechanical pressure element such as a metal diaphragm! or a metal ellows! or when the pressure is

transmitted to the strain gauge y an armature from the mechanical pressure element.

Two Types of Pressure transducer

"8# 'n Bonded Pressure Transducer

"2# Bonded Pressure Transducer

#n Bonded Press,re 'ransd,-er &n the 'n Bonded5type Pressure Transducer! the armature is

connected to a metallic ellows !or diaphragm . when a diaphragm is used ! the strain gauge measuresthe displacement of the diaphragm center! due to process pressure e-erted on the diaphragm. This is

done in one modern design y two four5legged springs intermeshed in a stainless5steel ring! with each

leg attached to the ring. Pins e-tending through the springs are inding posts for the strain windings.(ny moment of the armature e-tending from the pick up diaphragm to the centre of the two springs will

cause a simultaneous e-tension of one set of windings and rela-ation of the other. Thus the resistance ofthe windings ,aries proportionally to the gauge pressure applied. 6hen a gauge ,oltage is applied! an

electrical signal proportional to the applied pressure e-ists at the pressure transducer output terminals.This pressure transducer is made in a compact cylindrical stainless housing with pressure connections on

one end and electrical connections on the other.

Bonded press,re 'ransd,-er This works much the same as the unounded type! e-cept that thestrain gauge filaments are onded directly to a pressure5sensiti,e tue encased in a metal housing. 6hen

fluid pressure enters the tue! it e-pands the tue circumferentially and stretches the strain gaugefilaments. The resulting change in resistance unalance the ridge circuit. 6hen a fi-ed gauge ,oltage is

applied at the input terminals! the ridge unalance is reflected as a change in pressure transducer output

,oltage proportional to the applied gauge pressure. 6hen either onded or unonded strain gaugetransducers use as a ellows asolute pressure is measured. &f two pressure connections are pro,ided

differential pressure is measured.


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0$SCRP'O. O% PC


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The PLC type is0 S-henider $le-tri-

Software 0 PL/5P+D P+*%&'% 1*+S&D) A.@

$%& 0 1&


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Power s,ppl3

The Power supply unit pro,ides the isolation necessary to protect solid state

components from high ,oltage line spikes. The power supply unit con,erts power line

,oltages to those reuired y the solid state components. The power supply is rated for

heat dissipation reuirements for plant floor operation. This dissipation capaility allows

PLC to ha,e high Qamient5temperature specifications and represents an important

difference etween programmale logic controllers"PLCs# and personal computers"PCs#

for industrial applications. The power supply unit dri,es the &D logic signals! the central

processing unit! memory unit !and some peripheral de,ices.


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np,t 4 O,tp,t s3stem


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&nputs are defined as real 5world signals gi,ing the controller real5time status of

process ,ariales. These signals can e analog or digital! low or high freuency !

maintained or momentary .They are presented to the programmale controller as a

,arying ,oltage! current! or resistance ,alue Signals from thermocouples"TCs# and

resistance temperature detectors"+T=s# are e-amples of analog signals. Some flow

meters and strain gauges pro,ide ,ariale freuency signals! while push uttons! limit

switches! or e,en electromechanical relay contacts are e-amples of digital contact

closure type signals. . +egister input is another type of input signal that reflects the

computer nature of the programmale controller. The register input is particularly useful

when the process condition is represented y a collection of digital signal deli,ered to the

PLC at the same time. ( Binary coded decimal "BC=# thum5wheel is an e-ample of an

input de,ice that is compatile with a register input port.

There are three common categories of outputs0 =iscrete! register and analog.

=iscrete outputs can e solenoid ,al,es ! pilot lights! or enunciator windows"lamp o-#.+egister outputs can dri,e panel meters or displays. (nalog outputs can dri,e signals to

,ariales speed dri,es or to &P "current5to5air# con,erters and thus to control ,al,es.

(ll &D systems are modular in nature! that is ! systems are arranged in modules

that contain multiples of &D points. These modules can e plugged into the us structure.

The us structure is a high5speed multiple-er that carries information ack and forth

etween the &D modules and the central processor unit. Dne of the most important

functions of &D is its aility to isolate real5world signal from the low Qsignal le,els.

Real 'ime Central Pro-essing #nit

The central processing unit also called central control unit! performs the tasks necessary

to fulfil the PLC function such as scanning! &D us traffic control program e-ecution !

peripheral and e-ternal de,ice communications! special function or data handling

e-ecution and self5diagnostics

Memor3 #nit

The memory unit of the PLC ser,es se,eral functions .&t is the lirary! where the

application program is stored. &t is also where the PLCs e-ecuti,e program is stored. (n


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e-ecuti,e program functions as the operating system of the PLC. &t is the program that

interprets ! manages and e-ecutes the users application program. Finally! the memory

unit is the part of the programmale controller ! where the process data from the input

modules and control data from the output modules are temporarily stored as data tales.

Typically! an image of these data tales is used y the CP' and! when appropriate! sent

to the output modules.

%emory can e ,olatile or non5,olatile. The content of the ,olatile memory is

erased if power is remo,ed. D,iously! this is undesirale! in the units with ,olatile

memory pro,ide attery ack up to ensure that there will e no loss of program in the

e,ent of the power failure. )on51olatile memory does not change state on loss of power

and is used in cases in which e-tended power failures.

Programmer ,nit

The programmer unit pro,ides an interface etween the PLC and the user duringprogrammer de,elopment! start5up and trouleshooting. The instructions to e performed

during each scan are coded and inserted into memory with the programmer unit. The

programmer units ,ary from small hand5held units to desktop stand5alone intelligent

C+T5ased units.PLC manufacturers are now pro,iding controller models that use

personal computer "pc# which allows the computer to interface with a serial input module

installed in the programmale controller.

Programming units pro,ides automatic documentation of the e-isting program

using a printer attached to it. 6ith off5line programming! the user can write a control

program on the programming unit ! then take the unit to the PLC in the field and load the

memory the new program! all without remo,ing the PLC.

Peripheral devi-es


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Peripheral de,ices are grouped into se,eral categories such as programming aids

operational aids! &D enhancements and computer interface de,ices. Programming aids

pro,ides documentation and program recording capailities. The definite trend in

programming aids is PC5compatile software that allows the PLC to e emulated y the

personal computer.

Dperational aids include a ,ariety of resources that range from color graphics

C+Ts to euipment or support programs that can gi,e the operator specific access to

processor parameters .&n this situation the operator is usually allowed to read and modify

timer !counter and loop parameters ut not ha,e access to the program itself.

The &D enhancement group is a large category of PLC peripheral euipment. &t

includes all types of modules! from dry contact modules to intelligent &D to remote &o

capailities . Some &D simulators used to de,elop and deug programs that can ecategoried in the &D enhancement group. These are hardware modules which can e

plugged in to the PLC .

The computer interface de,ice group is a rapidly e-panding section of PLC

peripheral de,ices . These de,ices allow peer5to5peer communication! as well as

network interaction with ,arious computer systems .

Basi- str,-t,re

The inputs are read into the input memory register. (n input output register is notonly a it ut a yte. Conseuently! one input instruction gi,es the status of ? different

input ports. The instruction fetches the ,alue from the input register and operates only on

this or se,eral operands .The result of an instruction is stored either in some intermediate

register or directly in the output memory register. The output function is usually included

in the system programs in a PLC.


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( PLC is specifically made to fit an industrial en,ironment! where it is e-posed to

hostile conditions such as heat! dust! humidity! unreliale power! mechanical shocks and

,irations. PLCs ha,e oth hardware and software features that make them attracti,e as

controllers of a wide range of industrial euipments

PC PRO1R!MM.1

The use and understanding of PLC programming depends on the following factors0

7nowledge of the process to e controlled

'nderstanding of electrical schematics

(n appreciation for logic operations and for ,arious types of logic and relay

de,ices.

( PLC is usually programmed ,ia an e-ternal unit called programming

unit .The programming units range from small hand5held portale units! to

personal computers .The personal computer as programming unit has ecome

,ery popular with a graphical display. The display typically shows se,eral ladder

diagram lines at a time and also indicates the power flow within each line during

the operation to make deugging and testing simpler Dther units are programmed

with logical gates instead of a ladder diagram.

The programming software is installed into a PC programming terminal.

This software enales the user to generate PLC programs and to download the

resulting programming into the PLC ,ia a standard +S52;2 PC port or ,ia a

supplier Qspecific data highway communication link.

adder ogi-


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Ladder logic is the main programming method used for PLCs. (s mentioned

efore! ladder logic has een de,eloped to mimic relay logic. The decision to use therelay logic diagrams was a strategic one.

( relay is a simple de,ice that uses a magnetic field to control a switch. +elays

are used to let one power source close a switch for another "often high current# powersource! while keeping them isolated. (n e-ample of a relay in a simple control

application. &n this system the first relay on the left is used as normally Closed! and will

allow current to flow until a ,oltage is applied to the input (. The second relay isnormally open and will not allow current to flow until a ,oltage is applied to the input

B. &f current is flowing through the first two relays then current will flow through the coil

in the third relay! and close the switch for output C. This circuit would normally e drawn

in the ladder logic form. This can e read logically as C will e on if ( is off and B is on.6hen a process is controlled y a PLC it uses inputs from sensors to make decisions

and update outputs to dri,e actuators! as shown in Figure. The process is a real process

that will change o,er time. (ctuators will dri,e the system to new states .

This means that the controller is limited y the sensors a,ailale! if an input is nota,ailale! the controller will ha,e no way to detect a condition.


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The control loop is a continuous cycle of the PLC reading inputs! sol,ing the ladder logic! and

then changing the outputs. Like any computer this does not happen instantly. Figure shows theasic operation cycle of a PLC. 6hen power is turned on initially the PLC does a uick sanity

check to ensure that the hardware is working properly. &f there is a prolem the PLC will halt

and indicate there is an error. For e-ample! if the PLC ackup attery is low and power was lost!the memory will e corrupt and this will result in a fault. &f the PLC passes the sanity check it

will then scan "read# all the inputs. (fter the inputs ,alues are stored in memory the ladder logic

will e scanned "sol,ed# using the stored ,alues 5 not the current ,alues. This is done to pre,entlogic prolems when inputs change during the ladder logic scan. 6hen the ladder logic scan is

complete the outputs will e scanned "the output ,alues will e changed#. (fter this the system

goes ack to do a sanity check! and the loop continues indefinitely. 'nlike normal computers! the

entire program will e run e,ery scan. Typical times for each of the stages is in the order ofmilliseconds.


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adder ogi- np,ts

PLC inputs are easily represented in ladder logic. &n Figure there are threetypes of inputs shown. The first two are normally open and normally closed inputs!

discussed pre,iously. TheIIT "&mmediate &nput# function allows inputs to e read after

the input scan! while the ladder logic is eing scanned. This allows ladder logic toe-amine input ,alues more often than once e,ery cycle.

adder ogi- O,tp,ts

&n ladder logic there are multiple types of outputs! ut these are not consistently

a,ailale on all PLCs. Some of the outputs will e e-ternally connected to de,ices

outside the PLC! ut it is also possile to use internal memory locations in the PLC. Si-

types of outputs are shown in Figure. The first is a normal output! when energied theoutput will turn on! and energie an output. The circle with a diagonal line through is a

normally on output. 6hen energied the output will turn off. This type of output is not

a,ailale on all PLC types. 6hen initially energied the OSR "Dne Shot +elay#instruction will turn on for one scan! ut then e off for all scans after! until it is turned

off. TheL "latch# and U "unlatch# instructions can e used to lock outputs on. 6hen an L

output is energied the output will turn on indefinitely! e,en when the output coil is de5energied. The output canonly e turned off using a U output. The last instruction is the

IOT "&mmediate Dutput# that will allow outputs to e updated without ha,ing to wait for

the ladder logic scan to e completed.

Ladder Logic Dutputs


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$le-tri- a-t,ator

(ctuators are used for the automation of industrial ,al,es and can e found in all kinds of

technical process plants0 they are used in wastewater treatment plants! power plants and

e,en refineries. This is where they play a major part in automating process control. The

,al,es to e automated ,ary oth in design and dimension. The diameters of the ,al,es

range from a few inches to a few metres.

=epending on their type of supply! the actuators may e classified as pneumatic!

hydraulic! or ele-tri- a-t,ators.
http://en.wikipedia.org/wiki/File:Drehantrieb_in_raffinerie_01.jpg


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D$si(n

*lectric multi5turn actuator with controls

Motor (5)

+oust asynchronous ;5phase (C motors are mostly used as electric motors! for

some applications also 85phase (C or =C motors are used. The motors are specially

adapted for ,al,e automation reuirements. =ue to their design! they pro,ide higher

torues from standstill than comparale con,entional motors. This feature is reuired to

e ale to unseat sticky ,al,es. *lectric actuators are used under e-treme amient

conditions. Fan motors do not pro,ide sufficient enclosure protection and can therefore

not e used. (ctuators can generally not e used for continuous operation since the
http://en.wikipedia.org/wiki/File:Schnittbild_drehnatrieb_01.jpg


42/44

motors ha,e to cool down after a certain operating time. This suits the application since

,al,es are not continuously operated.

imit and tor6,e sensors (7)

The limit switching measures the tra,el and signals when an end position has

een reached! the torue switching measures the torue present in the ,al,e. 6hen

e-ceeding a set limit! this is signaled in the same way. (ctuators are often euipped with

a remote position transmitter which indicates the ,al,e position as continuous current or

,oltage signal.

1earing ";#

Dften a worm gearing is used to reduce the high output speed of the electric motor. This

enales a high reduction ratio within the gear stage! leading to a low efficiency which is

desired for the actuators. The gearing is therefore self5locking i.e. it pre,ents accidental

and undesired changes of the ,al,e position y acting upon the ,al,es closing element.

This is of major importance for multi5turn actuators which are a-ially loaded with the

weight of the gate ,al,e disc.

Valve atta-hment"A#

The ,al,e attachment consists of two elements. First0 The flange used to firmly connect

the actuator to the counterpart on the ,al,e side. The higher the torue to e transmitted!

the larger the flange reuired.

Second0 The output dri,e type used to transmit the torue or the thrust from the actuator

to the ,al,e shaft.


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Man,al operation"@#

&n their asic ,ersion most electric actuators are euipped with a hand wheel foroperating the actuators during commissioning or power failure. The hand wheel does not

mo,e during motor operation.

!-t,ator -ontrols"3#

Both actuator signals and operation commands of the =CS are processed within the

actuator controls. This task can in principle e assumed y e-ternal controls! e.g. a PLC.

%odern actuators include integral controls which process signals locally without anydelay. The controls also include the switchgear reuired to control the electric motor.

This can either e re,ersing contactors or thyristors which! eing an electric component!

are not suject to mechanic wear. Controls use the switchgear to switch the electric motor

on or off depending on the signals or commands present. (nother task of the actuator

controls is to pro,ide the =CS with feedack signals! e.g. when reaching a ,al,e end

position.

$le-tri-al -onne-tion"/#

The supply cales of the motor and the signal cales for transmitting the commands to

the actuator and sending feedack signals on the actuator status are connected to the

electrical connection. The electrical connection is ideally designed as plugsocket

connector. For maintenance purposes! the wiring can easily e disconnected and

reconnected.

%ield2,s -onne-tion"?#

Field us technology is increasingly used for data transmission in process automation

applications. *lectric actuators can therefore e euipped with all common field us


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interfaces used in process automation. Special connections are reuired for the

connection of field us data cales.

CONCLUSION"

By using this system we can maintain the pressure in the set range and can a,oid the

o,er pressures. The operation and maintenance is made easy y using this system. 6e can

increase the life of the furnace y using this system. )ow the system is working effecti,ely

without any complications. Schneider electric plc is used for this system ecause of its ease of

programming

Documents

Pressure Control Flare Stack