Hydrotest Pressure Vs Design Pressure.docx

8/18/2019 Hydrotest Pressure Vs Design Pressure.docx

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Hydrotest Pressure Vs Design Pressure.

Design pressure is usually the pressure set by process engineer,

based on the results of a simulation or similar study. Hydrotest

pressure is the actual pressure the vessel is tested at. Usually thehydrotest pressure is 1.3 times the design pressure (AS!

re"uirement#.

So if the design pressure is 1$$ %&a(g#, the hydrotest pressure

'ould be 13$ %&a(g#. herefore the rule (or re"uirement# is called

1$)13 rule.

Maximum allowable Working pressure (MAWP) Vs Designpressure

Design pressure is usually the pressure set by process engineer,

based on the results of a simulation or similar study. A*& is the

pressure based on the actual characteristics of the

vessel)e"uipment ('hich is usually manufactured to e+ceed the

specications set by process engineer#. a+imum allo'able

'or-ing pressure is al'ays greater than or e"ual to design

pressure.

Permissive interlo!k " Di#eren!e

he &!/SS/0!S, are some conditions that need to be satised

before you can start the machine. or e.g. a compressor can be

started only 'hen there is su2cient suction pressure.

/!456%7 During the process, if a condition fails, interloc-s are

activated. or e.g. a pump shutdo'n interloc- is activated 'hen

the level of drum goes lo'.

An interloc- can also be a permissive, but the converse is not

true. or the compressor e+ample (in &ermissives#, if insu2cient


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suction pressure is a permissive, the compressor 'ill not

shutdo'n, if there is insu2cient suction pressure. /t is 8ust a

condition for the system to start. 9ut if insu2cient suction

pressure 'as an interloc-, the system 'ill shutdo'n, 'hen ever

the suction pressure goes belo' a +ed value. 9ut onceshutdo'n, all the permissives need to be satised before the

system can start again.

Hot bolting

Hot bolting is a method of replacing the bolts on a live line.

ormally done one bolt at a time. Hot bolting should be used only

'hen there is no other reasonable choice.

he criteria typically follo'ed is something li-e7

: he operating pressure must be less than ;


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: !+isting ?ange bolts)nuts must be tight and of the correct siEe

and grade.

Hot $olting% &al!ulations

/ am loo-ing for advice regarding the appropriate calculationmethod to nd the ma+imum operating pressure 'e can allo'

'hen 'e perform a Hot 9olt procedure (ie, removing one bolt at a

time for maintenace purposes#. / can run the calculations using

an AS! Section 0// calculator (r. &edersenFs#, but 'hen you

reduce the number of bolts by 1, it simply reGdistributes the

remaining bolts over the diameter. /f / remove half the bolts (to

accurately re?ect the increased distance bet'een ad8acent bolts#

to get the correct spacing, the bolt stress for A*& is tooconservative as compared to removing only one bolt (/ am loo-ing

at my limiting factor being bolt stress from either A*& or

seating perspectiveG 'hichever is greater#.

/ have never heard of anyone ta-ing one bolt at a time for

maintenance purposes from a pressurised vessel, sounds

e+tremely dangerous to me.

ossA9 G yes, one bolt at a time...but not necessarily IreplacingIG 'e often 8ust remove one bolt, clean it up, put some sort of

lubricant on it (the lubricant issue is a 'hole other can of 'orms#,

and then reGinstall the bolt)nut. *e do this on ?anges associated

'ith piping AD on vessel man'ays....most often in preparation

for turnaround maintenance, but also on the rare occasions 'hen

'e nd a bolt has some corrosion or 'hen 'hen nd a Ishort

boltI (ie, a bolt that is too short and the nut is not fully

engaged...usually on facilites 'e ac"uired at one time or another#or 'hen 'e nd a nut or bolt that is not the correct grade....in any

of these cases 'e 'ould then replace the bolt and)or nut.

desertfo+ G / donFt believe it is Ie+trememly dangerousI G the

industry has been doing this forever. ost of the larger

companies have specic procedures for this operation (/ have


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copies of the 9&, 6onoco&hillips, and the !!UA /nformation

sheet for Hot 9olting#. ol-s, than+ for your interests...and loo-

for'ard to your thoughts and suggestions for the ?ange limit

calcs.

Hot bolting is fairly common, /Fve been around it "uite a bit

before. /tFs simply replacing the bolts on a live line. Jou do it a

bolt at a time. hat being said, hot bolting should be usedo nly

'hen there is no otehr reasonable choice.

he criteria typically follo'ed is something li-e7

: he operating pressure must be less than ;$B

ahrenheit.

: All ?anges and associated system e"uipment must be

ade"uately supported, i.e. no e+cessive vibration or pulsation.

onitoring for hydrocarbosn is also a must during the operation.

Cenerally the procedure for hot bolting is the same se"uence as

for a tightening operation.

: he gas-et area must not sho' signs of lea-age. &iping, ?anges,

and bolts must not be severely corroded, i.e., to the point of

aecting their integrity.

: !+isting ?ange bolts)nuts must be tight and of the correct siEe

and grade.

/n my opinion, the ans'er to your stud bolt "uestion is.... Iit

dependsI....KKK/t depends mostly on the cost and degree of


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corrosion on the bolt. /f the bolt is of large diameter and of

e+pensive materials, it pays to be carefull and reuse it. Smaller,

more common materials may be replaced as a mater of policy

*e have hot bolted at 1L


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&5*! &4A 5&!A/5

9J UO/J55

95/4!

Denition

As per /ndian 9oiler Act 1NL3, 9oiler is dened as any closed

vessel e+ceeding LL.;< liters in capacity 'hich is used e+clusively

for generating steam under pressure and includes any mounting

or accessories attached to such vessel, 'hich is 'holly or partially

under pressure, 'hen steam is shut o.A good 9oiler should have some essential "ualities.

1. 6apable to meet large load ?uctuations.

L. uel e2cient i.e. to generate ma+imum steam 'ith minimum

fuel consumption.

3. Ability to startGup "uic-ly.

. !asy in maintenance and inspection.

. 4o'er friction loss in 'ater and ?ue gas circuit

;. 4ittle attention for operation and maintenance.

Systems in a 9oilerA 9oiler mainly contains follo'ing systems 7

1. eed 'ater system.

L. Steam system.


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3. Air system.

. lue gas system.

. Ash handling system.

9oiler ountings

ittings on a 9oiler 'hich are re"uired for its safe and e2cient

operation are called mountings. hese are as follo's 7

1. Safety valveL. *ater level sight glass (gauge glass#

3. &ressure gauge

. 9lo' do'n valve

. eed 'ater chec- valve (0#

;. Air 0ent

@. StartGup vent

N. anhole

9oiler Accessories

he devices 'hich are used in a 9oiler as an integral part andhelp to run the 9oiler e2ciently are called 9oiler Accessories.

hese are 7

1. Super heater

L. DeGsuper heater


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3. !conomiEer

. Air &reGheater


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During circulation of 'ater in tubes, steam is generated and

collected at the upper part of the Drum. his is called SaturatedSteam corresponding to 9oiler drum pressure. his steam is

further heated in Superheaters and becomes superheated steam.

9oiler Drum is lled 'ith fresh feed 'ater. he feed 'ater, before

entering into drum is heated at !conomiEer. !conomiEer is placed

at the ?ue gas path. ost of the heat of the ?ue gas is utiliEed

inside the 9oiler. Still considerable amount of heat energy isavailable in it. his heat is utiliEed in !conomiEer to heat up the

feed 'ater.

or burning of fuel, re"uired 5+ygen is obtained from atmospheric

air. Air is re"uired in 9oiler furnace for combustion. his is

supplied by orced Draught (D# fan. his air is heated at air preG

heater (A&H# before being sent into furnace. /f cold air is usedthen there 'ill be loss in energy. Air preGheater is placed at the

?ue gas path after !conomiEer. Air preGheater is a heat e+changer

'hich e+changes the heat of ?ue gas to the cold air, 'hich is to

be used in furnace. 9y heating the air, burning of fuel is easier

and loss of energy is minimiEed. /f hot ?ue gas 'ould not be used

to heat up feed 'ater at !conomiEer and air at Air &reGheater then

it 'ould escape into atmosphere.

inally the ?ue gas passes through !lectrostatic &recipitator (!S

and e+hausted to atmosphere through chimney. At !S& the dust

particle in the ?ue gas is trapped and clean gas escapes to

atmosphere.


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Ash 'hich is produced in the 9oiler due to combustion of solid fuel

is collected at 9oiler bottom and also in !conomiEer, Air &reG

heater and !S&. his ash is disposed o 'ith the help of suitableash handling system.

&reparations for 6old StartGup

1. All the manhole doors should be in close condition. ightness

of the uts and 9olts of the man hole doors to be chec-ed

properly.

L. All the 'ater 'all drain lines should be in close condition.

3. All the steam drain lines should be in open condition.

. StartGup vent oot anual isolation valve should be in open

condition.

. 6ontinuous 9lo' Do'n (69D# and /ntermittent 9lo' Do'n(/9D# drains should be in close condition.

;. All the super heater vents including Drum vent and &uppy

Header vent should be in open condition.

@. 9efore and After /solation valves at eed 6ontrol Station

(6S# should be in open condition.

N. Attemperation 6ontrol valve before and after isolation valve

should be in open condition .

1$. Hydra step should be in healthy condition.

11. Safety valves should be in healthy condition.


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1L. ain Steam stop valve and byG pass valve should be in close

condition.

13. Soot blo'er manual isolation valve and control valve should

be in close condition.1.9oiler Drum Cauge glass steam side and 'ater side isolation

coc-s should be in open condition.

1. Solution in H& Dosing agitator tan- should be at normal

level.

1;. 9oiler eed &umps should be in healthy condition.

[email protected] 'ater level should be maintained at >$= by ta-ing

D ransfer pump in service.

1N. Air compressors should be in healthy condition.

L$. Ash handling systems should be in healthy condition.

L1. !S& should be in healthy condition.LL. /D fan damper should be in Pero position.

L3. All the interloc-s and protection should be chec-ed properly

viE. Drum level lo', Deaerator level lo', 9oiler eed &ump (9

discharge pressure lo', lue gas temperature at &ost 6ombustion

6hamber (&66# outlet high, silo level.

6old StartGup process


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1. After %iln lightGup, 'hen ?ue gas temperature at &66 outlet

increases to more than . 9y ad8usting damper opening raise the 9oiler pressure upto

< -g)cmL and @< deg 6.

;. StartGup vent should be in open condition since the

admittance of hot ?ue gas in boiler.

@. 5pen the ain steam line drains in bet'een 9oiler ain

Steam Stop 0alve (SS0# and C SS0.

N. 5pen the SS0 by pass valve to remove all the condensate in

main steam line and ensure that C SS0 is in close condition.

1$. After removal of all the condensates in ain steam line and

proper line heating, open ain Steam stop valve of 9oiler.

11. 6lose Super heater drains.

1L. &ut Drum level controller in Auto mode.

13. &ut Attemperator controller in Auto mode.

1. 6lose Start up vent as per the steam demand of C set.


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1


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>. Slo'ly open damper of /D fan. *atch Drum level.

;. egulate 9oiler pressure by opening startGup vent.

@. Super heater temperature has to be maintained 'ith the

help of attemperator control valve.

N. aise the 9oiler pressure upto < %g)cmL and temperature to

@< deg 6.

1$. 5pen the drains of ain steam line in bet'een ain Steam

Stop 0alve (SS0# of 9oiler and urbine.

11. 5pen 9yGpass valve of SS0.

1L. 6ondensate, if any, 'ill be drained out and main steam lineheating 'ill be carried out by opening of byGpass valve.

13. After ensuring proper ain steam line heating, open ain

1. steam stop valve.

1. 6harge !S& 'hen ?ue gas temperature at !conomiEer outlet

reaches 1>$ deg 6

1;. &ut drum level controller and attemperator controller in Auto

mode.

1@. egulate the pressure of 9oiler 'ith the help of startGup vent.

1N. 6lose StartGup vent as per the steam demand of C set.

L$. ormaliEe /D fan damper by gradual opening and loading of

9oiler.

6harging of DeGareator


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/t removes the dissolved gases from the condensate mechanically

by follo'ing t'o la's

1. HenryQs 4a'

L. DaltonQs 4a' of &artial &ressure.

R According to HenryQs 4a', Solubility of dissolved gases

decreases by increasing 'ater temperature. So by charging steam

in Deaerator 'ater temperature increases and soluble gases in

condensate departs.

R According to DaltonQs 4a' of &artial &ressure &m &sT&a

*here &m &artial pressure of i+ture&s &artial pressure of Steam

&a &artial pressure of Air

R he partial pressure of air present inside the Deaerator

comes out

R through Deaerator vent for e"uilibrium state.

&rocedure 5f 6harging

1. !nsure D Storage an- level is more than >$=.

L. Start D ransfer &ump by opening ecirculation valve.

3. !nsure Deaerator level is >$=. /f the level is less then ta-e the

ma-e up 'ater .

. 5pen all drain lines of &egging &DS line and observe that

condensate is completely drained out.


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>. Cradually increase the pressure to L.@ %g)cmL by increasing

pegging &DS pressure control valve.

;. Slo'ly heat the Deaerator by opening the heating line isolation

valve and raise the Deaerator temperature to N$ deg 6.@. 5pen the before and after isolation valve of Deaerator &ressure

6ontrol valve. hen open the pressure control valve gradually.

Slo'ly increase the Deaerator pressure upto L -g)cmL .After that

put the Deaerator &ressure control valve in Auto mode.

N. Start 4& Dosing pump.

1$. /n 4& Dosing HydraEine is used. HydraEine removes o+ygen

by chemical reaction.

11. !UA/5G LHT5LLHL5TL

1L. 9y adding HydraEine dissolved o+ygen becomes 'ater and

itrogen gas releases.

*H9 /nterloc-s

1. /f Drum level becomes very lo' i.e. L


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. *hen all running 9&s rip, then Drum level falls drastically.

o protect the 9oiler from starvation heat ?u+ input should be cuto.

;. /f Deaerator level becomes very lo' i.e.L


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1@. !S& can not be charged 'ithout starting of &urge Air 9lo'er.

L$. his is to Seal the !S& by the air from &urge Air 9lo'er

before charging it.

LL. !S& can not be charged till ?ue gas inlet temperature reaches1>$ deg 6.

L3. his is to avoid deposition of moisture and oil content in?ue

gas on !S&.

1. Decrease in Drum level

a. ripping of eed &ump

/f 9oiler feed &ump trips then eed 'ater supply to 9oiler

interrupts and leads to lo'ering of Drum level. /f this has

happened then ensure that the auto standGby 9oiler feed pump

has started in Auto mode. /f the auto standGby 9oiler eed pump

has failed to start in Auto mode then start the 9oiler feed pump

manually other'ise 9oiler 'ill suer from starvation andultimately it 'ill lead to 9oiler trip to protect the 9oiler.

b. ube failure in !conomiEer

/f 9oiler !conomiEer tube fails then 'ater supply to 9oiler Drum

'ill be aected. his leads to decrease in drum level and eed

6ontrol valve 'ill open more to compensate the Drum level to

ormal 'ater level, 'hich leads to overloading of 9oiler eed

pump.

5bserve the steam ?o' and feed 'ater ?o'. /f feed 'ater

demand to drum is increasing then observe any sound from the

furnace. /f tube has failed inside boiler then hissing sound comes


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and it can be noticed from outside. Simultaneously chec- the

smo-e from the chimney. /f it is of 'hite colour then tube failure in

side the furnace is conrmed.

c. Unit getting into /sland mode

*hen Unit comes to /sland mode, it follo's the load connected to

the Cenerator. Suppose Unit is generating more po'er than the

Unit load and e+porting to Crid.

At the time of /slanding, Cenerator 'ill follo' the load connected

in this Unit and the Coverning 6ontrol 0alves 'ould close

according to load and allo' the steam to pass through urbine. he surplus amount of steam 'ill remain in 9oiler 'hich increases

the Drum pressure. his drum pressure 'ill e+ert a do'n'ard

thrust to the drum level and it decreases drastically.

d. *hether 69D valve, !9D valve or /9D valve opened

/f any operating personnel has opened any of these valves

'ithout proper reason or intimation then also drum level

decreases rapidly. !nsure rst then close the valve or regulate it

observing the drum level.

L. /6!AS! / DU 4!0!4

a. *hether 6old startGup in 9oiler is in progress

During 6old startGup 'hen 'ater temperature reaches N$$ 6 then

formation of bubble starts. his is -no'n as s'elling


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phenomenon. /f this is the case then blo' do'n has to be given to

maintain the drum level at ormal 'ater level.

b. *hether /nstrument air compressor tripped and air loc- unitat feed control station failed

/f /nstrument air compressor trips, then air loc- unit of control

valve at feed control station -eeps the control valve at a position

at 'hich it 'as, before supply of instrument air. his is -no'n as

stay put condition. /f air loc- unit fails to -eep the feed station

control valve at stay put condition, then 'hen supply of

instrument air fails, it leads to 1$$= opening of control valve. /f

this happens, start the instrument air compressor as early as

possible and regulate the feed station control valve.

c. *hether StartGup vent has opened or safety valve popped

up

9y opening startGup vent, 'hen 9oiler is in steaming condition,

supply of steam to urbine Drum level increases rapidly due to

release of pressure in drum. /f the steam demand in C has

reduced to a large e+tent then it results 9oiler drum pressure rise

"uic-ly and at that instant drum level falls rapidly. *hen startGup

vent is operated to release the surplus steam or safety valve pops

up, then drum level increases rapidly. /n this case at rst ensure

for 'hat reason the pressure in 9oiler has increased. /f drum level

is increasing drastically then give blo' do'n to regulate it.

9ecause at higher side drum level, the steam "uality 'ill be


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aected and carry over of 'ater particles to super heaters and

turbine 'ill ta-e place, 'hich is very much harmful.

d. *hether StartGup vent has opened or safety valve poppedup 6ontinuedV.

5peration should not be carried out 'hen 9oiler is in loaded

condition. Donot close the eed 6ontrol valve fully if drum level

rises because if the control valve is closed completely, the feed

'ater in !conomiEer tubes, 'hich 'as passing to Drum, 'ill

became steam due to heat in ?ue gas and 'hen feed 'ater

supply through !conomiEer 'ill be again established through eed

control valve then hammering in !conomiEer tubes due to

presence of steam. his may lead to !conomiEer tube failure.

After ensuring the reason, close the startGup vent and dump the

surplus steam in 6ondenser. !nsure that the safety valve has

been reset in its position and no passing is observed.

e. *hether drum level transmitter is malfunctioning

/f drum level transmitter is malfunctioning then observe the level

in hydrastep and immediately inform shift in charge and

instrument personnel about this.

f. *hether rapid heat supply to 9oiler

/f heat supply to 9oiler 'ill be increased suddenly 'ith a huge

amount then it aects the drum level and it s'ells. o avoid this

regulate the heat input supply in a gradual loading manner.

Sudden and huge amount of heat supply 'ill overheat the grain

structure of the tubes and it suers from fatigue. /n course of time

tube fails.


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g. *hether standGby 9oiler eed &ump has started

*hen standGby 9oiler feed 'ater pump has started 'ith running

9oiler feed 'ater pump, then Drum level increases because atthat opening in 9oiler feed 6ontrol valve 'hen feed 'ater

pressure increases, more feed 'ater ?o's to drum due to that

opening of control valve and leads to increase in drum level. his

case normally happens during scheduled !"uipment change over

of 9oiler feed 'ater pump. At rst the standGby feed 'ater pump

is started and discharge valve of the respective feed 'ater pump

is opened. After that the previously running 9oiler feed pump is

stopped. !nsure 'hether it is a scheduled e"uipment changeover.

h. *hether C has come to /sland mode

/f C has come to /sland mode then 9oiler pressure increases as

there is a cut o steam demand as Cenerator has to follo' the

load, connected to it in this unit. /f unit 'as e+porting the po'er

to Crid then the surplus po'er 'ill be reduced at that instant,

'hich the Covernor of the C set 'ill follo'. /t closes the control

valve and steam pressure rises in 9oiler accordingly. !nsure that

the unit is running under /sland mode. 5pen the start up vent to

release the pressure. !nsure that the Safety valve has popped up

or not. /f popped up then it has reset properly or not. 5bserve the

drum level during this operation. 5bserve the Dump control valve

is functioning properly or not. /f it is responding properly then tryto supply steam to condenser by closing startGup vent after

ensuring that 9oiler pressure has reduced and safety valve has

reset.


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h. *hether C tripped

/f turbine trips then steam demand in urbine 'ill cut o and

resulting 9oiler pressure rise. !nsure Dump circuit is healthy.

5pen the 6ontrol valve of dump and close the startGup vent afterensuring that the safety valve reset.

i. *hether any 6ooling 'ater pump in C has tripped

*hen 6ooling 'ater pump in C for 6ondenser condensate

cooling trips then the vacuum in condenser drops "uic-ly and at

that instant if the auto standGby pump fails to start then the load

set point at Cenerator has to be reduced 'ith immediate eect.5ther'ise the C 'ill trip due to lo' vacuum. *hen load set point

at Cenerator decreased suddenly then 9oiler pressure increases.

/n this case communicate 'ith the C operator and open startGup

vent and lo'er the 4oad set point. ry to start the ain cooling

'ater pump manually. After restoration of cooling 'ater pump

divert the steam from startGup vent by closing it to the dump

circuit and normaliEe the load of Cenerator.

3. Decrease in 9oiler Steam &ressure

a. *hether ?ue gas inlet temperature has reduced

/f ?ue gas inlet temperature reduces then it steam generation

reduces in 9oiler and pressure drops. his has to be observed

very carefully and the generator 4oad set point has to be lo'ered,

other'ise the C 'ill trip 'hen the ain steam pressure becomes

lo'.


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b. *hether more steam demand at C end

/f the unit is running at lo' load as steam generation in 9oiler is

lo'. /f as a mal operation 4oad set point at Cenerator is given

more than steam generation then 9oiler pressure decreases. and C is running 'ith lo' load set point. Unit is importing po'er from

Crid. /f unit came to /sland mode then the Cenerator 'ill follo'

the load 'hich is connected to it and load set point at Cenerator

increases than the steam generation in 9oiler. So 9oiler pressure

decreases. As 'e can not change the load set point of Cenerator

by putting lo'er set point value, 4oad on the Cenerator has to be

lo'ered by cutting o the load connected to it. 6hoose the less

important load connected to Cenerator and cut o it as "uic-ly as

possible other'ise the unit 'ill suer from 9lac- out condition

due to C trip at ain steam pressure lo' and Crid po'er is

unavailable.

he same case happens 'hen the steam generation in 9oiler is

lo'

c. *hether superheater tube failed

/f superheater tube fails then 9oiler steam pressure decreases.

5bserve steam ?o' and feed 'ater ?o'. /f steam ?o' is at

lo'ering trend and feed 'ater ?o' is at increasing trend then it

indicates that tube has failed. /f the tube failure has occurred in

side the furnace then 'hite smo-e comes out from chimney.

*hen steam pressure decreases then reduce the Cenerator set

point accordingly to avoid C trip at main steam pressure lo' and

ensure 'hether tube has failed or not. /f tube has failed then

9oiler shut do'n has to be ta-en to replace the failed tube 'ith a

ne' tube.


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b. *hether Soot 9lo'ing is in progress

During soot blo'ing, steam temperature rises because more

steam is re"uired for soot blo'ing and heat input to the 9oiler hasbeen increased by opening the /D fan damper. So during soot

blo'ing, main steam temperature has to be observed carefully. /f

attemperator control valve fails to control the rise in main steam

temperature in auto mode, then it has to be controlled ta-ing it to

manual mode.

c. *hether Attemperation control valve is in manual mode or'rong value command input by the operator

ormally it happens 'hen there is a high ?uctuation in main

steam temperature. he attemperation control valve fails to

control the temperature in Auto mode. So the concerned operator

has to ta-e the attemperation control valve to manual mode to

control the temperature. 9ut if he forgets to put this control valve

in Auto mode after stabiliEation of main steam temperature, then

it 'ill remain in manual mode and during more heat input from

%iln, the main steam temperature 'ould rise. Also sometimes

operator puts 'rong value command for attemperation control

valve opening from control station in manual mode, 'hich 'ould

result in increase in main steam temperature.

d. *hether forget to open before and after isolation valves of

attemperation 6ontrol valve

his situation comes during cold startGup of 9oiler, if the

inspection and chec-ing 'as not done properly by the operation

personnel. During initial period, this thing cannot be noticed but

at the time of main steam temperature rise by opening


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attemperation control valve ?o' of 'ater cannot be established

as before and after isolation valves are in close condition. So care

has to be ta-en for proper inspection and chec-ing before startG

up.


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*hen &ost 6ombustion 6hamber temperature increases more

than 1$. UA6! DAUCH 5*ADS &5S//0! S/D!

a. *hether tube failure has occurred in side furnace

/n furnace, the draught is maintained at negative side to carry outthe hot ?ue gas, ash and other suspended particles from -iln to

chimney through /D fan. /f 9oiler tube fails inside furnace then

draught goes to'ards positive side. As steam density is higher

than air density. Also it adds an additional load on /D fan. So /D

fan ta-es more current in this situation.

b. *hether draught transmitter is sho'ing 'rong value

his can be -no'n if other draught transmitters in ?ue gas path

are sho'ing right value and one of these is sho'ing erratic value.

his problem should be brought to the notice to shift in charge

and instrumentation personnel.

;. 45C !A6A94! S55 945*! /S 5 A /S 5/C/A4

&5S//5

a. *hether 4ong etractable soot blo'erQs chain has bro-en

during Soot 9lo'ing operation


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/f chain brea-s at intermediate position of lancer tube during soot

blo'ing by 4S9, then motor 'ill be unable to retract it to the

original position i.e. home position. 6hec- the position of lancer

tube, 'hen soot blo'ing operation is in progress and chain has

bro-en. /n this situation, donot cut o steam ?o' through lancertube. /t is because it is situated in high heat Eone i.e. at

convection Eone. As steam acts as a coolant, it 'ill ta-e the heat

added to the lancer tube and 'ill protect the lancer tube from

over heating and bending. he lancer tube has to be dra'n out

manually. After ensuring that it has been dra'n to its home

position, steam through the lancer tube can be cut o and chain

maintenance 'or- can be carried out.

b. *hether home position limit s'itch is malfunctioning

his may happen after completion of soot blo'ing by 4ong

etractable Soot 9lo'er. he limit s'itch at home position may

not give home position feed bac- of the 4S9 due to malfunction.

/f this case happens then immediately the position of the lancer

tube has to be chec-ed. 4imit s'itch at home position has to be

rectied by /nstrumentation department.

c. HA!/C 5 A/ S!A 4/! DU/C 6HAC/C.

Usually main steam line hammering occurs if the condensate

present in that line is not properly drained out and pipe line is in

cold condition. /f huge amount of steam is allo'ed to pass

through that pipe line then line hammering ta-es place 'hich isvery much harmful for the pipe line. So to avoid this case

happening al'ays open the drain of the pipe line. 5bserve the

condensate is drained properly from that pipe line. After

completion of condensate draining, 'armGup the pipe line 'ith

very less "uantity of steam. Cradually increase the pipe line


30/122

temperature. After conrmation that the line is properly heated,

more steam ?o' can be allo'ed.

Steam urbine

Steam turbine is a mechanical device that e+tracts thermal

energy from steam and converts it into mechanical 'or-.

/nteriors of a turbine consists of several sets of blades. Some set

of blades are +ed at casing ( i+ed 9lade# and some set of blades

are +ed on the rotor ( oving 9lade# .

i+ed blades convert potential energy of the steam into -inetic

energy and direct the ?o' to moving blades. oving bladesconvert this -inetic energy in to force, caused by pressure drop

and result in rotation of turbine shaft. Steam is allo'ed to enter

into the turbine through control valve. his steam after passing

through dierent stages of blades is allo'ed to e+haust. he

e+haust steam is condensed in a condenser and condensate then

reused in boiler.

1. /mpulse urbine

L. eaction urbine

1# /&U4S! U9/!7

/n /mpulse turbine instead of set +ed blades a set of noEEles are

tted in the casing. &ressure drop of steam ta-es place in these

noEEles and velocity of steam increases. his high velocity 8et of

steam contains signicant amount of -inetic energy. his high

velocity steam is passed through a set of moving blades, 'here

pressure of the steam remains constant and velocity decreases.


31/122

L# !A6/5 U9/!7

/n reaction turbine +ed blades are +ed in the casing. Shape of

these blades is such that the space bet'een the blades has cross

section same as shape of noEEle. oving blades are +ed to therotor. i+ed blades guide the steam to moving blades . 9lade

shape is so designed that steam glides over the blades. Steam

'hile gliding over moving blades produces reaction on the blade.

his reaction force produce the rotates the rotor.

1. 6asing

L. otor

3. oving 9lade

. i+ed 9lade

. 9earing

W Ooural 9earing

W hrust 9earing;. Cland

@. !+haust Hood

N. !mergency Stop 0alve

1$. Coverning 0alve And 6ontrol 0alve

11. 9arring Devices.

1L. Coverning Systems

v 6AS/C


32/122

6asing of turbine plays important role for the performance of a

turbine. his is the outer shell of turbine. i+ed blades and noEEles

are attached to this. 6asing facilitates to accommodate moving

parts and provides passage for steam. ormally it is formed by

casting. As the temperature of steam for operating turbine is highso, normally 6r, o alloy steel casting is used for casing of a

turbine. etal to metal 8oint sealing is done to ensure no lea-age

of steam.

v 55

otor is the moving part of a turbine 'hich e+tracts 'or- from

steam. his is the heaviest part of the turbine. ormally total

shaft is manufactured by forging. otor consist of shaft moving

blade and inter stage sealing labyrinth. hrust collar is provided

to ta-e care of a+ial thrust of rotor during various load conditions.

otor of the turbine is allo'ed to e+pand uniformly. otor of the

turbine should not be allo'ed to remain stand still 'hen it is hot.

Due to its self 'eight there is a chance of sagging or deformation.otor

v oving 9lades

!nthalpy of steam is converted into rotational energy as it passes

through turbine blade sets. /n each stage of the turbine there are

moving and +ed blade. As in each step pressure of steam

decreases, its volume increases. he blade has to handle more

volume of steam. 9lade has to 'ithstand high pressure andtemperature of steam. Cood tensile and fatigue strength is

re"uired. Cood vibration damping property, lo' ductility,

resistance to corrosion and erosion is essential. 9lade can be

divided into three portions.

1. ip


33/122


34/122


35/122

. 6554/C *A! SJS!

urbine 6old Startup Se"uence ethod

5peration of steam turbine is a comple+ process. 9efore starting

the rolling of a turbine, au+iliary systems are to be properly put in

service. ormally for start up of a turbine some operations are

follo'ed in se"uence.

v 6harging of Steam &ipe 4ine

rom 9oiler, steam is carried to turbine main steam pipe line. /n

cold condition, special care is to be ta-en to heat up the steam

line and allo' gradual thermal e+pansion, before giving full load

on the turbine.

Drain points are provided at the steam line to drain out

condensate present in steam pipe line, that is formed due to

condensation of steam. irst of all, these drains are opened beforecharging steam on the pipe line. After condensate is drained out

boiler main steam stop by pass valve is opened slo'ly .

Some steam is allo'ed to ?o' through the pipe line and it starts

gaining heat from the steam and steam is condensed. At the

beginning, condensate along 'ith some steam is allo'ed to come

out through the drain. hese drains are throttled slo'ly and

closed 'hen no more condensate but only dry steam comes out

from the drain.

Steam traps provided in the pipe line are -ept in line once drains

are closed. hen ain Steam Stop 0alve of the boiler is opened

slo'ly so that the line temperature is increased gradually. !nsure

e+traction is not restricted any'here. *atch the temperature of


36/122

bypass reaching the normal level after 'hich stop valve of boiler

can be opened fully.

o circulate cooling 'ater in the 6ondenser, cooling 'ater pumps

are to be started.

9efore starting pump

1. !nsure Sump level of the cooling to'er basin is normal

(X@$=#

L. %eep suction valve of the pump in open condition Y

discharge in closed condition.3. !nsure inlet Y outlet cooling 'ater valves of 6ondenser

distributer valves of cooling to'er are in open condition .

. !nsure vents provided at 6ondenser 'ater bo+ are in open

condition to remove trapped air.

. 5bserve 'hether cooling 'ater is falling on the cooling to'eror not.

;. !nsure that distribution of cooling 'ater in all chambers is

e"ual, other'ise ad8ust the valves provided at the distribution

header .

@. 5bserve 'hether all the cooling 'ater pumps are sharing

load or not.

N. 5nce urbine is started and loaded, cooling to'er fans canbe started one by one as per re"uirement.


37/122

Starting 5f .5.& ( ain 5il &ump #

1. 9efore starting of .5.& chec- the healthy condition of ain

5il an- ( .5. # lo' level s'itch from H../ .

L. 9efore starting .5.&, chec- oil level in .5.& oil cup as 'ell

as oil level in A.5.& Y !.5.& oil cups.

3. !nsure again suction Y discharge valves of .5.&, A.5.& Y

!.5.& are in open condition .

. Start .5.& .

. &ut A.5.&, O.5.& Y !.5.& in auto selection mode.

a-ing 5il 6ooler into 4ine

1. *hen .5.& starts, oil circulates to the circuit through oil

cooler

L. o ensure oil is passing through the oil cooler or not, see

through the vie' glass after opening the air vent of oil cooler

3. After conrming oil is passing through the vent valve to

.5., close the vent valve

. 5pen the oil e"ualiEing line of standby oil cooler and 'ait for

some time to ll it 'ith oil, then close the e"ualiEing valve


38/122

a-ing 5il 6ooler into 4ine

1. *hen .5.& starts, oil circulates to the circuit through oil

cooler

L. o ensure oil is passing through the oil cooler or not, seethrough the vie' glass after opening the air vent of oil cooler

3. After conrming oil is passing through the vent valve to

.5., close the vent valve

. 5pen the oil e"ualiEing line of standby oil cooler and 'ait for

some time to ll it 'ith oil, then close the e"ualiEing valve


39/122

vi. Alternator ear Oournal

9earing Z 1 %g)cmL

3. 6hec- individual bearingFs return oil line vie' glass 'hether

oil is passing through it or not.. 6hec- overhead tan- oil return line vie' glass , ensure oil ?o'

through return oil line then close "uic- lling valve of overhead

tan- .


40/122

@. 6lose all drain valves

N. &ut the &60 in Auto mode 'ith desired pressure set point

1$. 5pen manual isolation valve of 60 ( emperature 6ontrol

0alve#

11. 5bserve the temperature and then put 60 in auto mode

'ith desired temperature set point

6harging of Cland Header

1. 5pen all drain valves of gland steam header

L. 5pen gland steam header manual isolation valve

3. 5pen gland steam header &60 by


41/122

o put the condensate system in operation, follo'ing steps are

re"uired to be follo'ed7

1. !nsure condenser hot 'ell level is ade"uate, other'ise ll the

hot 'ell 'ith ma-e up D *aterL. 5pen Suction and discharge valves of the pump. !nsure

dierential pressure of the strainer is normal

3. 5pen condensate inlet and outlet valves of gland seal

condenser, e8ector condenser and 4& Heater

. &ut the reGcirculation control valve in auto mode


42/122

1. !nsure availability of au+iliary steam at desired pressure Y

temperature

L. !nsure the vacuum brea-er valve of the condenser is closed.

3. !nsure cooling 'ater is circulating in the condenser andturbine gland is charged fully

. 5pen steam valve of the starting e8ector

. 5pen e8ector air valve

;. 5bserve vacuum inside condenser is increasing slo'ly.

@. ain e8ector is to be ta-en into line once turbine is loaded and

starting e8ector is to be stopped then.

o put main e8ector into line, follo'ing steps to be follo'ed 7

ain e8ector is to be ta-en into line once turbine is loaded.

Starting e8ector is to be stopped then. o put main e8ector in line,

follo'ing steps to be follo'ed.

1. !nsure 6ondensate !+traction &ump (6! is running .

L. !nsure cooling 'ater inlet and outlet valves of the e8ector

condenser are opened.

3. 0ent out air from 'ater bo+ of the e8ector condenser by

opening rotametre valve.

. 5pen e8ector condensate trap before and after isolationvalve


43/122

;. 6lose all drain valves of e8ector

@. 5pen the main isolation valve of the e8ector steam line

N. Slo'ly open the air line valve of the e8ector and observe

vacuum is increasing.

*hen vacuum is stable, then the slo'ly e8ector can be stopped by

closing air valve rst then the steam valve of e8ector.

5nce Au+iliary systems are in operation and full vacuum is

obtained inside, condenser turbine can be started. urbine is

re"uired to be started in t'o dierent conditions.

1. 6old StartGUpL. Hot StartGUp

/n cold startup turbine is started from cold condition. /n this case,

special care is ta-en for proper heating of casing and rotor for

proper thermal e+pansion. As both rotor and casing are in cold

condition it re"uires time for heat up. 9ut in case of hot start up

both casing and rotor are in hot condition. So it can be started

'ithin a short period.

Startup 6urve

o allo' proper thermal e+planation of casing and rotor, the

turbine manufacturerQs advise is to be follo'ed for start up

procedure.

W steam should not enter immediately to turbine as it may

damage the turbine due to uneven e+pansion.

W anufacturers suggest soa-ing time for lo' idle speed and high

idle speed for proper thermal e+pansion bet'een rotor and

casing means to hold the turbine at the particular speed for a

particular time, then allo' the turbine speed to higher range.


44/122

Soa-ing time is dierent for cold startup and hot startup.

anufacturerQs advice should al'ays be follo'ed strictly for

soa-ing and start up curve in cold startup and hot start up

conditions.

urbine olling &reparation..contd

o start rolling of turbine, some steps are follo'ed depending

upon mode of starting (Auto or anual# and types of governing

system (Hydraulic or !lectro Hydraulic#

9efore rolling of turbine chec-, ensure the follo'ing points 7

1. 4ube oil level and control oil pressure are normal

L. 4ube oil temperature is bet'een L to . !nsure the casing drain, C inlet steam line drain, C 'arm

;. up vent and drain are in open condition

@. !nsure Accumulator is in line

N. !nsure over head oil tan- is full and return oil ?o' is visible

in the vie'ing glass

1$. !nsure 6ondensate !+traction pump (6! is in operation


45/122

11. !nsure !+haust hood spray solenoid valve is in operating

condition.

1L. 5pen the bypass of urbine Steam stop valve (SS0#

13. !nsure complete removal of condensate from C inlet lineand ensure the temperature of C inlet steam is rising after

throttling drain valves. 5pen urbine Steam Stop 0alve (SS0#

1. hrottle the 'arm up vent as per re"uirement and observe

steam temperature is rising. 5nce steam temperature reaches at

desired temperature, then prepare for C rolling.]

C olling

1. eset the governor from 'ood yard S5S

L. eset from H/

3. !ngage trip lever and ensure build up of trip oil pressure at

governing console. 5pen !.S.0. (!mergency Stop 0alve# from H../.

. Cive run command from H/

;. 5bserve the rise in rpm gradually. & goes up and after

reaching 1$$$ rpm (4o' /dle speed# automatically, it 'ill hold for

1< minutes in hot start up and 3$ minutes in cold startup (in case

of auto rolling#. 5ther'ise hold the speed as advised by the

manufacturer.

@. !nsure oil pressure is normal. 6hec- vibration and any

abnormal sound


46/122

N. irst stop barring gear then stop 8ac- oil pump (O.5.

1$. Cet the relay reset before L$$$ rpm

11. After completion of the hold time at 1$$$ rpm, .&.. goes

from lo' idle speed to high idle speed L


47/122

. !8ector and 0acuum System


48/122

Also called ull lood 4ubrication)*edge lm lubrication

*edge lm formation due to geometry Y speed.

a. /n hydrodynamic principle ?uid viscosity is not su2cient to

maintain a lm bet'een the moving surfaces Y higher pressurere"uired to support the load until the ?uid lm is established, the

re"uired pressure generated internally by dynamic action.

b. he 'edge lm lifts the 8ournal and allo's complete

separation

c. he formation of a thic- ?uid lm that 'ill separate t'o

surfaces and support a load as the t'o surfaces move 'ith

respect to each other.

9y feeding oil from an e+ternal source under heavy pressure into

the poc-et machined into the bottom of the bearings, the 8ournal

can be lifted and ?oated on ?uid lms.

*hen the 8ournal reaches a speed su2cient to create

hydrodynamic lms the e+ternal pressure can be turned o and

the bearing 'ill continue to operate in hydrodynamic manner.

6omponents of 4ubricating 5il System

ain components of lubricating oil system are 7

1. 5il tan-

L. 5il pumps

3. 5il lter

. 5il centrifuge


49/122

>. Accumulators

5il tan-

otal oil for the system is stored in the this tan-. he tan- has

ade"uate capacity to hold su2cient oil during running Y stop

condition. he tan- base is made sloped to one side, so that the

sediment in oil can be collected in the lo'er area and can be

drained out by opening drain valve. he tan- has level

measurement facility to give alarm for lo' oil level. Also a level

glass is provided to nd out tan- level at any instant. Suitable

tapings are provided to facilitate oil suction for oil pumps, draining

of return oil from bearings and governing system, connection for

oil centrifuge, ll up of fresh oil etc.

5ne oil mist fan is provided on the tan- to vent out any oil vapor

and -eep the tan- slightly belo' atmospheric pressure.

5il &ump

o pump oil from the oil tan- to various lubrication points and

controlling purpose, oil pumps are provided. ormally three

pumps are provided. hese pumps are 7

1. ain oil pump ( .5.& #

L. Au+iliary oil pump ( A.5.& #

3. !mergency oil pump ( .5.& #

5il 6oolers

ormally t'o oil coolers of 1$$= capacity are provided to cool

do'n entire oil supplied to turbine bearings,gearbo+,and


50/122

generator bearings for lubrication. Coverning oil is not cooled at

oil cooler. his oil ta-en out before oil cooler. 5ne cooler is put on

line and another one is -ept as standby. 5nline changeover facility

is provided to ta-e the standby cooler in to service, 'ithout

interruption of oil supply, 'hile turbine is running.

9efore changeover, it is to be ensured that the standby cooler is

lled 'ith oil and air is vented out properly. 5ther'ise there 'ill

be air loc- and oil supply to bearings may interrupt.

5il cooler is a shell and tube type heat e+changer. 6ooling 'ater

?o's inside the tube bundle and oil ?o's at the shell side. 6ooling

'ater for oil cooler is obtained from main cooling 'ater system of

po'er plant. egulating valves are provided at the inlet and outletof the cooling 'ater supply line.

o increase and decrease oil temperature, cooling 'ater ?o' is

decreased and increased respectively through these regulating

valves. Al'ays the cooling 'ater outlet valve is regulated to vary

?o' of cooling 'ater. At any case cooling 'ater inlet valve is not

to be throttled as su2cient cooling 'ater 'ill not available inside

tub and tube may damage.

Drain point is provided at the cooler to drain out settled sediment

at bottom of the cooler.

5il ilters

5il coming out from cooler is passed through oil lter to remove

any contaminated particle or debris. ilter is normally bas-et type

'ith removable lter cartridge. 4i-e cooler there are t'o lters of

1$$= capacity each 'ith suitable online changeover

arrangement. he oil is ltered up to L$GL< micron level on these

lters before circulating in bearings.


51/122

Dierential pressure across the lter is measured 'hich indicates

the cho-ing condition of lter cartridge. /f dierential pressure is

high it indicates, lter is cho-ed and needs cleaning.

9efore changeover of oil lter 'hen turbine is in operation, it is tobe ensured that standby lter is completely lled and no air is

trapped inside. ilter cartridge of standby lter is al'ays to be

-ept clean, so that at any moment this can be ta-en in to line, if

re"uired.

5il 6entrifuge..contd.

6entrifuge is a machine 'hich separates 'ater and solid particlesfrom oil. his is achieved by centrifugal force of a high speed

rotating bo'l inside the separator. Due to centrifugal force,

heavier particles are displaced to'ards the outer periphery of the

bo'l and the lighter oil is displaced to'ards center of the bo'l,

'here it is collected and sent bac- to main oil tan-.

Steam !8ector And 0acuum System

0acuum is maintained by continuously evacuating non

condensing gases from the condenser 'ith the help of steam

e8ector. &ressure of non condensing gases decrease condenser

e2ciency. or removing non condensing gas to create vacuum in

the condenser normally steam e8ector is used. his is li-e a pump

in 'hich venturi eect of a converging and diverging noEEle is

used to convert pressure energy of steam to velocity energy to

create suction eect.

*5%/C &/6/&4! 5 !O!65


52/122


53/122

Surface 6ondenser

his type of condenser is 'idely used at po'er plants. 6ooling

'ater is not mi+ed 'ith condensate in this case. 6ondensateobtained is pure and can be used in boiler. his is a shell type and

tube type heat e+changer. Shell of the condenser is closed. ubes

are arranged inside the shell in 'hich cooling 'ater ?o's.

6ondenser nec- is connected to the e+haust hood of turbine. An

e+pansion 8oint is provided inGbet'een to facilitate thermal

e+pansion.

Steam from turbine ?o's at the shell side of condenser and

cooling 'ater ?o's inside the tube. ain components of a surface

condenser are 7

G Shell G Hot 'ell

G Air outlet G ube

G apture dis- G *ater bo+

5verhead an-

5il accumulator is provided on the governing or control oil line of

the turbine. his accumulator maintains oil pressure in the line

during momentary ?uctuation of oil pressure during oil pump

change over or sudden operation of servomotor of governing

valve.

/n the accumulator an inert gas lled bladder is provided. Cas

pressure inside the bladder is maintained slightly belo' the

normal oil pressure.


54/122

During normal operation, oil pressure of the line compress the

bladder and oil is occupied in the oil space of the accumulator.

*hen, pressure at the line drops, the bladder is e+panded, due to

the inside gas pressure. So it pushes out oil of space to the line

and ta-es care momentary oil pressure ?uctuation.

5il Accumulator

5il accumulator is provided on the governing or control oil line of

the turbine. his accumulator maintains oil pressure in the line

during momentary ?uctuation of oil pressure during oil pump

change over or sudden operation of servomotor of governing

valve.

/n the accumulator an inert gas lled bladder is provided. Cas

pressure inside the bladder is maintained slightly belo' the

normal oil pressure.

During normal operation, oil pressure of the line compress the

bladder and oil is occupied in the oil space of the accumulator.

*hen, pressure at the line drops, the bladder is e+panded, due to

the inside gas pressure. So it pushes out oil of space to the line

and ta-es care momentary oil pressure ?uctuation.

!mergency Situation /n Steam urbine

Steam urbine is a critical rotating e"uipment. High temperature

and pressure steam is used to rotate the turbine at high speed.

ass of the rotating part is high. here is al'ays chance of

severe misshapen leading to fatal accident and damage of high

cost e"uipment. /ncase of any system goes 'rong generation of

po'er may be interrupted for a longer period leading to heavyloss to the plant. So the po'er plant engineer should be trained

enough to face any emergency situation, at any time and properly

handled emergency situations.

1# 5verspeed


55/122

Due to failure of governing system the turbine speed may become

dangerously high. otor can rotate momentarily 'ithout damage

up to 11$= of rated speed. At higher speed rotor stress increases.

Due to high centrifugal forces the blades 'hich are +ed to the

rotor may come out. ailure of blade root can cause severeaccident and damage to turbine. o avoid dangerous over speed

turbine is provided 'ith mechanical and electrical over speed trip

arrangements. ripping limits are set in such a 'ay that turbine

speed does not e+ceed 11$= of rated speed. hese overspeed

tripping limits are to be chec-ed regularly. echanical overspeed

device is to be set 'ithin set limit and chec-ed at suitable

intervals. At any circumstance overspeed tripping limit is not to

be bypassed. /f overspeed tripping does not 'or-, immediatelystop the turbine by applying emergency trip push button. or the

1@.< * turbine at ata Sponge, overspeed tripping limit is ;@><

rpm.

L # ailure 5f 4ubrication 5il System 7

4ubrication 5il is used to lubricate and cool do'n bearing metal.

Sometimes the lubrication oil supply may be interrupted due to

failure of pumps, lea-age in oil line or cho-ing of oil lter. hiscondition may damage bearings and gear bo+. /f such an incident

happens for any reason, the turbine is re"uired to be stopped as

soon as possible. 4o' lube oil header pressure tripping is

incorporated 'ith turbine to trip the turbine immediately. /f lube

oil header pressure becomes 1-g)cmL, oil supply is to be restored

as early as possible. After resuming oil supply, if possible, turbine

is to be rotated manually to nd out any damage (inspect

bearings#.3. High 0ibration

otor of the turbine rotates at high speed. Any deformation or

unbalance of the rotor produces high vibration. Sometimes

deposits on blades and damage of any rotating part may create


56/122

heavy vibration. Damage of 8ournal bearing may also produce

vibration. he moving and rotating parts of the turbine are closed

spaced. Due to disturbance in rotor shaft or dierential e+pansion,

there is chance of rubbing. ubbing creates high vibration and

abnormal sound, so at any case high vibration of turbine is not beoverloo-ed. /ncase of high vibration the turbine should be stopped

immediately and turbine internals to be inspected to avoid further

damage. High vibration protection in logic is incorporated 'ith

turbine to trip the turbine 'hen turbine front and rear 8ournal

bearing vibration goes to 1 icron and gear bo+ front and rear

8ournal bearing goes to 3$ microns.

# High 9earing emperature

High bearing temperature occurs due to inade"uate oil ?o' in the

bearing or metal to metal contact in bet'een bearing and rotor.

High temperature damages 9abbitt material of the bearing. /n

case of high temperature of the bearing, a turbine is re"uired to

be stopped. 5il supply to bearing is to be chec-ed and if re"uired

bearing is to be opened for inspection. High bearing temperature

protection logic is provided to turbine. or dierent bearing 11


57/122

in condenser increases and enters into turbine through e+haust

hood. 6ondenser vacuum reduces drastically in this condition. /f

at any case 'ater enters into a running turbine it creates a

serious situation and damages the turbine. 4oad is to be reduced

on turbine in this situation. /f situation is not controllable, turbineis to be stopped.

N# High Steam &arameter

4i-e lo' steam temperature and pressure, high steam

temperature and pressure is not desirable for turbine operation.

High steam temperature may damage turbine as the metrology of

the turbine is designed for a particular temperature.

1$# 4o' 6ondenser 0acuum

Due to vacuum in condenser the steam from turbine is easily

e+hausted into condenser. /f vacuum inside the condenser drops,

it restricts e+haust of steam of turbine. his creates bac- pressure

inside turbine. 0acuum may drop due to failure in cooling 'ater

system, failure of e8ectors, or lea-ing condenser air line. Standby

e8ector or starting e8ector is to be immediately ta-en into line.

4ea-ing air line is to be arrested promptly or cooling 'ater supplyto be increased. /f vacuum is not improved, the turbine is to be

stopped immediately. 4o' vacuum protection logic is provided to

trip the turbine 'hen condenser vacuum drops to G$. -g)cmL.

11# ailure 5f 6ooling *ater Systems

Due to failure of cooling 'ater pumps or cho-ing in cooling 'ater

circuit, cooling 'ater supply may be reduced or interrupted. /n

this case turbine e+haust steam cannot be condensed. his 'illincrease the pressure of the condenser and drop the vacuum.

apture dis-s of the condenser may rapture, heavy bac- pressure

'ill be created in turbine. /n this case load is to be reduced rst

and care is to be ta-en to normaliEe cooling 'ater supply. /f

situation does not improve then turbine is to stopped.


58/122

9lac- 5ut maneuver ethod for *H9 &o'er &lant

9oth the C fails and Crid not available 7 (94A6% 5U 65D//5#

1. /n the above cases ( otal blac-out condition # ensure

availability of DC emergency po'er to all the emergency drives

of both the 6&& 'ithin 1$ seconds (i.e. 9oiler main steam stop

valve, Au+iliary oil pump, 9arring gear, !mergency oil pump,

9oiler feed pump discharge valve, 6&& area lighting Y Oac- oil

pump Y C steam stop valve #

L. !nsure from eld pressure gauge that lubrication continues in

both the C by gravity method (oil ?o's from over head tan- to

all the C bearings and returns to main oil tan- by drain header #

3. !nsure from H/ Y eld that !mergency oil pump is running

through D6 po'er Y oil supply continues to all the bearings.

. Start the Oac- oil pump of C.

. After resuming of emergency po'er, close main steam stop

valve of all the three 9oilers and maintain the drum pressure

through startGup vent.

;. /n blac-out condition, ensure that %iln stac- cap 'ill remain

1$$= open till the availability of boiler feed pump. /f stac- cap is

closed or partially closed, then contact %iln control rooms to open

the same through Shift /n 6harge 6&&.


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assessment)specication phase of the lifecycle. he study goes

further to state that many of these errors occurred because the

S/)S/S designer incorrectly considered the interactions of one S/

to the rest of the process. /n essence, the activation of one S/

'hether demand or spuriously based 'hich then causedunforeseen demands, and haEards in other areas of the process.

During a recent panel discussion, one of the panelists challenged

the audience 'ith the "uestion [*hy are they called shutGdo'n

systems, shouldnQt 'e really call them -eep running systems\

His premise 'as that the engineering discipline as a 'hole had

become enamored 'ith or [sold on\ the [failGsafe\ design. otonly is this not re"uired by the standard, but as mentioned above

spurious activation of a S/ can in fact cause haEards else'here

that may not have been considered during the haEards

assessment)S/ specication phase of the lifecycle.

/f the user has a comparative process indication that is

independent of the initiating event, it is possible to design the S/

to be [fault tolerant\ 'ithout increasing hard'are count or cost.

/n the e+ample belo', you can see that S/G$$3 is a LooL voted

sensor arrangement, 'hich based strictly on voting architecture is

an e+tremely reliable design. Also note that there is an

independent high pressure sensor and associated high pressure

alarm. /n this case the S/ designer could have used a 1oo1

voting architecture for S/G$$3. 9y using the comparative process

indication the engineer could have implemented a deviation

alarm based on any dierence bet'een the S/ sensor indication

and the comparative 9&6S sensor indication. ot only 'ould thatarrangement be signicantly safer, it 'ould be almost as reliable,

'ith 1)3 less cost to install and maintain.


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!"uipment ailures 9&6S (basic process control system#

component failure.

Utility failure.

0essel)&iping failure due to 'ear, fatigue, or corrosion.

0essel)&iping failure caused by specication, design, or

manufacturing defect.

0essel)&iping failure caused by over or under pressuriEation.

0ibration induced failure (e.g. rotating e"uipment#

ailures caused by inade"uate maintenance)repair.

ailures caused by temperature e+tremes.

ailures resulting from ?o' surge or hydraulic hammer.

Human ailures ailure to properly e+ecute a tas-, by omitting

steps, or improperly se"uencing steps of a tas-.

ailure to observe or respond appropriately to conditions or

prompts by the system or process.

At this point it is necessary to dierentiate initiating events from

latent or root causes. /nitiating events are distinctly dierent from

root or latent causes. /n general, root or latent causes create

latent 'ea-nesses in a system. *hen a challenge arises or a

demand is made on the system, these 'ea-nesses give rise to an

initiating event. or e+ample7

: [/nade"uate operator training\ is not an initiating event, but is

a potential underlying cause of an initiating event of the _humanfailureQ type.

: [/nade"uate test and inspection\ is not an initiating event, but

is a potential underlying cause of an initiating event of the

_e"uipment failureQ type


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LGhe dierence bet'een Isegment 'iring diagramsI and

Iinstrument termination diagramsI.

9oth can be part of instrument loop diagram... depending on

comple+ity Y no of terminations involved... segment 'iringdiagrams Y instruments termination diagrams are referred in

/nstrument loop diagrams.... segment 'iring diagram sho's only

one segment of the entire loop 'hereas instrument termination

diagrams sho's ho' instrument is connected to 9&6S... e.g. a

Cas 6hromatograph (C6#.. to 9&6S it is instrument, but it depends

on ho' C6 is sending data to 9&6S or ho' 9&6S is reading data

from C6... it could be via t'o. three , four , < , 1$ or L< 'ire

connection or via some industrial communication protocol.. no'

/nstrument termination diagrams sho's ho' both instrument Y

9&6S are connected...

3G/s data sheets preparation regarding I&60I and I&S0I in

instruments scope of 'or- Ho', &S0 and &60 are siEed

/f you are involved in commissioning of ne' plant, then data

sheet 'ill be provided to you as part of As 9uilt documents by

!&6.../f you are in maintenance then in case there is ne'

installation of &S0 or &0 or 60 then it is responsibility of

instrument engineer to collect data from &rocess

!ngineering)&ro8ect !ngineering and prepare a data sheet...SiEing

of &S0 or &0 is not easy and / 'ould suggest that you should

start 'ith simplest 6ontrol 0alve rather than 8umping directly to

&S0 or &0... !ach vendor provides siEing tools for its

60)&S0)&0s... and basics of 60 siEing remains same most of the

time.. but it may dier, all is sub8ect to ho' vendors has designed

the 0alve...


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G*hat is dierence bet'een Iail closeI and Iail openI position

of control valves.

9oth terms are used 'hen Safe State of 0alve is considered..(&lease refer to &lant HAP5& documents for denition of Safe

State for each valve#... ail 6lose or ail 5pen means in case of

failure of air supply, GL$mA or L0dc or 60 diaphragm rupture,

the valve 'ill go to preGdetermined safe position i.e. 6lose or

5pen respectively...


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system boo-s.... /t 'ould be benecial for you and also for rest of

the members if you as- "uestion too the point and if necessary

give an e+planation 'ith some e+amples...

Have a fe' more comments on a fe' of your "uestions.3G SiEing of &0 and &S0 are not necessarily the responsibility of

the /nstrument !ngineer. Sameen is correct as far as ne'

installation is concerned. 9ut for maintenance, it depends from

plant to plant since responsibility may be distributed separately in

dierent organiEations. As an e+ample, the plant / 'or- at,

designing Y siEing of all -inds of valves falls under the domain of

&rocess !ngineering. hey 'ill develop data sheets 'hich they 'ill

then hand over to the instrument engineer for procurement of thevalve. 5nce valve is procured, the pro8ect engineer (mechanical

engineer# 'ill have it installed in the eld and the instrument

section 'ill be responsible for electrical and pneumatic

connections. As for the &S0, that is completely out of /nstrument

!ngineerFs domain. /t is designed by the &rocess !ngineer and

installation and maintenance falls under domain of stationary

e"uipment maintenance section.

;G / agree 'ith Sameen that it is not possible to have it the other

'ay round. Digital signals have 8ust $L states (on Y o#. or

control purposes, generally the re"uirement is to have innite

intermediate values bet'een say $ G 1$$=, something that is

"uite unachievable through use of digital signals.

e7 Dierence bet'een HAP5& and &HA

by 9lac- 5ny+ ` 1$ Oul L$1L, 1>733

abeel,


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c. 6hec-list ethod

d. !A (ailure ode Y !ect Analysis#

e. A (ault ree Analysis#

/n addition sometimes, various other studies are carried as part of

&H, such as, acility Siting, Human actor (H# analysis etc.

ollo'ing fe' outlines could help to asses the criticality of ne'

site.

&rocess safety information.

*or- place Y process haEard analysis, consultation and action

planning.

esponsibilities Y participation of personnel.

*ritten operating procedures for all operation phases and

limitations.

&ermit system.

6ompliance auditing.

!mployee Y contractor safety information Y training.

echanical integrity evaluation Y maintenance systems.

Design, fabrication Y installation.

!mergency planning, response Y training.

&reGstartup safety revie's.

anagement of change procedures.

/ncident investigation.


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&iper Alpha /ncident

by ashfa"an'er ` L< ov L$1$, $

he accident that occurred on board the oshore platform &iper

Alpha in Ouly 1N@@ -illed 1>; people and cost billions of dollars in

property damage.

/t 'as caused by a massive re, 'hich 'as not the result of an

unpredictable [act of Cod\ but of an accumulation of errors and

"uestionable decisions. ost of them 'ere rooted in theorganiEation, its structure, procedures, and culture.

Some of the causal factors of the incident include7G

1. &latform Design issues

L. Site gt 'as not authoriEed to shutdo'n the plant 'ithout prior

approval from top gt stationed onshore.3. 9last 'alls 'ere not available

. emporary underGrated blind installed in place of removed &S0


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N. /nade"uate reghting e"uipment

y ndings are as belo'7G

1. &* permit to 'or- system is not upGtodate at that time. o' a

days &* has a -ey, loc- and -ey safe system 'hich ensures that

the person issuing the permit can only 'ithdra' a permit after

unloc-ing the loc- 'ith the -ey, 'hich is in the costody of

anager 5perations.

L. he facility is designed for pumping oil only, it can not be

modied for Cas e+traction due to pressure dierence in oil and

gas e+traction.

3. o 0s non return valves are placed on branch pipe lines

connecting 'ith main pipe line.

A!!ident o A$$ *enerator at +amnagar ndia

SAJ SA!KKK A//C, A//C, AD 5! A//CKKKKKKK

Accident of A99 Cenerator (13$.


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he main reason for this incident is I645S/C 5 6554 5/4

!U 4/! AUA4 /S54A/5 0A40!S 5 S5!

A/!A6! *5% AD 5 5&!!D A! 65&4!/5 5

H! *5%I.

he generator !+citer end and urbine end Shaft 'as found

sheared o and shaft thro'n into pieces. he steam turbine got

blasted and all high pressure)temperature steam hot li"uid poured

into all the cables and au+iliary systems surrounding it. he scene

is entirely li-e a 'ar Pone.

indings7

/n the control oil (Hydraulic s-id# ?uid coolers isolation valves (in

return line# in ?uid side 'ere all found in closed condition. 5n

investigation, it is understood that the mech. main. too- permit to

replace hydraulic oil in the 6ontrol 5il Hydraulic S-id. he

mechanical maintenance had done their self isolation on the

?uid coolers isolation valves in ?uid side 'ithout informing

operation , 'ithout reopening)normaliEation (as re"uired# they

had cleared the &ermit.

*hen there 'as a turbine trip, the ?uid could not drain fromhydraulic operated servomotors. hus, obstructing the stop valve

closure function. Due to pressure buildGup in the return line the

connector on drain line busted and the stop valves remained open

even after the trip re"uest (until the rupture of the piping

connection that acted as drain#.Due to the closed condition of

?uid coolers isolation valves (in return line# the problem 'as

e+perienced even during the startup before accident. he control

valves lost control and led to "uic- speedup (loss of control andfast speed up# this resulted in servo valve drain port

pressuriEation to abnormal level, thus avoiding the correct closure

Y movement of the control valves.

As per inspection, and also after e+amination of event recorder

log indicated all the trip re"uests 'ere present, so it 'as


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concluded that the cause of the accident is located on the

hydraulic part of the control

system, i.e. an improper status of the above said isolation valves,

left 'ithout normaliEing after maintenance 'or-. he defectiveclosure of stop and control valves upon trip re"uest has generated

a turbine)generator overGspeed situation (even it 'as not possible

to establish the speed value accurately as speed reached beyond

sensing scale, but surely at least X$$$ rpm# .

Safety /ncident 6ircular of a &ressure 0essel Hydrotest ailure in

6hine in early L$$@.

his vessel 'as manufactured by a vessel vendor in 6hina and

the plate 'as of 6hinese mill origin. Unfortunately this is another

e+ample of serious e"uipment)material failures 'ith e"uipment

being sourced out of the rapidly developing economies such as

6hina, !astern 9loc and others. hese e+amples are becoming

almost a 'ee-ly occurrence no' and are e+hibiting failure modes

not seen in the mature manufacturing economies since the

1N3$Fs. Again 'e need to ensure vigilance in the acceptance ofmanufacturers and once more / stress the need to -no' 'here

the base materials are sourced from. Apparently this pressure

vessel had reached fty percent of the re"uired test pressure

'hen the shell ruptured. A metallurgical failure report is not

available ho'ever from the photographs a number of

observations could be made regarding the "uality of the material

and the 'elding.

4essons Y 4earnings7

(1# All base metal re"uirements shall be specied in &.5

e"uisition per pro8ect)/ndustry 6ode re"uirements.

(L# 6onsult specialists (i.e., aterials and 6orrosion !ngineers#

'henever you doubt.


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(3# All inspection (from base materials to nal products# should be

performed per the codes, specs Y standards.

(# !specially 'hen you selected the manufacturers in 6hina, the

above (1#, (L# Y (3# 'ill be a very important message.octane, let me put some light on &HA methodologies, 'hich are

ualitative HaEard ) is- Assessment

Oob Safety Analysis (OSA#

4ogic diagrams

*hatGif)6hec-list

ailure odes and !ects Analysis (!A#

HaEard and 5perability Study (HAP5

uantitative HaEard ) is- Assessment

ault ree Analysis (A#

/nGprocess energy modeling

!vent probabilities

is-)cost tradeGo

!very method has its o'n limitations including pros n cons. or

e+ample !A method is fre"uently used to asses the haEards

and ris- 'ith in any logic or control loops. And HAP5& techni"ue is

used for huge and comple+ processes, due to its systematical

approach. *hereas *hatGif ) 6hec-list is a very detailed and

usually recommended of simple processes due to lac- of inGscope)outGscope features.

S/4


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he concept of safety integrity levels (S/4s# 'as introduced during

the development of 9S ! >1


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and the severity of the haEards. arget S/4s are assigned to S/Qs

of the S/S identied in the &HA studies. 0arious methodologies are

available for assignment of target S/4s. As in the case 'ith &HA

studies, the assignment of arget S/4s must involve people 'ith

the relevant e+pertise and e+perience. ethodologies used fordetermining S/4s include, but are not limited to7

:6onse"uence only

:is- Craph

:4ayered is- atri+

:is- matri+

:4ayer of protection

:ault tree analysis

*hich ever tehnic is used the greatest increase in cost occurs

'hen the decision is made that the S/4 must be higher than S/4 1.

he selection of S/4 L or S/4 3 forces the S/S design to'ard device

redundancy and diversity. *ith this recognition, many companies

are ta-ing the approach that Ia safety system is a safety system

and therefore should be S/4 3I. his eliminates the arguments

about 'hether escape is possible, someone 'ill be in8ured or

-illed or the impact 'ill be onGsite and)or oGsite. /t saves time in

the &HA process, reduces documentation in 8ustifying the S/4

choice, and ensures consistency across process units.

Unfortunately, there is no easy ans'er 'hen it comes to assigning

S/4s. he choice involves e+amining safety, community,

environmental, and economic ris-s. ost importantly, tools must

be developed at the corporate level to ensure that the choice of

S/4 is consistent 'ith a companyQs ris- management philosophy

and that the assignment method is congruent 'ith the e+isting

characteristics of the corporate ris- assessment methodologies.

ollo'ing can ho'ever be used as a conservative guide,


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&ipeline hydrotesting

After sectional(partial#replacement 'e are planning to carry out

hydrotesting of cross country pipeline.Ho'ever, due to time

constraint one section of corroded piping are composite 'rappedat corroded location to 'ithstand the ma+imum allo'able

operating pressure of the pipeline. y "uestion is for calculating

hydrotest pressure 'hether only remaining corroded thic-ness

'ill be ta-en in consideration 'ithout composite 'rapping or both

'ill be considered. Any reference standard to reply is highly

appreciated. he test shall be done at test pressure

recommended by the construction code. *hatFs the code in this

casehe test pressure shall not be compromised for ne' piping

sections 8ust because of one composite repair. / 'ould have only

accepted the ne' sections once they are tested at 1.< times of

design pressure if follo'ing AS! 931.3 as construction code.

e7 /S /solators Y unctional Safety

4et me e+plain this by e+ample. A device is /ntrinsically safe if it

does not carry enough energy to cause an e+plosion incase ashort circuit or overGcurrent condition e+ists causing ignition

conditions at the device. or this purpose you have intermediate

isolating devices 'hich lie outside of the 6lassied (Pone$ )Div1#

area in a control cabinet, and further feeds the instruments

(usually Sensor#.

he purpose of an /ntrinsically Safe instrument (or loop using an

/S isolator# is "uite dierent from that of an S/S System. /S isolator

is used to limit chances of an e+plosion as stated in *asifFs

e+planation. Ho'ever, an S/S system is normally a protection

system to protect the operating e"uipment in case of a

parameter)process upset, often by initiating a partial or complete

process shutdo'n.


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5f course, an /S isolator may be used in an S/S system. Ho'ever,

even in that case the purpose of the isolator 'ould be to reduce

chances of e+plosion and not to improve or alter the availability of

the system. An S/S may also be used 'ithout an isolator (in 'hich

case again there 'ill be no impact on the availability of thesystem#, but you may run the ris- of letting e+cess energy into a

classied area 'hich might itself cause an e+plosion. /n that case,

/Fd say Jes, you are aecting the safety gures. An isolator in an

S/S system does ma-e the overall system more safe, but it does

not aect the availability provided that the mtbf of the isolator is

not belo' that of all other components in the S/S system. 5f

course, S/4 rating of the isolator 'ill also come in play then. / hope

/ have understood your "uery and responded accordingly.

Dear Ali, /S /solators are part of the S/S loops.. 'e agree on that..

Since S/4 6alculations are done on the loop level not at the

system level.. herefore, availability gures of /S /solators Y all

possible scenarios of failures of /S /solators are also re"uired.../

agree 'ith concept that /S /solators are used to reduce probability

of e+plosion in the haEardous area.. 9ut / donFt agree 'ith the it

doesnFt alter availability of system../n functional safety there are

t'o things 'hich are greatly emphasiEed7

1# Safety 'hen all components are integrated together Y Safety

at component level

L# Availability of smallest items can aect the availability of the

'hole system (system is strongest as its 'ea-est lin-#

/n simple 'ords, failure of /S /solators 'ill result in failure of loop

functionality.. 'hich in turn 'ill result in failure of safety function..

IIHigh Availability does not al'ays ensure SafetyIIA safe device is

made 'ith intention to ensure safety...

A available device is made 'ith intention to ma+imiEe

availability... y "uery 'as 'hat -ind of impact 'eFll see in S/S


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system due to /S /solator failures Y 'hat -ind of /S /solator failures

'e should loo- in to 'hen designing a S/S System

90 or 50

90 is a emote 9loc- 0alve. /ts basically an isolation valve or

!SD valve.uestion7 /s there any standard that determines

pneumatically operated valves or motor operated valves for

purposes of isolation of a natural gas line during a re5-ay, 'ell, yes volume isolation needs to be enforced for pipeline

applications.50Fs AJ be used for shutdo'n applications, there

is a variety of S/4G3 certied !H valves available on the mar-et

'ith spring return (enabling failGsafe position#. Jou 8ust have to

ta-e notice of your process re"uirements. ost signicantly, the

closure time. !specially 'ith li"uids, closure time is very sensitive.

Jou need "uic- closure, but you donFt need slamGshut, other'ise a

surge can occur. hen, since this is going to be a remote location,you need to consider the supply of po'er to the 50 G chec- 'ith

your electrical disciplines 'hether you can ta-e 40 cables to the

distance that you re"uire. Additionally, you 'ill need a 1


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more comple+. ests are performed to gure out all the possible

failure scenarios and measures are ta-en so that if system fails it

Documents

Hydrotest Pressure Vs Design Pressure.docx