BOILER Question Answer

7/29/2019 BOILER Question Answer

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Difference between dry bottom type and wet bottom type furnace

The boiler in which ash fusion temp . is lower than the furnace tempr. is called wet bottom

type boiler.

The boiler in which ash fusion temp r. is higher than the furnace tempr. is

called dry bottom type boiler.

1. Write the report on proximity analysis and ultimate analysis of coal

used in a thermal power station of 210 MW capacity.

In proximity analysis we get the percentage of fixed carbon (FC); volatile matter (VM);

ash and moisture in coal by weight basis. For an ideal coal the percentage are: -FC 50%, VM 22%, ASH 24%, MOISTURE 4%.

In ultimate analysis we get the percentage analysis of carbon; sulpher; hydrogen;

oxygen; nitrogen and ash by weight basis.

2. ABBREVIATIONS: -

PERT: - Program Evaluation and Review Technique.

NPSH: - Net Positive Suction Head.

IBD: - Intermittent blow down.

CBD: Continuous blow downPI: - Polarity Index.

IVR: - Infinite Variable Resistant.

PLC: - Programmable Logic Control.DCS: Distributed Control System

IDMT: - Inverse Definite Minimum Time.

PPM: - Parts Per Million.MCC: - Motor Control Centre.

MTBF: Mean Time Between Failure

PRDS: Pressure reducing and de-superheating

ISPUG: Initial Steam Pressure Unloading GearLLD: Liquid Level Detector

DPR: Differential Pressure Regulator

3. Two identical pressure vessels containing water and air seperately.

The two cylinders are pressurized with some pressure. The vents of

same size are opened at a time. The pressure of which vessel will fall

faster and why.

As air is more compressive fluid than water, air pressure falls faster than that of water.

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Y1 bar Y1 bar

4. In summer the ambient tempr. is hotter than the tempr. of water of

cooling tower. How is it possible?

In cooling tower evaporation occurs and the rate of evaporation is directly proportional to

the surface area of liquid and the rate of elimination of vapour over the surface of liquid.In cooling tower the first one is satisfied by breaking the water flow in small part

by the help of V shaped PVC net and second one is satisfied by suction of dry air fromatmosphere with the help of cooling tower fan. So evaporation increases which helps tointeract latent heat from the water. In this way the temp r. of water of CW basin fallsbellow the ambient temperature.

5. In a 3 X 125 MW plant the following are the data fore a particular

date:

PLF = 80%, Oil Consumption = 18 KL, Aux Power Consumption =

684 MWH.

Calculate the (1) Oil rate; (2) Aux Power Consumption.

The total energy generated in that day = 3*125*0.8*24 MWH

18 * 106 ml

Oil rate = = 2.5 ml/KWH3 *125 * 0.8 * 24 * 103

684

% Aux Power Consumption = * 100 = 9.5%3 * 125 * 0.8 * 24

6. In the above power plant, for a single unit coal consumption in thatday = 1350 MT; energy generated = 2500 MWH; calorific value of

coal = 4500Kcal/Kg; calculate the heat rate of the unit.

2

Air

X bar

H2O

X bar


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Calorific value of assumed coal = 1350 * 103 * 4500 Kcal

1350 * 103 * 4500

Heat Rate = = 2430 Kcal/KWH.2500 * 103

7. What are the base load and peak load power station?

The PowerStation which run to satisfy the average demand of load is called base load

power station. Ex Thermal & Nuclear Power station.

The power station which runs to satisfy the peak demand of load is called peak

load plant. Ex Gas Turbine & Hydel Power Station.

8. What is low forwarded and reverse forwarded relay?

During normal /forced shutdown or any other abnormal condition there is a danger of

over speed of the generator. If the generator ckt breaker is opened before steam V/V s are

completely closed. Again if mechanical power input to the generator is stopped wellbefore generator breaker open there is a chance of motoring action of generator which

may damage the turbine. Therefore it is essential to ensure that mechanical power

supplies to turbine and hence the electrical power output to the generator has dropped toless than 1% before the generator ckt breaker is tripped. To achieve this a low-forwarded

power relay with interlock, TLR is provided. In case of failure of low forwarded power

relay reverse power relay will operate for protection against motoring action of generator.

9. Most of the boiler auxiliaries are fans & most of the turbine

auxiliaries are pumps discuss.

The main flow of boiler auxiliaries are air and coal dust and flue gas produced in the

furnace. So to circulate these, different type of fans i.e.; PA, FD, ID are provided.

Moreover for protection of bearing and gearbox of coal mill from coal dust seal air fanare provided.

But in the turbine area the main flow are feed water, cooling water, auxiliary

cooling water, DM water etc. so to circulate these water, varieties of pumps are necessaryi.e.; BFP, CW, ACW, DMCW pumps etc.

10. what is the use of Trivector metre?

It is used to measure MVARH, MWH, and MVAH

11. Bearing 7: where and why it is insulated?

It is insulated at its lower part that is pedestal is placed on insulation.It is insulated to avoid the circulation of induced current between earth and rotor.

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12.Why turbine and stator are earthed?

Due to friction between main steam and turbine blade and stator a static energy is

generated. This energy may cause damage to the system. So the above mentioned

equipment are earthed to flow this energy to the ground.

13. Difference between

In case of motor (I) without bias and (II) harmonic resistant. In case of transformer

above two have been used.

14. Difference between relay of generator and transformer

In case of generator (I) without bias and (II) harmonic resistant. In case of transformerabove two have been used.

15. What is LP & HP dosing and where these are fed?

At running boiler LP feeding is (i) Hydrazine (N 2H4) and (ii) Cyclo Hexile Amine[C6H11(NH2)]. It is fed to remove the dissolved O2 from water. Chemicals are fed at (i)

CEP discharge, (ii) BFP suction.

HP feeding is done by (i) Tri Sodium Phosphate Na3PO4 (ii) Calgon (metalphosphate, Na(PO3)6.

It is fed to maintain the drum water PH. Point of feeding is boiler drum.

16. How solid contents of boiler water are maintained?

By blow down through CBD (Continuous Blow Down)

17. Phosphate hideout in boiler water

From Trisodium Phosphate (Na3PO4, 12H2O) phosphate disappear at high load and

tempr.. This phosphate precipitate on the tube surface, drum water PH reduces. Again at

low load it comes out. At hide out condn. to maintain PH calgon is fed through HP dosing

pump.

18. Sudden lead damping effects on boiler performance. discuss.

At sudden load damping the following effect will occur.

i. Steam pressure will be high and safety may pop.

ii. Steam tempr. will be high and hence may overheat.

iii. Drum level may be very high

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iv. Boiler thermal efficiency will reduce.

19. Drum safety & SH safety which one will pop earlier and why?

SH safety will pop earlier because if drum safety pop earlier SH coil will starve and will

be overheated.

20. Main cause of economiser tube leakage.

Erosion by ash.

21. Passivation of boiler tube.

Passivation of boiler tube is done after chemical cleaning of boiler tube to prevent rusting

by giving layer of magnetic on surface. Passivation is done by solution ofhydrazine and ammonia; pressurize the boiler up to 41.5 kg/cm2 and raising the

tempr. proportionately at 41.5 kg/cm2. Boiler is kept for 24 bars and at 5 kg/cm 2

hot draining is done.

22. If reheating would not be done what would be problem regarding

the performance of turbine.

In the reheat coil steam tempr.is increased because after HPT if low tempr. steam enters

IPT, at the end of the stage steam will be saturated and effect the blade and work

done is reduced. To avoid that reheating is done.

23. Steps towards total flame failure and total power failure.

TOTAL FLAME FAILURE:

i. MFR will operateii. Oil V/v is to be closed check.

iii. Make speeder gear position zero to avoid wear and follower tip.

iv. Put on the barring gear.

v. Give Start Purge command and MFR reset.

TOTAL POWER FAILURE:

i. Close oil V/v.ii. Check if not purge out H2.

iii. Run JOP and barring gear.

iv. Start DG set.v. Close MS V/v.

vi. Give stop command to running equipment.

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24. How the temp. of reheater is controlled?

RH temp. can be controlled by burner position ( 30) of BHEL boiler, for ABL boilerby RH damper.

i. Controlling the air flow, temp. can be controlled.

ii. Avoiding the secondary combustion RH temp. can be controlled.iii. By RH attemperation.

26. Disadvantage of running turbine in in open condition.

As LP stage pressure is low and steam at last stage is almost saturated in presence of Air,corrosion will occur. So to avoid corrosion of turbine, turbine does not run in open

condition.

27. Use of reheat coil.

As our turbine is multistage turbine, to reduce the moisture % in steam at last stagereheat is done after HPT. It decreases the thermal efficiency but increase the work done.

28. Cause of fluctuation in furnace draft.

i. Change in flame.

ii. Change in air flowiii. Change in oil pr.

iv. Change in coal flow.

29. Use of BAS and TAS

Boiler Auxiliary steam (BAS) is used for

i. Atomizing of oil, HFO line heating.

ii. SCAPE charge for AH (BHEL)

iii. Shoot blowing (AH & Boiler)

Turbine Auxiliary steam (TAS) is used for

i. Starting ejector (vacuum)ii. Main air ejector (vacuum)

iii. Gland sealingiv. GC 1 vacuum pulling

v. Pegging and heating steam (at deaerator)

30. Define attemperation and where it is used?

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Attemperation is used to control the tempr. At the following places attemperation is used

i. TAS stationii. BAS station

iii. MS tempr. Control (at 1st stage and 2nd stage)

iv. HP and LP Bypass system.

31. Function of FD, ID, PA, and SA Fan.

FD Fan: It supply the secondary air. Each unit has 2 FD fans. It takes suction from

atmosphere and supply through AH.

ID Fan: It sucks the flue gas from furnace and maintains the furnace draft. Each unithave 2 ID Fans.

PA Fan: It supplies the primary air which carries the coal from coal mill to furnace. In

BHEL boiler there are three no of PA fan and take suction from atmosphere. A

part of primary air passes through AH. This is done to maintain tempr of mill by

mixing hot and cold air accordingly. In ABL boiler there are 6 nos of PA Fan andtake suction from FD discharge.

32. Grindibility index and fineness carryover

HGI (Hard grove grindibility index) indicates the easiness of pulverization of coal. Indiancoal has 50 60 HGI. Coal Mill life efficiency depends on HGI.

After grinding coal carryover by PA through classifier vane. Fineness 70% of 200

micron (BSM) wire gauge.

33. Starting permissive of coal mill gear.

i. SA Fan running

ii. PA Fan running

iii. Seal air pressure ok.iv. Oil and gas pressure ok. (ABL)

v. Mill lube oil pressure ok.

34. Use of oil burner.

i. Initially burner is used to light up the boiler.

ii. At low load, oil burner is required to support the coal firing.

35. Advantage of rotary AH.

i. High efficiency

ii. Low maintenance cost.

36. Difference between vent and drain.

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Vent line is trapped from top of line and used for air venting from any water/steam line.Drain line is trapped from the bottom of line and is used for water draining from

steam line.

37. Pollution control actions.

i. ESP (Stage 1 98.5% and Stage II 99.7%)ii. Chimney height (Stage 1 120m and Stage II 220m)iii. Green plantation.

iv. Neutralizing OK (DM Plant)v. Manual oil catchier (oil recovery unit)

vi. Skimming tank (decantation tank).

38. Difference between ABL & BHEL boiler

i. In ABL boiler heat transfer/unit area is higherii. For SA control air register in ABL boiler and SADC in BHEL boiler.iii. Mill ball type in ABL and bowl type in BHEL.

iv. BHEL boiler burner has tilting arrangement ( 30).v. PA Fan no 6 in ABL 3 in BHEL.vi. PA suction from FD discharge in ABL, from atmosphere in BHEL.

vii. Rotary type AH in BHEL and tubular type in ABL.

viii. Oil burner 24 nos in ABL (BMS system)

12 nos in BHEL (FSSS system)ix. SA Fan no 6 in ABL no-3 in BHEL.

x. ABL have RH/SH damper, divisional wall. // BHEL have no divisional wall.

xi. BHEL volumetric feeder/ ABL drag link feeder.xii. ABL front fir (down comers 4 nos)// BHEL corner fire (Down comers 6

nos)

39. MFR TRIP. REASONS:-

MFR will trip due to following reason:i. Boiler drum level very high/low.

ii. Total furnace flame failure.

iii. 6.6 Kv unit BAS tie to reserve breaker open.

iv.6.6 KV unit BAS incomer breaker open.v. Both ID and/or both FD fan stopped

vi. HP bypass V/v closed when TLR is operated.(RH Protection)

vii. One or both ESV and one or both IV closed.viii. Any mile or LD oil gun in service in boiler.

ix. ULR operated.

x. Furnace pressure very high/low.xi. Emergency fuel trip push button operated.

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40. Fluidizing of ash hoppers

It is one type of ash handling system. In this system two no of air blower, each of 00%

capacity have been provided for each unit to supply fluidizing air at about 0.5 kg/cm2

through porous tubes to all ESP hoppers. Out of two blowers, one is operating and otheris standby. Total 4 nos of air heaters, two in service have been provided to supply hot air

to ESP hoppers of each for fluidization. One series of heater is operating and another

series is for standby for each unit.

41. Fundame2ntal differences between rapper and vibrator

Rapper: - There are 76 x 2 nos of rappers used in each unit to dislodge dust from thecollecting plates. These rappers are called MIGI (Magnetic Impulse GravityImpact) one electromagnet ---------- of steel plunger surrounded by a concentric

coil, both enclosed in a water tight steel case. The supply 2of this coil is short

duration DC is controlled by an electronic controller.

Vibrator: - To dislodge a small portion of dust in the emanating electrodes, there are (48

X 2) no of electromagnetic vibrators in each unit. The coil of vibrators isenergized by mean of AC and controlled from an electronic controller. Each

vibrator remains on for a certain time intervals and then remains off for certain

time interval.

42. Necessity to maintain the flue gas tempr. Before AH well above the

dew point.

Pressure of Alpha quartz and pyrites in the fly ash accelerates the erosion of boiler tube.This type of erosion normally appears at the low tempr. Zone of the boiler ie at the

economiser, primary SH, primary RH zone. The main reasons is that the particles in the

ash is hard enough at the low tempr.. this type of erosion is prominent at the section

where the flue gas changes its path as the particles of the ash directly hits the tube. Due

to this erosion, tube becomes thin and ultimately fails at normal pressure and tempr. So toprevent it, flue gas tempr before AH is maintained well above the dew point.

43. How NO2 problem (pollution) can be eliminated

By reducing excess air quantity

44. why not anion exchanger is placed before cation exchanger

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acidic cation reacts with alkaline solids and neutral salts of water to produce acid.

Ca(HCO3)2 + 2R COOH CO2 + H2O + (R COO)2Ca(weak) ( H2CO3)

Mg(HCO3)2 + 2R SO3H (R SO3)2Mg + H2O + CO2(strong)

NaCl + R SO3H R SO3Na + HCl

CaSO4 + R SO3H (R SO3)2Ca + H2SO4

This acids are nutralized by basic anion

HCl + R NH2R NH2Cl

(weak)

HCl + R N(CH3)3OH R . N(CH3)3Cl + H2O(strong)

So water after cation first and their anion exchanger is free from any impurities (alkaline,

neutral etc) and is slightly acidic due to the pressure of CO2. For this reason anion

exchanger is placed after cation exchanger and not before cation exchanger.

45.If HP LP bypass not operated after tripping of TLR MFR will trip

after 6 sec why?

MFR will trip to protect RH coil from starvation.

46.What is takeup device?

Take up device is used in conveyor belt to maintain its tension

47.Write three reasons of belt swaying.

i. Non uniform jamming of headend and taiend.

ii. Broken deflector plateiii. Unequal tension

48.If belt specification is given by 800/4, what does it indicate?

800ton/1000 mm width, 4 ply.

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49. For a small belt, the upper ply

50. What is the pressure point of boiler in which acid cleaning and

steam blowing is required

Acid Cleaning: -

i. Boiler Drum.

ii. Down Comer

iii. Riser

Steam Cleaning: -

i. SH tubes.

ii. RH tubes.

51. What are the common welding defects?

Common welding zone deffects are as follows.

1 2

43. Welding deffects due to porosity44. Misfil of tube, which results to restriction of flow and ultimately weakening of

welding joint

45. Porosity

46. Cracking47. Surface defect.

52. Why fluidising air is used in fly ash cleaning system?

Fluidising air is used in ash hopper to increase the fluidising of fly ash so that it does not

stick to the hopper inner surface.

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53.

It increases the spark rate inside the ESP by increasing voltage after sparking.

54. Why vacuum switches are required at the time of ash removal?

Vaccume switches are used to satisfy 3 olperated condition at the time of ash removal.

Vacuum switch 3Y full load 300 mmHg.Vacuum switch 2Y plugged hopper 150-180 mmHgVacuum switch 1Y hopper changeover 85 mmHg

55. if the gauge pressure is 16.72 Kg/cm2 what is the absolute pressure?

Absolute pressure = atmospheric pressure + gauge pressure

Now 1 atmospheric pressure = 1.033 Kg/cm2

= 1.033 Bar = 14.7 lb/inch2

Absolute pressure = (1.033 + 16.720) Kg/cm2

= 17.753 Kg/cm2

56. what should be pressure of stator cooling water if H2 pressure is 3.5

Kg/cm2

less than 3.5 Kg/cm2

57.

From anywhere as pressure around the compressed air line is equal.

58.

52. if dust collector is used with the ESP, that will be extra cost involvement.

53. If it is used without ESP boiler will decrease

54. Define circulation ratio.

Circulation ratio is the ratio of amount of circulation to the amount of steam for used

55. why chimeny is used

it is used to create a natural draught and provide the air for combustion. But chimeny are

also used as an efficient channel for proper dispersal of gaseous pollutants to avoid the

populated area from air pollution.

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56. How much air is required for complete combustion of 1 kg coal

having calorific value of 5000 Kcal/kg

C + O2CO212 16*2

=32For complete combustion

32 gm of air is required for 12 gm of coalor, 12/1000 kg of coal is completely combusted by 32/1000 kg of air.

I kg coal is completely combusted by (32/1000) * (1000/2) = 8/3 kg of air.

57. Why DM water is used?

i. for conditioning of raw water.

ii. To reduce % of SiO2.

The improved quality water is required in high pressure boiler can only be obtained byion exchange demineralising.

PROCESS: All natural water have residue of mineral matters when evaporated andforms scale. On heat transfer surface surface scale has a very low thermal conductivity

and as a result it impede heat transfer. Which may cause overheating of boiler tubes and

and consequently outage due to tube failure. So modern modern high pressure boilerdemands demineralised water for satisfactory operation.

58. Why hydrazine is used instead of Sodium Sulphate?

Small quantity of disolved O2 are capable of causing severe corrosion pitting in boilers

off all pressure. Dearator cant eleiminate O2 completely. Hence some chemical of O2scavenges is used. Sodium Sulphate is such chemical decay generator.

2Na2SO3 + O22Na2SO4The main disadvantage of Sodium Sulphate is it increases the TDS in the boiler waterwith consequent heat loss in additional blow down and further more at high pressure it

can decompose to form corrosive gases SO2 in the steam. Hydrazine has neither of these

disadvantages.

N2H4 + O22H2O + N2

59. what is PA and mill differential pressure?

Orific placed at PA fan discharge. The differential pressure is thus called PA

differentials.

Differential pressure between the mill I/L and O/L pressure is called milldifferential.

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60. Use of air heater and Economiser.

61. Function of ESP

The main purpose of ESP is to collect fly ash present in the gases by creating a high

voltage DC field. The ash thus arrested in the collecting electrode ( called the + ve

electrode) are removed in aglomerated form by means of rapping mechanism. To fall inthe ash hopper from where it is cleared through vacuum pulling system of ash handling

plant.

62. Start permissive of coal mill.

63. BFP:

Discharge:Speed:

Pressure:

NPSH MWC = Dea. Pressure.

Water column * density (water saturation pressure at the dearator tempr. + frictionloss)

Booster P/p speed:-Flow:-

Discharge:-

NPSH:-

CEP::

RAM

St. HeadDischarge

NPSH

BFP:: Permissivei. L. Oil healthy

ii. Suction V/v open (full)iii. Dea level is adequet.

iv. Booster Pp suction pressure > 202 kg/cm2v. Scoop min.vi. BFP open.

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Tripping

i. Low lub oil (0.5)

ii. Differential pressur across strainer high (0.5) with a tempr. Diff.iii. Differential tempr. Of F.W across BFP high with tempr. Diff.

iv. BFP flow high

v. Balance leakoff flow highvi. Working oil tempr., high.

vii. Dearator level very low

viii. BFP motor bearing tempr. Highix. TLR trip.

64. Define Base load plant and Peak Load plant

The plant which runs with a highest possible load for a appreciable part of a year, known

as Base Load Plant.The plants which are utilized during a part of a year to satisfy the peak used are called

Peak Load Plant.

65.

(80/100) = (MWhr generated)/(3*25*24)

MWhr generated = (80*3*125*24)/100 = 7200 MWhr. Oil Rate = (18*106)/(7200*103) = 80/72 = 2.5 ml/KWhr % Aux power consumption = (684*100)/(3*125*24*80) = 7.6%.

66. In the above power plant for a swage unit coal consumption in that

day = 1350 MT, Energy generated = 2500 MWhr. Calorific value of

coal = 4500 Kcal/kg. Calculate the heat rate.

Heat rate = (1350*103*4500)/(2500*103) = 2430 Kcal/KWh

PI = (IR for min)/(2R for 1 min)

Absorption factor = (2R value for 1 min.)/( 2R value for 15 s)

67. Caustic and hydrogen __________________ of boiler tube.

Caustic soda reacts with iron of the boiler tube at elevated tempr to form sodium ferrite.

As a result tube leakage will occur because it will be thin.

Iron of boiler tube and steam at reaction with the carbon of the tube and createsmethane. This exerts pressure on the tube and one time the tube will fail.

MgCl2 + H2O MgO + 2HCl2HCl + Fe FeCl2 + 2H+

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steam is passed over hot (red) iron at (600-800oC) and then

3Fe + 4H2O Fe3O4 + 4H2ferrasoferic

oxide68. Why

After acidulation (H2SO4), it reacts with Bi carbonate and form carbolic acid which is

easily breakable (H2CO3CO2 + H2O) in contact with air. To remove the CO2, make up has given at_______

Ca(HCO3)2 + H2SO4CaSO4 + 2H2CO369.

It is because all the contraction la

70. What is nucleate boiling and film boiling?

In the nucleate boiling steam is generated in the form of bubbles and is not collected on

the surface of tube.But in the film boiling steam make a film on the surface of tube and overheated

the tube as conductivity of steam is low. For boiler nucleate boiling is preferable.

71. Stress receiving of boiler tube:

At the welding joint stress is developed and normalized by stress relieving. In thisprocess the tempr. Of welding joint increased up to 700 oC in a certain period and hold for

a time and cool down at same rate which is normally 3 and 3 hrs respectively. This time

varies with thickness and for alloy metal tempr. is higher.

72. Cold pull.

At normal atmospheric tempr, steam pipe will remain in stressed condn. and will be

normalized at working tempr. After thermal expansion. This is a back dated technology,

now it has been replaced by bend, notch etc. Only HPT and IPT steam admission pipes

are in cold pull.To avoid extra stress in steam pipes at hot condition cold pulling is provided.

73. Function of Rapper and Vibrator

Rapper is used in receiving ash from collecting electrode and vibrator is used to remove

the ash from emitting electrode (-ve). Both are dropped hammer mechanism.

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74.

It improves the steam quality at outlet of drum by receiving water from steam.

75. Corrosion of AH is more with oil support than coal firedwhy?

As oil contains more sulpher than coal, H2SO4 is high in oil firing which causes more

corrosion of AH.

76. Detection of SH and RH tube leakage and water wall tube leakage.

Due to mentioned leakage below mentioned parameter will change with normal running.i. DM water consumption will be high

ii. Drum level controller will not work properly.

iii. Flue gas tempr. Will decrease.

iv. Furnace will change, ID loading will increase.

77. Simmering what is it?

It is an audible characteristic of S/v. which is caused by steam passing before safety pop.

78.

i. it is a water seal which prevents the furnace ingress of air inside as furnace remainin ve pressure.

ii. It absorbs the furnace ________________________ (in 275 mm) which is in

hanging condn.

iii. As it is a water seal, it easily breaks and allows to pass away the flue gas/air if in

any case boiler becomes high pressurized. as in other way it is a safety device of

SH and RH coil..

79.

In the rotary AH flue gas cannot bypass ultimately to avoid H2SO4 corrosion of which

arrangement is in ABL tubular boiler.So in BHEL boiler

80. difference between recuperative (tubular) and regenerative(rotating) AH.

In recuperative type AH flue gas passes through tube and air outside the tube. It is used inABL boiler.

In the regenerative type AH there is a rotory part with corrugated sheet. Three

segment of rotor:i. 108o secondary air

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ii. 108o flue gas

iii. 72o primary air.

Flue gas passes from top to bottom and PA and SA passes bottom to top. It is lowmaintenance AH with high efficiency.

81.

To avoid the starvation of reheater tube (while the boiler is in critically emergency

condn.) which will cause over heating of steam tube and as a result tube failure.)

82. why oil burners are used in low load?

At low load to ensure proper combustion of coal by increasing furnace heat energy by

burning oil through gun.

83.

To ensure proper combustion in ABL boiler control by air registers and in BHEL boilercontrolled by SADC.

84.

To avoid explosion as high rate fuel

85. Boiler efficiency decreases in the HPH in service, but the overall

efficiency increases. why?

In this system feed water tempr increases by heating with the steam extracted from

different stages of turbine. Heat transfer in boiler reduces but steam produces more; heat

loss in condenser reduces. As a result overall thermal efficiency increases.

86. Difference between natural and induced draft.

Natural draft is due to the pressure difference created by chimney height.

In the induced draft, flue gas flow from boiler to out side and it is created by ID

fan in between boiler and chimney.

87. Main cause of loss of heat in steam generator.

Heat carries away through the chimney to the atmosphere. Heat in condenser tocirculating water.

88. Cause of secondary combustion and its remedies.

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i. Secondary air flow high/low.

ii. PA temprlow.iii. Coal fineness (big size)

iv. Impeller damage. (ABL boiler)

v. Excess air.vi. Erosion of impeller.

vii. Pulverised coal tempr at the inlet of furnace = 70 through 200 BSM and >

ignition tempr.

viii. Coal quality detoroits. Vm less and ash high.

89. In boiler where radiation, convection and conduction heat transfer

occurs?

1. Radiation heat transfer: To boiler tube, water walls, platen SH from luminousgas.

2. Convection heat transfer: To the remote once boiler tube, final SH, RH coil, AH,economiser, primary SH,and RH. ( conduction from metal of tube to water or steam.)

3. Conduction heat transfer: conduction through boiler, economizer and AH surface.(Convection in water or steam inside tube, flue gas in vestibule and cage zone.)

90. Difference between S/v, Relief V/v and control V/v.

i. Safety V/v: popping pressure is higher than the resetting pressure. It is used in

steam, air line (compressible fluid line). It pops at setting value and reset at valuelower than the set value. (1) Set pressure: (2) popping pressure:

(3) reset pressure:

ii. Relief V/v:popping pressure and resetting pressure is equal. It is used in liquidline (non compressible fluid line). It pops at setting pressure. If the pressure is

greater than setting pressure thus drained and again setting pressure is maintained.

iii. Controlle V/v: it controls the fluid inside the line.

91. Main principle of steam tempr control.

By the combination of final, platen and primary SH.

Platen Zone: in platen zone mode of heat transfer is radiation. As a result with increase

in load tempr

falls.Final SH: in this mode of heat transfer is convection. As a result temp r is proportional

to load because quantity of flue gas is also proportional to load.

By attemperation in i. Final SH and platen SH.

ii. Platen SH and Primary SH.

By using gas damper (primary SH and Primary RH) in ABL boiler.

By using tilting device ( 30o grounded) BHEL boiler.

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92.

Radiant Zone:

QR= (TG 4 TSi4 ) = K (constant)

TR = (QR/MS CP ). QR and CP are constant. (1/MS ) (1/load)

Convection Zone:

QC = MG CP (TG TSi)

TC = (QC /MS CP ) = [MG CP (TG TSi)]/ MS CP= (MG/ MS) * (TG TSi) load

Radiant heat transfer depends upon the tempr . the furnace tempr does not varies

considerably with load but with rate of steam flow increases. As result tempr for

convection heat transfer increases with load as of the flue gas increases.

93. Difference between natural and forced circulation of boiler.

The type of circulation depends upon the working pressure of the boiler. Because the

circulation depends upon the density difference between water and steam. Upto boiler

pressure 2200 PSI ( . ) due to density difference between water and steam, water steammixture will go upper through riser tube and water will come down through down

comers. This is called natural circulation.

Above pressure 3200 PSI water and steam density are equal. As result forcirculation through riser tube and down comer required force which is done by providingpump, take suction from bottom ray header. This is called forced circulation.

94. Necessity of HP LP Bypass.

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95. Basic principle of various turbovisory parameter measurement.

It measured by eddy current probe (eccentricity), variable relactance type detector (axial

shift,), pneumatic type detector (overall thermal expansion), microp----- (seal

interference) and speed transducer (speed of turbine).

96. Start permissive of BFP, FD, ID.

97. Principle of flow, temprand level measurement.

Flow: it is measured by the orifice (low pressure) and flow nozzle (high pressure). A

differential pressure is created at the flow nozzle orifice due to restriction of flow in the

line. Flow is measured by the proportional to square root of P I, e;Q = K P.

Flow is also measured by rotameters which have float at the top of orifice. By theposition of float flow can check from local. As for example centrifuge flow meter.

Temperature: it is measured by

i. Thermocouple: principle of thermocouple staes that due

to tempr difference a milivolt range current will flow.Chromel Alumel, Chromel Copel type thermocouple

are used.

ii. Resistant thermometer: resistance varies with temperatureis the basic principle

98. Abbreviations

MIGI Magnetic Impulse Gravity Impact.FSSS Furnace SafeGuard and Supervisory System.

SADC Secondary Air Damper Control.

PLCC Power Line Carrier Communication.

PLC Programable Logic Control.PIV Positive Infinite Variable.

SPID Single Pole Ignition Device.

FFY First Firing Yield.TDS Total Dissolved Solid.

EHT Electro Hydraulic Transducer.

TTS Turbine Trip Solenoid.OPDE Oil Pressure Drop Relay.

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CRT Cathod Ray Tube.

PRT Platinum Resistant Thermometer.

STP Steam Throw off Device.SAS Steam Auxiliary System.

CHU Constant Header Unit.

CCM Continous Condensate Makeup.IBD Intermittent Blow Down.

CBD Continuos Blow Down.

ILPB Indication Lamp Push Button.OLTC On Load Top Changer.

MAG Magnetic Air Gauge.

WTI Winding Temperature Indicator.

LLD Liquid Leakage Detector.ILI Induction Liquid Indicator.

PERT Program Evaluation and Review Technique.

NPSH Net Positive Suction Head.

PI Polarisation Index.IVR Infinite Variable Resistant.

ILMS In Line Magnetic Separator.MP Magnetic Pulley.

99. At generator H2 and CO2 filling line positions are top and bottom

respectively. Why?

Due to lighter weight of H2 and heavier weight of CO2 and to avoid mixture of H2 andCO2.

100. What is the signification of observing vacuum at the time of ESPhopper cleaning.

ESP hopper fly ash is extracted from hopper for remove. By creating vaccuum in theconveying pipe lime with the help of pressurised water pumped by ash water pump to ash

slurry sump. During ashing we have three vacuum switch operated at different condn .

VS 3 full load vacuum switch.VS 2 plugged hopper vacuum switch.VS 1 hopper change over vacuum switch.

101. Booster pump reduces the required NPSH for BFP-Explain.

Booster pump boost up the pressure and discharge it to the BFP suction. As a result

reduces the chances of cavitations at suction and for the same reason NPSH is alsoselected for a pump. So Booster pump reduces the NPSH of BFP(MWC-18).

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102. A slight vacuum develops in

About 40mm Hg vacuum is maintained by vapour extraction to prevent oil vapour

leakage from bearing housing and to remove H2 which may mix with turbine oil

(servoprime-46).MOP is required with 2nos of vapour extraction fans, with the help of

these fans the bearing pedestals are also kept with --------- vacuum to avoid the leakage of

oil oil vapour from housing.

103. --------------------

104. How ferrous material is removed at CHP.

By using magnetic pulley(MP), cross belt magnetic separator (CBMS),In line magnetic

separator(ILMS).

105. Basic difference between short and long belt ---------------------

The surface hardness is higher in short belt than long belt as frequency of load impact is

higher. Top cover thickness is more of short belt for handling sharp and hard material. No

of ply may be more.

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106. Total path of coalin --------------------form with important point.

107. Define take up pulley, snup pulley and troughing angle.

Take-up pulley:By take up pulley we maintain [(screw-short belt),(gravity-long belt),(trolley used in coal injection)]the tention in belt.

Snup pulley: It is used at the bottom part of the belt athead end to increase the grip angleof belt with head end pulley.

Troughing angle: Angle between idler axes on decking plate over which belt move.It is

maintained between 20-300 .This is the angle of the belt -------- with the ---------..This ismaintained to avoid spillage of coal and to increase load carrying capacity.

108.

At wt we record how much coal has been unloaded and at belt 8 the wt indicate how

much has been fed to bunker. Difference of these two will give the stock position.

109.

4 nos rubber ply.200 indicate strength 200 KN/1000mm width.

110. Protectection of CHP belt.

Mechanical Protection: (a) belt sway, (b) Pull Chord, (c) Self allignment Roller, (d)Zero speed Switch, (e) Hydraulic Coupling (oil draining by fusible plug melting)

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Electrical Protection: (a) instantaneous over/current, (b) E/F, (c) under voltage, (d)

over voltage.

111. Flue gas contents.

1. CO2, 2. SO2, 3. NO2, 4. CO, 5. Ash, 6. H2 O, 7. O2.

112. Allowable ---------- in flue gas at ---------------

Must not be more than 100mm/m3 .

113. How does----------------

It is strong acid contain resin which removes the bi-carbonate salt, strong acid salt from

natural water.

114. -----------------------

115. Function of WAC,SAC,WBA,SBA,MB.

WAC: Weak acid cation will exchange only cation from bi-carbonate salt.

Ca(HCO3 )2 +2R- COOH (RCOO)2 Ca+2CO2 +2H2 O

SAC: Strong acid cation will exchange the cation of strong acid and salt and also

function of WAC.

NaCl+R-SO3H RSO3Na+HCl

CaSO4 +2R-SO3 H (RSO3 )Ca+H2 SO4

WBA: Weak base anion will remove the anion of H2 SO4 & HCl.

HCl+R-NH2 RNH2HCl

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SBA: Strong base anion functions as WBA and further will remove the anion of H 2SiO3and H2CO3

H2SiO3 +2R-N(CH3 )3 OH [R-N(CH3 )3 ]2 SiO3 +2H2 0

MB: Mixed bed contains SAC and SBA. It is a ----------------- unit of DM plant.

116. What--------------

117. Why------------------

118.

119. Usefulness of spent brine solution

The spent brine is collected in the spent brine tank. This injected to softer bed beforefresh brine injecting during regeneration.

120. What is the differences between anionic load of SAC outlet and

WAC inlet.

The anionic load at WAC (weak acid cation) inlet MO (MethylOrange)+EMA(Equivalent Mineral Acid)

MO indicates total alkalinity.

The anionic load at SAC (Strong Acid Cation) outlet EMR+CO2+Silica+MO

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121. Function of------------------------------

At the WAC H2CO3 is formed by mixing CO2 and H2 O.This H2CO3 is very weak and

break easily in contact with air.In the--DWT---------------- (between SAC and WBA)

H2CO3 is removed by ----------------------

122.

123.

124.

125. PTPL the main--------------------------

i) To reduce the turbidity by using alum/polyelectrolyte in clorifoculator .Natural water

contains 20ppm turbidity.ii) To remove the bi-carbonate which are cause of forming scales in condenser tube?

126. Chlorination of cooling tower-Why?

Chlorination is done at cooling tower basin to prevent the bacteriological growth.

127. CT Fan trip----------------------------

As CT Fan trip, circulating water temp r will be higher as a result condenser vacuum willbe affected. To maintain vacuum load has to be damped which will reduce turbine and

----- cycle efficiency.

128. Example of pneumatic operated v/v, motor operated v/v, oiloperated v/v.

1) Pneumatic operated v/v: a) Continuous condensate makeup

b) TAS pressure controller.

2) Motor operated v/v: a) MS v/v, by pass, regulating b) Pegging steam controller.

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3) Oil operated v/v: a)

b)HP LP by pass v/v.

129. Main causes of condenser vacuum -----------

i) Ejector steam pressure low (generally maintain 7kg/cm2 ).

ii) Ejector loop,GC- loop water level low

iii) Starting ejector in line, vacuum break open.

iv) CW pump trip out of 3 running (33%capacity each).

v) Gland steam pressure low (maintain gauge pressure 0.2kg/cm2

).vi) GC vacuum low (maintain 80-100 mm Hg).

vii) Hot well level very high.viii) CT Fan of cooling tower trip.

ix) Scale not in condenser tube.

x) Ejector nozzle problem.

130. ------------

It is so called because cooling tower fan suck air from atmosphere into the cooling tower.

When air passes from side walls to top of cooling tower it flows against the hot water

falling downwards and at that time it go out carrying heat of hot water and water iscooled down.

131.

Rotor heating: To avoid rotor contraction employed during hot start up the HPT and

LPT having rotor heating facility by the steam taken from MS line(RHS) in between ESV

and MSV or aby steam from 4th (LPH-4)extraction.This is done to maintain thedifferential expansion of HPT and IPT.During that down period HPDE and IPDE become

0.8mm and 0.15mm respectively, due to fast rotor cooling than casing of heavier

masses.IPT rotor cooling must be must be done for -------------- start up.HPT rotor heating is also

applied when necessary.

Before speed up HPDE 0.8,IPDE-0.15 and LPDE-----------------

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Flange and Stud heating: This is also applied to maintain HPDE and IPDE in limit that

is done by steam taken from MS line (RHS)in between ESV and MSV. Casing at flange,

joint have jacket through which steam passes for flange heating. There is in built groovein between the flanges through which steam passes for stud heating.

In order to maintain proper tightening of flange joint.

(a) Stud tempr

should not be more than flange.(b) Flange and Stud tempr should not exceed 200

In the following conditions stud and flange heating require:

(a) When turbine is started from cold condition.(b) When rotor expansion is +ve than +1 mm.

(c) Tempr of HP casing (upper is above 2500 ).

132.

If hot rotor is left in rest condition ,hogging will occar due to rapid cooling of lower part

than upper.To avoid that when rotor speed become zero barring gear is put in service

immediately after engaging by hand rotation.

133.

134.

135. Why hammering occurs in liquid lines?

Hammering occurs due to air trap in the line. So during filling of liquid line vent is keptopen. So that trap air may release to atmosphere.Due to charging of cold line with liquid at elevated temp r without proper warm up

hammering will occur.

136. Boiler in light up condn and TLR in tripped condn HP bypass v/v

open but LP bypass v/v closed what will happen?

At this condition immediately start up vent has to be open otherwise:

(i)RH safety will pop.

(ii)Temp

r

will be higher and tube will be overheated which may cause tube rupture.

137.

Natural water contain high quantity of Ca(HCO3 )2 which is the condenser come into

circulating flow by cooling water circulation and from CaCO3 by condenser heat. It is ahard scale. Na, K also forms this type of scale in the same way.

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This scale may effect heat transfer of condenser surface. Condenser cooling temp r will be

high, vacuum will be low, feed cycle efficiency will be low.

To avoid the formation of CaCO3 (and other form of Na, K) we use H2 SO4 which willreact to form CaSO4 which is more easily soluble.This action is taken for stage-1.

In stage--- we use -------------- bed which is SAC, ---------- to remove bi-carbonate.

Na2 R+Ca(HCO3 )2 CaR+2NaHCO3Na2 R+MgSO4 MgR+Na2 SO4

138. Detection of condenser tube leakage and its remedy.

In chemical laboratory hot well sample is checked after a certain interval. In case of tube

leakage PH value will be low, conductivity will high, chloride and silica will be high andhot well level will be in high side than operation, as well as DM water consumption will

low.--------- level drops down.

Detection and remedy: At condenser in vacuum if we place this poly thin sheet on the

face of tube, vacuum will suck the sheet through the tube leakage particularly at that tube.

By filling hot well keeping water box side dry water will come down through damagetube to the water box side. After detecting the damage tube it will be replaced.

139.

After LP turbine the steam becomes almost saturated and by gravity collected at the

bottom point of the condenser (hot well). After condensing by circulation water passesthrough tubes.

140.

It has been provided In stage -------------------- 60 kl from where stator water makeup.

DMCW makeup and chemical tank (HP & LP) makeup supply. The above mentionedsystem required high pure water as --------------------- dumping from ----------- has taken

to CST. Dumping line taken from GC 2 and LPH I/L makeup with the other makeup

walk like DMSW stator water cycle

141.

In that case if there is any leakage in water tube water will enter into the generator.Stator cooler water pressure 3.03.5 Kg/cm2

H2 cooler water pressure 3.33.5 Kg/cm2

142. function of damper tank, hydraulic seal tank (in seal oil line) and

expansion (in stator water line).

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DAMPER TANK it has been provided for emergency purpose. When AC seal P/p and

DC Seal oil P/p fail to take start at seal oil pressure low ( 5.94.9 Kg/cm2 ) damper tank

will provide oil for seal system for half hour by which time H2 gad to be purged out byCO2 filling.

It also provide oil to seal system at change over from injector supply to P/p supply

and vice versa.

HYDRAULIC SEAL TANK seal oil drain -----------H2 side drain is collected to

hydraulic seal tank from turbine side and excitor side by 500 mm loop. Hydraulic Sealtank ensure the prevent of escape of H2 from seal side drain. From hydraulic seal tank

through float V/v oil sent to bearing drain oil line, ultimately to MOT by H2 pressure.

EXPANSION TANK it is used in stator water system and is kept under 200300mmHg vaccuum. The disolved H2 nad O2 in stator water seperated in the expansion

tank due to vacuum. And prevent hydrogen embrittlrment and copper pickup

respectively. Because H2 is responsible for H2 mbrittlrment and O2 is responsible for

copper pickup.

SURGE TANK it is provided in the stage II in order to separate the system.

143.

DPR(Differential pressure regulator) it maintain seal oil pressure 0.60.9 Kg/cm2

Higher than H2 gas pressure (3.5 Kg/cm2 ). To function DPR H2 gas pressure F/b is

aplied at top and seal oil F/B to bottom.

POR(Pressure oil regulator) it maintain constant thrust oil pressure on seal liner which

selected by dead wt. It is maintained near about 2 Kg/cm2

.

144. why vacuum is done for axial shift high and turbine lub oil

pressure very high.

To minimise the ---------------------- time of rotor. Because after vacuum breaks air willcome inside the casing and it will provide resistance to rotor.

In this case ULR operate through TLR.

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So lub oil pressure very low (0.3 kg/cm2 ) to avoid large damage (bearing babit

metal) and at axial shift very high to avoid the damage of thrust bearing (working and

non working pad) vacuum break is done.

145.

To avoid the entrance of water in the hot turbine (HP casing by 9 th and 112 th and IP

casing by by 15 extrn ) through the extraction line. Though there are NRV in extractionline whos direction direction of flow from turbine to heater.

At HPH level very very high 13m, TLR will operate ULR.

146. TLR Tripping philosophy of each case.

(1) Generator field breaker open.

(2) Thyristor fans failure.

(3) Regulator supply failure.(4) Grid control unit (m) supply failure during auto/man change/over.

(5) Rectifier 7th tempr high.

(6) Stator water specific resistivity low


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148. Defination of troughing angle and take up pulley.

The edge of conveyor belt is kept curved along its length. The angle between the tangent

of the curvature and the conveying plane is called troughing angle.

This is done to avoid the spillage of coal and to increase the coal carryingcapacity of the belt.

Increase of troughing angle increases the coal carrying capacity of the belt up tocertain limit. Beyond this limit the coal carrying capacity will decrease and there is a

chance of cracking of belt through the curvature and belt life decreases.

TAKE UP PULLEEY: to maintain the tension of the conveyor belt an idle pulley isused in the return path of the belt by gravity it maintains the tension and acts as a dead

loads used with spring load also.

149.

150.

In sort belt the top grade

151. causes of belt swaying

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i. unequal tension along the length of the belt.

ii. If the material received by the upstream belt is not at the control position, I,eeccentricity feeding of improper distribution of material along the width.

iii. Self aligning idler laid at long interval.

iv. Non uniform jamming of the belt at head and tail end.v. If idler bracket as a whole are at inclined position the direction perpendicular to

belt length.

vi. Deflector plate.

152.

i. nylon take more tension than any other belt.

ii. Its impact resistance is high.iii. Nylon belt is more flexible (such long curvature can be made, small pulley can be

used , troughing angle can be increased). (longitudinal and transverse flexibility.)iv. Reduce belt thickness.

v. Less no of plies for same strength.vi. Superior rot resistance.

153.

SNAP PULLEY:

It is used at the bottom part of the belt at head end to increase the grip angle of the beltwith head end with the pulley. If the angle of contact increases friction increases and head

pulley can carry the belt easily.

154. Coal weighted at wagon trippler and at belt no 8 why?

At wagon tripler coal weighting is done to see how much coal is unloaded. at belt no 8,the weighting is done for recording the amount of coal feed to bunkers. The difference

clarifies the amount of coal stock yard or reclaimed.

155. Reasons of -----------------speed of belt

i. exclusive handling of coal

ii. loosening of takeup tension.iii. If the belt is slipping over the head pulley.

iv. Jamming of coal iether in chute or pulley.

156.

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157. function of CBMS

function of cross belt magnetic seperator magnetic pulley is to remove tramp irrus and

other magnetic materials from the coal. So that they do not entered into the crushers and

save the crushers from damaging. By viewing ILMS: CBMS; MP.

ILMS 3A/B, 10A/B; metal detector11A/BCBMS MP 3A/3B, KTPP not used in BKTPP

158. Basic difference between short and long belt.

i. At the surface toughness is higher in short belt than long belt as frequency of load

impact is higher.ii. Top cover thickness is more of short belt for handling sharp and hard material.

iii. No of ply may be more

iv. In short belt the belt is flat at both driving and non driving end. Hence thetroughing angle is less.

159. --------protection of CHP belt.

i. pull chord: - these switches are provided along with the conveyor belts tied with

the chord with each switch. So that the conveyor motor can be stopped from anyposition by pulling the chord whenever any hazards situations occurs.

ii. Belt sway switch: these switches are provided for tripping the conveyour motor

in case of excessive swaying of the belt on either side.iii. Belt under speed or zero speed : under speed may cause the jamming of ------

160. Total path of coal in schematic form with important pouints.

161.

Paddle feeder or plough feeder is provided at track hopper to feed coal from the hopper to

the conveyor 1A and 1B. there are four nos of paddle feeders in total. 2 nos of conveyor1A & 2 nos of conveyor 1B.

162.

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i. coal reached / unloaded is in excess of the bunker requirement.

ii. Coal is stored in the yard is less than the required.

iii. Can be used from the yard.

163. Short type

i. source of coal in BKTPP Sonepur Bazari; ECL, Bengal emta group colliary,[Tara East and West; bhamora]

ii. take up drive used in belt to maintain its tension.

iii. Coal in surge hopper 800T/hr.

Coal size (020)mm 20%

Crushing rate (80/100)*800T/hr = 640 T/hr.iv. increase of troughing angle coal carrying capacity will be increased.

v. Non coaking coal free burning.

vi. Belt speed 2.66m/sec (rated)/ 2.58m/sec (KTPP)RBFD 1m/s // 8m/sec (KTPP)

vii. bunker feeding by mobile tripperviii. pollution control in CHP

1. dust seperation systemtrack hoppere2. weight dust extraction system.all transfer point.3. Ventilationall tunnels4. Dust separation by using telescopic chute reclaim hopper (uncrushed coal)

i. from where the sources of 6.6 kv in CHP from reserve BUS OSA & OSB415 V from ESP for 11A/Bj. battery source of CHP and its utililizationk. coal rate 0.65kg/KwHr(KTPP)

l. belt is joined by volcanization process.m. BOBR capacity n. Before crusher(300mm, after crusher 20, after mill 7 % through 200mesh.

164. Write the report on proximate and ultimate analysis of coal used

in thermal power station--------------------

In proximate analysis we get the percentage of fixed carbon , volatile matter (Vm ) ,ash

and moisture in coal in weight basis.

For Indian coal these are Fe 50%, Vm 22%,Ash 34%,Moisture 8 to 10%

In ultimate analysis we get the percentage analysis of carbon ,sulphar, hydrogen, oxygen,nitrogen and ash by weight basis.

C42%,H3%,S3%,N %,O25.5%,M10%,Ash30%.

165. Diffrence between KTPP and BKTPP.

KTPP BKTPP

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(I) vibrating screen. (I) Roller screen.

(II) Uncrushed coal stack yard provission (II) Uncrushed coal stack yardis not there. filled by telescopic chute.

(III) 4 nos of belt in every transferred point. (III) 2 nos of belt in every

transferred point.(IV) 3 nos of S/R and 2 nos of WT. (IV) 1nos of S/R and 1 nos of

WT.(under construction).

(V) In TH both lines for BOBR. (V) In TH one lines forBOBR and one for side

Dischargeed wagon.

(VI)Troughing angle 200 (VI)Troughing angle350

(VII) Bunker sealing belt is absent. (VII) Bunker sealing belt ispresent.

(VIII) Puddle feeder drivemotor drive. (VIII)Puddle feeder

hydraulic drive.

(IX) CBMS3A/B,8A/B/C/D (IX) ILMS3A/B,10A/B.MP3A/B/C/D,ILMS MP and CBMS are not used.

(X)TH is bigger than BKTPP.

166. Different types of coupling used in CHP.

(i) Hydraulic couplingMotor and gear box input.

(ii) Gear couplingOut put of gear box.

(iii) Pin bushed couplingGear box input for (reversible belt feeder).

167. How power is transmitted from motor to head pulley.

Motor to gear box through hydraulic coupling, gear box to head pulley through geared

coupling.

168. Why hydraulic coupling---------------------------

Motor takes high starting current during starting and rotates with high rpm during starting

to overcome the moment of inertia.

i. If hidraulic coupling is used, then motor first overcomes theinertia of motor, at the same time oil in the hidraulic

coupling is pumped and rotate the turbine. After that

overcomes the inertia of gear box.ii. If the rigid coupling is used then motor have to overcome

both the inertia of motor and gear box at the same time

during starting so that motor takes high starting currentthan first case and chance of tripping due to high current.

169.

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If big size stones strikes with hammer and the hammer cannot crushed it, hammer

protects holders axis. If it is fis\xed with hammer holder, it will crack due to its high

brittleness.So this type of filling increases the hammer longevity.

170. Advantage and disadvantages of roller and vibrating screen.

i. Rigidity is higher than vibrating string.

ii. Coal can be better ensured that is only small size coal can be pass through by passchute, when roller screen is used.

iii. Longevity is higher than vibrating screen. Jaming of big size coal may crack the

vibrating screen but in roller screen the jamming coal is sent to crusher mannuallywith the help of shovel.

171. Why paddle feeder blade is curved?

i. For one rotation it can removed more coal.ii. If straight blade is used then some coal may spread outside from the correct

feeding zone.iii. In straight blade grip is not ok and it bypasses coal tangentially.

172.

To separate the big size stones and magnetic particles. Otherwise there is a chance chute

paddle feeder jamming. Big size stones cant removed by ILMS and it will jam the chuteand ultimately chute overflow occurs which damage the crushers.

173.

If it is given in driving end then driving pulley-------------. But this is a allignment

between driving pulley and gear box and gear box and motor. If driving pulley fluctuatethen gear box and motor fluctuate accordingly. But gear box and motor are fixed with

platform.

Moreover chute also fuctuates for that feeding may not be uniform.

174. Function of chute.

It conveys the coal along a guided path from one conveyor to another without anyspillage of coal and dust maintaining cleanliness.

175. Difference between idler and pulley.

Idler Pulley

i. no effect for sleeping of belt. i. belt speed reduces when sleep occurs

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ii. lubrication is not done during running.

But whole time lubrication is done beforefitting.

ii. lubrication required.

iii. flat, make through joinning by moreidler.

iii. always flat.

iv. bearing cannot seen from outsiide. iv. bearing is seen from outside, so there isbearing house.

v. idler can take impact load. v. pulley cannot take impact load.

vi. rotate but it support is fixed. vi. rotate always with shaft.

176.

Idler give mechanical support without developing any friction.

i. carrying idler 35o (troughing angle)ii. return idler 10o

iii. impact iidler dia is big and periphery is surrounded by impact absorbingmaterial.

iv. Transition idler rest before head and tail pulley. Troughiing angle isless 10-25o .

Pulley: it transmits powers from one shaft to another by means of belts and roaps.

i. Head pulley is used to transmit the coal from conveyor to chute.ii. Drive pulley is used to transmit the power to the conveyor.iii. Tail pulley is used to return the conveyor from thye feeding zone.iv. Snap pulley is used to increase the friction between conveyor and head

pulley.

v. Take-up pulley increases the tension of belt conveyors.

vi. Deflector pulley increases the tension of belt in the return line so thatbelt can run uniformly upon the idler.

177.

The belt is used to transmit the power from one shaft to another by means of pulley.

When the belt is used to transmit coal or any other material in a cyclic process

from one place to another place (feeding zone), it is called belt conveyor.(i) belt conveyor, (ii) screw conveyor, (iii) bucket conveyor. Etc.

178.

(i) flat belt (ii) V belt (iii) circular belt

according to the material used

i. Lather belt. (ii) Cotton or fabric belt. (iii) Rubber belt, (iv) balala belt.

Property:

i. The belt must be strong, flexible, and durable.

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ii. Should have high------------ efficient of friction.

Ply one synthetic layer and rubber matrix form the ply. Rubber matrix is used to heldthe synthetic path.

Carcas no of ply joining together form carcas.Cover rubber cover is given both sides of carcas to protect it. Top cover is 1012mmand bottom cover is 24mm because top cover takes the load of material impact

otherwise carcas will be affected.

179.

The coal is transferred from yard to boom conveyor through bucket wheel.

Direction of belt in carrying side towards main body of slacker cum reclaimer is

reclaimed.

180.

The heating value/unit quantity of a fuel is known as its calorific value. The no of heat

units liberated/unit weight of the fuel when completely burned in oxygen.

i. gross calorific value ( GCV) higherii. net calorific value (NCV) lower.

GCV the total no of seal unit liberated/unit quantity of fuel. Weight of--------------------------

NCV GCV 2442 (m + GH) kg/ks of fuel.

GCV of coal is determined by -------- calorimeter.

Orsat apparatus.

181. Why

If it is fixed with suspension ---------------------------------------- portion of hammer will beused in crushing coal, thus other portion of its periphery keeping ----------------------- . so

gradually erosion will take place in that portion and crushing quality will be detoriated.

It facilitate removed hammer during maintainence.

182. Difference between

183. crushing rate

184. ACTUAL PROXIMITY ANALYSIS OF

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185. which matter in coal is reform ----------------------- and ignition

temprof coal.

i. volatile matter

ii. ignition tempr 900o C.

186. what is grindibility index and furnace carry over?

It indicates the easiness of pulverization of coal. Indian coal have so

------------------------------

After grinding coal carryover --------- through classifier vane. Fineness 70% through 200

mesh.

1. dust suppression system: i. all feeding zone.

ii. Uncrushed coal stack yard.iii. Crushed and stack yard.iv. Track hopper.

2. dust extraction system:i.

ii.iii. bunker.

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BOILER Question Answer