Why & How these in Boilers??

1-How do you decide Right hand side & Left hand side of a Boiler?

Boiler front is decided based on boiler outlet duct.

If you stand by facing towards boiler out let duct, then the most front part of you is deemed as Boiler front , next to that is boiler rear & LHS & RHS side of you is deemed as Boiler left hand side & right hand side.

2-Why in Some HP boilers drums are aligned at an angle 2 to 4⁰ towards right or left?

Drum slanting side depends on the connection of CBD line. If CBD line is connected at LHS side of the drum then the drum is slanted towards LHS side that is it is made down by an angle 2 to 4^0. This is because to avoid the blow down of excess water throughout the drum length & for such drums CBD line is extended for only for short distance only .And also it is been ensured that all the sludge will collect at slant position only.

Why do the Boilers Explode???

3-How it is been decided that RHS or LHS safety valve of steam drum is set at higher pressure?

It is decided based on the slanting angle of steam, drums & CBD line connection.

If drum is aligned horizontally then you can set any side of the Safety valve at higher pressure as there is uniform spreading of sludge in drum.

Whereas if drum is slanted (made down)towards right or left from where CBD line is connected then it is needed to set that side safety valve at higher pressure to avoid carryover of sludge into the safety valve if t blows first. Such sludge will deposit on safety valves disc & seat which again leads into leakages & wrong operation related issues. So safety valve of such location is always set at higher pressure.

4-Why thickness of steam drum dish end is somewhat lesser than other area

Because dish end has spherical shape, so there develop hoop or circumferential stresses & on the other part of the drum longitudinal stress.

 For Hoop stresses

σc =  Pd/2tη

Thickness t = Pd/(2 ησ)

& For longitudinal stresses σl = Pd/4tη

Thickness t = Pd/(4 ησ)

Where P = Pressure acting & d is internal diameter of the drum

Based on above relations thickness for spherical part of the drum that is dish end, the thickness is lesser than other part of the drum.

Boilers troubleshooting guide

5-Why the start up vent is used in Boilers?

Start up vent is used for

• To provide minimum steam flow from the boiler during start up, shutdown & sudden load cut off
• It is used to manual relieve of excess pressure
• Used to give excess flow for temperature rising during start up or partial loads
• Used to take excess load on boilers during peak load test

6-Why the super heater safety valve is set at lower pressure than drum safety valve

If drum safety valves set at lower pressure, then there will be very less or no steam flow to super heaters.

In order to save super heater coils from starvation due to no flow of steam during steam blow from drum safety valves, the super heater safety valves are always set at lower pressure than drum safety.

7-Why LHS/RHS water wall panels expand more (towards down) than front & rear water wall panels?

Side water panels are usually straight hence expansion readings show more value  where as front & rear water wall panel will have bends.

8-Why pressure gauges fitted at boiler firing floors show more pressure than actual (that of fitted at steam drum EL.level)

Pressure gauges show 2 to 3 kg/cm2 higher pressure due to addition of hydraulic head in PG impulse line laid from actual location to firing floor

9-Why there is a pressure difference between main steam line pressure & drum pressure?

Main steam line pressure shows lower pressure than drum pressure due to pressure loss in super heater coils. And this pressure difference increases as the number of super heater coils & steam flow increase.

10-Tips to reduce LOIs in Boilers

10-Why do high pressure Boilers have higher efficiency & lower fuel consumption?

Because:

1-High pressure boilers have higher  saturation temperature

2-High pressure boilers have higher feed water temperature at economiser inlet

3-High pressure boiler have lower enthalpy of evaporation (latent heat)will be less

H = Hf + Hfg + Cps x (Tsup-Tsat) -

Where,

Hf = Enthalpy of liquid at operating pressure

Hfg = Latent heat

Tsup = Suepr heated steam temperature

Tsat = Saturated temperature of steam

Example:What amount of heat would be required to produce 5000 kg of steam at a pressure of 65 kg/cm2 and temperature 485 °C from water at temperature 175 °C?

Steam pressure P = 65 kg/cm2

Steam temperature Tsup = 485 °C

At above parameters, saturated temperature Ts = 282.7 °C

hf = 298.82 kcal/kg, hfg = 364.47 kcal/kg

Now, enthalpy of 1 kg of superheated steam

Hsup= hf + hfg + Cps (Tsup - Ts)

hsup = 298.82 + 364.47 + 0.5 X (485 - 282.7)

hsup = 764.44 kcal/kg

Amount of heat already associated with 1 kg of water = 1 X 1 X (175 – 0) X 175 kcal/kg

Therefore net heat to be supplied per kg is 764.44 – 175 = 589.44 kcal/kg

Procedure for Boiler gauge glass line up

11-Why there is more CO in flue gas?

More CO in flue gas is due to improper combustion, that is due to

• Less excess air
• In adequate turbulent
• Lower furnace/bed temperature
• Higher FC in fuel

IBR acts, regulations & IBR forms

12-Why Does boiler furnace pressure fluctuate?

• Interrupted fuel flow
• Leakage in boiler pressure parts
• Furnace combustion controller not working properly
• Malfunctioning of fans pneumatic dampers
• Higher moisture in fuel

13-Why there is more NOX in flue gas?

• Higher NOx is due to
• Higher bed temperature or furnace temperature
• Higher excess air
• More N2 in fuel

14-Why there is no Temperature gauge (TG) is fitted on steam drum of any Boiler?
In steam dream the phase of water is at saturated state, so no any necessary of providing TG. However temperature gauges are provided at drum inlet feed water line & drum outlet saturated line.

In some drums whose thickness is > 100 mm, there you may find thermo couples for measuring skit temperature. So in order to avoid  weakening of steam drums due to making number of drill holes for unnecessary instruments, the TG is not generally provided for drums.

For example if  drum PG showing  pressure 110 kg/cm2, then its temperature will be around 320 deg c. (Refer steam table for saturation temperature). And generally not used in any calculation or performance analysis, if required one can refer steam tables for saturated water

The temperature gauge or thermo couple provided at the drum outlet lines is used during plant start up.

It's all about HP heaters

Also read 16-Perfect reasons for increasing the fuel consumption of Boilers

Why does Boilers main steam temperature increases more than design?

Why do the vibrations occur in machines???

What do you mean by the term VIBRATION?

A periodic motion of the particles of an elastic body or medium in alternately opposite directions from the position of equilibrium when that equilibrium has been disturbed.

Why do the VIBRATIONS occur in machines?

Vibrations in the machine due to:

• Misalignment of the driver & driven equipments
• Bearing failure or more clearance in bearing
• Unbalance in machine
• Loose parts in machine
• Loose foundation bolts
• Lack of lubricant
• Low viscosity or high temperature of lubricants
• Bent shaft or more run out of shaft
• Over loading of machine
• Operation of machine in critical speed band
• Wrong design of machine or its parts
• Wrong installation of machine & accessories

 What are the forces responsible for vibrations in a machine?

Three basic types of forces which cause vibrations in a machine:

• Impact – loose parts, hammering in a piping system, rolling element in a bearing hitting a spall.

• Periodic – repetitive force such as unbalance or misalignment.

• Random – varies with time, for example, turbulence in piping, pump cavitations.

Each type of force produces a different reaction in the machine.

What are the effects of VIBRATION on machine?

• Bearing failure
• Coupling failure
• Machine parts failure
• Internal rubbing & seizing related problems
• More lubricants consumption
• More power consumption
• More noise
• Machine is required to run at lower loads & hence lesser machine efficiency
• Eventually machine will fail

 Questions & Answers on Bearings

If a machine has higher vibration in only vertical/horizontal/axial direction then what does it indicate?

• If there is more vertical vibration and other direction vibrations are minimum, then indicates looseness in machine components.

• If there is more horizontal vibration and other direction vibrations are minimum, then indicates unbalance of rotating part.

• If there is more axial vibration and other direction vibrations are minimum, then indicates misalignment.

Protections & Interlocks in power plants

Methods of Vibration measurement:

In power plants, generally equipments vibrations are measured in displacement & velocity

Let us discuss on the methods of vibrations measurement

1-Displacement amplitude:

Displacement amplitude measures the distance the vibrating part travels in one direction from a reference position during oscillations. (Note that the peak-to-peak displacement value, which measures total travel in both directions, is sometimes used.) This vibration measurement is important because vibrations with high displacement amplitude can cause machine components to exceed their yield point and experience catastrophic failure. Displacement measurements are typically used when vibration frequencies are low.

2-Velocity amplitude

Velocity amplitude measures the speed of the oscillation. This measurement is typically considered the industry standard for evaluating the condition of a machine based on its vibrations; because it takes into account both vibration frequency and displacement. (Recall that velocity is the rate of change of displacement.) In fact, ISO standards refer to velocity amplitude when specifying the severity of machine vibration. Velocity amplitude can be expressed in terms of peak value or, more often, in terms of the root mean square (RMS) value, which is an indicator of the vibration energy.

3-Acceleration amplitude

Acceleration amplitude is directly related to the force imparted by the vibration and is especially useful for assessing the likelihood of fracture for equipment that rotates at high speed. The high forces associated with acceleration can also cause lubrication breakdown, which can lead to excessive wear, heat, and premature failure. Acceleration is typically measured in “g,” or multiples of earth’s gravitational acceleration.

Units of vibrations measurement:

• Displacement: mm, microns, mils
• Velocity: mm/sec., inch/sec.
• Acceleration: mm/sec2.

How do you avoid machine VIBRATIONS?

Vibrations can be avoided by

• Running the machine/equipment at or below the rated load
• Following preventive maintenance regularly
• Following Condition based maintenance (CBM) regularly
• Replacing worn-out parts timely
• Implementing proper design & installation methods
• Following lubrication schedule timely with correct quantity & quality lubricants
• Following precision alignment (Rim & Face type) method

Relation between displacement, velocity & acceleration & their conversions

Velocity = (2pi X RPM/60) X Displacement (microns peak-peak)

Acceleration = (2pi X RPM/60) X Velocity (mm/sec. pk)

Acceleration = 4 pi X (RPM/60) X Displacement (microns pk-pk)

What is the critical speed of a machine? On what factors critical speed of a machine depends?

Critical speed of a shaft is the condition, where the number of natural vibrations or natural frequency equals the shaft speed in rpm.

At this speed rotating shaft becomes dynamically unstable and vibrations occur.

Critical speed depends on,

• Shaft speed
• Distance between the supports
• Type of support

Questions & ANswers for power plant fitters & Maintenance Engineers

Guidelines for selection & installation of machine foundations:

• For centrifugal machines, Mass of the foundation = 3 X Mass of the machine

• For reciprocating machines, Mass of the foundation = 5 X Mass of the machine

• The top of the foundation block should be at least 12” above the finished floor level

• The width of the foundation should be 1.25 to 1.5  X Vertical distance from the base to the machine centre.

Thumb rules for steam Turbine displacement vibrations measurement:

• Normal vibrations in microns = 2400 / √Turbine speed in RPM

• Alarm vibration in microns = 4500 / √Turbine speed in RPM

•  Trip vibrations in microns = 6600 / √Turbine speed in RPM

Why do the Boilers Explode???

Turbine oil and transformer oil standard testing parameters

18-reasons for turbine bearings vibrations

Tools tackles used in power plant maintenance

Tools & Tackles are the main resources for power plant maintenance..Thsese are classified into Hand tools,machine tools, lifting tools & measuring tools.

Power plant maintenance tools & tackles

Powerplants of capacity 10 MW to 100 MW need following tools for routine preventive, predictive & breakdown maintenance works.

A. Hand Tools:

• Spanners (Ring, flat, box, tubular and Allen types)

• Files (Rectangle, square, triangular, round, half round)

• Chisels 6", 12"

• Screw spanner 6", 12"

• Pipe wrench 12", 24"

• Plumb

• Hammer and mallets

• Pliers (Nose and circlip pliers)

• Shim cutter

• Torque wrench

• Pipe bender

• Hole and letter punches

• Screw drivers

• Line testers

• Bench vice

B. Machine Tools:

• Single phase Hand drill machine

• Hand angle grinding machine (AG-4, AG-5 and AG-7)

• Pipe cutting machine (Chop saw machine)

• Air blower

• Vacuum cleaner

• Hot gun

• Bearing heaters

Power plant Maintenance Calculations

C. Lifting/Pulling Tools:

• Chain blocks (1T, 2T, 3T, 5T and 10T)

• Dee shackles (1T to 10T)

• Eye bolts (0.5T to 10T)

• Polyester/Nylon Lifting belts (1T to 10T)

• Chain puller (1T)

• Pulley block (0.5T to 5T)

• Hydraulic jack (25MT)

• Screw jack (2T to 10T)

• Coupling puller

• Wire ropes (1/2" and 1")

• Slings (1/2", 1", 1.5")

D. Measuring Tool (Instruments):

• Vernier caliper ( 0–150 and 0–300 mm LC: 0.02 mm)

• Measuring tape (3 meter and 5 meter)

• Inside and outside micrometer screw gauges (0–25 mm and 50–200 mm LC: 0.01 mm)

• Dial gauge (LC: 0.01 mm)

• Inside and outside calipers

• Ultrasonic thickness checking machine

• Infra-red temperature gun

• Tachometer

• Multimeter

• Clamp meter

• Earth leakage tester

• Earth resistance checker

• Insulation resistance checker

• Pressure gauge calibrator

• Balance weigher

• Sound level meters

Boiler safety valves overhauling steps

Constructional materials & welding electrodes used in power plant

What are the various materials used in power plants construction???
1-Low Carbon Steel IS 2062, IS 1239: For structural steels like plates, angles, channels, beams, platform, walkways & LP steam lines etc.

2-High Carbon Steel SA 106 Gr. B/C, SA210 Gr, B/C, SA 516 Gr. 70: For Boiler pressure parts like water wall panels, headers, economiser coils, down comers, feed water lines, steam drum etc.

3-Alloy Steel SA 213 Gr. T11, T22, T91 and SA 335 P11/P22: Super heater coils and main steam pipe lines.

4-Cast Iron: Travelling grate materials, pulley, coupling etc.

5-Copper: Air conditioning cooling lines.

6-Brass: Surface condenser and oil cooler tubes.

7-Stain Less Steel SS 304, 316, 410 etc: Ejector tubes, surface condenser/oil cooler tubes, control valve stems & valve trim materials

8-Plastics: PVC pipe lines, valves, tanks etc.

9-Steam Turbine

• ESV: Cast alloy steel
• HP Casing: Cast alloy steel
• LP Casing: Carbon steel
• Rotor: Forged chromium, molybdenum and vanadium alloy steel
• Blades: Alloy steel
• Bearings: Liner Babbitt or white metals
• Labyrinth: Phosphorous, lead and aluminum

Power plant Maintenance Calculations

What welding electrodes are generally used in power plants various welding works???

Sl No.	Particular Material and Grade	Type of Welding	Welding Electrodes Used	Application
1	Low carbon steel IS 2062/1239	Arc	E 6013	General welding works like structures, non IBR pipe lines plates etc.
2	Carbon steels SA 106 Gr.B/C, SA 210 Gr.A/C, SA 516 Gr.70, SA 234, etc.	TIG Arc	ER 70 S2 E 7018	Boiler water wall panels, economizer coils, evaporator headers, process steam lines etc.
3	Low alloy steel SA 213/SA-335 Gr.T11/P11	TIG Arc	ER 80S B2 E 8018 B2	Primary super heater coils, headers, soot blower lines etc.
4	High alloy steel SA 213/SA-335 Gr.T22/P22 and T91/P91	TIG Arc	ER 90S B3/90S B9 E 9018 B3	Secondary and radiant super heater coils, main steam line etc.

Why thermal expansion is necessary in Boilers

Understanding the term expansion & contraction

                                

When a body is heated it will expand & when it cooled it contracts. So body expands & deforms when heated & cooled. Change in temperature of a free body causes body to expand & contract without inducing stress. When the deformation of the body is restricted by means of any external force, there will be huge chances of stress induction. Such induced stresses are called temperature stresses. These may be tensile or compressive in nature.

Boiler calculations for Boiler operation engineer (BOE) exam

Viva Questions & answers for preparation of BOE exam & interview

Here L = Original length of the steel bar

∆t = Change in metal temperature deg C

ɑ = Coefficient of thermal expansion

Temperature strain e = Free deformation / Original length = ∆L / L

E = L ɑ ∆t / L = ɑ ∆t

Temperature stress σ= Young’s modulus X Strain = E X e

Temperature stress σ = E ɑ ∆t

Stress induced in a rigid or constrained body

P = Force exerted by a rigid support of constraint

We have σ = P / A

P = E ɑ ∆t A

Expansion in Boilers

Boiler is made up of plates, tubes, pipes and simple steel of various grades depending upon the duty conditions. Depending on the service such as cold air/hot air/cold flue gas/hot flue gas/cold water/hot water/saturated steam/super heated steam, thermal expansion movement of steel materials takes place to different extent in Boiler. Ignorance of thermal expansion movement of boiler components in design/installation may lead to failure of boiler components. The damage to boiler components can be costly affecting human life in some cases.

There are two types of expansions in Boilers

Factors considered for Boilers Engineering & Design

Absolute Expansion: Boiler whole mass expands.

Differential Expansion: Individual parts expansion. There are places where there is a relative expansion movement, which can cause stress in those parts.

In boilers expansion pointers are attached to all the pressure parts header to under stand the direction & value of expansion.

Expansion pointers are used for verifying the expansion movement of the boiler. These are attached to the drum ends/bottom or top header ends. When the boiler is under commissioning stage the expansion must be monitored. Depending on the anchor points in X-axis and Y-axis, the expansion is predicted by designers. The same is counter checked at site. Deviations in the form of non-uniform expansion should be checked.

Modern boilers expand towards bottom, during start ups & shutdown it is very important to observe the Boiler expansion.

Expansion of the metals depends on;

• Change in metal temperature

• Length & area of the materials

• Coefficient of expansion of the materials

It's all about HP heaters

Provisions for thermal expansions in boilers:

• Boilers all headers bottom space should be free from obstacles

• For air & flue gas ducts expansion bellows may be of metal or fabric should be provided

• Expansion loops for all steam lines should be provided

• Spring supports & hangers for steam line & hot water lines

• Rocker washers for steam drum & super heater headers supports

• Provision of stay bolts

IBR acts, regulations & forms used

 Precaution to be taken for free expansion:

• After shutdown, ensure all foreign material from Boilers & ductings have been removed completely

• Ensure all temporary supports & platforms have been removed from boilers & ducting

• Ensure there is no welding between any pressure part & hot ducts with platform or other or beams which can restrict the expansion

• Ensure enough space is available for all bottom headers for free expansion

• Ensure steam line drains line are free to expand with steam lines

• Ensure there are no any uneven expansions

Procedure for Boiler Gauge glass line up

Examples:

A square rod of size 20mm X 20 mm in cross section & 2000 mm in length is allowed to expand by fixing both of its ends. Determine the force developed if the rod is heated from 25 degree c to 150 deg C.

L = 2000 mm

A =20 X 20 = 400 mm2

E = 2 X 10⁵ Mpa

ɑ  = 12 X 10^{-6 0}C

∆t = 150-25 = 125 ⁰C

We have             P = σA

P = E ɑ ∆t A

P =2 X 10⁵ X 12 X 10^-6 0C X 125 X 400 = 30000 N
Force developed at the end P = 30 KN

What is the expansion of Boiler side water wall panel , whose total length is 18 meters & metal temperature is 295 deg c. Consider atmosphere temperature 30 deg c &  ɑ  = 12 X 10^{-6 0}C

Expansion of side water wall panel ∆L =L ɑ ∆t = 18 X = 12 X 10^-6  X (295-30) =0.068mm = 68mm

10-Tips to reduce LOI in Boilers

Restricted expansion in Boilers or steam lines will lead to..

• Damages to the restricted part

• Damage to the refractory & sealing

• Leakages

• Secondary failure

• Tube/pipe puncture

• Explosions

Why do the Boilers explode???

Also read 16-Perfect reasons for increasing the fuel consumption of Boilers

Available @ Flipcart/Amazon/Notion press

Boiler Feed Pumps Design factors & Pump Capacity calculation

Power plant Safety QnA

Why does Boiler back fire?

Why  does boiler back fire?

Following potential situations may cause back fire in biomass or bagasse fired boilers

Protections & Interlocks in power plants

1-Sudden trip of ID fans or closing of fans suction or discharge dampers:

If there is no interlock on ID fans trip to FD fans, a very huge back fire occurs in boiler which has potential to cause damages to the Boiler & operators.

Sudden closure of ID fans suction or discharge dampers will cause same back fire as above.

2-Malfunctioning of pneumatic dampers positioner may cause closure of ID fans dampers resulting into huge back fire in Boiler

3-APH tubes jam : Area required  for the flue gas flow is equals to Boiler capacity/9. Due to accumulation of ash in tubes, the flue gas flow area gets reduce. This situation causes backfire

This situation occurs if Boiler is run at lower load for long time without bypassing APH for FD/SA air, as at lower load flue gas temperature will be less, which get condense in APH tubes.

4-Higher moisture in the fuel: If the fuel has higher moisture that required, then there will be more requirement of combustion air, while maintaining this air fuel mixture back fire may occur.

5-Frequent variation in fuel moisture : This is experienced in sugar plants due to variation in bagasse moisture at mill outlet due to variation in imbibition water added to extract juice from cane.

Upon continuous variation of fuel moisture it become very difficult for operator to maintain balanced draught in furnace.

6-Improper spreading of fuel : Due to this furnace may experience bed heap combustion of fuel, due to this there will not be uniform distribution of bottom combustion air causing boiler back fire.

IBR acts, regulations & forms used

7-Sudden drop of boiler load: Due to this boiler air fuel ratio & draught system gets disturbed causing boiler back fire.

8-Fouling in Super heater coils : Higher moisture in fuel cause accumulation of bagasse & unburnt on super heater coils, which blocks the flue gas path causing boiler back fire

9-Accumulation & deposition of ash in ESP fields: This situation causes more resistance to flow of flue gas.

10-Improper air fuel mixture during start up & shutdowns may cause boiler back fire

11-Air leakage into & out of the system : Due to the air ingress & flue gas leakages, it becomes very  difficult for operator to maintain balanced draught.

12.Leakage or puncture of water wall tubes: Leakage or puncture of water wall tubes will result into high furnace pressure

Why do the Boilers explode???

16-Perfect reasons for increasing the fuel consumption of Boilers

Questions & Answers on AFBC Boilers

Question & Answers on ESP troubleshooting

                                 ESP TROUBLESHOOTING GUIDE

1-What are the potential reasons for large dust collection on collecting plates & discharge electrodes?

• Higher dust load on ESP

• Improper rapping

• Low velocity of flue gas

• Higher resistivity of ash

• ESP running under capacity

2-Why there is sparking in the fields?

• Excessive dust formation on plates

• Very less gap between collecting plate & emitting electrodes

• Improper alignment of electrodes

• Obstacle of foreign material in the field & touching the discharge electrode

• Improper charge ratio

3-What are the reasons for higher emission at stack outlet?

• Under size ESP or wrong design

• Improper rapping

• Higher spark rate

• Improper distribution of flue gas

• Transformer not working or under capacity

4-What are the reasons for damage/corrosion of ESP electrodes & casing plates?

• Operation of ESP at lower flue gas temperature <120 deg C continuously

• More ash deposition on plates

• Leakages in ESP, due to which air ingress & cause condensation of flue gas on electrodes & other internals

• No insulation or using lesser thickness insulation material

• Wrong operation of rapping system

• Not cleaning of ash in shutdowns

Boiler troubleshooting guide

5-Why there is a difference in hopper temperatures of ESP fields?

It is due to the different load on different fields. Field which discharge more ash has more temperature & field discharging low ash is having low hopper temperature

6-What do you mean by Back Corona effect?

A phenomenon that occurs when the gas within a high resistivity dust layer becomes ionized, which causes heavy positive ion back flow, which neutralizes negative ion current and reduces voltage levels.

7-Why there is fluctuation in ESP current & Voltage

• Movement or swaying of discharge electrodes & creating close contact with collecting plates

• Close contact of foreign material with discharge electrodes

• Loose connection of cables which are connected to control panel

• Leakage current & Induction

• High ash level in hopper & touching discharge electrodes

8-What are the reasons for failure of support insulators?

• Higher operating temperature

• Higher dust collection & electrical arcing

• Shock loads

9-Why there is more ash collection at ESP 1^st Field as compared to other fields?

In ESP 1^st field there is huge drop of flue gas velocity that is from 12 m/sec to around 1 m/sec, which causes more ash collection in 1^st field. So current for ESP 1^st field is kept lesser as compared to other fields.

10-Why ESP field voltage reduces when the current increased?

It is due to the back corona effect due to higher resistivity of ash. To get rid of this increase rapping frequency.

11-Why explosion occurs always in ESP? How do you avoid it?

Generally ESP has low velocity zone, where there is possibility of collection of explosive gases & unburnt fuel. The explosive gas namely carbon monoxide associated with unburnt fuel settles at ESP corners or at collecting plate rapping system, when the cold air or hot unburnt particle comes in contact with this gas it suddenly explodes.

So in order to avoid this need to take care on following points

• Maintain balanced draught in furnace to achieve good combustion as well as to avoid carryover of unburnt particles

• Arrest all lair leakages in ESP

• Avoid charging ESP at flue gas temperature < 125 deg C

• DO not bypass any of the ESP interlocks

• Ensure proper operation of rapping system

• Ensure healthiness of explosion vent provided at ESP inlet & outlet cones

Battery & Troubleshooting

12-How the air ingress affects on ESP performance?

• Air ingress lowers the flue gas temperature, there by corrosion of ESP internals

• Pressure drop across ESP increases

• Load on ID fans increases

• Leads secondary combustion of unburnt particles in ESP

13-What operation parameters affect on ESP performance?

• Flue gas temperature

• Flue gas volume

• Flue gas composition

• Inlet dust load

• Density of ash

14-How do you calculate the ESP efficiency?

ESP efficiency = ( Dust in –Dust out) X 100 / Dust in

It is around 99% for best performing ESPs

15-What do you mean by the term Emission?

Emission is the release of pollutants into the air from a source.

16-What do mean by Aspect ratio? How doe it affect on dust collection?

It is the ratio of collecting plates length to the height. It should be around 0.5 to 2

If collecting plates height is more than their length, then there is a possibility of carryover of dislodged dust particles with flue gas

Read How to calculate ESP efficiency???