### Why does vacuum in steam condenser reduce or drop??

1-High exhaust temperature: Vacuum drops or maintains at lower side due to high exhaust steam temperature flow into steam condenser. This high exhaust temperature is mainly due to 1-Operation of Turbine at lower loads 2-More clearance in labyrinth seals 3-Not operating exhaust hood sprays 4-More load on condenser 5-Breaking of ejector U loop 2-Low circulating cooling water flow Vacuum in condenser reduces due to inadequate cooling water flow through steam condenser. This is mainly due to; 1-Problems associated with pumps 2-Air pockets in pipe line 3-Leakages in cooling water line 4-Stuck of discharge valve of pump 3-High cooling water temperature at condenser inlet Higher cooling water temperature at condenser inlet results into reduction of vacuum due to poor heat transfer from steam to water 4-Poor heat transfer in condenser Very less or poor heat transfer in steam condenser reduces vacuum to very low level resulting into high exhaust temperature &am

## Coal handling plant (CHP) consists of ;

• Coal storage yards
• Coal vibrofeeders
• Coal vibroscreen
• Magnetic seprators
• Coal crusher
• Coal weigher
• Series of Conveyors
• Water sprinkling system
• Coal shuttle conveyor
• Coal storage bunkers

Inorder to calculate the coal handling and coal storage bunkercapacity, first we need to know the coal requireent per day for a plant, coal handling maintenance stratergy

We shall calculate the coal handling & bunker capacity by taking an example of 25 MW thermal power plant consuming coal of GCV 4900 kcal/kg & having heat rate 3200 kcal/kwh running at 100% PLF.

Plant running load = 50 MW X 100/100 = 25 MW

We know that coal consumed = Heat rate X Power generation / (Coal GCV)

Coal consumed =3200 X 25 / 4900 = 16.32 MT/hour

Coal consumed in a day = 16.32 X 24 =391.68 MT take round figure 392 MT/day

A-Coal handling capacity calculation

Consderations:

• Coal handling plat is operated 14 hours in a day
Note: Some designer consider operating hour of the plant is 10-12hours
• 10 hours used for cleaning and preventive maintenance
CHP capacity =392/14 =28 Tonnes / hour

Take 50% extra margin on capacity

CHP capacity = 28 X 150% = 42 Tonnes/hour

B-Coal yard design

For 25 MW power plants coal can be supplied through truckes & lories .It is sufficient to keeping the stock of 7-8 days coal in coalshed.

Coal shed capacity = Lenght 50 meter X Width 30 meter X Avg Height of coalheap 4 meters X coal density 800 kg/m3 = 4800 MT

Which han hold the coal for 12 days of full load operation days

If the plant is of bigger size, then the coal is supplied through railway & Wagons & stored at yard..

Yard capacity =Length X Width X avg.Height of 6 meter X Coal densitykg/3

Coal from Shed & yard is then shifted & dozed to vibrofeeder hopper through chain & tractor dozers

C-Selection of bunker capacity

Buker capacity is generally designed for 12-14 hours of full load operation

Let us calculate with 12 hours of operation hours

Coal consumption in 12 hours = 392 X 12 /24 =196 MT

Volume of bunker = 196 X 1000/800 = 245 M3

Take 10% of extra margin on bunker as some of coal stucked on bunker wall surface cannot be used for Boiler. Which is unaccountable

So total water volume of Bunker = 245 X 110% = 269.5 take round figure =270 M3

### Boiler feed pumps (BFP) questions & answers for interview

Boiler feed pumps (BFP) questions & answers for interview: 1-What is the function of Boiler feed pumps (BFP) in power plant? Functions: To supply the feed water to boilers To conduct the Boiler hydraulic tests To supply the desuperheating & attemperator water required for process steam lines & boilers respectively TOP-6 BEST POWER PLANT O&M BOOKS Boiler calculations for Boiler operation engineer (BOE) exam Viva Questions & answers for preparation of BOE exam & interview  2- What are the type of prime movers (drives) used for BFPs? Prime movers: LT drive (415 V) HT drive (11 KV) Turbo drive (Steam driven) 3-What are the auxiliaries associated with BFP? BFP auxiliaries Cooling water pump & lines Lube oil system ARC valve Mechanical seal flushing system Balance leak off line & its PRV 4-What are the various pipe lines connected to BFP? Questions & Answers on AFBC Boilers Suction pipe line D

### Basic things you must know about nut bolts & spanners

A Bolt is a mechanical device which has head on one end of a body and a thread on the other end designed for fastening of two parts. Bolt is inserted into holes in assembly parts, it is mated with a tapped nut. Tension is normally induced in the bolt to compress the assembly by rotating the nut. This may also be done by rotation of the bolt head. A Screw is a headed and threaded bolt used without a nut. It is inserted into an internally tapped hole and tension is induced by rotation of the screw head. A Stud is a fastener with no head but it has threads at both ends of the shank. It, like a screw, has one end those screws into a tapped hole. A nut is used on the other end to create tension. Major diameter – largest diameter of thread (D) Minor diameter – smallest diameter of thread Pitch – distance between adjacent threads.       Boiler calculations for Boiler operation engineer (BOE) exam TOP-6 BEST POWER PLANT O&M BOOKS Types of nut bolts & Washer

### Calculation of heat rate & efficiency of the power plant

Heat rate  is the amount of energy used by an electrical generator/power plant to generate one kilo Watt-hour (kWh) of electricity Heat rate (HR) = Heat input / Power generation =Kcal / Kwh Boiler calculations for Boiler operation engineer (BOE) exam Viva Questions & answers for preparation of BOE exam & interview Total heat input: The chemical energy available in the fuel (coal, biomass, oil, gas etc) is converted into heat energy in Boilers, this process is called as oxidation. The heat available in the fuel is measured in terms of Kcal/kg, KJ/kg or BTU units. The part of this fuel is used as useful heat and rest is lost as dry flue gas loss, moisture loss, un  burnt loss, radiation/convection losses etc.Based on Boiler efficiency this heat energy from the fuel is utilised, generally fuel heat utilisation is in the range of 60 to 90%. This heat generated in the boilers due to oxidation of fuel is used to generate high pressure & temperature steam. Thus genera

### STEAM CONDENSER,VACUUM AND CALCULATIONS

A steam condenser is device or an appliance in which steam condenses and heat released by steam is absorbed by water. Heat is basically shell & tube type heat exchanger, where cooling water passes through tubes & steam condenses in shell. The functions of the condensers are: It condenses the steam exhausted from Turbine last stage Increase the thermal efficiency of the plant reducing the exhaust pressure and thereby reducing the exhaust temperature It maintains a very low back pressure on the exhaust side of the Turbine Supplies feed water to Boiler through deaerator TOP-6 BEST POWER PLANT O&M BOOKS Condenser related components: Hot well Cooling water inlet & outlet system Cooling tower Support springs or expansion neck Air Ejector system Condensate extraction system Cooling water tubes & tube sheet Vacuum breaker valve Safety valve or rapture disc Water box Air & water vent lines Types of steam condensers: Surface Co

### 22-Most likely Question Answer Guide for Boilers troubleshooting

TOP-6 BEST POWER PLANT O&M BOOKS 1.What are the emergencies that are expected to happen in boiler operation? Emergencies that can happen in boilers operation are: Boilers tubes leakage Failure of feed water control station Unbalanced draft in furnace Furnace explosion Blow down valve failure Feed water pumps failure Secondary combustion in super heaters and ESP Also read 16-Perfect reasons for increasing the fuel consumption of Boilers 2.List out the potential reasons for boiler tubes failure. Reasons for boiler tubes failure: Failure due to overheating Failure due to internal scales Failure due to aging Failure due to uneven expansion Failure due to ash and flue gas erosion Failure due to material defects Failure due to internal and external tube corrosion Improper or effected circulation due to opening/passing of low point drains 3.List down the sequential action taken after boiler tube leakage to restore the boiler. Following activities ar

### Questions answers & calculation on Boiler draught & Chimney

1-What do you mean by the term draught? It is the pressure difference, which causes flow of gases to take places. 2-What is the function of draught in Boiler? To supply the combustion air required for proper combustion To evacuate the combustion products from the furnace or combustion chamber To evacuate the combustion products to the atmosphere So draught is the pressure difference between the inside the boiler and outside air. Inside the boiler pressure is due to combustion products (Flue gas) & outside pressure is due to fresh atmospheric air. 3-What are the different types of draughts used in power plant boilers? There are mainly two types of draughts. Natural draught & artificial draught Natural draught is generally obtained by Chimney Artificial draughts have main two types Steam jet: It is again classified into Induced & forced draught Mechanical draught: This is classified into Induced draught, forced draught & Natural draught

### Boiler calculations for Boiler operation Engineer Exam (BOE)

1-Oxygen percentage in Boiler outlet flue gas is 4.9%, then what will be the percentage of excess air? We have excess air EA = O2 X 100 / (21-O2)                                    EA = 4.7 X 100 / (20-4.7)                                    EA = 30.71% 2-Calculate the Oxygen level (O2) in flue gas, if excess air is 25% We have Excess air EA = O2 X 100 / (21-O2)                                    25 = O2 X 100 / (21-O2)                                    O2 = 4.2% 3-A Boiler’s combustion system requires 5.5 kg of air for burning 1 kg of fuel, then calculate the total air required for complete combustion if its flue gas has 4.1% of O2 We have, Total air = (1 + EA/100) X Theoretical air EA = O2 X 100 / (21-O2) EA = 4.1 X 100 / (20-4.1) = 25.78% Therefore Total air = (1 + 25.78/100) X 5.5 = 6.92 kg of air per kg of fuel burnt 4-A Coal fired boiler having total heating surface area 5200 M2 produces 18 kg of steam per square meter per hour of heating surface, then calculate the Boiler cap