Power plant and calculations

Power plant and calculation site basically includes the detailed study of power plant operation and maintenance, its related all calculations and thumb rules. It also involves detailed troubleshooting guides for operation and maintenance of power plant system/equipments like Boiler, fans, compressors, belt conveyors, ash handling system, ESP, steam turbine, cooling tower, heat exchangers, steam ejectors, condensers WTP. etc. Heat rate, efficiency

Saturday, 26 July 2025

Why do high pressure Boilers have higher efficiency??

High pressure Boilers will always have higher efficiency and lower fuel consumption as compared to low pressure Boilers.

In high pressure Boilers, heat transfer is more & losses are minimum, which has been proved theoretically in subsequent steps. Working of steam at higher pressure and higher temperature does more work than low pressure and low temperature steam.

Following are the major justified reasons for why high-pressure Boilers have higher efficiency??

Read more>>>>>Boiler and calculations

1-At higher pressure, steam can be generated at higher temperature.

Higher operating pressure of the Boiler facilitates higher steam temperature, which does more work than low pressure Boilers

2-More heat recovery options in High pressure Boilers.

High-pressure boilers often incorporate regenerative feedwater heating like HP and LP heaters more effectively, improving overall efficiency.

3-High pressure boilers have lower fuel consumption:

Because of high team generation is at higher pressure, feed water at economiser also enters at higher temperature leading into lower fuel consumption.

That is sensible heat addition is lesser in high pressure Boilers

4-High pressure and temperature boilers will have more enthalpy

5-Stam generated at higher pressure will have lower specific volume, hence Boiler will be compact in size.

6-Turbine consuming high pressure steam will generate more power at lesser quantity of steam input, that is lesser specific steam consumption & fuel consumption. High enthalpy steam means more energy per kg, so less steam is needed to produce the same power output.

7-Heat losses in High pressure Boilers are generally less as compared to low pressure Boilers

8-Operate at higher temperatures and pressures, improving the Rankine cycle efficiency, that is More work output from the same amount of fuel (better fuel economy).

9-High pressure leads to faster heat transfer and quicker steam production, improving responsiveness.

10-Advanced high-pressure systems allow better instrumentation and automation, improving safety, monitoring, and control.

Let us have discussions through calculation.

Let us discuss the heat content in 1 kg of steam at pressure 65 Kg/cm2 and 125 Kg/cm2.

For 65 kg/cm2 pressure Boiler, steam temperature will be 490 deg C (Tsup)

And feed water temperature at economiser inlet will be around 130 deg C

Therefore,

Steam enthalpy = 812 kcal/kg

Enthalpy of feed water Hfw= 132 kcal/kg

Enthalpy at operating pressure Hf =296 kcal/kg

Saturation temperature of water at steam drum, Ts= 284 deg C

Enthalpy of evaporation Hfg =367 kcal/kg

Therefore heat content in 1 kg of steam Hg = Hf + Hfg + 0.5 X (Tsup-Ts) –(1 X Hfw)

Hg = (296 + 367 + 0.5 X (490-284))-(1 X 132) = 634 kcal/kg

For 125 kg/cm2 pressure Boiler, steam temperature will be 550 deg C

And feed water temperature at economiser inlet will be around 210 deg C (Tsup)

Therefore,

Steam enthalpy = 832 kcal/kg

Enthalpy of feed water Hfw= 212 kcal/kg d

Enthalpy at operating pressure Hf =364 kcal/kg

Saturation temperature of water at steam drum, Ts= 327 deg C

Enthalpy of evaporation Hfg =271 kcal/kg

Therefore heat content in 1 kg of steam Hg = Hf + Hfg + 0.5 X (Tsup-Ts) –(1 X Hfw)

Hg =( 364+ 271 + 0.5 X (550-327))-(1 X 212) = 534 kcal/kg

From the above two calculation, it shows that steam generated at higher pressure needs lesser (534 kcal/kg) heat addition than steam generated at lower pressure (634 kcal/kg)

Following chart gives the heat required to generate 1 kg of steam at various pressure and feed water temperature.

SL NO.	BOILER DESCRIPTION	UOM	1	2	3	4	5	6
1	Operating pressure (P)	Kg/cm2	21	45	67	87	110	121
2	Operating temperature (T)	Deg C	350	450	490	515	540	550
3	Eco. Inlet feed water temperature	Deg C	105	125	125	125	125	125
4	Enthalpy at operating pressure (Hf)	Kcal/kg	223	271	302	325	349	360
5	Enthalpy of evaporation at operating pressure (Hfg)	Kcal/kg	445.3	397	361	331	296.9	280
6	Saturation temperature (Ts)	Deg C	214.07	259.00	286.10	305.41	323.85	331.66
7	Heat supplied to generate 1 kg of steam at rated parameters	Kcal/kg	631.27	638.50	639.95	635.80	628.97	624.17

Friday, 18 July 2025

How to calculate the belt conveyor speed?

Belt conveyors have been using in industries like steel, pharmaceutical, food, textile, sugar, distillery etc. Knowing or deciding the speed of the conveyors is very vital for designing the capacity of the conveyor.

How belt speed is related to the capacity of the conveyor?

Higher the belt speed, more is the conveyor capacity and Vice Versa.

Generally, the speed of the conveyors is around 0.8 to 2 m/sec.

Actually, there are two methods followed to calculate the belt speed

1-Practical method

In this case, time taken to travel the belt from head pulley to tail pulley or from Head to Head.

Belt Speed (m/s)=Time Taken (s) / Distance Travelled (m)

For example: A belt conveyor of length 125 meter takes 4 minutes for complete rotation, the conveyor speed is calculated as

Belt speed = Distance traveled / Time elapsed in one complete rotation

Belt speed =

Belt speed = (250) / (4 X 60 sec)

Belt speed = 250 / 240 = 1.04 m/sec.

2-Theoretical method.

In this method Belt conveyor speed is calculated by using theoretical calculation method.

Input required:

1-Head pulley (D) in meter

2-Gear box input and out put speed in RPM or Gear box reduction ratio

3-Motor speed in RPM

Conveyor speed / Belt speed in m/sec = π X D X N / 60

Where, D is Diameter of Head pulley in meter

N is the speed of the Pulley in RPM

Speed of the pulley = Motor speed / Gear box reduction ratio.

Examples:

1-A belt conveyor of length 350 meter, takes around 740 seconds for complete rotation. Calculate the speed of the belt.

Belt speed = Distance traveled / Time elapsed in one complete rotation

Belt speed = (350 X 2) / 740

Belt speed = 700 / 740

Belt speed = 0.95 m/sec.

2-Calculate the speed of the belt conveyor having following details.

Motor output speed: 1450 RPM

Gear box reduction ratio:45: 1

Head Pulley Diameter D = 500 mm

Now, calculate the Gear box out put speed = Motor speed / Reduction ratio

Gear box output speed = 1450/45 = 32.22 RPM

Since gear box out shaft is directly connected to conveyor pulley. Hence speed of the Gear box out put shaft and Head pulley are same.

Gear box out put speed = Head Pulley speed

Therefore, Conveyor speed V in m/sec = π X D X N / 60

Therefore, Conveyor speed V in m/sec = π X 0.5 X 32.22 / 60

Conveyor speed V in m/sec = 0.84 m/sec

What are the factors affecting the belt conveyor speed??

Following are the major factors, which affect the conveyor speed.

Head pulley diameter
Motor speed
Gear box reduction ratio
Load on the conveyor
Friction between rotating idlers and belt
Conveyor inclination
Environmental factors like rain, dust etc

Saturday, 28 June 2025

20- metallurgical differences among Carbon steel, Alloy steel and Austenitic (Stain less) steel tubes in Boilers.

SL No.	Carbon steel Tubes	Ferritic alloy steel tubes	Austenitic (Stain less) steel
1	Tubes are seamless & metal temperature is up to 454 deg C	Tubes are seamless, Metal temperature for T1 & T2 materials is 538 deg C and T5, T9, T11, T12, T22 and T91 is 649 deg C	Tubes are seamless Metal temperature is 816 deg C for TP 304, TP310, TP 316, TP 321 and TP 347 tubes. And 427 deg C fr TP 304 L & TP 316 L materials
2	Are both hot finished and cold drawn tubes	Are both hot finished and cold drawn tubes	Are both hot finished and cold drawn tubes
3	Steel is manufactured from Open hearth or electrical process or any other oxygen process	Steel is manufactured from Open hearth or electrical process or any other oxygen process	Steel is manufactured from Open hearth or electrical process or any other oxygen process
4	Carbon content is more and in the steel of Grade A, B & C varies from 0.06 to 0.35% maximum	Carbon content is medium and in the steel of Grade T91 to T1 varies from 0.05 to 0.2% maximum	Carbon content is less and in all grades of steel. And it varies from 0.04 to 0.1% maximum
5	Manganese content in the steel of Grade A, B & C varies from 0.27 to 1.06% maximum	Manganese content is medium and in the steel of Grade T91 to T1 varies from 0.3 to 0.8% maximum	Manganese content is more and in all grades of steel. And it varies up to 2.0% maximum
6	Silicon content in the steel of Grade A, B & C varies from 0. to 0.25 % maximum	Silicon content is more that is 0.1 to 1%	Silicon content is up to 0.75%
7	Sulphur and Phosphorous content limit to 0.035%	Sulphur and Phosphorous content limit to 0.025%	Sulphur and Phosphorous content are 0.03 to 0.04%
8	No chromium content	Chromium content varies from 0.5 to 10%	Chromium content is more & varies from 16 to 24% in different grades of austenitic steel.
9	No Molybdenum content in carbon steels	Molybdenum is present in the range of 0.4 to 1.2%	Molybdenum is present in only steel grades of TP 310 S, TP 316, TP 316 H&L. And the range is 0.75 to 3%
10	No Vanadium content in carbon steels	Is present in only T 91 materials	No Vanadium content in Austenitic steels
11	No Nickel content in carbon steels	No content in all grades of Ferritic alloy steels except 12 X 1 M steels	Nickel is present in all grades of steel varying from 8 to 22%
12	Hot finished tubes are not heat treated	Hot finished tubes also heat treated	Hot finished tubes also heat treated
13	Cold drawn tubes are heat treated. Shall be given a sub critical annealing, full anneal or normalising heat treatment.	Cold drawn tubes are heat treated as per procedure.	Cold drawn tubes are heat treated as per procedure.
14	Permissible variation in out side diameter of the tubes after manufacturing is 0.1 to 0.4 mm over size for the tubes having out side diameter ranging from 25.4 mm to 228.6 mm	Permissible variation for all grades of tubes in outside diameter of the tubes after manufacturing is 0.1 to 0.4 mm over size for the tubes having outside diameter ranging from 25.4 mm to 228.6 mm	Permissible variation for all grades of tubes in outside diameter of the tubes after manufacturing is 0.1 to 0.4 mm over size for the tubes having outside diameter ranging from 25.4 mm to 228.6 mm
15	Permissible variation in outside diameter of the tubes after manufacturing is 0.1 to 1.14 mm under size for the tubes having outside diameter ranging from 25.4 mm to 228.6 mm	Permissible variation for all grades of tubes in outside diameter of the tubes after manufacturing is 0.1 to 1.6 mm under size for the tubes having outside diameter ranging from 25.4 mm to 228.6 mm	Permissible variation for all grades of tubes in outside diameter of the tubes after manufacturing is 0.1 to 1.6 mm under size for the tubes having outside diameter ranging from 25.4 mm to 228.6 mm
16	Permissible variation in thickness for seamless hot finished tubes for over size is 28% to 40% for tubes having Out side diameter up to 101.6 mm and Thickness from 4.6 mm to 2.4 mm. Note: Variation is allowable for over thickness not under thickness. And Tubes having lesser thickness have higher tolerance on over side and tubes having higher thickness have lesser tolerance on higher side. Read>>>Procedure for pre and post weld heat treatment For cold drawn tubes variation in thickness is allowable up to 20-22%	Permissible variation in thickness for seamless hot finished tubes for over size is 28% to 40% for tubes having Outside diameter up to 101.6 mm and Thickness from 4.6 mm to 2.4 mm. Note: Variation is allowable for over thickness not under thickness. And Tubes having lesser thickness have higher tolerance on over side and tubes having higher thickness have lesser tolerance on higher side. For cold drawn tubes variation in thickness is allowable up to 20-22%	Permissible variation in thickness for seamless hot finished tubes for over size is 28% to 40% for tubes having Outside diameter up to 101.6 mm and Thickness from 4.6 mm to 2.4 mm. Note: Variation is allowable for over thickness not under thickness. And Tubes having lesser thickness have higher tolerance on over side and tubes having higher thickness have lesser tolerance on higher side. For cold drawn tubes variation in thickness is allowable up to 20-22%
17	Tests carried out during manufacturing are Tensile test, Hardness test, flattening test, Expanding or flaring test and Hydraulic test.	Tests carried out during manufacturing are Tensile test, Hardness test, flattening test, Expanding or flaring test and Hydraulic test.	Tests carried out during manufacturing are Tensile test, Hardness test, flattening test, Expanding or flaring test and Hydraulic test.
18	Yield strength for Grade A, B & C of carbon steel tubes varies from 180 Mpa to 275 Mpa	Yield strength varies from 205 Mpa to 415 Mpa	Yield strength varies from 200 Mpa to 300 Mpa
19	Tensile strength for Grade A, B & C of carbon steel tubes varies from 325 Mpa to 485 Mpa	Tensile strength varies from 380 to 585 Mpa	Tensile strength varies from 200 Mpa to 300 Mpa
20	Rockwell Hardness B for Grade A, B & C of carbon steel tubes varies from 77 to 89 HRB	Rockwell Hardness B varies from 80 to 90 HRB	Rockwell Hardness B varies from 70 to 90 HRB

Thursday, 26 June 2025

What is the Function of Boiler start up vent Control valve??

The Start-Up Vent also called Start-Up Vent Line or Start-Up Vent Valve in a boiler plays a critical role during boiler start-up, shutdown, and low-load operations.

Start-up vent valve is generally manual, motorized or pneumatic operated. Now a days all Boilers have start up vent with motorized valve followed by pneumatic control valve.

Start-up vent line is always tapped from main steam out let line before or after safety valves and extended to suitable height. Start-up vent lines are equipped with silencers to reduce sound level of super heater steam upon venting. Steam carrying capacity of the line is 30-35% of Boiler MCR (Maximum continuous rating) or boiler capacity.

Generally, there is no flow meter for this line.