9-Functions of Boiler steam drum

A steam drum is a crucial component in many types of boilers, particularly in water-tube boilers. Its primary function is to separate steam and water to ensure the proper operation and safety of the boiler. Here are the main functions of a steam drum in a boiler:

1-Steam-Water Separation:

One of the key functions of the steam drum is to separate steam from the water in the boiler. When water is heated in the boiler's tubes, it turns into steam. The steam drum provides a space where this separation can occur. Steam, which is lighter than water, rises to the top of the drum, while water remains at the bottom.

2-Steam Storage:

The steam drum acts as a reservoir for steam, providing a buffer to ensure a continuous and steady supply of steam to the downstream processes or turbines. This helps maintain a more stable and consistent steam output.

3-Water Level Control:

The water level in the steam drum needs to be carefully controlled to ensure safe and efficient boiler operation. Control systems are used to maintain the desired water level within a specific range. If the water level falls below or rises above the recommended range, it can result in operational problems, including overheating, tube damage, or even a dangerous situation known as "dry-firing."

4-Pressure Control:

The steam drum also plays a role in controlling the pressure within the boiler. Pressure is maintained by controlling the rate at which steam is released from the drum to meet the demand of the system. A safety valve is typically installed on the steam drum to release excess pressure to prevent over-pressurization.

5-Steam Quality Improvement:

The steam drum helps in improving the quality of the steam. By allowing time for the separation of water droplets from the steam, it ensures that the steam leaving the drum is of a higher quality with fewer moisture content and impurities.

6-Blowdown Collection:

Impurities and sediment tend to accumulate in the bottom of the steam drum over time. The blow down process, where a portion of the water is periodically drained from the bottom of the drum, helps remove these impurities, maintaining the boiler's efficiency and reducing the risk of scale and corrosion.

7-Heat Storage:

The steam drum can also act as a heat storage unit, helping to stabilize temperature fluctuations in the system. It can store excess heat, releasing it as needed to maintain a consistent steam temperature.

In summary, the steam drum in a boiler is a critical component that ensures the efficient and safe operation of the boiler. It facilitates the separation of steam and water, provides storage for steam, controls water level and pressure, and contributes to the quality and stability of the steam produced. Proper maintenance and control of the steam drum are essential for boiler safety and performance.

8-Sudden Load Changes:

During sudden changes in steam demand or load, the steam drum provides a buffer for the system. It can release additional steam or absorb excess steam, helping to stabilize the pressure and ensure a continuous supply of steam to meet the load requirements.

9-Temperature Control:

The steam drum can help control the temperature of the superheated steam leaving the boiler. By adjusting the feed water flow rate and temperature, the drum can help maintain the desired steam temperature for specific industrial processes.

Overall, the steam drum is a critical component of a boiler system, responsible for maintaining steam quality, pressure, and water levels to ensure safe and efficient operation. Proper control and maintenance of the steam drum are essential for the longevity and performance of a boiler.

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What is the function of Balance piston in steam Turbines???


In a steam turbine, a balance piston is not a dummy piston but rather a real and essential component designed to improve the efficiency and performance of the turbine. A balance piston is used in certain types of steam turbines, particularly in reaction turbines, to help maintain axial balance and reduce the axial thrust force on the rotor.

A steam turbine consists of a rotor with blades attached to it. Steam is directed onto these blades, causing them to spin. As the blades turn, they exert a force on the rotor in the axial direction, along the length of the rotor.

Here's how a balance piston works in a steam turbine

Role of Balance Piston:

Steam turbines are designed to convert the energy of high-pressure steam into mechanical rotational energy, which is then used to generate electricity or perform other mechanical work.

During the operation of a steam turbine, steam enters the turbine blades or buckets and expands, creating a force that drives the rotor in a rotary motion.

However, this expansion of steam also generates an axial thrust force along the length of the rotor. This axial thrust force can be significant, especially in larger turbines.

Purpose of balance piston

To counteract the axial thrust force and prevent excessive axial movement of the rotor, a balance piston is often used.

The balance piston is typically located at the opposite end of the rotor from the steam inlet. It is exposed to the same steam pressure as the turbine's inlet.

The balance piston is attached to the rotor, and its movement is opposed by a set of springs or hydraulic systems.

How balance piston Works:

When high-pressure steam enters the turbine and imparts a force on the rotor blades, it also exerts an equal and opposite force on the balance piston.

This opposing force on the balance piston helps to balance out the axial thrust force generated by the steam expansion on the other side of the rotor.

The balance piston essentially acts as a hydraulic or mechanical counterbalance, minimizing the net axial thrust force on the rotor.

The pressure acting on the dummy piston generates an equal and opposite axial force. This force counterbalances the axial thrust generated by the turbine blades. By adjusting the pressure on the dummy piston, operators can control and balance the axial forces within the turbine.

Why balance piston is required:

By reducing the axial thrust force, the balance piston helps to maintain the stability and longevity of the turbine.

It also reduces the wear and tear on the thrust bearings, which are responsible for supporting the axial load of the rotor.

Overall, the use of a balance piston contributes to the efficient and reliable operation of the steam turbine.

It's important to note that the design and location of balance pistons can vary among different types and manufacturers of steam turbines. While balance pistons are common in reaction turbines, they may not be present in all steam turbine designs.

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Powerplant and calculations

How do you calculate the quantity of sulphur dioxide produced in Boilers???


To calculate the generation of sulfur dioxide (SO2) in boilers, you need to consider the sulfur content in the fuel being burned, the combustion process, and the sulfur conversion efficiency. Here's a general method to calculate SO2 generation:

Determine Fuel Sulfur Content:

Find out the sulfur content of the fuel you are using in the boiler. This information is typically provided in the fuel specifications and is usually given in weight percent or parts per million (ppm) by weight.

Calculate Sulfur Mass Flow Rate:

Determine the mass flow rate of the fuel being burned in the boiler. This can be measured or estimated based on the flow rate and properties of the fuel.

Calculate Sulfur in the Fuel:

Multiply the fuel mass flow rate by the sulfur content of the fuel to calculate the mass of sulfur being introduced into the combustion process.

Mass of Sulfur in Fuel (kg/hr) = Fuel Mass Flow Rate (kg/hr) × Sulfur Content (% by weight or ppm)

Determine Sulfur Conversion Efficiency:

The combustion process may not convert all of the sulfur in the fuel into sulfur dioxide (SO2). The sulfur conversion efficiency depends on various factors, including combustion temperature, excess air, and the type of combustion equipment. You can estimate the sulfur conversion efficiency based on boiler design and operating conditions. Common values range from 90% to 99%.

Calculate SO2 Generation:

Multiply the mass of sulfur in the fuel by the sulfur conversion efficiency to determine the mass of SO2 generated during combustion.

Read more>>>>How to calculate the mass of flue gas generation in Boilers


Calculate the Sulphur dioxide generated per day in a 100 TPH boiler, where coal burned is having 0.6% of sulphur. Consider steam to fuel ratio  6 & Boiler operates on full load for 24 hours.

Assume sulphur conversion efficiency 90%

We have S + O2 = SO2

32 + 32 = 64

1 + 1 = 2

That is 1 kg of sulphur generates 2 kg of Sulphur dioxide on complete combustion.

Total coal consumed in a day = Steam generated in 24 hours / Steam to coal ratio

Total coal consumed in a day = 100 X 24 / 6

Total coal consumed in a day = 400 Tones/day

Total sulphur in coal = 400 X 0.6/100 =2.4 Tones

Therefore total SO2 generated = 2.4 X 2 X 90% =4.32 Tones

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How do you calculate the mass of flue gas generated in Boilers???

 How do you calculate the mass of flue gas generated in Boilers???


The mass of flue gas generated in boilers can be calculated using the principles of stoichiometry and the knowledge of the fuel composition and combustion process. Here are the steps to calculate the mass of flue gas:

1-Determine the Fuel Composition:

You need to know the composition of the fuel being used in the boiler. Typically, this includes information about the types and proportions of elements in the fuel, such as carbon (C), hydrogen (H), sulfur (S), oxygen (O), and other impurities. This information is usually provided in the fuel's specifications.

2-Write the Combustion Equation:

Write the balanced chemical equation for the combustion of the fuel. For example, if you're burning natural gas (CH4) in air (which contains oxygen), the combustion equation would be:

CH4 + 2O2 → CO2 + 2H2O

3-Calculate the Stoichiometric Air-Fuel Ratio:

Calculate the stoichiometric air-fuel ratio, which is the theoretical amount of air required for complete combustion. This ratio depends on the chemical composition of the fuel and the combustion equation. For the example above, one mole of methane requires two moles of oxygen for complete combustion.

4-Determine the Actual Air-Fuel Ratio:

In real-world situations, the actual air-fuel ratio is usually not exactly stoichiometric due to factors like incomplete combustion, excess air, and variations in combustion efficiency. You may need to measure or estimate the actual air-fuel ratio in your specific boiler operation.

5-Calculate the Mass of Fuel:

Determine the mass of fuel being burned in the boiler. This is typically measured or known based on the flow rate and properties of the fuel being supplied to the boiler.

6-Calculate the Mass of Air:

Using the actual air-fuel ratio and the mass of fuel burned, calculate the mass of air required for combustion. You can do this by multiplying the mass of fuel by the actual air-fuel ratio.

Read more>>>>How to calculate quantity of SO2 generation in flue gas

7-Calculate the Mass of Flue Gas:

The mass of flue gas is equal to the mass of the combustion products, which includes the mass of the carbon dioxide (CO2), water vapor (H2O), and any other combustion products produced in the combustion process. Use the balanced combustion equation to calculate the masses of these products.

For example, in the combustion of methane (CH4) from step 2, you can calculate the mass of CO2 and H2O produced based on the moles of CH4 burned and their molar masses.

8-Sum Up the Masses:

Add up the masses of all the combustion products to find the total mass of flue gas generated in the boiler.

Keep in mind that this is a simplified calculation, and real-world combustion processes can be more complex due to factors like incomplete combustion, impurities in the fuel, and variations in combustion efficiency.

Therefore, it's important to consider these factors for a more accurate estimation of flue gas mass in a specific boiler system. Additionally, measuring instruments and gas analyzers can provide real-time data on flue gas composition and mass flow rates in practical applications.


A Boiler uses imported coal to generate 150 TPH of steam, the O2 & CO2 in flue gases are 6% & 15% respectively. Calculate the mass of flue gas generated if following is the ultimate analysis of fuel.

Carbon C = 54%

Hydrogen H2 = 3.4%

Oxygen O2 = 9.1%

Sulphur S = 0.6%

Nitrogen N2 = 1.3%

We have Theoretical air, Th = (11.6 X %C + 34.8 X (H2-O2/8) + 4.35 X S) / 100

                     Th = (11.6 X 54 + 34.8 X (3.4-9.1/100) + 4.35 X 0.6) / 100

                     Th = 7.44 kg/kg of fuel

We have excess air EA = O2 X 100 / (21-O2)

                                      = 6 X 100 /(21-6) = 40%

Total air = (1 + EA/100) X Theoretical air

Total air = (1 + 40/100) X 7.44 = 10.42 kg of air per kg of fuel burnt

Mass of flue gas generated Mfg = Mass of CO2 in flue gas + Mass of N2 in fuel + Mass of N2 in air + Mass of O2 in the flue gas + Mass of SO2 in the flue gas

Mass of flue gas generated Mfg = (Carbon percentage in fuel X Mol.weight of CO2) / Mol.weight of Carbon + 0.013 + (10.42 X 77 / 100) + ((10.42-7.44) X 23 / 100) + (0.006 X Mol.weight of SO2) / Molecular weight of sulphur

Mass of flue gas generated Mfg = (0.54 X 44 / 12) + 0.013 + 8.02 + 0.68 + (0.006 X 64) / 32 =10.7 kg of flue gas per kg of fuel burnt.

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Top-85 interview questions for power plant shift incharge

 Top-85 interview questions for power plant shift incharge

General questions

1. What is the job profile or job description in your previous organization?

2. What are the challenging situations that you have faced in Boiler operation?

3. What re the challenging situations that you have faced in Turbine operation?

4. How you have managed multiple tasks during emergency operation?

5. What are the emergencies that you have come across during your shift operation & how you have handled those?

6. How do you handle conflicts or disagreements among team members during a shift?

7. In our industry, safety is a top priority. How do you promote and enforce safety protocols among your team?

8. What are the different types of LOTOs used in your plant?

9. What are the different types of work permits that you have come across?

10. Explain the JSAs of confined space work?

11. Explain the JSAs of hot work?

12. What do you mean by Near miss, TBT, PTW, RCA in safety?

13. Have you supervised the rigging task?

14. How do you coordinate with maintenance team?

15. How do you handle emergency situation in electrical system?

16. What are the reporting and documentation skills you have? and how often you do handle these?

Read powerplant O&M reference books 

17. Have you done Root cause analysis of any failure or plant tripping? Explain

18. What do you mainly observe during your shift field rounds?

19. How do you guide your subordinates like control room engineers,field engineers and E&I team in your shift operation?

20. What methods do you use to motivate and manage your team to achieve their best performance?

Technical Questions

1. What are the major losses in Boilers?

2. What are the major reasons for more fuel consumption in Boilers

3. What do you mean by SFC, SSC, SFR, PLF, SHR, SMP, SOP?

4. What do you understand plant heat rate?

5. WHat are your plan of actions to reduce plant heat rate?

6. How vacuum is related to steam consumption in Turbine?

7. How do you calculate the efficiency of steam condenser?

8. How do you calculate the efficiency of cooling tower?

9. What do you mean by Approach in cooling towers?

10. How do you calculate the Evaporation loss in cooling towers

11. What are the various chemicals used in cooling towers?

12. How does feed water inlet temperature at economizer inlet affects the Boiler performance?

13. What do you mean by TTD & DCA in heat exchanger?

14. What is the pressure/draft loss in Economizer, APH and ESP?

15. What are the reasons for increase in Turbine bleed steam pressure?

16. What are the reasons for increase in Turbine wheel chamber pressure?

17. Name the various drum pulleys used in belt conveyors?

18. How do you specify the conveyor belt?

19. What is the function of VGTU?

20. Which is the smallest pulley in belt conveyors?

21. What is the speed of belt conveyors? And how do you calculate it?

22. What is the heat required to raise water temperature from 25 deg c to 100 deg C at atmospheric pressure?

23. Why the dry saturated steam is being used for process heating?

24. What do you mean by Enthalpy?

25. Write down the formula for Plant heat rate calculation

26. What are the various circuit breakers used in your electrical system?

27. What is the function of AVR?

28. What is the significance of reactive power in electrical system?

29. What are your plan of actions to reduce Auxiliary power consumption of power plant?

30. What are the major reasons for more steam consumption of steam Turbine?

31. What are the different types of bearings used in power plant?

32. What is the difference between bearing prefix and suffixes?

33. Where do you use taper roller bearing?

34. What do you mean by back lash in gears?

35. Name the significance of viscosity in lubricant oil?

36. What are the major/critical parameters of Turbine oil that you get tested yearly?

37. Differentiate between 3-element and 2-element drum level controllers?

38. What do you see/observe in plant P&I drawing?

39. What are IOs in DCS system.NAme some IOs

40. What is the acceptable limit of Boiler safety valve blow down?

41. What parameters are checked in coal ultimate and proximate analysis?

42. What is the function of chemical TSP in boilers?

43. What are the chemicals used for regeneration in DM plant?

44. What chemicals are used in HRSCC and explain their function?

45. What is the significance of RO plant?

46. What is the Turbidity level at inlet and outlet of HRSCC?

47. What is meant by MSDS? What does it contain?

48. Define absolute pressure and gauge pressure

49. What are the maintenance activities carried on Boilers during annual shutdown

50. Differentiate between preventive and break down maintenance?

51. What do you mean by Proactive maintenance and CBM?

52. What are the units of measurement of vibration and sound levels?

53. What are the interlocks provided for Boiler and Turbines?

54. What is the significance of vacuum breaker valve and Rapture discs provided in steam condensers?

55. What do you mean by critical equipment?

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15-Emergencies in power plant operation

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