11-steps for steam Turbine major overhauling

 Major overhauling of a steam turbine is a comprehensive maintenance process that involves disassembling, inspecting, repairing, and reassembling various components to ensure the turbine's optimal performance and reliability. This process is typically carried out after a certain number of operating hours or as part of a scheduled maintenance program. Below are the key steps involved in a major overhaul of a steam turbine:


  • Develop a detailed overhaul plan, including a schedule and a list of required resources.
  • Ensure all necessary safety precautions are in place.
  • Secure the necessary permits and approvals for the overhaul.

2-Shutdown and Isolation:

  •  Safely shut down the steam turbine in accordance with established procedures.
  • Isolate the turbine from the steam supply and electrical systems.


  • Remove the outer casing and insulation.
  • Disassemble the various components, such as rotors, blades, diaphragms, and seals.
  • Inspect each component for signs of wear, damage, or corrosion.


  • Perform thorough inspections using various techniques, such as visual inspection, dye penetrant testing, magnetic particle testing, and ultrasonic testing.
  • Measure clearances and tolerances to ensure components meet specifications.
  • Assess the condition of bearings, gears, and other auxiliary components.

 5-Repair and Replacement:


Repair or replace damaged or worn components.

Balance rotating elements, such as the rotor, to ensure smooth operation.

Recondition or replace seals and gaskets.




Clean all components thoroughly to remove dirt, debris, and deposits.

Use appropriate cleaning methods, such as steam cleaning, chemical cleaning, or abrasive blasting.




Reassemble the turbine components according to the manufacturer's specifications and tolerances.

Ensure proper alignment and fit of all parts.


8-Testing and Commissioning:


Conduct functional tests to ensure proper operation of the turbine.

Perform performance testing to verify that the turbine meets specified efficiency and power output.

Address any issues identified during testing.




Document all maintenance activities, including inspections, repairs, and tests.

Update maintenance records and logbooks.



Gradually bring the turbine back into operation, closely monitoring performance.

Address any issues that arise during the startup process.


11-Post-Overhaul Analysis:

Evaluate the success of the overhaul and identify areas for improvement.

Implement any recommended changes to the maintenance program.

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What are the statutory and Legal compliances for Power plant installation,operation and maintenance???


Ø Water pollution and prevention:Rules - 1975 , Act -1988 Issued by CPCB or SPCB,Record:Water consent

Ø Water cess act:Act - 1992,2017 Rules - 2003 Act - 1992,Issued by CPCB or SPCB

Ø Air pollution and prevention rule:Act-1987,Issued by CPCB or SPCB

Ø Notification  - National Ambient Air Quality Standards 1994 &  Ambient Air Quality Standard for Ammonia (NH3) 1998,Issued by CPCB or SPCB

Ø The Environment (Protection) Act, 1986, form V,Issued by CPCB or SPCB

Ø Noise pollution (regulation and control) rules,14-02-2000 ,Issued by  SPCB

Ø The Batteries (management and handling) rules, 2001,Issued by CPCB or SPCB: Record: stock register

Ø The Plastics(Manufacture, Usage and Waste Management) Rules,2009,,Issued by CPCB or SPCB: Record: Purchase order

Ø Plastic Waste Management (Second Amendment)Rules, 2021

Ø The Manufacture, storage and import of hazardous chemical rules, 1989, Record: MSD,,Issued by CPCB or SPCB:

Ø The Hazardous Wastes (Management, Handling & Transboundry  Movement) Rules, 2010, Issued by CPCB or SPCB: Record: Generation data

Ø The Bio-medical waste (management and handling) rules, 1998,Generation & Disposal record

Ø The Ozone depleting substances (regulation and control) rules, 2000 , Issued by:Ministry of Environment and Forests.Record: Gas details

Ø The Public liability insurance Act,1991,issued by:Ministry of Environment and Forests, Records: Insurance copy

Ø Explosives:Petroleum Act 1934, Rules 1976, Issued by: PESO, Record: License copy

Ø Gas Cylinder rules, 1981,Issued by: PESO, Record: License copy

Ø BARC -Radiography Protection rule-2004,Issued by: BARC. Record: Radiography Operator Certificate

Ø Factories Act 1948 :

Ø Approval of plans from the chief inspector of Factories (FA1948 Sc 6, MFR1963 Rule 3), Issued by DISH officer.Record: Form No.I

Ø Stability certificate (FA1948 sc 6, MFR1963 rule 3A),Issued by DISH officer.Record: Form No.IA

Ø Testing of drinking water (MFR 1963 Rule 43),Issued by DISH .Record:Test certificate

Ø Maintain report of examination of Lifting Machines, ropes & lifting tackles (FA1948 sc31,MFR1963 Rule 65),Issued by DISH.Records: Form No. 13 & Boiler passing Certificate

Ø Maintain Muster roll (FA1948 sc 92-106, MFR 1963 rule 122),Issued by DISH.Records: Form No. 29

Ø Workers participation in Safety Management (FA1948 sc 41G,MFR1963 Rule 73J)

Ø Health and safety policy, written statement.(FA1948 sc41 B, 7 A (3),MFR1963 Rule  8,121,122,73 - L, Record: HSE policy

Ø Fire Fighting Equipments in good working  condition - Maintenance record.

Ø Prepare & Disclose the information regarding On Site Emergency Plan.

Ø 1. Use of portable electric light  below 24 V inside any chamber, tank….

Ø 2. Use of flameproof fitting light below 24 v inside confined space of flammable gases area.

Ø Availability Of first aid Boxes

Ø Portable fire extinguisher -1 for every 500 sq. meter and placed max. 30 meter (MFR 1963 Rule 71 b (7))apart. ( As per IS stds -2190 )

Read Boiler IBR standards for inspection

Ø Factory Act 1948, Sec-21-Fencing of machinery.-

Ø Factory Act 1948, Sec-32-Floors, Stairs and Means of Access (1) Training 2) Work on height permit. 3) PPE's to be used. 4) safe working procedure to be followed.)

Ø Factory Act 1948, Sec-35-Protection of Eyes.- PPE"S are provided and used

Ø MFR 73-J (Under Sections 41 & 41-G of FA)-Safety Committee:1) Safety Committee members list 2) Attendance sheets of  meetings 3) Minutes of the meetings.

Ø Workmen compenstion / ESI, 1948, issued by ministory of labour

Ø The Contract Labour ( Regulation & Abolition ) Act 1970, issued by ministory of labour

Ø The Contract Labour (Regulation & Abolition ) Act 1970,

Ø Indian Boiler Act 1923 & Indian Boiler Regulations, 1950 ,The  Boiler Rules - 1966, Issued by Inspectorate of Boilers: Record: Boiler operators certificates

Ø Indian Boiler Act 1923 & Indian Boiler Regulations, 1950, The  Boiler Rules - 1967,Issued by Inspectorate of Boilers: Record: Competant person test reports

Ø Energy Conservation Act 2003, Issued by: BEE

Ø The Indian Electricity Rules, 1956

Ø Central Electricity Authority (Measures      relating to Safety and Electricity Supply) Regulations, 2007 DRAFT

Ø Central Motor Vehicles Rules 1989, Issued by Ministry of Road Transport and Highways, Records: PUCC

Ø INDIAN WIRELESS TELEGRAPHY ACT 1933(ACT XVIII OF 1933),issued by:Ministry of Communication, WPC Wing, Sanchar Bhawan, 20 Ashoka

Road, New Delhi-110 001, Record:Application for a licence to possess Wireless

Receiving and or Transmitting Apparatus

Ø THE DISASTER MANAGEMENT ACT 2003, Issued by: State Disaster Management Authority, Records: Mock drill reports

Ø The Chemical Accidents (Emergency Planning, Preparedness and Response) Rules, 1996,Issued by Ministry of Environment and Forests.Records:Mock Drill reports to District Collector

Ø Inter State Migrant Worker Act- 1979, issued by:Ministry of Labour.Record:Obtain licence under ISMW act

Ø Rule 40-Excavation or tunnel suitable measures are taken to avoid exposure of building workers to health hazards

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What is the difference between condensing cum extraction Turbines and back pressure turbines??


SL No.

Condensing cum extraction Turbine

Back pressure Turbine



In a condensing turbine, steam is expanded in the turbine until it reaches a very low pressure, and then it is condensed back into water.

In a back pressure turbine, steam is expanded in the turbine until it reaches a predetermined pressure, known as the back pressure.



The condensation of steam at the turbine exit creates a vacuum, which increases the efficiency of the turbine by lowering the back pressure.

The exhaust steam from the turbine is released at a higher pressure, and it is often used for industrial processes where both power and heat are required.





Condensing turbines are often used in power plants where the objective is to maximize the power output from the steam and achieve higher efficiency. The condensed water is usually returned to the boiler for reuse.

Back pressure turbines are commonly used in combined heat and power (CHP) systems, where the steam is extracted at different pressures for various industrial processes, and the remaining steam is allowed to expand through the turbine to generate power.




Condensing cum extraction turbines generally provide higher overall efficiency compared to back pressure turbine.

The combination of condensation and extraction processes allows for better utilization of the available energy in the steam.

Lower over all efficiency


More power out put at same steam inlet

Lower power out put

Power out put reduces by 4 to 5% at same inlet steam flow.


No much effect on power generation if extraction steam consumption reduced, since this steam can be diverted to surface condenser

Power consumption reduces if exhaust steam consumption reduces, since there is no any option to expel the steam to generate power.


Lower temperature of extraction steam around 145 to 155 deg C

High exhaust temperature around 150  to 175 deg C, which is loss


Power can be generated even at no or minimum extraction

Constraints in power generation during no or minimum extraction


Or steam needs to be vented out if electrical power requirement is more.


Auxiliary power consumption of the plant is little bit higher for handling cooling water pumps and cooling tower fans

Auxiliary power consumption is lesser since there is no condenser and hence no cooling water pumps and fans


Initial cost of the project is more due to surface condenser, cooling tower and cooling water pumps

Cost of the project is less as compared to condensing turbines


Heat rate is comparatively more

Heat rate is less since there is no loss of heat in condensers


Operation is little bit critical

Simple operation


Limited extraction steam flow

Exhaust flow will be more since there is no condenser and same steam can be diverted to process as exhaust steam


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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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15-Emergencies in power plant operation

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