What is the significance of Terminal temperature difference (TTD) in feed water heaters ???

 

 

 

 

 

 

 

 

 

The Terminal Temperature Difference (ΔT or delta T) is a crucial concept in the field of heat transfer and thermodynamics. It represents the temperature difference between the hot and cold fluids in a heat exchanger at the point where they leave the heat exchanger. The significance of terminal temperature difference lies in its impact on the efficiency and performance of heat exchange processes.

 

Terminal temperature difference is the difference between the saturation temperature at the operating pressure of the inlet steam to the heater and the temperature of the feed water leaving the heater.

The heating steam temperature they are talking about is the saturation temperature of the steam for the given supply pressure. The highest pressure heater is almost always receiving steam that is still superheated (Energy above saturation temp/pressure) If the incoming steam has 15 degrees of superheat, and the outgoing feed water absorbs all of that and is heated to 2 degrees above the saturation temperature of the supplied heating steam pressure, You have a negative 2 degree TTD.

Most of the other heaters are heated with steam from further down the turbine steam path, and have very little or no super heat in their steam, therefore, no negative TTD.

 

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Terminal temperature difference provides feedback on the feed water heater’s performance relative to heat transfer

 Significance of TTD.

 

1-It gives the feed back on performance of heat exchanger

2-Higher TTD is nothing but thee is more difference between saturation temperature of steam and feed water leaving the heater.This indicates the poor performance of heater.Similarly lower TTD is nothing but thee is small difference between saturation temperature of steam and feed water leaving the heater.This indicates the good heat transfer between steam and feed water & hence there is better performance of heater

3-The concept of "temperature approach" is closely related to ΔT. The temperature approach is the difference between the temperature of the hot fluid and the temperature of the cold fluid at the end of the heat exchanger. A smaller temperature approach is often desired to maximize heat transfer efficiency, but it is limited by practical considerations.

4-the terminal temperature difference is a key parameter in the analysis, design, and optimization of heat exchange systems. It plays a vital role in determining heat transfer rates, efficiency, and the size of heat exchangers, ultimately impacting the performance and cost of thermal systems in various engineering applications

5-Station heat rate will improve

6-Cycle efficiency will increase

7-Less steam consumption for feed water heating

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 Calculation of TTD of feed water heater.

 1-A HP heater is used to heat the feed water from 125 °C to 160 °C by using MP steam at pressure 13 kg/cm2 at temperature 280 °C, calculate the TTD.

We have,

TTD = Saturation temperature of inlet steam - Feed water outlet temperature

Saturation temperature of inlet steam at 13 kg/cm2g pressure = 195.6 °C

TTD = 195.6 - 160 = 35.6 °C

Note: For best performance, heaters are designed to get TTD 3 to 5 °C at full operation capacity.

 2-A LP heater is used to heat the feed water from 80 °C to 110 °C by using LP steam at pressure 2.5 kg/cm2A at temperature150 °C, calculate the TTD.

 We have,

TTD = Saturation temperature of inlet steam - Feed water outlet temperature

Saturation temperature of inlet steam at 2.5 kg/cm2g pressure = 125°C

 TTD = 125-110= 15 °C

 3-A HP heater is used to heat the feed water from 105°C to 140 °C by using MP steam at pressure 8 kg/cm2 at temperature 220 °C, calculate the TTD.

We have,

TTD = Saturation temperature of inlet steam - Feed water outlet temperature

Saturation temperature of inlet steam at 8 kg/cm2g pressure = 170 °C

TTD = 170 - 140 = 30 °C

 Note: For best performance, heaters are designed to get TTD 3 to 5 °C at full operation capacity.

 4-A LP heater is used to heat the feed water from 47 °C to 78 °C by using LP steam at pressure 0.62 kg/cm2A at temperature 87 °C, calculate the TTD.

 We have,

TTD = Saturation temperature of inlet steam - Feed water outlet temperature

Saturation temperature of inlet steam at 0.62 kg/cm2g pressure = 87 °C

TTD = 87 - 78 = 9 °C

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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:

1-Preparation:

• 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.

 3-Disassembly:

• 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.

 4-Inspection:

• 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.

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6-Cleaning:

 

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

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

 

7-Assembly:

 

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.

 

9-Documentation:

 

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

Update maintenance records and logbooks.

 

10-Startup:

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
1	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.
2	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.
3	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.
4	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
5	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.
6	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.
7	Lower temperature of extraction steam around 145 to 155 deg C	High exhaust temperature around 150  to 175 deg C, which is loss
8	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.
9	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
10	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
11	Heat rate is comparatively more	Heat rate is less since there is no loss of heat in condensers
12	Operation is little bit critical	Simple operation
13	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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