Steam Turbines Informative Summary

Overview:

This text acts as a practical guide for engineers working with steam turbines in the early 20th century. The book begins with a detailed look at the Curtis steam turbine, covering its construction, operation, and key features like its mechanical valve-gear and governor. It dives into how to adjust and set the valves to ensure efficient operation.

The next sections shift focus to the Westinghouse-Parsons turbine. This segment delves into the turbine’s design, the function of its blading, and the importance of maintaining tight clearances to prevent steam leaks. The author also covers the governor and valve gear, lubrication system, and packing glands.

Key Findings:

Turbine efficiency is greatly affected by moisture in the steam. Dryer steam leads to improved performance and lower fuel costs.
High vacuum significantly boosts turbine efficiency. Maintaining a high vacuum in the condenser is critical for optimal performance.
Proper lubrication is crucial for turbine operation. The author emphasizes the importance of using pure mineral oil and maintaining a clean and well-functioning oiling system.
Careful attention to auxiliaries like condensers and pumps is essential for turbine operation. The book details the importance of inspecting and adjusting these components to ensure smooth operation.
Turbine design and operation require a balance between theoretical understanding and practical considerations. The text highlights the importance of understanding and addressing real-world challenges that can arise during operation.

Learning:

Steam Turbine Basics: Readers will learn about the different types of steam turbines, their internal workings, and how they convert steam energy into mechanical energy.
Clearance and Steam Leakage: The text emphasizes the importance of precise clearances between moving and stationary parts to minimize steam leakage and maximize efficiency.
Lubrication Systems: Readers will learn about different lubrication systems used in turbines and the importance of using the correct type of oil and maintaining a clean system.
Governor and Valve Gear: The book explains how governors and valve gears control steam flow to regulate turbine speed and power output.
Condenser Operation: Readers will gain knowledge of different condenser types, their function, and the importance of maintaining a high vacuum to enhance efficiency.

Historical Context:

The text was written in 1909, a time when steam turbines were relatively new technology. The author highlights the challenges faced by engineers in understanding and operating these new machines, particularly as compared to traditional reciprocating engines. The book provides a valuable glimpse into the early days of steam turbine development and the practical considerations that shaped their design and operation.

Facts:

Steam turbines are simpler to operate than reciprocating engines. The absence of intricate valve gears and moving parts makes them easier to maintain and operate.
The Curtis turbine uses multiple stages of expanding nozzles and stationary buckets to extract energy from steam. This design optimizes steam flow and energy extraction across multiple stages.
The Westinghouse-Parsons turbine utilizes a combination of impulse and reaction principles for steam expansion. This design allows for efficient energy extraction from the steam.
Labyrinth packing is employed to minimize steam leakage around the shaft and balance pistons. This type of packing uses a series of closely spaced grooves to create a seal.
The turbine governor controls the speed of the turbine by adjusting the steam flow. This mechanism ensures that the turbine operates at a consistent speed.
The safety-stop governor is a critical safety device that shuts off steam flow if the turbine exceeds its safe operating speed. This prevents catastrophic failure from overspeeding.
High superheat improves turbine efficiency. Superheated steam contains less moisture, leading to better performance.
High vacuum in the condenser significantly increases turbine efficiency. A higher vacuum allows for more complete expansion of the steam, resulting in more energy extracted.
Surface condensers are particularly well-suited for use with steam turbines. This type of condenser allows for the recovery of high-quality condensate for boiler feedwater.
The oil used in turbine lubrication must be pure mineral oil, free from animal or vegetable oils and acids. Impurities in the oil can damage turbine components.
A central gravity oiling system offers several advantages for large turbine installations. This system allows for a large volume of oil to be stored and settled, minimizing oil deterioration.
A jet condenser utilizes a spray of water to condense the steam. This type of condenser is compact and simple to operate.
Relief valves are essential safety devices that prevent excessive pressure from building up in the turbine and condenser. These valves release steam to the atmosphere or to other condensers in case of a pressure surge.
Properly designed cooling towers are essential for efficient condenser operation. These towers provide a large surface area for cooling the circulating water.
Air leaks in the condenser can significantly reduce vacuum and efficiency. Careful inspection and sealing of the condenser are essential.
Turbines should be run up to speed slowly to minimize vibration and potential damage to the machine and its foundation. Rapid acceleration can cause instability.
The gland steam or water flow must be carefully adjusted to ensure proper sealing of the turbine shaft. Excessive gland flow can lead to increased steam consumption.
A steam turbine’s efficiency can be affected by variations in steam pressure, vacuum, and superheat. Careful monitoring and adjustments are required to maintain optimal performance.
The steam consumption of a turbine is often affected by boiler priming, which can introduce water into the steam line. This can cause performance issues and increase fuel consumption.
A thorough understanding of turbine operation and the interaction between the turbine and its auxiliaries is essential for successful steam power plant operation. Careful attention to all components is necessary to ensure safe and efficient operation.

Statistics:

A 1500-kilowatt Curtis turbine typically has a speed range of 2% between no load and full load.
The governor on a 1500-kilowatt Curtis turbine is adjusted for a speed range of 4% between the first and tenth valves. This allows for some flexibility in load management.
The baffler in a Curtis turbine helps to maintain a constant oil film in the step-bearing. This improves lubrication and reduces wear.
The Allis-Chalmers steam turbine governor uses an oil pressure of about 20 pounds per square inch to operate the steam valves. This system provides for quick and reliable valve operation.
The Westinghouse-Parsons turbine has a radial blade clearance of 0.025 to 0.125 inches. This clearance is critical for preventing blade rubbing and ensuring smooth operation.
The axial clearance in a Westinghouse-Parsons turbine varies from 1/8 to 1/2 inch. This clearance allows for slight axial movement of the rotor during operation.
The oil pressure in the bearings of a Westinghouse-Parsons turbine should not exceed a few feet. This ensures proper lubrication without excessive pressure on the bearings.
The water used to seal the turbine glands should be free from scale-forming impurities. Impurities can lead to deposits that hinder proper gland operation.
The temperature of the oil flowing to and from the bearings in an Allis-Chalmers turbine should not exceed 135 degrees Fahrenheit. This temperature range ensures optimal lubrication without excessive oil deterioration.
A jet condenser can typically maintain a fairly high vacuum even with the air pump shut down. This is due to the pumping action of the falling water.
The turbine relief valve should be set to open at a relatively low pressure, around 40 pounds by gage. This prevents excessive pressure from building up in the turbine in case of a vacuum failure.
The cooling towers used to cool the circulating water in a condenser should have sufficient surface area to effectively reduce water temperature. Insufficient cooling surface can lead to vacuum problems and reduced efficiency.
The oil flow rate in a turbine bearing system must be carefully adjusted to ensure optimal lubrication without excessive oil consumption. Too high of a flow rate can lead to wasted oil, while too low of a flow rate can result in insufficient lubrication.

Terms:

Governor: A device that controls the speed of a machine by regulating the flow of energy, in this case, steam to the turbine.
Valve-gear: A system of valves and mechanisms that control the flow of steam to the turbine.
Clearance: The space between moving and stationary parts of a machine, ensuring that they do not come into contact during operation.
Labyrinth packing: A type of packing used to prevent leakage of steam or fluids around a shaft. It uses a series of closely spaced grooves to create a seal.
Balance pistons: Devices used in multi-stage turbines to balance the axial thrust on the rotor, preventing the rotor from moving end-to-end.
Condenser: A device that condenses steam back into water, creating a vacuum that improves turbine efficiency.
Hot-well: A tank that collects the condensed steam from the condenser.
Superheat: The process of raising the temperature of steam above its boiling point at a given pressure.
Vacuum: A pressure lower than atmospheric pressure.
Oiling system: A system that supplies oil to lubricate the bearings of a machine.

Examples:

Curtis Turbine: The author describes the detailed construction and operation of a 1500-kilowatt Curtis turbine, providing insights into its valve gear, governor, and step-bearing system.
Westinghouse-Parsons Turbine: The text includes a detailed breakdown of the Westinghouse-Parsons turbine, showcasing its blading, balancing pistons, governor, and packing glands.
Circulating Pump Failure: The author recounts a specific instance where a steam plant experienced problems with its circulating pump, leading to reduced vacuum and turbine performance. This example highlights the importance of proper auxiliary equipment and design.
Condenser Design: The author provides a detailed description of a vertical surface condenser, showcasing its components and explaining how it works.
Relief Valves: The author discusses the importance of various relief valves in a steam turbine system, explaining their functions and the potential consequences of their failure.
Steam Consumption Testing: The author provides a step-by-step guide on how to conduct a steam consumption test for a turbine, detailing the necessary equipment and procedures.
Oil Contamination: The author highlights the importance of using pure mineral oil and avoiding adulteration with other oils, emphasizing the potential damage that impurities can cause to turbine components.
Governor Regulation: The text discusses how to adjust governor settings to maintain a steady load on a turbine operating in parallel with other machines.
Blade Inspection: The author stresses the importance of regularly inspecting turbine blades for damage or deposits, which can affect performance.

Conclusion:

This 1909 text offers a valuable guide for engineers working with early steam turbines. The book provides a deep understanding of the internal workings of these machines, emphasizing the importance of proper operation, maintenance, and auxiliary equipment. It also highlights the critical role of steam quality, vacuum, and lubrication in achieving optimal turbine efficiency. The insights offered in this text remain relevant today, demonstrating the importance of a strong foundation in basic principles for understanding complex machinery.

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