Question & Answers on Steam Turbines

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The steam turbine is one kind of heat engine machine in which steam's heat energy is converted to mechanical work. The construction of steam turbine is very simple. There is no piston rod, flywheel or slide valves attached to the turbine. So maintenance is quite easy. It consists of a rotor and a set of rotating blades which are attached to a shaft and the shaft is placed in the middle of the rotor. An electric generator known as steam turbine generator is connected to the rotor shaft. The turbine generator collects the mechanical energy from the shaft and converts it into electrical energy. Steam turbine generator also improves the turbine efficiency.

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Some of the Content inside the PDF 

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1. What is a stage in a steam turbine?

Answer:

In an impulse turbine, the stage is a set of moving blades behind the nozzle. In a reaction turbine, each row of blades is called a "stage." A single Curtis stage may consist of two or more rows of moving blades.

2. What is a diaphragm?

Answer:

Partitions between pressure stages in a turbine's casing are called diaphragms. They hold the vane-shaped nozzles and seals between the stages. Usually labyrinth-type seals are used. One-half of the diaphragm is fitted into the top of the casing, the other half into the bottom.

3. What is a radial-flow turbine?

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Answer:

In a radial-flow turbine, steam flows outward from the shaft to the casing. The unit is usually a reaction unit, having both fixed and moving blades. They are used for special jobs and are more common to European manufacturers, such as Sta-Laval (now ABB).

4. What are four types of turbine seals?

Answers:

1. Carbon rings fitted in segments around the shaft and held together by garter or retainer springs.

2. Labyrinth mated with shaft serration’s or shaft seal strips.

3. Water seals where a shaft runner acts as a pump to create a ring of water around the shaft. Use only treated water to avoid shaft pitting.

4. Stuffing box using woven or soft packing rings that are compressed with a gland to prevent leakage along the shaft.

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47.In which turbines, is this pressure-velocity compounding principle employed?

Answer:

In the Curtis turbine.

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48.In which zone of steam turbines has temperature-creep rupture been observed?

Answer:

Damage due to creep is encountered in high temperature (exceeding 455°C) zones. That is, it has been found to occur in the control stages of the high-pressure and intermediate-pressure turbines where steam temperature sometimes exceed 540°C. In the reheat stage, it has been observed that creep has caused complete lifting of the blade shroud bands.

49.Is there any adverse effect off full-arc admission operation?

Answer:

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