What is a steam turbine? What are its components?

by Amili R. SEO

Power is a crucial component is today’s fast-paced world. From high-speed trains to super computers, it is the power of electricity that drives the world towards growth and innovation. In most of the cases, power generation companies bank upon the expertise of a leading steam turbine components manufacturer to meet their technical needs. And whenever a discussion about power generation takes place, steam turbines always remain the major point of discussion. Let us know more about steam turbines, their components and their functioning.

What is a steam turbine?

A Steam Turbine is typically a device that converts kinetic energy into mechanical energy by extracting thermal energy from pressurized steam and utilizes the same to generate mechanical energy to rotate the output shaft. It is now easy to understand that how turbines convert the energy of fluids into mechanical energy to rotate the turbine which is driven by high pressure steam.

The pressure of the steam and the flow of steam in relation to the axis of the rotor define where the steam flows in just one direction or if it flowers in more than one direction.

Turbines can be classified on the basis of the direction of steam flow in relation to the turbine wheel or drum – radial, axial, tangential, mixed or helical, and reentry. There are several steam turbine components that play a vital role in the functioning of a steam turbine. Some of the primary components are:

Frame (Base) – It is the basic turbine frame that supports the rotor, stator and governor pedestal.,

Shell – It includes casing, cylinder, steam chest, nozzles and bearing.

Rotor – It can be comprised of small, intermediary, and high pressure stage blades, and probable stub shaft for governor pedestal constituents, thrust bearing, journal bearings, turning gear & main lube oil system.

Governor Pedestal – It contains the turbine speed controller, EHC oil system and safety equipments.

Steam turbine rotor

All multi-staged steam turbines are manufactured with sturdy forged rotor construction. These rotors are highly engineered from solid alloy steel forgings. An integrated forged rotor tends to provide improved reliability specifically for high speed applications. This is why the complete rotor assembly is dynamically balanced at operating speed and over speed is tested in a vacuum enclosure to ensure utmost safety.

Turbine Casing

The primary objective of a turbine casing is to reduce any distortion due to variation in temperature. The steam power plant manufacturers in India construct it in two halves along a horizontal joint to enable easy opening for inspection and maintenance. With the upper cylinder casing detached the rotor can also be practically eliminated without interfering with the configuration of the bearings.

Turbine Casing Flanges

In order to join the top and bottom halves of the cylinder casing of the turbines, flanges are used with machined holes. Bolts are then implanted into these fabricated holes to secure the highest and lowest halves together. To prevent leakage from the joint between the uppermost flange and the bottom flange, it is necessary to set the joint faces precisely.

Steam Turbine Blades

The design of turbine blade is extremely crucial as it helps in attaining high turbine stability and efficiency. A large inventory of effective blade profile have been created and proven by extensive field service enabling optimal blade selection for all service conditions. Blades are made using high quality stainless steel with stringent specifications for required strength, damping and corrosion resistant properties.

Stationary Blade or Diaphragm

Diaphragms are defined as the partitions between pressure stages in a turbine’s casing. They carry vane-shaped nozzles and seals between the stages. In most of the cases, labyrinth-type seals are employed.

These nozzle rings and diaphragms are designed and built in such a way to manage the high pressure, temperature and volume of the steam. The nozzles used in the preliminary step nozzle ring are derived from stainless steel. Steam passageways are them precisely refined into nozzle blocks before they are welded together to build the nozzle ring.

Besides the above mentioned steam turbine components, there are many other components in a turbine that play their designated role during the operations. It is very much important to consult a leading steam turbine components manufacturer for the best quality components that are safe and easy to operate.