In addition to being subject to tough environmental standards, tight budgets, and penalties for supply interruptions, today’s power companies must ensure efficient and reliable operations to keep up with high demand. This means that power-generating turbines often run under more intense conditions than ever, including 24/7 cycles and frequent stopping and starting. Modern steam turbine oils must be able to handle less downtime, higher loads and temperatures, and longer oil drain intervals if they are to be of any effective use. Here’s how steam turbine oils can be selected and used efficiently under demanding operational conditions.

Selecting a Steam Turbine Oil

Maintenance and plant managers can optimize equipment efficiency and cut costs by selecting a steam turbine oil that serves several important functions. First, it must be able to lubricate all bearings, gears, flexible couplings, hydraulic controls, and oil shaft seals. Second, it must be able to resist high temperatures and provide effective cooling. And third, it should prevent corrosion, sludge, and rust while the turbine is spinning. Maintenance professionals can ensure that these performance criteria are met by monitoring several of the oil’s qualities, including its viscosity and viscosity index, demulsibility, rust and corrosion prevention, foam resistance, and oxidation stability.

Viscosity and Viscosity Index

Proper viscosity is what allows oil to efficiently reduce friction between moving parts, making it the most important quality to look for in a steam turbine oil. The size and output of a given piece of equipment will determine its required oil viscosity, with smaller turbines needing lower viscosities and larger turbines needing higher. An oil’s viscosity index, which shows how changes in temperature can affect overall viscosity, is also important. A higher viscosity index indicates that an oil is more likely to maintain its velocity under drastic temperature changes.

Demulsibility

Hydro-electric and steam turbines are especially susceptible to water contamination, which can degrade oil and corrode parts. An effective turbine oil will thus have good demulsibility, which is the ability to separate from and resist water. Demulsibility can be measured by mixing 40 milliliters of distilled water with the same amount of turbine oil, stirring for five minutes at 54 degrees Celsius. This emulsion should separate to 3 ml of emulsion remaining within 15 minutes.

Rust and Corrosion Prevention

An effective turbine oil will also need to prevent both rust formation and chemical corrosion. This is achieved through oil additives that attach themselves to metal surfaces and protect them from both metallic oxide formations (rust) and attacks from strong acids and bases (corrosion). It should be noted that excessive amounts of rust and corrosion inhibitors can interfere with other critical oil additives, so it’s important to achieve a balanced formula.

Foam Resistance

A small amount of foam in turbine oil is normal and can generally be permitted. Excessive amounts of foam in oil, however, can overflow and contaminate the whole circulating system, causing damage to pumps, bearings, or other parts and systems. Properly formulated oil will have an adequate amount of anti-foam additives that should help to eliminate excess foam and air.

Oxidation Stability

While it’s stored in the machine’s reservoir, the oil in a steam turbine is exposed to oxygen over long periods of time. This can lead to oxidation, which drastically diminishes the oil’s effectiveness. It’s therefore critical that maintenance and plant managers select a turbine oil with high oxidation resistance, especially in the presence of high temperatures and metallic contaminants, which can speed up the oxidation process.

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Although electricity was discovered as early as the 18th century, humans have made significant strides in producing electrical power through various means since that time. Among the most common means of producing energy is with turbines of different types, including gas and steam turbines. At the core of a turbine’s energy-producing operations is the spinning of its rotors. Here is a breakdown of how this spinning generates large quantities of electricity.

The Basics of Electrical Generation

Put simply, generators convert kinetic energy, which is based on movement, into electric energy. However, there are a number of different ways that this kinetic energy can be achieved. Most commonly, this electrical generation is created by using electromagnetic induction and by harnessing mechanical energy that causes a generator to rotate. Therefore, one of a generator’s most principal operations is the creation of kinetic energy.

How Gas Turbines Operate

Gas turbines, which are also known as combustion turbines, are composed of a gas compressor, a downstream turbine, and a combustion chamber known as the combustor. Air is drawn into the compressor where it meets with fuel, most commonly natural gas. This results in combustion, and the high-temperature and high-pressure gas then spins rotating blades, which draw more pressurized air into the combustor and spin the generator.

How Steam Turbines Operate

Operating on similar principles, steam turbines instead use extremely high temperature and highly pressurized steam to extract thermal energy. In the process, water is heated in a boiler to create steam, which is then pumped into the turbine to spin turbine blades. After, the steam is often cooled back into a liquid state and then used to create more steam. Much like in a gas turbine, the spinning generator is crucial to creating electricity.

How Spinning Creates Electricity

Today’s generators work on the same principles of electromagnetic induction that were discovered in 1832. In this year, a man named Michael Faraday discovered that electrical charges could be created when an electrical conductor was moved in a magnetic field. This movement resulted in a difference of voltages between the two ends of the wire or conductor, resulting in a flow of the electrical charge and finally an electrical current. In modern generators, the rotating elements are surrounded by a large magnet and coils of copper wire. The magnet is rotated as a result of the spinning wheels, and this results in a powerful stream of electrons, therefore converting the mechanical energy into electric energy.

The Efficiency of Turbines

As oil and gas are demanded more and more on a global scale, power production companies have been forced to consider the efficiency of turbines. Because of the many factors involved in energy production through turbines, there are a number of stages where efficiency is lost. Although the stage of spinning is where electricity itself is created, the preceding stages that require large amounts of heat and combustion can result in a loss of efficiency. In general, steam turbines are a more efficient model than gas turbines, because they require less in maintenance and equipment fees on average. Also, because they require a source of consistent heat, the operations generally involve a consistent heat source, resulting in higher efficiency. However, they also require a large amount of time to reach operating levels. The combustions involved in gas turbines mean that there is a significant fluctuation of temperatures, resulting in a loss of efficiency. However, many plants make up for this loss of efficiency by using a combined-cycle system. In this system, the hot exhaust gas from a gas turbine is transferred to a steam turbine, therefore greatly increasing the efficiency of the operations as a whole.

Because the spinning stage of turbine operation is so crucial to the creation of energy, it is important for power plants to have consistent control operations on their turbines, rotors, and facilities. For more information about how Petrotech provides intelligent control systems for power generation plants, explore our featured white papers.