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The steam.
Steam passing through a turbine spinning at a speed of 3600rpm will have a tip velocity on it largest wheel of about 1800 feet per second. In order to reach that speed the steam must be moving at least that fast through the blades. that is about 1200 miles per hour, or more than 1 1/2 times the speed of sound. The steam also over time picks up impurities from the steam pipe to the turbine, these will cause erosion similar to sand blasting. The water in the boiler has impurities that can't be removed effectively, one is silica. At high temperature in the boiler the silica vaporizes into the steam passages, as it passes through the turbine the steam cools and the silica solidifies again into deposits on the turbine blades. There are other causes but these are the most common.
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What is the effect of silica on steam turbine blades?
Although several factors influence the formation of deposits on turbine components, the general effect is the same no matter what the cause. Adherent deposits form in the steam passage, distorting the original shape of turbine nozzles and blades. These deposits, often rough or uneven at the surface, increase resistance to the flow of steam. Distortion of steam passages alters steam velocities and pressure drops, reducing the capacity and efficiency of the turbine. Where conditions are severe, deposits can cause excessive rotor thrust. Uneven deposition can unbalance the turbine rotor, causing vibration problems.The nature of silica deposits found on turbine blades varies greatly. lists a number of silica compounds that have been identified in various studies of turbine blade deposition. Of these, amorphous silica (SiO2) is the most prevalent.Localized Silica Saturation. Turbine deposits are also formed where localized silica saturation occurs and silica condenses from the steam in those areas of the turbine. Partial evaporation of the precipitated silica can then occur with only a portion of the silica being dissolved by the continuous steam flow. Deposits remain as a result.Turbine Velocity. Another factor affecting the location of turbine deposits is the velocity in the turbine. Steam flows from the inlet to the outlet of the turbine in only a fraction of a second. Consequently, deposition is shifted downstream from the saturation point by the high steam velocities.Prevention of Silica DepositsThe most significant factor in minimizing turbine silica deposits is the maintenance of low silica concentrations in the boiler water. External treatment equipment must be operated carefully to limit the amount of silica entering with the makeup water, and the condensate must be monitored to minimize contamination. After silica enters the boiler water, the usual corrective action is to increase boiler blowdown (to decrease the boiler water silica to acceptable levels) and then to correct the condition that caused the silica contamination.
Why would you not heat the steam coming out of turbine and feedback to turbine?
Steam is redirected back into the boiler from the high-pressure turbine for reheating, but the steam from the low-pressure turbine enters into a condenser to become water again.
What is heat rate of steam turbine How to calculate heat rate of steam turbine?
manish
What is positive axial displacement of steam turbine?
axial shift of a steam turbine is the shifting of turbine rotor in the forward and backward direction due to steam thrust on blades of rotor.
What is a steam turbine?
It is an engine.A steam turbine is a heat engine that uses the expansion of steam passing through stationary nozzles and blades on a shaft to turn the shaft. The steam can move through the turbine axially (one end of shaft to the other end), radially (shaft to outer casing), or tangentially (around the outer edges of the turbine wheel). In an impulse turbine, the steam is expanded in nozzles and pushes the blades. In a reaction turbine the steam is expanded in the nozzles AND in the blades, the reaction of the expansion of the steam pushes away from the blades spinning the wheel in the process. The expansion of the steam is necessary to increase its velocity through the turbine.
What is the effect of silica on steam turbine blades?
Although several factors influence the formation of deposits on turbine components, the general effect is the same no matter what the cause. Adherent deposits form in the steam passage, distorting the original shape of turbine nozzles and blades. These deposits, often rough or uneven at the surface, increase resistance to the flow of steam. Distortion of steam passages alters steam velocities and pressure drops, reducing the capacity and efficiency of the turbine. Where conditions are severe, deposits can cause excessive rotor thrust. Uneven deposition can unbalance the turbine rotor, causing vibration problems.The nature of silica deposits found on turbine blades varies greatly. lists a number of silica compounds that have been identified in various studies of turbine blade deposition. Of these, amorphous silica (SiO2) is the most prevalent.Localized Silica Saturation. Turbine deposits are also formed where localized silica saturation occurs and silica condenses from the steam in those areas of the turbine. Partial evaporation of the precipitated silica can then occur with only a portion of the silica being dissolved by the continuous steam flow. Deposits remain as a result.Turbine Velocity. Another factor affecting the location of turbine deposits is the velocity in the turbine. Steam flows from the inlet to the outlet of the turbine in only a fraction of a second. Consequently, deposition is shifted downstream from the saturation point by the high steam velocities.Prevention of Silica DepositsThe most significant factor in minimizing turbine silica deposits is the maintenance of low silica concentrations in the boiler water. External treatment equipment must be operated carefully to limit the amount of silica entering with the makeup water, and the condensate must be monitored to minimize contamination. After silica enters the boiler water, the usual corrective action is to increase boiler blowdown (to decrease the boiler water silica to acceptable levels) and then to correct the condition that caused the silica contamination.
What are reasons for over speed tripping of steam turbine genarator in a combined cycle power plant?
wHAT??
Why extraction taken from steam turbine?
Why extractions are taken out from steam turbine.
What is the function of super heater?
A superheater increases the temperature of the steam for use in a turbine or an engine. Without the additional heat, a multi-stage turbine or engine will get moisture (water) in the lower pressure stages as the steam cools, causing erosion of the blades or cylinders.
Reasons of positive axial shift in steam turbine?
Sudden change of load Sudden drop of vacuum Sudden drop of Main steam temperature.
Why would you not heat the steam coming out of turbine and feedback to turbine?
Steam is redirected back into the boiler from the high-pressure turbine for reheating, but the steam from the low-pressure turbine enters into a condenser to become water again.
What are the preventive maintenance of steam turbine?
The preventive maintenance of steam turbine mainly entails frequent servicing of the parts. This will ensure a smooth performance of the steam turbine.
What is heat rate of steam turbine How to calculate heat rate of steam turbine?
manish
What type of cycle used in steam turbine?
Rankine cycle is used in steam turbine
Why you are maintain the vacuum in steam turbine explain me briefly?
why we are maintain vacuum in steam turbine at steam outlet or exhaust side
Nozzle clearance how to steam turbine?
Steam turbine nozzle clearance is the total energy content available in steam. This is through a valve.
What should be the possible reasons of vacuum drop of turbine?
In the low pressure side of a steam turbine, the vacuum is maintained by the condensation of steam in the condenser. At high loads, the condenser may not satisify the demand, allowing steam to remain gaseous for a longer period of time. This can cause pressure to rise.
