A turbine rotor can go into over speed when its rotational speed exceeds its designed or safe operating limits. This can occur in various types of turbines, such as steam turbines, gas turbines, or even wind turbine.A turbine rotor can go into over speed when its rotational speed exceeds its designed or safe operating limits. This can occur in various types of turbines, such as steam turbines, gas turbines, or even wind turbine.
Now a days steam turbines are designed for rotation speed more than 10000 RPM.For low capacity turbines the speed is generally more than that of high capacity turbines.
Following are the most relevant reasons for Turbines to go into high speed or over speed.
Sudden Load Loss: If the load on the turbine suddenly decreases, the turbine may accelerate beyond its design limits due to the reduced resistance. This can occur, for example, if there's a sudden disconnection of the load or if a generator or other equipment connected to the turbine experiences a fault.
Malfunctioning Governor: Turbines often have governors that control the amount of steam input to the turbine in order to maintain a specific rotational speed. If the governor malfunctions, it might not be able to regulate the turbine's speed properly.
Sudden cut off of extraction steam:Sudden cut off or closure of extraction steam valve may leads to over speed of Turbine.
Control System Failure: The control systems that regulate the speed of a turbine may malfunction, leading to an inability to control the turbine's speed effectively. This can occur due to electrical failures, software glitches, or other issues with the control system.
Loss of Blade Load: Turbine blades are designed to extract energy from the fluid (steam, gas, or water) passing through them. If there's a sudden drop in the fluid flow rate or pressure, the blades might not experience enough load to keep the turbine's speed in check, leading to over speed.
Failure of Throttle valves: Damages to the any of the throttle valve lead to over speed of the Turbines
Stuck up of throttle valves: Stuck up of throttle valves due to burs, scoring marks or due to dust and dirt may lead to over speed of the Turbines
Looseness in linkages:Looseness in HP or KP valve linkages may lead to mal-operation of the throttle valves leading into more steam flow and hence over speed of the Turbine
To prevent overspeed and its potentially catastrophic consequences, turbines are equipped with safety measures such as mechanical overspeed protection systems, which may include centrifugal force-based devices that trip and reduce the flow of fluid into the turbine when a certain rotational speed is exceeded. Regular maintenance, monitoring, and adherence to operational guidelines are essential to ensure the safe and reliable operation of turbines.
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