Fluctuations in steam turbine speed
Thread Content
Our factory uses Shengli Steam Turbine’s condensing steam turbines. These days, the rotational speed is not as stable as before; usually it is set at around 10,000, with fluctuations of no more than 20 units. These days, although the speed is still set at 10,000, it fluctuates between 9,000 and 11,000. Does anyone know what the reason is? ????
This depends on the waveform of the trend chart to determine whether it is a problem with the speed measurement instrument. The most straightforward indicators of changes in rotation speed are whether the steam pressure is stable, whether there are issues with the intake valves, and whether there are any leaks in the heat exchangers used for condensing the vapor. For reference.
1. Look for problems in the control system of the turbine itself. The speed control system of the turbine is a PID type; it is possible to adjust the PID parameters using instruments. Additionally, check whether there are any fluctuations in the pressure of the control oil； 2. Identify the causes from process aspects such as whether there are fluctuations in the compressor’s air intake volume and whether there have been recent changes in the composition.
1. Check the speed probe. 2. Check the speed control system and adjust the control parameters; if possible, stop the machine to inspect the slide valve to ensure that there are no impurities inside that could affect its movement. 3. Confirm the fluctuation range of the main steam pressure parameters. 4. Verify whether the levels of silica and calcium/magnesium ions in the main steam meet the required standards, and check whether the silica content in the desalinated water at the outlet of the desalination station is within acceptable limits. Industrial steam turbines have a small blade spacing; therefore, it is advisable to use mixed-bed reactors or other secondary purification processes to reduce the silica content in the desalinated water. 5. The downtime can be utilized for steaming; or during rotation at low speeds, steam with a high moisture content can be used for steaming in order to remove impurities from the blades or impellers.
Check the load, and see if the intake pressure, flow rate, vacuum level, etc., fluctuate simultaneously.
It is recommended to check the steam control valve to determine the duration of the fluctuations, and to closely monitor it for any abnormal variations
The coal quality was poor during those days, the gas composition was not satisfactory, and fluctuations in the main steam pressure also affected our turbines
Is the control system Shengyu’s own or Wood’s?
Speed control system failure. Condensing steam turbines rely on a speed control system to maintain a set speed and ensure stable operation. If the speed control system fails or malfunctions, it will cause fluctuations in speed. The steam quality is unstable. Condensing steam turbines require a balanced and stable supply of steam; otherwise, it will affect the stability of their rotational speed. If there are significant changes in parameters such as steam flow rate, pressure, and temperature under operating conditions, this can also lead to fluctuations in rotational speed. Fault in the mechanical transmission system. The mechanical transmission system of a condensing steam turbine includes components such as gearboxes, hubs, and bearings. Any failure or wear of a component can cause fluctuations in speed. Affected by external environment. External environmental disturbances such as electromagnetic interference, temperature changes, and pressure fluctuations can all interfere with the operation of turbines, thereby causing fluctuations in their speed.
“The rotation speed is set at 10,000, but it fluctuates between 9,000 and 11,000 – shouldn’t the compressor surge under such conditions? Estimate the speed measurement problem.