Technical Measures to Prevent Steam Turbine Shaft Bending
Source: Bearing Network | Date: April 8, 2013
Steam turbines are critical components in power generation systems, and their proper operation is essential for the efficiency and safety of the entire unit. One of the key concerns during operation, maintenance, and startup is the prevention of shaft bending or tortuosity, which can lead to severe mechanical damage and operational failure. To ensure the safe and reliable performance of steam turbines, several technical measures must be strictly followed. First, before rushing the turbine, it's important to check the large shaft misalignment, ensuring it is less than 0.076 mm. The large shaft runout should not exceed 0.02 mm from its original value. After an overhaul, use a dial gauge to measure the oil film runout on each bearing, making sure it remains below 0.0254 mm. Second, if the temperature difference between the upper and lower cylinders exceeds 42°C—particularly in the high-pressure and intermediate pressure cylinder exhaust zones—the turbine should be stopped immediately. The main steam valve inlet temperature must have at least 56°C superheat to prevent condensation and potential water hammer. Third, cold and hot starts should follow the recommended "main steam parameters," "cold-state rotor heating curve," and "hot-state recommended values" to avoid thermal stress and uneven expansion. Fourth, during any start-up, the first-stage steam temperature must not deviate by more than 56°C below or 111°C above the top metal temperature. This helps maintain consistent thermal conditions across the turbine rotor. Fifth, during a hot start, steam should be supplied after the steam seals are engaged. Before sealing, ensure complete drainage of moisture, and only then proceed with steam supply to the seals. Sixth, the steam supply must have a superheat of over 14°C, with low-pressure steam temperatures maintained between 121°C and 177°C to prevent condensation and erosion. Seventh, prior to starting the unit, the steam seal supply should be shut off to prevent unnecessary moisture accumulation. Eighth, if the steam temperature for high and medium pressure steam seals drops below 150°C or the temperature difference between the steam seal and the high-pressure cylinder end wall is less than 85°C, the steam seal spray should be closed to prevent excessive moisture entry. Ninth, during the startup process, follow the "recommended turbine speed maintenance values," "cold rotor heating regulation," and "hot state recommended values" curves. Warming up should begin once the medium-pressure cylinder inlet steam temperature reaches 260°C. Tenth, during the startup, a dedicated person should monitor the vibration of each bearing. The shaft vibration should remain below 0.125 mm. If the bearing vibration exceeds 0.1 mm or the relative shaft vibration goes beyond 0.254 mm at critical speed, the turbine must be stopped immediately. Forcing through critical speed or reducing speed for warming is strictly prohibited. Eleventh, during normal operation, the bearing vibration should not exceed 0.03 mm, and the relative shaft vibration should not go beyond 0.08 mm. If these values increase, the cause must be identified and resolved. If the relative shaft vibration exceeds 0.254 mm, the turbine should be stopped. Sudden changes in vibration (±0.015 mm for bearings or ±0.05 mm for shafts) require immediate investigation and corrective action. Twelfth, according to the "Central Control Operation Regulations," if signs of water hammer in the turbine are observed, the unit must be stopped immediately to prevent catastrophic damage. Thirteenth, all high-pressure, low-pressure, and deaerator water levels should be regularly monitored and tested. If a heater is found leaking, it should be isolated and the exhaust check valve closed. Fourteenth, after shutdown, the turning gear should be engaged promptly. If the current is higher than normal or unusual noises occur, notify the relevant departments immediately. If steam seal issues are severe, the rotor’s high point should be positioned at the top, and the cylinder drained. Monitor the temperature difference between the upper and lower cylinders and the rotor’s torsion. Once the torsion returns to normal, manually turn the rotor 180° to straighten it. If the rotor does not move, do not force it. If the turning gear fails, suspend the process and continue monitoring the rotor’s torsion. Once the rotor is stable, resume the turning gear as needed. Fifteenth, during start-up, operation, and shutdown, strictly adhere to the "Technical Measures to Prevent Cold Steam and Water from Entering the Turbine." Be cautious when switching valves to prevent cold air, moisture, or condensate from entering the extraction pipes or drain lines. Sixteenth, each shift should verify the local water level gauges and CRT readings for the deaerator and heaters to ensure accurate monitoring.
Recommended for friends: Comments | Close Window
Bearing Related Knowledge
- Cp-4617-5-f: Key skills in the production of lubricating oil bearings for gears and bearings (2) - Preparation for "Before ZWZ Bearing Unit" - Aiglidur® engineering plastic sliding bearings used in automotive linear motion ball bearing applications This article links to http:// Please indicate China Bearing Network http:// Previous: The problem that should be dealt with when KOYO bearing attack is excited. Next: What is the need for overhaul of crankshaft? we are professional manufacturer of Casual Silent Booth,Sound Isolation Pod,Portable Isolation Pod,Casual Silent Booth Brand. We focused on international export product development, production and sales. We have improved quality control processes of Casual Silent Booth to ensure each export qualified product.
If you want to know more about the products in Casual Silent Booth, please click the product details to view parameters, models, pictures, prices and other information about Casual Silent Booth.
Whatever you are a group or individual, we will do our best to provide you with accurate and comprehensive message about Casual Silent Booth!
Casual Silent Booth,Sound Isolation Pod,Portable Isolation Pod,Casual Silent Booth Brand
Shenzhen Filmbase Technology Co., Ltd. , https://www.globalfilmbase.com