Analysis and Disposal of Oscillation Causes of Turbine with Transmission
Shower And Bath Valve,Bath Valve,Bathtub Valve,Tub And Shower Faucets JANGMEN MOON SHOWER SANITARYWARE CO.,LTD , https://www.moonshowerglobal.comAnalysis and Disposal of Oscillation Causes of Turbine with Transmission
The 2# steam turbine generator set of the 8# unit at Xinjiang Steel Co., Ltd. is a 3MW extraction condensing unit. The steam turbine is horizontally mounted on an island-type base at an elevation of +5.00m. The 2# turbine is a CN3-24/5 single-cylinder, extraction condensing unit produced by Hangzhou Steam Turbine Works. It consists of a double-stage reheat section, a regulating stage, and six pressure stages. The front bearing is a tilting pad radial thrust combined spherical bearing, while the rear bearing is a tilting pad bearing integrated with the cylinder. A gear coupling connects the steam turbine rotor to the pinion, and a rigid coupling links the large gear to the generator. The generator model is QF-K3-2, manufactured by Hangzhou Power Generation Equipment Factory. The unit has been in operation for about 10 years, with no major overhaul in the past five years. During mid-November 2006, some issues were identified and resolved accordingly.
The oscillation of the tilting pad bearings in the turbine is similar to that of other units, but due to the unique design of the bearings, there are specific considerations. The 1# and 2# bearings consist of tilting pads arranged in three lower and two upper sections. These pads are made of curved Babbitt material, allowing them to pivot freely around their fulcrum. This enables the bearing to adjust dynamically to different speeds, loads, and oil film thicknesses during operation, forming multiple oil wedges around the shaft. The lubricating oil enters through the gap between the tiles and exits via the oil seal rings. If the friction forces and inertia are neglected, the oil film exerts force through the center of the shaft, ensuring stability and preventing oil whirl. This makes tilting pad bearings highly effective in damping vibrations.
Tilting pad bearings offer several advantages, including high stability, strong load capacity, and energy efficiency. However, they are more complex to maintain and can be costly. Despite this, they are increasingly used in high-power units due to their superior performance compared to cylindrical or elliptical bearings.
The alignment of the tilting pads must be precise, with axial spacing errors not exceeding 0.02 mm. These components are usually processed by the manufacturer and should not be modified on-site. After cleaning and inspection, the bearings are reassembled without any scraping. During a recent maintenance, it was found that the horizontal oscillation of the 2# bearing was caused by improper alignment of the pinion and steam turbine coupling. After adjusting the coupling center, the oscillation was reduced. However, at critical speed (~3000 r/min), the oscillation reached 0.106 mm, indicating an issue with the oil film thickness and clearance of the tilting pads.
Further analysis showed that the lower right tilting pad had a gap of 0.16 mm with the shaft, while the left pad had a gap of only 0.04 mm. Adjustments were made by adding a 0.10 mm gasket to the back of the lower right pad, which helped reduce the oscillation. After further testing, the oscillation dropped significantly, confirming that the oil film instability was the main cause.
In the installation of large-scale units, proper alignment of rotors and couplings is crucial. For smaller units, the lighter components make adjustments easier. However, the accuracy of the large gear’s measurement is vital. Multiple measurements by skilled personnel help reduce errors. Key steps include measuring the concave and convex values of the large gear, checking parallelism, and determining the meshing clearance using dial indicators. Proper adjustment ensures smooth operation and reduces vibration.
The turbine bearing system and the fine adjustment of the gear play a critical role in the safe and efficient operation of the power plant. Strict process control and quality supervision are essential during both production and installation to prevent future issues and ensure long-term reliability.
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