The Main Shaft Seal Of Pump Turbines

For the newly built large and medium-sized hydropower stations, the water turbine generator units are required to carry out central control, which can complete the start-up, parallel network or shutdown of the unit with one instruction. It is required that the operation conditions of hydroelectric generating sets can be monitored centrally, and some important operational parameters can be inspecting roving. It is required that the hydroelectric generating sets can adopt the microcomputer monitoring system, and realize the telemetry, and remote control, so that no one is on duty, and few people are on duty. All of them put forward new requirements for the seal of the main shaft of the hydraulic turbine. It requires that the seal of the main shaft of the turbine can work for a long time in a safe and reliable state. The repair and replacement period of the main shaft seal can at least guarantee a period of overhaul. It is required that the main shaft seal of the turbine can be self compensated or no need to be adjusted, and the working state of the main shaft seal of the turbine can be detected by the sensor.

The main shaft seal of hydraulic turbine often adopts packing seal, also called packing root seal, which is usually made up of stuffing box, packing ring and gland. The packing seal relies on the compression deformation produced by the external force of the packing ring and eliminates the need for sealing clearance so as to achieve the purpose of sealing. Packing rings usually have three types: soft packing, hard packing and forming filler. The greater the number of soft packing rings is, the harder it is to compress the packing ring in the deep, which can not reach the expected effect of the multi-ring packing. If the packing ring is fully pressed, the packing ring at the orifice is excessively compressed and worn seriously. In order to compress the rings uniformly, we usually adopt two sets of packing rings in series, and the first class packing box acts as the next level of the cap so as to improve the sealing effect. In the design of the packing seal structure of the turbine, the soft filler is used in the deep part, and the hard filler is used in the hole, which is also an effective method. In order to avoid the damage of the packing ring, the fastening of the packing ring usually adopts the method of pressing into fastening.