Cylinder in the process of design and manufacture of considerations

Cylinder in the process of design and manufacture of considerations for steam turbine cylinder is very important, it is in the process of design and manufacturing has a lot of problems need to be taken into account. It complicated shape and the cylinder at the stationary part of work under the high temperature and high pressure. Its role is to put the steam from the atmosphere, the formation of steam complete closed space of energy conversion. The regulating stage nozzles installed in the cylinder chamber and the diaphragm, diaphragm cover, rotor and other parts. Steam flow in steam turbine steam parameters decreased after work, in the cylinder of high pressure part of steam pressure, low pressure part part of the cylinder body need to bear the external atmosphere. Sda thin cylinder in the process of operation, due to the temperature of the steam and the volume change is bigger, the stress of each part under cylinder has bigger difference distribution along the cylinder. Cylinder in the process of design and manufacturing, still need to consider many problems, which mainly include: cylinder and combined with the rigor, steam turbine start the cylinder in the process of thermal expansion, thermal deformation and thermal stress and stiffness and strength of the cylinder and steam flow characteristics, etc. To facilitate the processing, assembly and maintenance, in the cylinder made of horizontal form, its main features are: usually the cylinder is divided into two parts, the rotor through the center of the radial, in order to make the cylinder steam under high pressure and not leak, cylinder fluctuation two parts with fastener connection, the most commonly used is to use bolts, nuts, they split up and down along the cylinder diameter flange will be up and down cylinder closely linked together. In order to ensure the flange joint surface rigor, cylinder in faceted in the manufacturing process must be smooth, level off. Flange bolts connection generally adopt hot tight way, namely when installing bolts to bolt pre-tightening force, after a period of time can guarantee the stress relaxation of flange rigor. In addition, mal admission part of miniature cylinder scattered arrangement as soon as possible, lest cause local thermal stress is too big, cause the deformation of cylinder. As the unit capacity increases, the steam parameters, metallurgy cylinder inside and outside differential pressure also increased greatly. In order to guarantee the points below steam tightness, prestressing force of joint bolt needs to have a big, thus making bolts, flange, cylinder walls are very thick. This will lead to the working condition of steam turbine start-up, stop and change between the cylinder wall and flange, flange and bolt will have a large thermal stress due to temperature difference is too large, and even make the cylinder deformation, the bolt pulled apart or cause drag mark. And sealed performance is good and reliable flange also is very difficult, in order to solve these problems, large steam turbine ( At the beginning of the parameters above. MPa, ℃ above) Often make double cylinder structure, between the inner and outer cylinder filled with certain is lower than the initial parameters of the steam pressure and temperature, which greatly reduced under differential pressure and temperature difference between inside and outside the cylinder, each layer of cylinder wall and the thickness of the flange can be thinned, greatly reducing the working condition of start, stop, and change of the thermal stress, to improve the unit startup and load adaptability. At the same time, because of the sandwich steam cylinder can get effective cooling, can reduce to the requirement of the cylinder material. In general, the positioning of double cylinder method is: outside the cylinder with a cat's paw in the bearing support, cylinder inside and outside the cylinder adopts bolt connection, and the positioning positioning pin and guide pin and guide. In the design and manufacture, though considerations, but notes that are also very much, these questions are need to pay attention.