Thermal Power Plant By A Large Steam Turbine Combined With The Surface Deformation Theory And Practice Of The Leak

Power industry is one of the basic industries of modern society. Capacity of power production is an important way to measure the levels of economic development of a country. Thermal electric generation is the biggest part of modern power industry, , which is followed by hydro-power and nuclear power. In most of thermal power plants and nuclear power plant,to produce electricity, generators are driven by steam turbines, which are important power generating machines in modern world.Along the horizontal split, turbine casing, the outside shell of steam turbine, can be divided into two halves, the upper and lower parts, which are bolted together by level flanges.The jointing surface of steam turbines is the level flanges. In recent years, Deformation of the jointing surface can cause leak-off of steam from turbine casing, which is a great defect in new power units and long-term operating units. The leakage can be a considerable impact on the security and economic of steam turbine sets.First, on the basis of many references, this article comes theoretically to the characteristics of the structure of jointing surface of steam turbine, the forces exerted during operation, and analyzes the main causes of deformation leakage, which may comes out from the period of production, of erection and repair, and of operation.Next, in according to the peculiarities of different turbines in China, the article divided the radial deformation of jointing surface into two categories: inner opening and outer opening; axial deformation into: regular and irregular ones. Then it gives two principles on how to resolve the problem of deformation of jointing surface, that is, erasing of high-spot, and filling of dent. These two principles have their own methods in machining, lapping-in, brush painting and welding of potted line. Every method has got its merits and drawbacks.There are many kinds of jointing surface deformation of steam turbine and are very complicated. Reparation could be very difficult. according to different categories of deformation and considering different requirement of project time limit, and of project cost, this article brings forth three schemes. They are complete erasing of high-spot, combination of erasing and filling, and complete filling of dent. Scheme 1 gives an instance of complete machining method on deformation of HP inner casing of an imported 600MW unit. Scheme2 gives an instance of a domestic 300MW unit, which adopted the method of machining on the joint surface of upper casing of IP inner casing, and of lapping-in, welding of potted line on the joint surface of lower casing. Scheme3, an instance of a domestic unit, which carried out the method of welding of potted line on upper joint surface of HP&MP casing, and of brush painting on lower surface.At the same time, it introduces in detail the features of every method, their specific procedure, their effect, negative impact, and their remedies. Practices prove that all these three schemes are effective. In the end, it concludes a general scheme on deformation leakage of casing joint surface of steam turbine.The author hopes that this article can bring some instruction on the problem solving of deformation leakage of steam turbine casing in other power plants.