First, the concept of multi-stage pump string Running multi-stage boiler feed pump due to the presence of axial force and the role of balancing devices, so that the rotor in a dynamic equilibrium state, that is, the rotor in the non-stop axial series. According to experimental data, the string of momentum is about 0.10mm-0.15mm, the number of stringing 10-20 / min. This string of momentum is not discussed in this article, the pump string momentum, the string to be discussed in this article is the amount of movement of the impeller in the suction side with the wear of the balance. The amount of water pump has always had a different view, a view that, when the pump assembly is completed, without a balance device, the rotor is fixed, the suction end, the impeller lip close to the ring, we put this The quantity is called b1. And then pull to the discharge end, the impeller's back cover close to the vane, the string called b2. This sum of b1 and b2 we call the pump of the string, both full string. There is another kind of string that is b1 + b2 / 2, which is what we mean by the working string. In fact, in fact, the views of these two series are not strict enough. Because in the pump operation, in addition to the start of the pump to the discharge end of a series of strokes, the operation in the axial force under the action of the rotor is always suction side. Really play a role in the previously mentioned b1, and b2 no practical significance. Due to the pump assembly error in the assembly process and other factors, under normal circumstances b1 ≠b2. The amount of the string should be the centerline of the impeller and guide vane alignment, the impeller suction side to the guide vane distance, which is mentioned earlier b1, to be exact that pump can be striked to the inhalation side of the maximum amount. When the vane center and impeller center of the multistage pump are fully aligned, the pump will have the least hydraulic loss and the highest efficiency, which is the ideal economic operation condition of the pump. The new pump factory and overhaul of the pump should reach this state. However, during the operation of the pump, due to the wear of the balance disc, the rotor is gradually moved toward the suction side under the axial force until the impeller hits the guide vane. Second, the adjustment of the pump string 1. The amount of economic operation of the string We all know the performance curve of the pump, such as the pump running guide vane center and impeller center will not be able to leave the best operating conditions point, the efficiency will be significantly reduced. The general performance of reduced traffic, head increased, the relative increase in power consumption, if allowed to go, you can go a long way in the whole string that b1. Although this reduces the maintenance time, but the efficiency will be lower and lower, the power consumption will be more and more. To do this, we must choose a small amount of maintenance, power consumption is not large string, the pump has a higher efficiency. Based on practical experience, the value of b1 we choose should be greater than b1 + b2 / 2. In the end should be much larger? According to the actual situation, we generally choose large 0.15mm-0.35mm. As in our company on the 2nd after the pump overhaul to adjust the string move, the b1 value of 3.13mm, b1 + b2 / 2 to 3.28mm. This string of values ​​is taking into account the efficiency of the pump and adjust the balance plate and other maintenance after the volume determined. 2. Overhaul of the series pump in the overhaul will inevitably be replaced, repair some or all of the impeller, due to the existence of manufacturing errors, can not guarantee the original string of momentum. Need to re-adjust. The method is to first measure the impeller in the inlet section and the middle of the first stage, and use this as a standard, one by one to measure the maximum amount of each impeller, its value is slightly larger than the inlet section, it can be regarded as qualified , Less than the water section, you must be trimmed. Under normal circumstances, is to take the middle of the pad or between the middle of the method of turning to adjust. Of course, before making any adjustment, it is necessary to ensure that the relative positions of the rotor parts in the shaft are not changed. After the final assembly, due to manufacturing quality and installation process and other reasons, but also a slight change in the amount of string, the measured value at this time shall prevail. Third, the multi-stage boiler feed pump balance plate gap adjustment For multi-stage boiler feed pump, there are many sources that the impeller, the balance plate and the balance between the sleeve should have about 0.10mm gap to prevent the balance plate Grinding occurs between the balance sleeve. This is actually not necessary. One is that the high-pressure liquid in the high-pressure chamber where the balance disc is located always causes the balance disc to move away from the balance jacket. Even if the pressure inside the pump is not established when the pump is started, the axial force caused by the recoil force of the liquid also occurs This effect. The second is to allow wear and tear balance device is worn by its wear and tear to ensure that the impeller is not worn, in fact, due to the role of high-pressure liquid pump in normal work balance plate and balance sleeve minimum clearance will be guaranteed at 0.10mm, direct Not many opportunities for grinding. Balancing the balance disc and the balance of the mill is often due to poor installation and manufacturing, so that balance disc skew caused. This fact has proved this point. Therefore, the provisions of the original issued standard requires a balance of disc sealing surface and the axis of the verticality of <0.03mm, which is what we call the balance pan.
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