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Talking about the Problems in Equipment Bidding and Purchasing for Water Supply and Drainage Pumping Station
In recent years, with the development of water supply and drainage, the production of equipment used in pumping stations has also developed rapidly. A large number of new types of equipment have come out in succession to replace the old model products. The manufacturers everywhere to sell, but a variety of product quality, performance gap, fish head mixed. Therefore, many companies on the "water supply and drainage pumping station equipment required" selection and procurement, also used the tender method. Now I talk about the "water supply and drainage pumping station equipment required" bidding in a few experiences, for your reference. First, the choice of pumps In the preparation of the tender pump, in addition to meet the flow, lift and other major technical parameters, but also from the energy point of view to consider the number of pumps, selection and other issues, and pump types can be divided into centrifugal pumps, Francis pumps, axial flow pumps, submersible pumps, etc., on its structural form is divided into horizontal and vertical pumps, centrifugal pumps to flow and lift larger and widely used in pumping station design, and axial flow pump Belonging to the large flow rate, low lift range, mixed flow pump between the two submersible pump with its simple structure, easy maintenance and installation, reliable performance, energy saving, saving infrastructure costs and other advantages, has been widely used in China, the author In the preparation of the tender documents that should pay attention to the following three points: 1, the number of pumps should be moderate Too many pumps, pump room scale is bound to increase, while more than one pump reduction in workload in parallel, a waste of energy, is bound to increase project investment; pump The quantity is too small, when the flow rate changes is big and not conducive to using the method of adjusting the pump open number to control the flow, it can only be controlled by the gate, which will inevitably cause energy loss Therefore, the number of pumps should be selected according to the actual situation. If the water changes can choose a few large pump; the other hand, may be appropriate to increase the pump type, reducing the number of pumps to reduce project investment. 2, according to changes in the water level selection Pumps directly associated with the water directly connected to the pump station Pump lift water level changes are directly related to water level if the change is small, the pump head of the choice easier, and vice versa more difficult. For example, when the water level of Songhua River changes by about 7m, the designer usually chooses the pump according to the parameters of high flow rate and high lift at the same time. In fact, the chances of the two occurring at the same time are very small, At this moment, the head of the pump selected is clearly too high, forcing the pump to deviate from the work of the high-efficiency zone, resulting in a serious waste of electric energy. The solution is to carefully analyze the frequency of water level changes, taking the frequently occurring water level as the basis for selecting the head of the pump, selecting the pump with adjustable impeller angle to solve the problem of head change within a smaller range, Equipped with different head pump solution to be resolved to ensure that the pump at various water levels can work in the high efficiency area to give full play to the pump energy. 3, according to pumping station process selection Pumps from the structural form can be divided into vertical pumps, horizontal pumps and submersible pumps. Vertical pump covers an area of ​​small, but the motor is installed above the pump, the operation is not stable enough, and less type; horizontal pump covers an area of ​​large, stable operation, a wide range of options, larger; submersible pump small footprint , Easy to install, stable operation, easy maintenance, many types, but in cold areas cold-season operation and maintenance have insulation measures. In the author's opinion, vertical pump or submersible pump should be used for combined water intake pump station. Because the water intake pump house is built in water, it is generally difficult to use the caisson method or the surrounding law to construct the vertical pump or submersible pump Reduce pump room area, greatly reduce project investment. In addition, for some need to increase the amount of water and the original pumping station area need to maintain the same pump station renovation project, increase the number of pumps is difficult, but also the original horizontal pump into a vertical pump or submersible pump, in order to achieve the original area The purpose of increasing the number of water pumps to increase the amount of water before the change. Second, the pump auxiliary equipment selection 1, the choice of gate valve In recent years, the gate valve as a tool to control the direction of water flow and the amount of its form has also changed. In the past commonly used flashlight dual-purpose gate valve is gradually replaced by flashlight dual-use butterfly valve, butterfly valve has the advantages of small size, light weight, easy installation, drag coefficient. The disadvantage is that if the processing and installation accuracy is not enough, or when the water is more likely to lead to the butterfly valve is not tight, there is leakage phenomenon, while the traditional gate valve is not easy to leak, but the bulky; especially large diameter gate valve, large and bulky, installation and removal Are inconvenient; more importantly, due to bulky, resulting in increased pump room area, the project cost increases. Therefore, pumping station design, bidding and selection of valves should consider the following two aspects of the problem: (1) the use of occasions not subject to site restrictions, more debris in the water, easy to plug the important position of the valve, dual-use flashlight gate valve can be used; Butterfly valve can be used, especially in the pump room reconstruction project can be used butterfly valve, in order to effectively use the original pump room space, to achieve the premise of the original pump room to improve the supply (row) of water purposes. (2) manufacturers choose a larger, longer production life, stresses credibility, quality clearance and is responsible for installation and commissioning of the valve manufacturer. With the continuous improvement of the precision of the butterfly valve, the quality will get better and better, and the water leakage problem will be solved. At that time, the butterfly valve will replace the old gate valve, which is the development trend of valves. 2 grille decontamination machine selection Grille decontamination machine used to remove sewage, rain and sewage treatment plant inlet trash trash and a variety of floating debris, grille decontamination machine according to the mechanical structure can be divided into chains Traction grille decontamination machine, rope traction grille decontamination machine and the arc grille decontamination machine, according to the decontamination method can be divided into tooth rake front-type decontamination machine, tooth scraper post-type decontamination machine and self Qing-cleaning machine three categories. In the choice of pump auxiliary equipment, the choice of grille decontamination machine is very important. In the preparation of the tender documents in addition to considering the above types should also consider the nature of the pumping station (sewage, rain), the degree of automation required by the construction unit in the evaluation should pay attention to the choice of grid is not easy to block, drag coefficient, smooth flow of water, Easy installation, maintenance and management is simple, low power consumption, low prices. Third, the pump energy-saving pump is the industrial and agricultural production and people's lives in the use of a very wide range of equipment, to the drainage project, for example, the pump is to drain the system of major energy-consuming equipment, urban water supply pump station, pump station , Pressurized pump station, urban drainage rainwater pumping station, sewage pumping station, sewage treatment plant. The lifting of water is very large, can reach hundreds of thousands to millions of cubic meters per day, often using large pumps, most of them are all day long operation, high power consumption, the general power consumption of the pump total power consumption More than 70%, ranking first in system operation cost. Some of these energy consumption was wasted, and in order to save energy, the condition of the pump should be adjusted. The pumps used in the water supply and drainage projects are mostly centrifugal pumps. Centrifugal pump adjustment methods are two types: one is through the pump outlet pipe to adjust the valve port to change the pipe properties, to achieve pump condition point adjustment; the other is to change the pump speed, thereby changing the pump characteristic curve, Pump conditions to achieve the point of regulation. The former is low energy efficiency, part of the excess energy consumption in the valve port; the latter is a highly efficient energy-saving regulation, so adjust the pump speed is to change the pump condition a better method, select the pump, it is recommended that the economic conditions allow Under, choose to adjust the energy-saving pump to reduce power consumption, reduce operating costs and reduce long-term operating costs. For small businesses in the water treatment process using this method of energy saving can also reduce operating costs, but also for other engineering pump selection. The above is the author in the pump station equipment bidding some of the superficial experience, some problems may not be enough depth, I hope we can further explore in order to pumping equipment in the future bidding for the equipment can choose the most suitable equipment , In order to ensure the greatest economic benefits with the smallest investment, so that our bidding can achieve the desired effect of the user.