1. Valves in the water supply pipe network function The water supply pipe network will send tap water sent to millions of households, so the water supply network located in every corner of the city, the water supply pipe network as few as hundreds of pipe length Km, up to thousands of kilometers. The irreplaceability of water and the necessity of people's existence determine the importance of safe operation of water supply network. However, due to many subjective and objective reasons, the pipeline often has some faults, and the pipe network always needs to be constantly updated and rebuilt. The water users often have to increase or decrease accordingly. Therefore, the phenomenon of water stoppage in local pipe sections is unavoidable. In order to reduce the scope of no-go water, it is necessary to properly install the control valve in the pipe network. Therefore, in an urban water supply network, the number of valves is tens of thousands, and irregularly distributed in the city streets below. Valve is a kind of "keeping a thousand days for temporary" control equipment, usually require the valve to open in place to reduce the water loss of pipe. Once needed, the valve should be able to close quickly and flow reliably. Valve integrity, related to the valve selection, valve manufacturing, piping design, valve assembly, valve opening and closing operations and valve management, of course, the most important reason is the quality of the valve. 2. Symposium on the investigation through the use of 20 tap water pipe network companies, through the inspection of the ten valve manufacturers, we realize that the valve in the water supply network in the role of a large number, wide distribution, a lot of problems. Valve operation in the water supply network is not frequent, long-term standby, once summoned, difficult to work. Therefore, in the valve selection, valve manufacturing, valve inspection, valve assembly, valve management, there are many things worth discussing. 2.1 Valve Selection (1) gate valve and butterfly valve in the water supply pipe network in order to reduce the depth of pipe overburden, the larger pipe size matching butterfly valve, the impact on the depth of the soil is not large, and strive to matching gate valve, caused by the caliber of the dividing line Should be based on specific circumstances to be considered. For nearly ten years of use, the butterfly valve has a higher failure than the gate valve, so expanding the use of the gate valve is noteworthy given the conditions permit. (2) gate valve In recent years, many domestic valve manufacturers, research and development, imitation soft seal gate valve, gate valve than the traditional wedge or parallel double gate valve has the following characteristics: a. Soft seal gate valve body, valve cover Using precision casting casting, a molding, the basic non-machining, do not use sealed copper ring, saving non-ferrous metals. b. soft seal gate valve at the bottom of pits, no accumulation of slag, valve gate opening and closing failure rate is low. c. Soft sealing rubber lined valve plate uniform, interchangeable. Therefore, the soft seal gate valve will be the water industry is willing to adopt a form. At present, the soft-sealed gate valve made in China has a caliber of 1500mm, but most manufacturers manufacture the caliber of 80-300mm. There are still many problems in the domestic manufacturing process. From the circumstances of the inspection, the valve body of a valve manufacturing company in Shanghai is entrusted Domestic foundry resin sand mold casting, soft seal valve plate is imported from a foreign company. The company believes that the key component of the soft seal gate valve is Lined plastic valve plate, and Lined plastic valve plate higher technical requirements, not all foreign manufacturers can achieve, often from the reliable factory purchase assembly. Domestic soft seal gate valve copper nut block is embedded in the liner rubber valve plate above, similar to the structure of the valve, the activity of the nut block friction easy to strip valve liner rubber stripping. A foreign company's soft seal gate valve, copper nut block is embedded in lining rubber gate, forming a whole, to overcome the above shortcomings, but the valve cover and valve combination of high concentricity requirements. When opening and closing soft seal gate valve, do not close the dead, as long as the water stop effect can be achieved, or not easy to open or rubber stripping. A valve manufacturing company in Shandong, the valve pressure test, the use of torque wrench to control the degree of closure, as the water company's valve operators should be more imitation of this hoist method. (3) the current butterfly valve butterfly valve selection of several issues of concern: a. The midline butterfly valve butterfly valve in the use of small diameter butterfly valve in China is very large, the effect is better. There are two major differences in the manufacturing method: a valve lining layer after the support frame (represented by the Tanggu products); there is no support frame after a rubber lining (represented by Zhengzhou products). The former rubber less volume, the latter flow area larger. Some people suspect the latter valve life is short, but according to the survey is not the case.
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