The water distribution network distributes the tap water discharged from the waterworks to millions of households. Therefore, the water distribution network is located in every corner of the city, ranging from a few hundred kilometers in length to as many as 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 will often have some faults, and the pipe network will always be continuously renovated and rebuilt. Water users often have to increase or decrease accordingly, so the phenomenon of water stoppage in local pipe sections is unavoidable. In order to reduce the scope of the water, properly installed in the control valve is very necessary. Therefore, in a city's water supply network, the valve tens of thousands, there is no regular distribution in the city streets below. Valve on the water supply network is not frequent, long-term standby, once needed, the valve should be able to close quickly, intercepted reliable; usually require the valve to open in place to reduce the loss of pipe head, so the valve is a " "The control equipment; valve intact rate, related to the valve selection, valve manufacturing, piping design, valve assembly, valve opening and closing and valve management, of course, the main reason is the quality of the valve. Valve in the water supply network in a large number of widely distributed, the role of large. Therefore, the valve selection, inspection, performance and management are many issues worth discussing. First, the valve selection Valve has a butterfly valve, gate valve, ball valve and plug valves, etc., in the water supply network using a different range. In order to reduce the depth of soil cover pipe, the larger diameter of the pipeline matching optional butterfly valve; little effect on the depth of soil cover, and strive to match the gate valve; ball valve and plug valve casting and processing difficult, the price is more expensive, generally applicable to medium and small diameter pipe. In recent years due to the improvement of foundry technology, the use of resin sand casting, to avoid or reduce the machining, thereby reducing the cost, so the feasibility of ball valve for large-diameter pipe worth exploring. As for the size of the dividing line should be divided according to the specific circumstances. The main disadvantage of the butterfly valve is that the butterfly plate occupies a certain cross section of the water and increases the head loss. Although there is no problem with the gate valve, the height of the large diameter vertical gate valve affects the depth of pipe covering and the length of the large diameter horizontal gate valve increases Pipelines occupy the lateral area, affecting the arrangement of other pipelines; ball valve and plug valve while maintaining a single valve, water flow resistance, reliable sealing, flexible operation, easy operation and maintenance. Plug valves also have similar advantages, but the cross section is not circular. In recent years, many domestic valve manufacturers to develop soft seal gate valve, the gate valve and the traditional wedge or parallel double gate valve has the following characteristics: 1. Valve body of the soft seal gate valve, valve cover casting by casting method, a molding, no longer machined, do not use sealed copper ring, saving non-ferrous metals; 2. No soft pitched valve gate at the bottom, not accumulate debris, gate valve opening and closing failure rate is low; 3. Soft seal rubber lined valve uniform size, interchangeability. Therefore, the gate valve will be the development of soft sealing valve, but also the water industry is willing to adopt a valve. Open and close the soft seal gate valve, do not close the death, as long as the water stop can be achieved, or not easy to open or rubber stripping. Most of the butterfly valves used in the water supply industry are soft-sealed butterfly valves. In view of the vulnerability of the rubber seals during the installation process of the butterfly valve, many manufacturers have introduced metal-sealed butterfly valves instead of rubber-sealing butterfly valves. Metal seal butterfly valve seal due to the smaller elasticity, the general use of eccentric structure, especially with three-dimensional eccentric structure is more reasonable. Second, the valve performance and testing The special nature of the valve requires its quality, excellent performance. Evaluation of valve performance and performance testing, should pay attention to the following points: 1. The valve opens and closes flexibly and lightly under the working water pressure, and detects the opening torque with a torque wrench under the working water pressure. 2. Valve close tight, at 1.1 times the working pressure does not leak or leak Meet the standard requirements (metal sealed butterfly valve), which requires both sides of the valve pressure, respectively, testing, and repeatedly opening and closing to achieve the same effect . Requirements of a variety of caliber, different types of valves should be in the manufacturer and testing qualified units with load hoist the life test. This test also includes the evaluation of the valve shaft sealing effect. 3. Valve over-flow ability to be stronger, especially the butterfly valve, butterfly flow resistance is smaller, over-flow effective area to be large. This requires a variety of caliber, different types of valves should be measured flow coefficient. 4. The ability of the valve body to withstand water pressure should be consistent with the pipeline, which is the valve open state, the valve can withstand the test pressure requirements of the pipeline. Third, the valve lining and anti-corrosion valve is the transport of drinking water equipment, body lining must be non-toxic, corrosion-resistant, wear-resistant, smooth, so that the water flow resistance as small as possible. Such as the valve platen, bolts and disc material is very prone to electrochemical corrosion, rust corrosion generated extended to the sealing surface, affecting the sealing effect of the valve, the other valve installed in the valve well, soaked in water, to prevent corrosion is very important Therefore, the lining should be well covered so as to prevent secondary pollution from water supply caused by corrosion. External corrosion of the valve can take polishing sand, and then for electrostatic spraying non-toxic epoxy preservatives, you can also brush 1-2 times red-red paint, and then brush twice after anti-rust paint. Fourth, the valve operation and management Valve can be opened and closed well, not only to select the appropriate valve, product quality, well construction and installation, but also thoughtful management, can play a "thousand days of military training, the deployment of a temporary" effect. Good operational management is reflected in the following three aspects: 1. Technical information Valuable technical information, including valve factory manual, the valve after the purchase of qualified single, the valve assembly and location card, valve maintenance records. For the street changes, the valve card should be updated in time, and strive to establish a GIS management system. 2. Valve operation and management thought valve operation and management of quality requirements, including the valve should be closed tight, the valve shaft seal packing string no leakage, the valve opening and closing light, indicating good. Valve operation and management of daily work, including the previous valve opening and closing single operation approval and record of the operation records of the improvement, the valve regularly detect the opening and closing records. For the valve has not been operated for a long time, according to the size of the caliber, set a different test cycle is necessary. For the discovery of the fault should be proposed maintenance programs, timely manner, especially after the closure of the valve can not be opened as the emergency pipeline should be treated as emergency. 3. Well Well Well Well Well including valve well masonry in line with industry standards and design specifications, well cover and road surface intact, the operation of the valve hole accuracy, no debris and sewage wells, the valve surface without rust. Where conditions permit, large-diameter valve wells should consider the long-term air convection well in the technical measures. The valve wells should be regularly visited, the cover of the loss and damage should be promptly addressed.
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