Water supply network to send the water from the waterworks distribution to millions of households, so the distribution of water supply networks in cities in every corner, at least hundreds of kilometers of its length, up to thousands of kilometers.
Irreplaceability of water and necessary for people to live, and determined that the water supply network of the importance of safe operation. However, due to various objective and subjective reasons, the pipeline tends to be some failures, pipe network is always to keep upgrading, water users often have a change, so the local control of water above it is difficult to avoid the phenomenon. In order to narrow the scope of water in the pipe network due to the installation of control valves is necessary. Therefore, in a city's water supply network, the number of tens of thousands of valves, there is no regular distribution in the city streets below.
Water supply pipe-line operation of the valve is not frequent, long-term standby, if necessary, should be able to close the valve rapidly, a reliable closure; usually request to open the valve should be in place to reduce the head loss pipe sections, so the valve is a kind of "Yang-bing A Thousand Days, 1:00 troops "of the control equipment; the good rate of valve related to the selection of valves, valve manufacture, pipeline design, the valve assembly, the gate valve and valve management, The main reason of course is the quality of the valve.
Valve in the water supply network in the large number of widely distributed, the role of big. As a result, valve selection, testing, performance and management of many of the issues are worthy of discussion.
First, the selection valve
There are butterfly valves, gate valve, ball valves and plug valves, such as several in the water supply network in the scope of the use of different. In order to reduce the pipeline depth of soil, the larger diameter pipes generally matching butterfly; little effect on the depth of soil to matching valve; ball valves and plug valves casting and machining difficult, expensive prices, generally applicable to small and medium-caliber pipe. In recent years, due to improvements in casting technology, the use of resin sand casting method can be avoided or reduced machining, thereby reducing the cost, so the ball valve for large diameter pipe is worth exploring the feasibility. As for the size of the line diameter should be considered throughout the division by the specific circumstances.
The main disadvantage is the butterfly butterfly board to occupy a certain cross section, add the head loss; valve no problem, but the large-diameter vertical pipe valve of a high impact on the soil depth of large diameter horizontal valve increased the length of horizontal pipe occupied area, the impact of other arrangements for the pipeline; ball valves and plug valves are maintained single valve, the flow resistance in small, sealed reliable, flexible movements, operation and maintenance of the advantages of convenience. Plug valves also have similar advantages, but not the cross section is circular.
In recent years, many valve manufacturers to develop soft-sealed gate valve, the valve and cut the traditional or parallel plate gate valve双闸compared the following characteristics:
1. Soft sealing valve of the valve body, valve cover the use of precision casting foundry, a molding, it is no longer machining, non-use of sealed铜环, saving non-ferrous metals;
2. Soft sealing gate valve at the bottom of pit-free, non-accumulation of Java objects, the gate valve failure rate is low;
3. Soft rubber lining the valve seal uniform size, strong interchangeability.
So soft sealing gate valve gate valve will be the development direction of the water supply industry is also reluctant to adopt a kind of valve. Soft sealing gate valve, the closure should not have to die, as long as the sealing effect can be achieved, otherwise difficult to open or peeling rubber lining.
Water supply industry is mostly used in soft-sealed butterfly valve butterfly valve, butterfly valve for the apron during the installation process easy to damage the impact of tightness, the introduction of many manufacturers to replace metal seal butterfly valve butterfly valve sealing apron. Metal seal butterfly valve seals due to the flexibility of small, generally eccentric structure, especially the use of three-dimensional structure is more reasonable eccentricity.
Second, the performance and test valve
The specificity of valves require reliable quality and performance. Performance evaluation of valve performance testing and should note the following:
1. Water pressure valve in the workplace under the headstock flexible, lightweight, water pressure in the work of testing using a torque wrench torque to open.
2. Valve tightly closed, in the 1.1-fold under the pressure of work does not meet the criteria for leakage or seepage requirements (metal sealed butterfly valve), which requires both sides of the rotation pressure valves were used to detect, and many sluicegate achieve the same effect. Requirements of various calibres, different types of valve manufacturer shall be qualified and have a detection unit with the life span of the load detection headstock. This testing also includes the effect of the valve shaft seal evaluation.
3. Better-off valve flow capacity, in particular, butterfly, butterfly plate flow resistance to small, over-current, to a large effective area. This requires a variety of voice, different types of valves should be the determination of flow resistance coefficient.
4. Body's ability to bear the water pressure should be consistent with the pipeline, that is, open the valve, the valve can withstand the test pressure pipeline requirements.
Third, valves lining and outer anti-corrosion
Is the transmission valve drinking water equipment, body lining must be non-toxic, corrosion-resistant, wear-resistant, smooth flow resistance as small as possible. If the valve plate, bolts and butterfly plates of different materials, it is prone to electrochemical corrosion, corrosion rust generated extending to the sealing surface, affecting the sealing effect of the valve, and valve wells installed in the valve, soak in water to prevent corrosion It is important, therefore, to cover perfect lining to prevent corrosion of the secondary pollution caused by water.
Valves can be taken outside the anti-corrosion after polishing sand-ching, for electrostatic spraying non-toxic anti-corrosion epoxy resin, can also brush 1-2 times Hongdan paint, brush and then twice in Antirust Paint.
Fourth, the valve operation and management
Good gate valve can not only appropriate valve selection, product quality, well construction and installation, but also thoughtful management, in order to play the role of "A Thousand Days Yang-bing, war time" effect. Good operation and management reflected in the following three aspects:
1. Technical details are available
Valve valve factory technical information, including manuals, test the valve after the purchase of single-pass, valve assembly and the location of cards, valve maintenance record. Changes in the streets, the valve should be to update the card to establish a GIS management system.
2. Valve Operation and Management thoughtful
Valve operation and management of quality requirements, including the valve should be closed tightly, the valve rod shaft seal packing string Department does not leak, the valve gate lightweight, well-directed. Valve operation and management of day-to-day operations, including gate valve, single previous approval of the records and operational records of the perfect, periodic testing of the gate valves and other records. Not for long-term operation of the valve off, according to the size of caliber, for the detection of different cycles is necessary. The fault should be found in the maintenance program, in time, especially after the closure of the valve can not open, like a burst pipe repairs as an emergency to deal with.
3. Well valve in good condition
Well the situation of valves including valve masonry well in line with industry standards and design specifications, and covers the road convergence intact, operate the valve hole bit accurate, wells and sewage debris-free, valve-free锈斑surface. Conditions permit, large diameter valves wells wells should be considered long-term convection air can be technical measures. Well on the valve should be inspected regularly, and covers the loss and damage should be dealt with promptly.
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