It should be noted that, due to the different parts of the body thickness, casting ball is more difficult, there should be appropriate measures to ensure the quality of castings. At present there are still some problems casting body, such as the physical and chemical indicators of ductile iron in addition to individual manufacturers, the majority of lax control, and the use of sand casting, a large number of mechanical processing molding. It is suggested that all manufacturers establish a strict quality control system. For the large number of small and medium caliber valves, the model of lost foam molding is adopted. The large-caliber valves are made of resin sand, and the castings should have effective measures to eliminate the internal stress so as to promote the shot blasting and sand removal measures . Casting defects, welding does not allow the way to eliminate, or should take measures to eliminate the internal stress caused by welding repair, a more rigorous test, and to explain to the user. In the inspection also learned that many valve manufacturers casting the use of outsourcing to solve the way to complement each other, the acquisition of outsourcing parts assembly is also a mode of operation, the key is to control the quality of the outer parts should be strict. Of course, the purchase of low-quality components, a little decoration, buckle their own labels, the sale of high prices should be stopped. (2) Stem recommended 2CR13 stainless steel. (3) stem nut recommended cast aluminum brass or cast aluminum bronze, and the nut hardness and strength greater than the stem. 2.3 Valve opening and closing torque In order to manually or machine hoist light, the valve opening and closing torque under the working pressure ≤ 240N · m, that is, a person can operate. Hope that the valve manufacturer first optimize the valve structure design, improve the concentricity of the components, moving parts of the contact surface finish, reducing the opening and closing resistance. If only by variable speed gearbox ratio, increase the number of ways to reduce hoist torque is not ideal. To this end, the means of mechanical processing can not be updated, such as a valve factory in Tianjin in order to improve the quality of machining, a large number of computer-controlled machine tools and machining centers, is commendable. 2.4 Stem packing seal Valve drip leakage often appear in the valve stem packing, especially large-diameter valve due to the maintenance of the filler without water, the price is expensive. Therefore, it is very necessary to improve the durability of the sealing packing. On the one hand, the materials are suitable and not easy to be aged. In the other hand, the wear of the packing is very small. In addition, the valve opening and closing times in the pipe network are limited, so it should not be replaced for several decades. In the study of a Shanghai company for DN100-2600mm various types of valve shaft packing are used three small apron and a plastic protective cover, as long as the valve body, valve cover assembly concentricity assurance, apron contact Surface finish is good, according to the company can guarantee ten years of opening and closing without dripping, this valve shaft seal than the herringbone, flexible graphite packing and other simple, and to reduce the opening and closing torque, etc., is worth learning. 2.5 valve gearbox large diameter valve due to the relationship between opening and closing torque, equipped with a variable speed gearbox. The following points are to be observed in the manufacture of such components: (1) The device has an opening and closing limit device on the housing, and the adjusting nut of such device shall be located in the housing. (2) Cabinet structure as small and firm as possible, if the opening and closing operation over, not to crack the box. (3) Transmission structure design is reasonable, when opening and closing can only drive the valve shaft to rotate, do not make it move up and down; transmission parts bite normally, do not produce separation and slipping with load hoist. (4) Gearboxes are often easily soaked in water in areas with a high groundwater level, so the enclosure should be sealed. Some valve manufacturers to the valve shaft packing housing and variable speed gearbox integral whole, once the packing leaks, it is easy to string into the box, which is worth improvement. 2.6 Valve operating mechanism Water supply pipe network usually buried in the pipeline, the valve is well protection, Ming rod valve is not applicable, the valve opening and closing force from the ground operation, so the valve opening and closing should be set side mortise, hand The wheel is not suitable. Opening and closing directions are required to turn the valve clockwise, order should be clear. The opening and closing of the valve should be marked plate, the plate should be observed from the ground, marking the scale of the plate should be cast in the casting, the brush can be phosphor, so eye-catching. Should not use aluminum and other materials, pointer and opening and closing limit scale should be installed before debugging, and locked. Recently, some manufacturers of small and medium-sized gate valve, also designed the appropriate opening and closing logo plate, which is commendable thing. 2.7 Valve Performance and Testing Valves performance and performance evaluation, we should pay attention to the following points: (1) the valve opening and closing in the working pressure flexible, lightweight, under the working pressure with water pressure torque detection torque. (2) close the valve tightly, at 1 1 times the working pressure, no leakage or drip Meet the standard requirements (metal sealed butterfly valve), which requires pressure on both sides of the valve rotation, respectively, testing, and multiple opening and closing Achieve the same effect. Requires a variety of caliber, different types of valves, should be in the manufacturer and testing qualified units, with the life of the load hoist detection. This test also includes the evaluation of the valve shaft sealing effect. (3) stronger ability to over-flow valve. In particular, butterfly valve, butterfly flow resistance to be small, over-current area to be large. This requires a variety of caliber, different types of valves should also be qualified to test units for the determination of flow resistance coefficient. (4) The pressure bearing capacity of the valve body should be consistent with the pipe, that is, the valve is open, the valve can withstand the test pressure requirements of the pipeline. (5) In the study of manufacturers, individual valve factory can be DN ≤ 600mm valve life, flow resistance, torque and other tests, many valve factory does not have such a means. 2.8 Valve lined with anti-corrosion valve is the product, the appearance of the quality of the product on the one hand the image, on the other hand installed in the valve well, and sometimes soaked in water, and sometimes located in wet space, to prevent corrosion is important. Valve is to transport drinking water equipment, valve lining material must be non-toxic, corrosion-resistant, wear-resistant, to be smooth, so that the flow resistance is small. Especially the butterfly valve butterfly plate, platen, bolts, disc material is very different, prone to electrochemical corrosion, corrosion generated rust extends to the sealing surface, affecting the sealing effect of the valve, so the lining to cover and improve. The ideal approach is the body, bonnet, shot blasting sandbox inside and outside the variable speed transmission, and then for electrostatic spraying non-toxic epoxy resin, you can achieve the above effect. In Tianjin, Shanghai-related companies have a line of small-diameter valves in this area. Most manufacturers inside and outside the body brush anti-rust paint, some paint lead and other harmful substances, does not meet the health requirements. 2.9 Valve manual Valve is a device, the instructions in the equipment factory should indicate the following technical data: Valve Specifications; Model; Working pressure; Manufacturing standards; Body material; Stem material; Sealing material; Packing material; Valve opening and closing direction ; Number of revolutions; Opening and closing of maximum torque under working pressure conditions; Manufacturer's name: Date of manufacture: Weight; Aperture, number of holes, center hole distance of connecting flange, and wish to indicate the length, width and height Control size; indicate the flow resistance coefficient; effective opening and closing times and installation, maintenance precautions and so on. 2.10 Valve procurement National valve manufacturers about more than 2,000, there are more than 100 in Henan Province, some manufacturers only a few people's workshops, so valve manufacturing quality and price sparse large. To this end, it is strongly urged the parties concerned to rectify the valve manufacturing industry, the establishment of quality licensing system, banned counterfeit products. When purchasing the valve, please pay attention to the following points: (1) The purchase of manufacturers not a single, shop around three. (2) The purchase of manufacturers strive to pass the ISO9001 quality system certification of the enterprise, and pay attention to the selected product is passed the quality certification of the product. (3) According to the different purposes of the valve, according to the above discussion of the issues mentioned in the argument, mention good technical requirements. (4) higher quality valves, the price is correspondingly more expensive, should be based on the overall situation of enterprises, the performance-cost ratio selected to meet the needs of business products, can not be a model, the same price. (5) valves in the pipe network, opening and closing is not frequent, but to replace the maintenance, but the economic and social benefits of the loss is greater, so buy better quality, long-term maintenance products are not common desire. If for a variety of reasons, the price will be lowered a little, it should focus on product after-sales service timeliness. (6) Valve is equipment, valve packaging should not be overlooked, small-diameter valves should strive for container transport, large-diameter valve to make the appropriate packaging, to ensure the integrity of the valve in the long-distance transport. Flange plate should be added if necessary, to protect the sealing surface of the material does not major changes. (7) Many of the water company to the procurement of the valve should be properly disassembled inspection, re-pressure test, unqualified products, non-payment measures, has a certain effect, there is no product that is currently free inspection. (8) The valve should be stored in the warehouse, if the valve is not large enough to be placed in the warehouse, the open display should also be placed at the bottom of the drainage, should be covered above, and should never be exposed to the sun and rain. Inspection found that many manufacturers have created a new valve on the open air sun and rain, the valve unit is also true, this must be corrected. 2.11 Valve assembly (1) the valve and the pipe connection In order to facilitate the installation and disassembly of the valve, the valve and pipe connections are generally installed on the side of the retenable retractable, and some companies for DN ≤ 400mm valve with a single disc coupling Live flange) instead of retaining the retractor. Now some valve manufacturers with retainer retractable valve products, is welcome, but the price is higher than the general price of the valve expansion valve is not reasonable, affecting its promotion. (2) the valve should not be premature to enter the construction site Pipeline construction is a long process, the construction person in charge is often worried about the material supply problems started to attach the valve and other ancillary equipment to the site, or even by installing the station one-time shipped to the scene , So that the valve in the construction site in a few months sun and rain, unmanned, the problem is easy to produce. Proposed pipeline construction process, the way to replace double pipe connection, until the pipe construction is completed, the pipe cleaning debris and valve wells (uphole precast reinforced concrete panels are not covered), and then the valve shipped to the site one by one on the installation Bit, and then completed the finishing work wells. Beijing Water Company large diameter valve installation is to take such measures, it is worth learning. (3) After the valve assembly inspection Inspection and supervision personnel at the valve valve site assembly, the assembly should be checked to see whether the drawings meet the requirements of the operation and management needs; opening and closing inspection, opening and closing instructions read and actual opening and closing situation Is consistent; whether the opening and closing rotation consistent with the specification; large diameter pipe should be drilled into the pipe inspection and cleaning sealing surface; and make acceptance records, the establishment of a good valve technology files. 2.12 valve operation and management Whether the valve can be opened and closed well, not only to the appropriate valve selection, product quality, careful 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: technical information is available; valve operation and management well; valve well in good condition. (1) the technical information of the valve Technical information of the valve, including the valve factory instructions; valve after the purchase of qualified single; valve assembly and position card; valve overhaul 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 of valve quality management requirements, including the valve should be closed tight or basic tightness; valve shaft seal packing no leakage; valve opening and closing light, indicating intact. Valve operation and management of daily work, including the valve before the opening and closing operation of the single batch of approval records and records of the operation of the improvement; valve regular weekly inspection of the opening and closing records. For long-term did not operate the valve, according to the size of the caliber, set a different week inspection cycle is necessary, generally only open and close the number of activities turn, if you want to make the complete shutdown operation is careful. The discovery of the fault should be put forward corresponding large and medium-sized repair plan, promptly dealt with, in particular, can not be opened after the closure of the valve should be the same as emergency repair burst pipe explosion. (3) Valve well condition Valve well condition including valve well masonry meets design requirements; manhole cover intact and road surface intact; Operates the valve hole accuracy; Well without debris and sewage; No rust on the valve surface. As the valve shaft is a closed space, easy to form anoxic, carbon dioxide levels rise, once the maintenance staff to go down well before the operation without strong blast, ventilation and other measures, it is easy to endanger human life. In conditions permitting, large-diameter valve wells should consider well-well air convection long-term technical measures as well. For valve wells should be regularly touring, timely treatment of buried problems, for the cover is lost, the damage should be treated as emergency pipe burst emergency treatment. Wuhan Water Supply Company proposed in the network management of the valve as equipment management requirements, the use of GPS satellite positioning system, the establishment of valve well coordinate data to assess the inspection rules and scoring standards, and strengthen management measures worth the same industry reference.
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