Pneumatic check valve general requirements: 1. The specifications and types of pneumatic valves produced should meet the requirements of the pipeline design documents. 2. The model number of the pneumatic valve should be specified according to the national standard numbering requirements. If it is a corporate standard, the description of the model should be specified. 3. Pneumatic valve working pressure requires ≥ working pressure of the pipeline. Under the premise of not affecting the price, the working pressure of the valve can be greater than the actual working pressure of the pipeline; any side of the pneumatic valve closing condition should be able to withstand 1.1 times Valve pressure value without leakage; valve open conditions, the valve body should be able to withstand the requirements of double the valve pressure. 4. Pneumatic valve manufacturing standards should be based on the national standard number. If it is a corporate standard, an enterprise document should be attached to the procurement contract. Pneumatic check valve Pneumatic check valve material: 1. The material of the valve body should be mainly ductile iron, and indicate the actual physical and chemical test data of the grade and cast iron. 2. Stem material, stainless steel valve stem (2CR13), large-diameter valve should also be stainless steel embedded valve stem. 3, nut material, cast aluminum brass or cast aluminum bronze, and hardness and strength are greater than the valve stem. 4, stem bushing material, its hardness and strength should not be greater than the stem, and under water immersion conditions with the stem, the valve body does not form electrochemical corrosion. 5, the sealing surface material: 1 Different types of pneumatic valves, different sealing methods and material requirements; 2 Ordinary wedge gate valve, copper ring material, fixing method, grinding method should be explained; 3 soft sealing gate valve, physicochemical and sanitary inspection data of valve plate lining rubber material; 4 The butterfly valve shall indicate the material of the sealing surface on the valve body and the material of the sealing surface on the butterfly plate; their physical and chemical testing data, especially the hygienic requirements, anti-aging properties and abrasion resistance of the rubber, must not be mixed with reclaimed rubber. 6, valve shaft packing: 1 Because the pneumatic valve in the pipe network is usually open and closed infrequently, the filler is required to be inactive for several years, and the filler is not aged, and the sealing effect is maintained for a long time; 2 Valve shaft packing should also withstand the frequent opening and closing, the sealing effect is good; 3 In view of the above requirements, the valve shaft packing is not intended to be changed for life or replaced in more than ten years; 4 If the packing needs to be replaced, the pneumatic valve design should take into account measures that can be replaced in case of water pressure. Gearbox: 1, the box material and internal and external corrosion requirements consistent with the valve body principle. 2. The box should have sealing measures. After the box is assembled, it can withstand the immersion of 3 meters of water column. 3. The opening and closing limit device on the box shall have the adjusting screw cap inside the box or outside the box, but special tools are required for operation. 4. The transmission structure is reasonable in design. When the valve is opened and closed, it can only drive the valve shaft to rotate. It does not make the valve shaft move up and down, and the transmission parts are suitable for biting. It does not produce separation and skidding when the load is opened and closed. 5, the transmission housing and valve shaft seal can not be connected into a leak-free overall, otherwise there should be a reliable anti-string leakage measures. 6, there is no debris in the box, the gear bite should have grease protection. Pneumatic check valve operating mechanism: 1. The opening and closing direction of the pneumatic valve should be closed clockwise. 2, due to the pneumatic valve in the pipe network, often manual opening and closing, opening and closing the number of rotation should not be too much, that is, large-diameter valves should also be within 200-600 rpm. 3, in order to facilitate a person's opening and closing operations, in the pipeline pressure conditions, a large opening and closing torque should be 240N-m. 4. The opening and closing operation end of the pneumatic valve shall be a square bracket with standardized dimensions and facing the ground so that people can directly operate from the ground. Wheeled valves are not suitable for underground pipe networks. 5, the opening and closing of the pneumatic valve display panel 1 The scale line for opening and closing the pneumatic valve shall be cast on the cover of the gearbox or on the outer surface of the display panel after the direction of conversion. The surface shall be facing the ground. The phosphor of the scale shall be brushed to show the eye catching. 2 indicates the material of the plate pin can be used in the case of better management of stainless steel plate, otherwise painted steel plate, do not use aluminum skin; 3 indicates that the disk pin is eye-catching and firmly fixed. Once the opening and closing adjustment is accurate, it should be locked with a rivet. 4.6 If the pneumatic valve is buried deep and the distance between the operating mechanism and the display panel is ≥1.5m from the ground, an extension rod facility shall be provided and it shall be fixed firmly so that people can observe and operate from the ground. In other words, the valves in the pipe network are opened and closed, so it is not suitable to go downhole. Pneumatic check valve performance testing 1. When a valve is manufactured in batches, an authoritative institution should be commissioned to perform the following performance tests: 1 The opening and closing moment of the valve under working pressure; 2 Under the working pressure condition, it can ensure the tight and continuous opening and closing times of the valve; 3 Check the flow resistance coefficient of the valve under the condition of pipeline water supply. 2, the valve should be tested before leaving the factory: 1 When the valve is in the open condition, the valve body should withstand the internal pressure detection twice the valve work pressure value; (2) Under the closed condition of the valve, both sides shall bear a valve pressure value of 1.1 times, no leakage; but the metal-sealed butterfly valve shall not exceed the relevant requirements. Internal and external anti-corrosion of pneumatic check valve 1. Inside and outside of the valve body (including the variable speed transmission case), the first step is to remove the rust by shot blasting, and try to electrostatically spray powder-like non-toxic epoxy resin with a thickness of 0.3 mm or more. When large-scale valves are difficult to spray with non-toxic epoxy resin electrostatically, they should also be painted and sprayed with similar non-toxic epoxy paints. 2. The interior of the valve body and all parts of the valve plate are required to be fully preserved. On the one hand, immersing in water will not rust, and no electrochemical corrosion will occur between the two metals. On the other hand, the smooth surface will reduce the over-water resistance. 3. The sanitary requirements of the epoxy resin or paint in the valve body shall be tested by the relevant authorities. Chemical physical properties should also meet relevant requirements. Pneumatic check valve packaging and transportation 1. Both sides of the valve should be provided with a light blocking plate for solid sealing. 2. The medium and small caliber valves should be bundled with straw ropes and transported in containers. 3, large-diameter valves also have simple wooden frame solid packaging, in order to avoid damage during transportation. Pneumatic check valves are valves that are driven by compressed air. Pneumatic valve procurement only clear specifications, categories, work pressure to meet the procurement requirements of the gas method, in the current market economy environment is not perfect. Because pneumatic valve manufacturers compete for products, each of them carries out different innovations under the concept of a unified pneumatic valve, forming their own corporate standards and product characteristics. Therefore, it is very necessary to propose technical requirements in detail when purchasing pneumatic valves, and to obtain consensus through coordination with manufacturers. This type of valve should generally be installed horizontally in the pipeline.
