Introduction to the major elements that we need to know when purchasing valves

At present, all valve manufacturers are carrying out different innovations, and their respective companies have innovated and perfected the valves. Therefore, we should thoroughly submit technical requirements when purchasing valves, and understand the major factors that need to be paid attention to when purchasing valves. A consensus with the manufacturer. What should we pay attention to when purchasing valves? The statistics are as follows:

1. General requirements 1.1 Valve specifications and categories should meet the requirements of the piping design documents. 1.2 The model number of the valve should indicate the national standard number requirement. If it is an enterprise standard, the relevant description of the model number should be indicated. 1.3 The working pressure of the valve requires ≥ the working pressure of the pipeline. Under the premise of not affecting the price, the working pressure of the valve should be greater than the actual working pressure of the pipeline; any side under the closed condition of the valve should be able to withstand 1.1 times the working pressure of the valve. The value does not leak; the valve body should be able to withstand twice the valve pressure requirements when the valve is open. 1.4 The valve manufacturing standard shall state the national standard number on which the instrument is based. If it is an enterprise standard, the enterprise contract shall be attached to the procurement contract.

2. Valve quality 2.1 The body material should be made of ductile iron, and the actual physical and chemical test data of the grade and cast iron should be indicated. 2.2 Stem material, stainless steel valve stem (2cr13), large diameter valve should also be stainless steel embedded valve stem. 2.3 Nut material, cast aluminum brass or cast aluminum bronze, and the hardness and strength are greater than the valve stem. 2.4 Stem bushing material, its hardness and strength should not be greater than the valve stem, and does not form electrochemical corrosion with the valve stem and valve body under water immersion conditions. 2.5 Sealing surface material 1 different valve types, sealing method and material requirements are different; 2 ordinary wedge type gate valve, copper ring material, fixing method, grinding method should be explained; 3 soft sealing gate valve, valve plate lining material Physical and chemical and sanitary testing data; 4 butterfly valve should indicate the sealing surface material on the valve body and the sealing surface material on the butterfly plate; their physical and chemical testing data, especially the hygienic requirements of rubber, anti-aging performance, wear resistance; Recycled rubber is strictly prohibited for use in clear rubber and EPDM rubber. 2.6 Valve shaft packing 1 Due to the valve in the pipe network, the opening and closing is usually infrequent. The packing is required to be inactive for several years, the packing is not aging, and the sealing effect is maintained for a long time. 2 The valve shaft packing should also be subjected to frequent opening and closing. 3, in view of the above requirements, the valve shaft packing is intended to be replaced for life or not replaced for more than ten years; 4 If the packing needs to be replaced, the valve design should consider measures to replace it under water pressure.

3. Valve operating mechanism 4.1 The opening and closing direction of the valve should be closed clockwise. 4.2 Due to the valve in the pipe network, it is often manually opened and closed, the number of opening and closing rotations should not be too much, that is, the large diameter valve should also be within 200-600 rpm. 4.3 In order to facilitate the opening and closing operation of a person, the maximum opening and closing torque should be 240n-m under the condition of pipeline pressure. 4.4 The valve opening and closing operation end shall be square and standardized in size and facing the ground so that people can operate directly from the ground. Valves with discs are not suitable for underground pipe networks. 4.5 The degree of opening and closing of the valve indicates that the scale line of the opening and closing degree of the valve should be cast on the outer cover of the display panel after the gearbox cover or the direction of the change, and the surface of the dial should be painted with phosphor on the scale line to show eye-catching; 2The material of the disc needle can be used in the case of better management. Stainless steel plate is used. Otherwise, the painted steel plate should not be made of aluminum. 3 The indicator needle is conspicuous and firmly fixed. Once the opening and closing adjustment is accurate, the rivet should be used. locking. 4.6 If the valve is buried deep and the operating mechanism and display panel are ≥1.5m away from the ground, the extension pole shall be provided and fixed firmly so that people can observe and operate from the ground. That is to say, the valve opening and closing operation in the pipe network is not suitable for downhole operation.

4. Valve performance test 5.1 When a certain specification of the valve is mass-produced, the authoritative mechanism should be entrusted to carry out the following performance tests: 1 The opening and closing torque of the valve under the working pressure condition; 2 Under the working pressure condition, the valve can be closed tightly. The number of consecutive opening and closing times; 3 The detection of the flow resistance coefficient of the valve under the condition of pipeline water delivery. 5.2 The valve should be tested before leaving the factory: 1 When the valve is open, the valve body should withstand the internal pressure detection of the valve pressure value twice; 2 Under the closed condition of the valve, the two sides respectively withstand 1.1 times the valve pressure value , no leakage; but the metal sealed butterfly valve, the leakage value is not greater than the relevant requirements.

5. Internal and external anti-corrosion of the valve 6.1 Valve body (including variable speed transmission box) inside and outside, first should be shot blasting to remove rust, and strive to electrostatically spray powdery non-toxic epoxy resin, the thickness of 0.3mm or more. When a large valve is electrostatically sprayed with a non-toxic epoxy resin, it should be brushed and sprayed with a similar non-toxic epoxy paint. 6.2 The interior of the valve body and the various parts of the valve plate are required to be fully anti-corrosive. On the one hand, it will not rust when immersed in water, and no electrochemical corrosion will occur between the two metals. On the other hand, the smooth surface will reduce the water resistance. 6.3 The hygienic requirements for epoxy resin or paint for corrosion protection in the valve body shall be tested by the relevant authority. Chemical and physical properties should also meet the relevant requirements.

6. Valve packaging and transportation 7.1 There should be light blocking plates on both sides of the valve to seal. 7.2 Medium and small-diameter valves should be bundled with straw ropes and transported by container. 7.3 Large diameter valves are also available in solid wood frame solid packaging to avoid damage during transportation.

7. Factory instruction The valve is the equipment. The following relevant data should be marked in the factory manual: valve specification, model, working pressure, manufacturing standard, valve body material, valve stem material, sealing material, valve shaft packing material, valve stem bushing material Internal and external anti-corrosion material; operation starting direction; number of revolutions; opening and closing torque under working pressure; manufacturer name; date of manufacture; factory number; weight; aperture of the connecting flange, number of holes, center hole distance; The method indicates the overall length, width and height of the control size; valve flow resistance coefficient; effective opening and closing times; relevant data of the factory inspection of the valve and precautions for installation and maintenance.

    The above factors that should be paid attention to when purchasing, I hope to play a role in purchasing the valve.