Valve is a fluid conveying system control components, with cut-off, regulation, diversion, to prevent countercurrent, voltage, shunt or overflow pressure relief functions. Valves for fluid control systems, ranging from the simplest cut-off valves to the most complex automatic control systems, have a wide variety and specifications. Valves can be used to control the flow of various types of fluids, such as air, water, steam, various corrosive mediums, mud, oil, liquid metals and radioactive media.
Valve According to the material is also divided into cast iron valves, cast steel valves, stainless steel valves, chromium-molybdenum steel valves, chromium-molybdenum vanadium steel valves, duplex steel valves, plastic valves, non-standard custom-made valve materials.
Valve purchase should pay attention to what technical requirements
1 Valve specifications and categories, should conform to the requirements of piping design documents 1.1 The type of valve should be indicated according to the national standard number requirements.
If the enterprise standard, should indicate the model of the relevant instructions.
1.2 Valve work pressure, requirements ≥ pipe work pressure, without affecting the price of the premise, the valve can withstand the pressure should be greater than the actual pipe pressure, the valve closed on either side should be able to withstand 1.1 times times the valve pressure value, but not leakage; valve opening condition, the valve body should be able to withstand twice times the requirements of valve pressure.
1.3 Valve manufacturing standards, should indicate the basis of the national standard number, if the enterprise standards, procurement contracts should be accompanied by enterprise documents
2 Choice valve Material 2.1 valve material, because the gray iron pipe is not recommended gradually, the valve body material should take the ductile iron as the main, and indicate the grade and the actual physical and chemical examination data of the casting.
2.2 Stem material, to stainless steel stem (2CR13), large diameter valves should also be stainless steel inlay the stem.
2.3 Nut material, using cast aluminum brass or cast aluminum bronze, and hardness and strength are greater than the stem
2.4 Stem bushing material, its hardness and strength should not be greater than the stem, and in the water immersion condition and valve stem, valve body does not form electrochemical corrosion. 2.5 Sealing surface Material ① valve category, sealing method and material requirements are different; ② ordinary wedge gate valve, copper ring material, fixed mode, grinding mode should be explained; ③ Soft sealed gate valve, valve plate lining material physical and chemical and sanitary testing data; ④ butterfly valve should be marked with the sealing surface material on the valve body and the sealing surface material on the butterfly board.
, their physical and chemical testing data, especially the hygienic requirements of rubber, anti-aging properties, wear-resistant properties, usually use of ding-eye rubber and EPDM rubber, etc., is strictly prohibited with recycled plastic. 2.6 Valve SHAFT FILLER ① because of the valve in the pipe net, it is usually not open and close frequently, requirements of fillers in a few years inactive, fillers are not aging, long-term to maintain the sealing effect; ② valve shaft fillers should also withstand frequent opening and closing, the sealing effect of good; ③ in view of the above requirements, valve shaft filler strive for a lifetime not to change or more than 10 years not to replace
If the ④ filler needs to be replaced, the valve design should consider the measures of replacing under the condition of hydraulic pressure.
3 Transmission box 3.1 box material and internal and external anti-corrosion requirements and valve body principle.
3.2 box should be sealed measures, the box assembly can withstand 3 meters water column condition immersion.
3.3 The opening and closing limit device of the box, the adjusting nut shall be in the box.
3.4 Transmission structure design reasonable, open and close can only drive the valve shaft rotation, not to move up and down, the transmission parts of the appropriate bite, do not produce with load when the separation skid.
3.5 Transmission box and valve shaft seal can not be connected to the whole without leakage.
3.6 Box body without sundries, gear bite parts should be grease protection.
4 valve operating mechanism 4.1 valve operation of the opening and closing direction, should be closed clockwise.
4.2 As a result of the valve in the pipe network, it is often artificially open and close, the number should not be too much, that is, large diameter valves should also be in 200-600 rpm.
4.3 In order to facilitate the opening and closing operation of a person, under the pressure of the pipeline, the maximum hoist torque should be 240m-m. 4.4 Valve Opening and closing operation end should be square tenon, and size standardization, and facing the ground, so that people from the ground can directly operate.
Valves with roulette do not apply to underground piping networks.
4.5 Display plate of valve opening and closing degree The tick-marks of the degree of ① valve should be cast on the casing of the display plate after the gearbox cover or the direction of conversion. All face the ground, tick-mark line brush fluorescent powder, in order to show eye-catching; ② indicating that the material of the needle in the management of a better situation can be used stainless steel plate, otherwise paint the steel plate, do not use aluminum production; ③ indicating disk needle eye-catching,
Fixed firmly, once the opening and closing adjustment is accurate, the rivet should be locked. 4.6 If the valve is buried deeper, operating mechanism and display disk from the ground distance ≥15m, should have lengthened bar facilities, and fixed firmly, so that people from the ground observation and operation.
In other words, the pipe network in the valve opening and closing operation, is not suitable for downhole operations.
5 Valve Performance Test 5.1 Valves A specification batch manufacture, authoritative institutions should be entrusted with the following performance testing: ① valve in the state of the operating pressure of the opening and closing moment; ② in the condition of pressure, can ensure that the valve closed close to the number of consecutive opening and closing times; ③ valve in the pipeline water condition of the flow resistance coefficient of detection.
5.2 Valve should be tested before the factory: ① valve in the open condition, the valve body should withstand valve pressure value of twice times the internal pressure detection; ② valve in the closed state, both sides under 11 times times the valve pressure value, no leakage, but the metal sealed butterfly valve, leakage value is not more than the relevant requirements