Imported valves mainly refer to valves from foreign brands, mainly European and American brands. The more representative brands are British Spirax Sarco, German Lite LIT, Japan Kitazawa KITZ, American Ritz RETZ, etc. The product types mainly include imported ball valves, imported shut-off valves, imported regulating valves, imported butterfly valves, imported pressure reducing valves, imported solenoid valves, etc., and the product has many parameters such as caliber, pressure, temperature, material, connection method and operation mode. Need to choose the right valve according to the actual needs and characteristics of the product; this article combines the German brand German Lite LIT, which has been well received by customers, to analyze the specific selection of imported valves:
First, the characteristics of imported valves have use characteristics and structural characteristics
1. Imported valve use characteristics
The characteristics of the valve are used to determine the main performance and scope of use of the valve. The characteristics of the valve are: the type of valve (closed valve, regulating valve, safety valve, etc.); product type (gate valve, globe valve, butterfly valve, ball valve, etc.); valve Main parts (body, valve cover, valve stem, valve disc, sealing surface); valve transmission method.
2, structural characteristics
The structural characteristics determine some structural characteristics of the valve installation, repair, maintenance and other methods. The structural characteristics are: the structural length and overall height of the valve, and the connection form with the pipe (flange connection, threaded connection, clamp connection, external Threaded connection, welded end connection, etc.); the form of the sealing surface (insert ring, thread ring, surfacing, spray welding, valve body); valve stem structure (rotating rod, lifting rod).
Second, the steps to choose a valve
Defining the use of the valve in the equipment or device, determining the working conditions of the valve: applicable medium, working pressure, working temperature, etc.; for example, want to choose a German Lite LIT shut-off valve, confirm that the medium is steam, the working principle is 1.3Mpa, the working temperature is 200 °C.
Determine the nominal diameter and connection method of the pipe connected to the valve: flange, thread, welding, etc.; for example, select the inlet shut-off valve and confirm that the connection method is flanged.
Determine the way to operate the valve: manual, electric, electromagnetic, pneumatic or hydraulic, electro-hydraulic linkage, etc.; for example, the manual shut-off valve is selected.
Determine the material of the casing and internal parts of the selected valve according to the medium, working pressure and working temperature delivered by the pipeline: cast steel, carbon steel, stainless steel, alloy steel, stainless acid-resistant steel, gray cast iron, malleable cast iron, ductile iron, copper Alloys, etc.; such as cast steel material selected by the stop valve.
Choose the type of valve: closed-circuit valve, regulating valve, safety valve, etc.;
Determine the type of valve: gate valve, globe valve, ball valve, butterfly valve, throttle valve, safety valve, pressure reducing valve, steam trap, etc.;
Determine the parameters of the valve: For automatic valves, determine the allowable flow resistance, discharge capacity, back pressure, etc. according to different needs, and then determine the nominal diameter of the pipe and the diameter of the seat hole;
Determine the geometric parameters of the selected valve: structural length, flange connection form and size, dimensions of the valve height direction after opening and closing, bolt hole size and number of connections, overall valve size, etc.
Use the existing information: valve catalog, valve product samples, etc. to select the appropriate valve products.
Third, the basis for selecting the valve
The purpose of the selected valve, the operating conditions and the control method;
The nature of the working medium: working pressure, working temperature, corrosion performance, whether it contains solid particles, whether the medium is toxic, whether it is flammable, explosive medium, viscosity of the medium, etc.; for example, choose the imported solenoid valve of German Lite LIT, medium And the environment is flammable, explosive, generally choose the explosion-proof solenoid valve; for example, to choose the German Lite LIT ball valve, the medium contains solid particles, generally choose V-type hard-sealed ball valve.
Requirements for valve fluid characteristics: flow resistance, discharge capacity, flow characteristics, seal rating, etc.;
Installation size and dimensions: nominal diameter, connection to the pipe and connection size, dimensions or weight restrictions;
Additional requirements for valve product reliability, service life and explosion-proof performance of electric drives (note when selecting parameters: If the valve is to be used for control purposes, the following additional parameters must be determined: method of operation, maximum and minimum flow requirements , normal flow pressure drop, pressure drop when closed, maximum and minimum inlet pressure of the valve).
According to the above-mentioned basis and steps of selecting the valve, the internal structure of each type of valve must be well understood in order to properly and correctly select the valve, so that the correct choice can be made for the preferred valve.
The final control of the pipe is the valve. The valve opening and closing member controls the flow direction of the medium in the pipe. The shape of the valve flow path allows the valve to have a certain flow characteristic, which must be taken into account when selecting the valve suitable for installation of the pipe system.
In summary, select several major factors: determine the valve to be used, confirm the temperature and pressure of the medium, confirm the flow of the valve and the required diameter, and confirm the material and operation mode of the valve;
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