Proper selection of a suitable inlet valve requires attention to the following points:
進口閥門主要是指來自國外的品牌的閥門，主要是歐美，日本品牌，比較多使用的有以下種類：進口截止閥，進口調節閥，進口蝶閥， 進口減壓閥，進口電磁閥等，而且產品的口徑，壓力，溫度，材質，連接方式，操作方式等各種參數很多，需要根據實際需要， 產品的特征來選擇合適的閥門；本文結合獲得廣泛客戶好評的德國品牌德國洛克DE LOCKE，分析下進口閥門的具體選型：
Imported valves mainly refer to the valves of foreign brands, mainly European, American and Japanese brands, which are mostly used in the following categories: imported stop valve, imported regulating valve, imported butterfly valve, imported pressure reducing valve, imported solenoid valve, etc. Moreover, there are many parameters of the product, such as caliber, pressure, temperature, material, connection mode, operation mode, etc., which need to be based on the actual needs, This paper analyzes the specific selection of the following imported valves based on the German brand Locke de Locke, which is widely praised by customers
1、 The characteristics of the imported valve are service characteristics and structural characteristics
（1）.Service characteristics of inlet valve
The service characteristics determine the main service performance and scope of use of the valve, which include: Valve category (closed-circuit valve, regulating valve, safety valve, etc.); product type (gate valve, globe valve, butterfly valve, ball valve, etc.); material of main parts of the valve (valve body, bonnet, stem, disc, sealing surface); valve transmission mode, etc.
（2） Structural characteristics
The structural characteristics determine some structural characteristics of valve installation, maintenance and other methods. The structural characteristics include: the structural length and overall height of the valve, the connection form with the pipeline (flange connection, thread connection, clamp connection, external thread connection, welding end connection, etc.); the form of sealing surface (insert ring, thread ring, overlay welding, spray welding, valve body); the valve Rod structure (rotating rod, lifting rod), etc.
（2）、 To select a valve
Define the purpose of the valve in the equipment or device, and determine the working conditions of the valve: applicable medium, working pressure, working temperature, etc.; for example, if you want to select a German Locke de Locke stop valve, confirm that the medium is steam, the working principle is 1.3mpa, and the working temperature is 200 ℃.
Determine the nominal diameter and connection method of the pipeline connected with the valve: flange, thread, welding, etc.; for example, select the inlet stop valve, and confirm that the connection method is flange.
Determine the way to operate the valve: manual, electric, electromagnetic, pneumatic or hydraulic, electro-hydraulic linkage, etc.; for example, select the manual stop valve.
According to the medium, working pressure and working temperature transmitted by the pipeline, the materials of the shell and internal parts of the selected valve are determined: cast steel, carbon steel, stainless steel, alloy steel, stainless and acid resistant steel, gray cast iron, malleable cast iron, nodular cast iron, copper alloy, etc.; for example, the material of cast steel selected for the stop valve.
Select the type of valve: closed-circuit valve, regulating valve, safety valve, etc;
Determine the valve type: gate valve, stop valve, ball valve, butterfly valve, throttle valve, safety valve, pressure reducing valve, steam trap, etc;
Determine the parameters of the valve: for the automatic valve, determine the allowable flow resistance, discharge capacity, back pressure, etc. according to different needs, and then determine the nominal diameter of the pipeline and the diameter of the valve seat hole;
Determine the geometric parameters of the selected valve: structural length, flange connection form and size, size of valve height direction after opening and closing, size and quantity of bolt holes for connection, overall size of the valve, etc;
Use existing data: valve product catalog, valve product samples, etc. to select appropriate valve products.
（3）、 Basis for valve selection
The purpose, working condition and control mode of the selected valve;
工作介質的性質：工作壓力、工作溫度、腐蝕性能，是否含有固體顆粒，介質是否有毒，是否是易燃、易爆介質，介質的黏度等；比如想選擇德國洛克DE LOCKE的進口電磁閥，介質和環境易燃、易爆，一般要選擇防爆電磁閥；再比如要選擇德國洛克DE LOCKE的球閥，介質含有固體顆粒，一般要選擇V型的硬密封球閥。
Nature of working medium: working pressure, working temperature, corrosion performance, whether it contains solid particles, whether the medium is toxic, whether it is inflammable and explosive medium, viscosity of the medium, etc.; for example, if you want to choose the imported solenoid valve of Locke de Locke in Germany, the medium and environment are inflammable and explosive, generally you need to choose the explosion-proof solenoid valve; for example, you need to choose Locke de in Germany Locke ball valve, the medium contains solid particles, generally V-type hard seal ball valve should be selected.
Requirements for valve fluid characteristics: flow resistance, discharge capacity, flow characteristics, sealing grade, etc;
Installation dimension and boundary dimension requirements: nominal diameter, connection mode and connection dimension with pipeline, boundary dimension or weight limit, etc;
Additional requirements for reliability, service life of valve products and explosion-proof performance of electric devices (attention shall be paid to the following additional parameters when selecting parameters: operation method, maximum and minimum flow requirements, pressure drop of normal flow, pressure drop when closing, maximum and minimum inlet pressure of valve) if the valve is to be used for control purposes.
According to the basis and steps of selecting valves mentioned above, it is necessary to have a detailed understanding of the internal structure of various types of valves when selecting valves reasonably and correctly, so as to make a correct choice for the preferred valves.
The final control of the pipeline is the valve. The opening and closing parts of the valve control the flow direction of the medium in the pipeline. The shape of the valve flow path makes the valve have certain flow characteristics. This must be taken into account when selecting the valve suitable for installation of the pipeline system.
Summarize and select several key elements: determine which function valve to select, confirm the temperature and pressure of medium, confirm the flow and required caliber of valve, confirm the material and operation mode of valve.