How to buy a good and suitable valve introduction

The valve is a control component in the fluid delivery system with a variety of different functions such as cut-off, regulation, diversion, backflow prevention, regulation, shunting or overflow relief. Therefore, it can be applied to many fields and its use is also very extensive.
 
     It can be used to control the flow of various types of fluids such as air, water, steam, various corrosive media, mud, oil, liquid metal and radioactive media...
 
     According to different materials, the valves can be divided into cast iron valves, cast steel valves, stainless steel valves, chrome molybdenum steel valves, chrome molybdenum vanadium steel valves, duplex steel valves, plastic valves, non-standard custom valves and so on.
 
     The prices of valves of different materials and different uses are different. There are more than ten pieces, dozens of pieces, more than one hundred, several hundred, and thousands of them. So what do we need to know before purchasing a valve? How can I choose the right valve?
 
     First, it is necessary to clarify the purpose of the valve in the equipment or device, determine under what conditions the valve can work, what is the applicable medium, how much the working pressure and temperature are, etc.;
 
     Secondly, understand the nominal diameter and connection method of the pipe connected to the valve: flange, thread, welding, etc.;
 
     Third, determine the way to operate the valve: manual, electric, electromagnetic, pneumatic or hydraulic, electro-hydraulic linkage, etc.;
 
     Fourth, according to the medium, working pressure and working temperature of the pipeline, the materials of the casing and the inner part of the selected valve are determined: cast steel, carbon steel, stainless steel, alloy steel, stainless acid-resistant steel, copper alloy, etc.;
 
     Fifth, select the type of valve, determine the valve type, parameters and geometric parameters of the selected valve, such as: structural length, flange connection form and size, dimension of the valve height direction after opening and closing, bolt hole size of the connection and Quantity, size of the entire valve, etc.
 
     In addition, when selecting the head valve, sometimes it is necessary to select not only the above several, but also the basis for selecting the valve:
 
     First, it is necessary to clarify the purpose of the selected valve, the working conditions and the control method. The valve specifications and categories should meet the requirements of the pipeline design document, and the working pressure should be greater than or equal to the working pressure of the pipeline.
 
     Second, understand 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.
 
     Third, understand the requirements for valve fluid characteristics: flow resistance, discharge capacity, flow characteristics, sealing grade, etc.
 
     Fourth, clear installation dimensions and dimensions: nominal diameter, connection to the pipe and connection size, dimensions or weight restrictions.
 
     Fifth, some additional requirements for the reliability of the valve product, the service life and the explosion-proof performance of the electric device.