Valves play a vital role in fluid piping systems, not only as control elements, but also for isolating equipment, regulating flow, preventing backflow, and regulating and relieving pressure. Selecting the right valve is critical to the proper operation of a piping system. The following is a detailed analysis of the characteristics of the valve, selection steps and basis, designed to help readers better understand the selection and application of valves.
First, the characteristics of the valve
Use characteristics:
These characteristics determine the valve’s main function and scope of application. Including the category of the valve (such as closed-circuit valves, regulating valves, safety valves, etc.), product type (such as gate valves, Globe valves, butterfly valves, ball valves, etc.), the main parts of the material (such as the valve body, bonnet, valve stem, valve valve valve, sealing surfaces), and transmission methods.
Structural characteristics:
These characteristics determine the valve installation, repair and maintenance methods. Including the structural length and overall height of the valve, the connection with the pipeline (such as flange connection, threaded connection, welding, etc.), the form of the sealing surface (such as inlays, surfacing, etc.) and the form of the valve stem structure (such as rotating rod, lifting rod) and so on.
Second, the valve selection steps
Clear use and working conditions:
First of all, you need to clarify the use of the valve in the equipment or device, and determine its working conditions, such as the applicable medium, working pressure and working temperature.
Determine the pipeline connection parameters:
Next, determine the nominal diameter of the pipe connected to the valve and the connection method, such as flange, threaded or welded.
Select the operation mode:
According to the operation requirements, select the transmission mode such as manual, electric, pneumatic or hydraulic.
Determine the material:
According to the characteristics of the medium transported by the pipeline, select the appropriate valve shell and internal parts materials, such as gray cast iron, carbon steel, stainless steel, etc.
Select the valve type and type:
According to the use and working conditions, select the appropriate type of valve (such as closed-circuit valves, regulating valves, etc.) and type (such as gate valves, globe valves, ball valves, etc.).
Determine the valve parameters:
For automatic valves, it is necessary to determine the allowable flow resistance, discharge capacity and other parameters, and determine the nominal diameter of the pipeline and the diameter of the valve seat hole.
Determine the geometric parameters:
According to the installation requirements, determine the structure length of the valve, flange connection form and size and other geometric parameters.
Utilize available information:
Check the valve catalog and samples, select the appropriate valve products.
Third, the valve selection basis
Use and mode of operation:
According to the use of the valve, working conditions and manipulation and control mode to select the appropriate valve.
Medium characteristics:
Consider the nature of the medium, such as working pressure, operating temperature, corrosive properties and whether it contains solid particles or toxic, flammable and explosive properties.
Fluid characteristics requirements:
According to the requirements of the valve fluid characteristics, such as flow resistance, discharge capacity, flow characteristics and sealing grade and other selection of suitable valves.
Installation and size requirements:
Consider the installation size of the valve and the external dimensions of the requirements, such as nominal diameter, connection, connection size and weight limitations.
Additional requirements:
Additional requirements for the reliability of the valve, service life and performance of electric devices.
Fourth, the selection of valves should follow the principle of
Cut-off and open medium with the valve:
For the need to cut off and open the medium of the occasion, usually choose a smaller flow resistance of the straight-through valve.
Control flow with the valve:
For the need to control the flow of occasions, choose easy to adjust the flow of valves, such as globe valves or rotary valves (such as plug valves, butterfly valves, ball valves).
Valves for reversing and diverting flow:
For the need to divert the flow of occasions, select the valve with multiple channels, such as plug valves or ball valves.
Valves for media with suspended particles:
When the medium with suspended particles, select the closing member can slide along the sealing surface and have a wiping effect of the valve, such as ball valves or plug valves.
Valves in the piping system is indispensable, whether in the petroleum, chemical industry or other fields, the application of valves are extremely wide. Correct selection of valves is essential to ensure the normal operation and safety of the piping system. We hope that the above will help you better understand the selection and application of valves.
Selection and Characterization of Valves in Fluid Piping Systems
