Today, more and more valves on the market, the type of valve is particularly complex, the structure and material are also different, the valve selection for the condition of long-period operation of the device is essential. The improper selection of valves and users do not understand the valve, are the source of accidents and security threats. In today's social industry, the demand for valve products is more and more widespread, and users should have further understanding of the valve and other aspects of knowledge.
Valve characteristics generally have two kinds, the use of features and structural characteristics.
Features: It determines the main use of the valve performance and scope of use, the use of the valve characteristics are: the type of valve (closed circuit valves, regulating valves, safety valves, etc.); product type (gate valve, globe valve, butterfly valve, ball valve, etc.) ; Valve main components (body, bonnet, valve stem, valve flap, sealing surface) of the material; valve transmission and so on.
Structural characteristics: It determines the structural characteristics of the valve installation, maintenance, maintenance and other methods, are structural features are: the length of the valve structure and the overall height of the connection with the pipeline (flange connection, screw connection, clamp connection, External thread connection, welding end connection, etc.); sealing surface form (set ring, thread ring, surfacing, spray welding, valve body); Stem structure (rotary rod, lifting rod) and so on.
Valve selection steps:
1. Clear the valve in the device or device uses to determine the working conditions of the valve: the medium, working pressure, working temperature and so on.
2. Determine the nominal diameter of the pipe connected with the valve and the connection method: flange, thread, welding, ferrule, quick loading and so on.
3. Determine the way to operate the valve: manual, electric, electromagnetic, pneumatic or hydraulic, electrical linkage or electro-hydraulic linkage.
4. According to the pipeline transportation of medium, working pressure, working temperature to determine the choice of the valve housing and internal parts of the material: gray iron, malleable iron, ductile iron, carbon steel, alloy steel, stainless steel, copper alloy.
5 Select the type of valve: closed-circuit valves, regulating valves, safety valves and so on.
6. Determine the type of valve: gate valve, globe valve, ball valve, butterfly valve, throttle, safety valve, pressure reducing valve, steam trap and so on.
7. Determine the valve parameters: For automatic valves, according to the different needs of the first to allow flow resistance, discharge capacity, back pressure, and then determine the nominal diameter of the pipe and the diameter of the seat hole.
8. Determine the geometric parameters of the selected valve: the length of the structure, the form and size of the flange connection, the size of the valve in the height direction after opening and closing, the size and number of bolt holes to be connected, the overall dimensions of the valve and so on.
9. Use existing information: valve product catalog, valve product samples to choose the right valve products.
Valve selection basis:
1. The choice of the use of the valve, the use conditions and operating conditions control mode.
2. The nature of the working medium: working pressure, working temperature, corrosion performance, whether it contains solid particles, the media is toxic, whether it is flammable, explosive media, medium viscosity and so on.
3 on the valve fluid characteristics of the requirements: flow resistance, emission capacity, flow characteristics, sealing grade and so on.
4. Installation dimensions and dimensions requirements: nominal diameter, pipe connections and connection dimensions, dimensions or weight restrictions.
5. The valve product reliability, service life and explosion-proof performance of electric devices and other additional requirements. (When selecting a parameter, note the following additional parameters if the valve is to be used for control purposes: method of operation, maximum and minimum flow requirements, pressure drop for normal flow, pressure drop when closed, maximum and minimum inlet of valve pressure.)
According to the basis of the above selection of valves and steps, reasonable and correct selection of the valve must also have a detailed understanding of the internal structure of various types of valves in order to be able to make the right choice of the right valve. The ultimate control of the pipeline is the valve. Valve opening and closing pieces control the flow of medium in the pipeline, the shape of the valve flow path to the valve with a certain flow characteristics in the choice of the most suitable piping system to install the valve must take into account this point.
