Imported valves mainly refer to valves from foreign brands, mainly European, American and Japanese brands. The more representative brands include Spirax Sarco, LIT, KITZ, RETZ, etc. This article combines the German brand LIT, which has won wide acclaim from customers, to analyze the specific selection of imported valves:

1.The characteristics of imported valves

Usage characteristics of imported valves

The usage characteristics determine the main performance and scope of use of the valve. The valve usage characteristics include: valve category (closed-circuit valve, regulating valve, safety valve, etc.); product type (gate valve, stop valve, butterfly valve, ball valve, etc.); material of the main parts of the valve (valve body, valve cover, valve stem, valve disc, sealing surface); valve transmission method, etc.

Structural characteristics

The structural characteristics include: the structural length and overall height of the valve, the connection form with the pipeline (flange connection, threaded connection, clamp connection, external thread connection, welding end connection, etc.); the form of the sealing surface (ring, threaded ring, surfacing, spray welding, valve body); the valve stem structure (rotating rod, lifting rod), etc.

2. Steps to select valves

Clarify 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.

Determine the nominal diameter and connection method of the pipeline connected to the valve: flange, thread, welding, etc.

Determine the way to operate the valve: manual, electric, electromagnetic, pneumatic or hydraulic, electro-hydraulic linkage, etc.

According to the medium, working pressure and working temperature of 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 acid-resistant steel, gray cast iron, malleable cast iron, ductile iron, copper alloy, etc.; for example, the cast steel material selected for the stop valve.

Select the type of valve: closed-circuit valve, regulating valve, safety valve, etc.

Determine the type of valve: 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 automatic valves, first 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, height direction of the valve after opening and closing, size and number of bolt holes for connection, overall valve size, etc.

3. Basis for selecting valves

Purpose, working conditions and operation control methods of the selected valves;

Nature of the working medium: working pressure, working temperature, corrosive properties, whether it contains solid particles, whether the medium is toxic, whether it is flammable or explosive, viscosity of the medium, etc.

4.Conclusion

In summary, there are several major factors in the selection: determine what function of the valve to be selected, confirm the temperature and pressure of the medium, confirm the flow rate of the valve and the required caliber, confirm the material and operation method of the valve.