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2020

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05

Features to note when selecting valves

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Usage characteristics: It determines the main performance and scope of use of the valve. The usage characteristics of the valve include: valve category (closed-circuit valve, regulating valve, safety valve, etc.); product type (gate valve, globe valve, butterfly valve, ball valve, etc.) ; Materials of the main parts of the valve (valve body, valve cover, valve stem, valve disc, sealing surface); valve transmission mode, etc.

There are generally two types of valve characteristics, usage characteristics and structural characteristics.

Usage characteristics: It determines the main performance and scope of use of the valve. The usage characteristics of the valve include: valve category (closed-circuit valve, regulating valve, safety valve, etc.); product type (gate valve, globe valve, butterfly valve, ball valve, etc.) ; Materials of the main parts of the valve (valve body, valve cover, valve stem, valve disc, sealing surface); valve transmission mode, etc.

Structural characteristics: It determines some structural characteristics of the valve installation, repair, 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, threaded connection, clamp connection , external thread connection, welded end connection, etc.); the form of the sealing surface (inlaid ring, threaded ring, overlay welding, spray welding, valve body); the valve stem structural form (rotating rod, lifting rod), etc.

 

Steps and basis for selecting valves

Selection steps:

1. 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.

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

3. Determine the method of operating the valve: manual, electric, electromagnetic, pneumatic or hydraulic, electrical linkage or electro-hydraulic linkage, etc.

4. Determine the materials of the selected valve shell and internal parts according to the medium transported by the pipeline, working pressure, and working temperature: gray cast iron, malleable cast iron, ductile iron, carbon steel, alloy steel, stainless acid-resistant steel, copper alloy, etc.

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

6. Determine the type of valve: gate valve, globe valve, ball valve, butterfly valve, throttle valve, safety valve, pressure reducing valve, steam trap, etc.

7. 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.

8. Determine the geometric parameters of the selected valve: structural length, flange connection form and size, height dimension of the valve after opening and closing, size and number of connecting bolt holes, overall valve dimensions, etc.

9. Use existing information: valve product catalogs, valve product samples, etc. to select appropriate valve products.