Selection and design of imported high temperature steam pneumatic control valves and high pressure explosion-proof boiler electric control valves

1. Understand the function of the pneumatic control valve:

It is used in equipment to regulate airflow or fluid flow.

Working conditions: consider the type of media, operating pressure, and temperature.

2. Determine the nominal diameter and connection method of the pipe connected to the pneumatic control valve: flange, threaded, or welded.

3. Choose the type of pneumatic control valve: gate valve, shut-off valve, ball valve, butterfly valve, throttle valve, safety valve, pressure reducing valve, steam trap, etc.

4. Decide on the action mode: linear stroke or angular stroke.

5. Select the appropriate type of pneumatic regulating valve: closed-loop, adjustable, or safety-type.

6. Define the parameters of the pneumatic regulating valve: For automatic systems, determine flow resistance, discharge capacity, back pressure, etc., based on specific requirements, then select the pipe size and seat hole diameter. (021famen.cn)

7. Decide on the operation method: manual, electric, electromagnetic, pneumatic, hydraulic, or electro-hydraulic.

8. Choose materials for the valve body and internal components according to the medium, pressure, and temperature: gray cast iron, malleable cast iron, ductile iron, carbon steel, alloy steel, stainless acid-resistant steel, copper alloys, etc.

9. Finalize usage precautions and maintenance guidelines.

How to Choose Valves Based on Flow Characteristics

The opening and closing parts and the shape of the flow channel determine the valve's flow characteristics. This should be considered when selecting a valve.

1. For shut-off valves:

Valves with low flow resistance and straight-through flow are usually preferred. These include gate valves, globe valves, and plunger valves. Downward-closing valves are less common due to their tortuous flow path and higher resistance. However, they may still be used in applications where higher resistance is acceptable.

2. For flow control:

Valves that allow easy adjustment of flow are typically chosen, such as control valves, throttle valves, and plunger valves. Their seat size is proportional to the stroke of the closure member. Rotating types like plug valves, ball valves, and butterfly valves, as well as deflection body types like pinch valves and diaphragm valves, can also be used for throttling, but usually only within limited sizes. In most cases, people use globe valves by modifying the flap shape for throttling. However, it's not recommended to use globe valves for throttling by adjusting the opening height, as this can cause excessive wear on the sealing surface and reduce effectiveness. Similarly, using a throttle valve for shut-off is not advisable.

3. For diverting or reversing flow:

If the application requires reversing or splitting the flow, valves with three or more channels are suitable, such as plug valves and ball valves. Most commutating valves use this type. In some cases, other valve types connected in multiple ways can also be used for flow division.

4. For media with suspended particles:

When dealing with media containing particles, it's best to choose valves with a wiping action on the sealing surface during opening and closing, such as slab gate valves. This helps prevent clogging and ensures smooth operation.