Considerations for Valve Selection and Piping Design The performance of tubular axial flow fans can be affected by radial clearance

Considerations for Valve Selection and Piping Design The performance of tubular axial flow fans can be affected by radial clearance

1. According to the place of use, use, and understand the relevant laws and regulations, specifications, standards, guidelines, allowed to be approved after the selection of suitable for various requirements of the valve;
2. Confirm the valve working conditions, applicable medium, working pressure, medium temperature;
3. Determine the nominal diameter matched with the pipeline: DN(mm);
4. Determine the connection mode with the pipeline: flange type, internal (external) thread type, welding type, clamp type, clamp type, etc.;
5. Determine the operation mode of the valve: manual, worm gear, pneumatic, electric, hydraulic, electromagnetic, electro-hydraulic, etc.
6. Confirm the type of valve: gate valve, globe valve, throttle valve, plunger valve, ball valve, butterfly valve, diaphragm valve, plug valve, check valve, safety valve, trap and other special valves;
7. Determine the use of valve form: switch type, regulating type, safety type, etc.;
8. Determine the material of valve shell and inner parts: gray iron, ductile iron, carbon steel, alloy steel, stainless steel, copper alloy, aluminum alloy, plastic, etc.
9. Determine the valve seal performance requirements, seal grade or seal leakage;
10. Determine the valve protective coating requirements, packaging requirements, transportation requirements;
11. Special needs of the valve should also be determined: structure length, valve height, size, flow resistance, discharge capacity, flow characteristics, protection grade, explosion-proof performance and other parameters;
12. Determine valve installation position and posture.
The performance of tubular axial fan is affected by radial clearance
The gas medium transported by the tubular axial flow fan is explosive and flammable gas such as carbon monoxide, petroleum gas, chemical gas or I gas containing dangerous powder. If the rotor part of this kind of fan is made of general carbon steel, it is easy to spark together and lead to gas combustion because of the collision between components, or the impurities such as sand or iron dust are sucked into the rotor, resulting in a serious accident. In order to avoid this kind of accident, when the fan delivers the gas medium with low explosive grade, the volute of the fan is made of steel plate, and the impeller is made of aluminum. But when the fan conveying the high explosive grade of gas used are made of aluminum materials.
The radial clearance of the tubular axial fan refers to the clearance between the blade and the inner wall of the casing, and the axial clearance refers to the clearance between the impeller cascade. The size of two kinds of clearance has an impact on the performance of the fan.
The radial clearance of the tubular axial flow fan is too large, and the negative pressure is high, which is bound to cause a large pressure difference between the blade tip and the two sides of the clearance of the casing. The pressure difference is the main reason for the axial air leakage. The leakage is pumped back by the blade and discharged to the atmosphere, forming a “circulating air flow. The work of this part of the air flow is wasted, so that the efficiency of the fan is reduced.
The rotor tells the rotation, along the axial spiral forward gas, because the air itself has weight and moisture and dust particles contained in the air, is told to spin the blade around, the air particles are dense near the casing, close to the inner wall of the forward spiral flow, along the radial direction to increase the airflow density and negative pressure. In this case, the radial clearance is too large and turns back to the clearance ring belt around the casing to produce a large number of tubular air flows along the axial direction in reverse, which impacts the normal air flow, so that the air consumes work in vain, thus reducing the efficiency.
When designing and modifying products, it is necessary to maintain a certain axial clearance between cascades, mainly to ensure that the subsequent cascades have uniform air intake and eliminate the influence between each other, otherwise the respective working conditions will be deteriorated. The uneven air flow may act as a vibration source, causing the blade behind to vibrate. On the contrary, the axial clearance is too large, will make the axial size too long. Therefore, the size of the axial clearance has an impact on the noise, vibration and axial size of the fan.
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