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Precautions when stainless steel fans are shut down

qiba — Tue, 30 Mar 2021 08:16:18 +0000

In our fan maintenance, in addition to the daily normal maintenance. There are also precautions when the stainless steel fan is shut down.
Today, I found some precautions when stainless steel fans are shut down on the Internet to share with you:
1. Normally, the stainless steel fan should be shut down after entering a small load, and after shutting down, close the air inlet and outlet valves.
2. When using forced oil-supply bearings, continue to supply oil to the bearings until the spindle stops completely.
3. For wind turbines that use cooling water to cool the bearings, the cooling water valve should be closed after shutdown.
4. For stainless steel fans that transport harmful gases, attention should be paid to the leakage of the shaft seal, and measures should be taken to prevent the gas from harming the environment.
5. For stainless steel fans that transport high-temperature gas, they should continue to operate until the gas temperature in the casing is lower than about 100°C.

Precautions when stainless steel fans are shut down for a long time
1. When the stainless steel fan stops running for a long time, apply ten words of lubricating grease or other anti-rust agent to the parts of each mechanical part that are prone to rust to prevent rust.
2. For stainless steel fans that use cooling water to cool the bearings, the cooling water in the bearing box and pipeline should be emptied to prevent freezing in winter and cracking of the pipeline.
3. Moisture-proof measures should be adopted for motors and other electrical devices.
4. The stainless steel fan should be repaired and maintained regularly.

Structure of explosion-proof axial flow fan

qiba — Tue, 30 Mar 2021 07:50:54 +0000

Explosion-proof axial flow fans are a type of axial flow fans that are widely used in fire fighting systems. The structure of the explosion-proof axial flow fan is the same as that of the ordinary axial flow fan. The main difference is that the motor adopts an explosion-proof motor and some special explosion-proof technology for processing. The main materials used are carbon steel and stainless steel. In many engineering constructions, fire-fighting facilities are installed, such as explosion-proof axial fans, smoke exhaust and fire dampers and other products. Of course, these products must meet the relevant requirements of the regulations.
Here is a look at the quality requirements for smoke exhaust fire dampers in engineering construction.
The main control parameters of the explosion-proof axial flow fan are working temperature, air volume, total pressure, efficiency, noise, motor power, speed and shaft power.
It should be able to operate normally for a long time under the condition that the temperature of the medium is not higher than 85℃.
When the conveying medium temperature is 280℃, it can work continuously for 30 minutes, and it can continue to operate normally when the medium temperature is cooled to the ambient temperature.
These are the correct selection methods for fire and explosion-proof axial fans. We must make the correct selection according to the needs, as long as this is the way to get a better effect.
Explosion-proof axial flow fan structure: steel impeller (molded cylindrical hub), outer cylinder (spinning forming, flange and cylinder integrated), inner cylinder and guide vanes, high temperature motor, cooling air duct and cooling impeller, foot .
With the continuous improvement of life, everyone also knows a lot about wind turbines. The following editor will briefly introduce you to the structure of wind turbines:
1. Check whether the performance of the explosion-proof axial flow fan meets the nominal air pressure and air volume. Only when the performance meets the nominal performance can the pumping and supply air volume required by the actual system be reached.
2. It depends on the high efficiency of the explosion-proof axial flow fan, the high efficiency of the fan and the energy saving, the low efficiency of the fan, and the power consumption.
3. Check whether the vibration value of the bearing part is high or not, the fan bearing is easy to be damaged if the vibration value is high, but the vibration value is low and the bearing life is long.

Structural characteristics of stainless steel fan

qiba — Tue, 30 Mar 2021 07:50:36 +0000

Stainless steel fans are generally used for high-pressure forced ventilation in forging furnaces, glass, electroplating, ceramics, lithium batteries, radio and other industries, and can be widely used for material transportation in food, feed, mineral powder and other processing industries. It is also suitable for carton machinery and equipment. , Toughened glass equipment and other supporting use.

The structural features are as follows:

It is mainly composed of impeller, casing, air inlet, motor, connector, cooling fan and other parts.

1. The impeller adopts a multi-wing single-entry centrifugal impeller, which is made of high-quality galvanized sheet or cold-rolled steel sheet. The blades are designed according to the principle of aerodynamics. The impeller is composed of 10 backward inclined airfoil blades, a curved front disc and a flat rear disc. The material is made of high-strength, good-durability and excellent steel plate, and has undergone strict dynamic and static balance correction. The air performance is good, the efficiency is high, and the operation is stable.

Second, the air inlet adopts a convergent streamlined vortex reduction form, with less air loss and high working efficiency of the high-temperature fan.

3. The high temperature fan case and the motor are installed and connected with metal castings. The heat dissipation fan blades are installed on the motor shaft head. The outer wall of the metal casting is provided with inlet and outlet pipe interfaces to cool the metal casting and shaft head to ensure that the motor is normal at high temperatures. run.

Fourth, the motor adopts a special high-temperature motor, and the fluid part of the high-temperature fan adopts temperature-resistant materials, and the cooling structure is reliable. Compared with other boiler induced draft fans, it has the advantages of simple structure, convenient maintenance and high cost performance. Small industrial fans have light structure, beautiful appearance, low noise and high static pressure. This product is suitable for supporting industrial machinery and equipment, small space extraction and exhaust, spray pressurization, thermal circulation system, high temperature air supply (more than 200 degrees, equipped with temperature resistant wind wheel), corrosion resistance, air conditioning purification equipment, etc. Can use stainless steel, PP, ordinary A3 spraying and other materials.

Precautions:

The conveyed medium is air and other non-spontaneous, harmless and non-corrosive gases. No viscous substances are allowed in the gas. Generally, the use temperature during ventilation should not exceed 80℃, and the dust and hard particles contained should not exceed ≤150mg/m3.

Anti-corrosion treatment method for boiler induced draft fan

qiba — Tue, 30 Mar 2021 07:50:19 +0000

Generally speaking, there are two methods for anti-corrosion of boiler induced draft fans. One is the anti-corrosion of the material and the other is the anti-corrosion of the process.

From the perspective of the boiler induced draft fan alone, the process method is not applicable, because the process method is external processing such as lining plastic, which is obviously not feasible. The following will talk about the anti-corrosion treatment method of the boiler induced draft fan from the material aspect.

Generally, the materials with good anti-corrosion effects include various series of manganese steel, 304 stainless steel, 321 stainless steel, etc. These stainless steels have the characteristics of high heat resistance temperature and good anti-corrosion effect. Titanium alloy materials are also effective anti-corrosion materials, but the cost is a bit high. You can decide according to your own situation.

Most of the boiler induced draft fan impellers are made of 30# manganese steel or stainless steel. The boiler exhaust temperature is theoretically 150-200℃. The temperature range is mainly for anti-corrosion, too high will cause waste.

The approximate temperature at which the steel material undergoes a phase change due to temperature is 400°C.

Regarding wear resistance, boiler dust has a great influence on the abrasion of the induced draft fan impeller. Regular cleaning and maintenance of induced boiler induced draft fans (including bearing box and damper flaps) are carried out. However, larger coal-fired boilers are installed The dust collector not only reduces the discharge of dust, but also effectively protects the induced draft fan of the induced boiler and reduces the wear of the impeller.

Remarks: Correct boiler usage methods such as controlling the exhaust gas temperature can also benefit the anti-corrosion work of the boiler induced draft fan.

Causes of axial fan wear

qiba — Tue, 30 Mar 2021 07:50:02 +0000

The wear and tear of the axial flow fan will cause the fan to vibrate, shorten the life of the fan, and cause the fan to fail to work normally in severe cases. In particular, the blades of wind turbines are the most worn out, which not only destroys the flow characteristics in the wind turbine, but also easily causes major accidents such as blade breakage and speeding. Therefore, it is very necessary to understand the reasons for the wear of the axial flow fan, and then take the corresponding anti-wear measures. Today, the editor collected some reasons for the wear of axial fans on the Internet, and shared with you
The basic causes of common axial fan wear are as follows:
1. Wear of dust on the fan
A large amount of microscopic dust during fan operation will cause damage to fan bearings, blades, and motors due to long-term accumulation. Due to the small particle size and many types of dust, a lot of dust cannot be effectively removed, and it is easy to cause damage to the vulnerable parts of the fan. . At the same time, in order to control costs and improve the ventilation effect of fans, some fan application units have reduced the application of fan dust collectors, which will cause strong damage to the fans by dust and increase the risk of fan wear and failure.
2. The operating conditions of the fan are unreasonable
Different positions and different function settings require different fans and different state adjustments to adapt. The gap between the design and the actual, the difference in functions and needs forms the problem of fan selection, which is very easy to cause fan overload work and increased fan wear. problem.
3. The fan runs too fast
Excessive running speed is another important cause of fan wear. According to the data analysis of fan wear, the degree of wear is related to the running speed of the fan. Under high temperature conditions, the running speed of the fan is doubled, and the wear of the fan is increased by 3 times.

The Harm of Excessive Vibration of Centrifugal Fan and Vibration Reduction Measures

qiba — Tue, 30 Mar 2021 07:49:47 +0000

The centrifugal fan is different from other fans in that its working medium flows in axially of the fan and flows out radially, and needs to work under the action of centrifugal force. Vibration is inevitable for centrifugal fans. It refers to the maximum bidirectional amplitude of the fan bearing, which is required to not exceed 0.10mm.

Once the vibration of the centrifugal fan is too large, it will cause the motor current to be too high, the temperature rise is too high, and in severe cases, it will cause the motor coil to burn; and it will also have an adverse effect on the bearing anchor bolts, bearings, shafts and other components. There are three reasons for the excessive vibration of the centrifugal fan. One is the manufacturing quality of the fan; the second is the installation quality; and the third is the operation.
Centrifugal fan

In order to reduce the vibration of the centrifugal fan, we must first strictly abide by the correct installation process, including facility inventory and inspection; basic inspection, marking, shim and anchor bolt configuration. Then proceed with the installation of the centrifugal fan, paying attention to the smooth installation of the parts; after the completion of the installation, the facilities should be aligned.

Before the centrifugal fan is put into use, a comprehensive inspection is also required. The content involved includes the manufacturer’s manufacturing quality and whether there is damage and deformation during transportation, including the curvature of the shaft, which must not exceed 0.10mm; this aspect is due to conditions As a result, only the theodolite can be used for rough inspection on site.

At the same time, check whether the blade exit angle of the centrifugal fan impeller is consistent with the manufacturer’s drawing preset; and use a vernier caliper to check whether the clearance between the main shaft and the impeller meets the drawing preset; also check whether the thickness of the wind casing and the reinforcement ribs conform to the drawing preset. Finally, don’t forget to check whether the regulating gate and current collector are normal.

Installation method of axial fan

qiba — Tue, 30 Mar 2021 07:49:24 +0000

The first type, the horizontal installation method of the axial flow fan:
The specific method is to fix the shock absorber at the installation position to the fan base through connecting bolts, adjust the level of each shock absorber with the center height adjustment pad, and fix the fan on the connecting steel plate that has been welded to the foundation with fixing bolts, such as The fan does not need a shock absorber due to anti-vibration and other reasons, just connect the screw holes on the fan base and the embedded bolts directly on the foundation.

The second type, the horizontal installation method of the side wall of the axial flow fan:
The basic requirements for the installation of axial fans are the same as those for horizontal installation, except that the mounting bracket is made of inclined arm support, and the bracket must have sufficient strength and rigidity. This type of installation is not suitable for fans above 10#.

The third type, the suspended installation method of the axial flow fan:
The specific method is to first connect the shock absorber and the fan with bolts, install the shock absorber symmetrically, and arrange them on both sides of the center of gravity of the fan, directly lift the fan and install it on the suspension bracket. The height of the suspension bracket depends on the actual space distance. Self-defined, fans above 16# generally do not use this type of installation.

The fourth, vertical installation method of axial flow fan:
The vertical installation method of the axial flow fan is the same as the horizontal installation, and the requirements for the strength and rigidity of the fan foundation are more stringent. The connection between the fan and the pipes at both ends must use flexible joints to isolate vibration and protect the fan.

Causes of noise from centrifugal fans and axial fans

qiba — Tue, 30 Mar 2021 07:48:50 +0000

Generally speaking, the sound of centrifugal fans and axial fans is relatively high. The reasons for their noise can be summarized as the following three:

1. Noise caused by aerodynamics.

2. The sound produced by mechanical vibration.

3. The noise generated by the interaction between the two.

Whether it is a duct fan or any other machine, understanding and mastering the noise source that produces its noise is the most fundamental and effective method of noise control.

1. Aerodynamic noise

1. Impact noise

When the impeller rotates at a high speed, the blades move periodically, the air particles are subjected to periodic force, and the impact pressure wave impacts the noise at the speed of sound.

The intensity of this noise varies with the geometry and size of the blade.

If the rotation speed of the impeller per second is n(rpe), when the number of blades is z, its basic frequency fc is determined by the following formula: fc=nz, Hz

The higher the pressure, the greater the circumferential speed of the impeller, and the greater the noise.

2. Eddy current noise

The noise caused by the vortex generated by the separation of the gas boundary layer when the impeller rotates at a high speed.

The frequency of eddy current noise: f=K(v/d), Hz

formula:

K-constant 0.15~0.22;

v- the velocity of the blade relative to the gas, m/s;

D- the width of the blade in the direction of the gas inlet, m.

Due to the irregular movement of the disaster current, it sometimes grows and sometimes attenuates, so that the flow noise has a wide range of rates.

2. Mechanical vibration voice

The vibration caused by the unbalance of the rotating body and the wear and damage of the bearing must be accompanied by noise. When the blade rigidity is insufficient, the vibration of the blade due to the airflow will also produce noise.

3. Noise generated by the interaction between the two

The rotation of the blades causes its own vibration to be transmitted through the pipeline, and often shocks and eddy currents occur in the bend of the pipeline, causing vibration to increase the noise, especially when the air pressure sound wave frequency is consistent with the natural vibration frequency of the pipeline, strong resonance will occur, and the noise will suddenly occur Increase, and cause damage to the machine in severe cases.

In addition, when the main shaft of the centrifugal fan and the axial fan is driven by the motor, gear speed increasing device or belt, it will also cause vibration and generate secondary noise. The noise of centrifugal fan and axial fan, from the characteristics of sound source, belongs to dipole source radiation noise (or called dual-source radiation sound).

The directivity pattern is a figure of eight, and the sound waves in the axial direction are stronger, and the sound waves in the direction perpendicular to the axis are weaker.

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