Centrifugal Fans Installation and Using Instructions

1. Before installing the centrifugal fan, prepare the materials and tools for installation in advance, and check the parts of the centrifugal fan:

A: Before installation, carefully check whether the centrifugal fan and cover are damaged or deformed due to transportation, otherwise, they should be repaired before installation;

B: Check whether the connecting bolts are loose or not. Before starting the centrifugal fan, check whether there are any objects in the fan duct that hinder the rotation;

C: Check whether the insulation performance of the motor is good, and check for frictional collision and abnormal vibration after turning on the power.

2. The following points must be paid attention to during installation and operation of centrifugal fan:

A: On some joint surfaces, in order to prevent rust and reduce the difficulty of disassembly, grease or mechanical oil should be applied.

B: For the bolts on the upper joint surface, if there are positioning pins, tighten the bolts.

C: Check the inside of the casing and other casings, and there should be no tools or sundries that have fallen into it.

3. Installation requirements to be paid attention to during actual operation:

A: When installing the centrifugal fan, the weight of the gas pipeline should not be added to the casing.

Correct the gap size between the air inlet and the impeller according to the drawings, and keep the shaft horizontal.

A protective net or other safety devices (provided by the user) must also be added.

B: When installing the air inlet pipe, you can directly use the flange link of the air inlet itself, and the air inlet flange can be freely punched to match the pipe connection.

C: After the centrifugal fan is installed, move the rotor with your hand or lever to check whether there is any over-tightening or collision. Only when there is no such phenomenon can you try to run.

D: After the motor is installed, if the air inlet is not connected to the air inlet duct, it is not the power required when the air outlet is fully opened in terms of the amount of reserve.

If the air outlet or inlet of the fan does not take over or run without external resistance, the motor is in danger of burning.

For safety, add a valve to the air outlet or inlet pipe of the centrifugal fan, close it when starting the motor, and slowly open the valve after the operation until the specified working condition is reached, and pay attention to whether the motor current exceeds the specified value.

The Main Faults and Causes of the Centrifugal Fan:

1. The bearing box vibrates violently of centrifugal fan

Reason:

• Friction between the casing or the air inlet and the impeller;
• The rigidity of the foundation is not enough or not strong;
• The impeller rivet is loose or the wheel is deformed;
• The impeller shaft disc and the shaft are loose;
• The connecting bolts of the housing and the bracket, the bearing seat and the bracket, the bearing cover and the seat are loose;
• Poor installation of the centrifugal fan inlet and outlet ducts;
• The rotor is unbalanced;
• The pipe network is too thin, and the wind speed is too fast.

2. The bearing temperature rise is too high of centrifugal fan

If the bearing temperature rises too high when operating at room temperature, it may be caused by the following reasons:

• The bearing box vibrates violently;
• The rolling bearing of the motor is damaged, and the fit-gap is small, which does not meet the requirements;
• The shaft and rolling bearing are installed skewed, and the front and rear bearings are not concentric;
• The power supply voltage is too low or the three-phase power supply is running in an open phase;
• The lubricating grease is of poor quality, deteriorated, contains dust, sticky sand, dirt, and other impurities;
• The tightening force of the connecting bolts of the bearing box cover seat is too large or too small;

3. Excessive current or high temperature of centrifugal fan

Reason:

• The gate or throttle valve in the intake pipe is not closed tightly when starting;
• The flow exceeds the specified value or the air duct is leaking;
• The density of the air conveyed by the fan is too high, which makes the pressure too high;
• The input voltage of the motor is too low or the single-phase power supply is cut off;
• Affected by the severe vibration of the bearing box

4. Centrifugal fan vibration

There are many reasons for centrifugal fan vibration, which can be tested from the following aspects:

• The impeller rubs against the blower, and makes abnormal noises and vibrations;
• The bottom corner bolts of the bracket are not tightened, and there will be greater vibration;
• The connecting bolts between the impeller and the shaft sleeve are loose;
• The loosening of the connecting bolts between the bracket and the motor causes the impeller to be unbalanced, and the bearing is damaged, causing severe vibration.

What Raw Materials Do Miracle Usually Use to Produce Centrifugal Fans?

Centrifugal fan sales in the market are getting higher and higher, customers often learn about the raw materials used by manufacturers in the production process when choosing, because the quality of raw materials is directly related to the quality of the equipment and the duration of use.

In the production of the equipment, the need by the casing, impeller, air inlet and other components, these parts in the production, Miracle will use which raw materials?

According to the characteristics of the centrifugal fan processing process, in order to ensure the adequate working performance of the equipment, the common key raw materials are as follows.

• Carbon steel. The composition of carbon in this steel is less than 2.11%, it is iron-carbon alloy steel, this material has the characteristics of easy processing, low cost, suitable for the production of fans operating at room temperature, the working environment generally requires no dust, corrosion resistance.
• Glass steel. This is also a manufacturer of fans is often used materials, it has good corrosion resistance, can resist most acids and alkali metal salts, because it has such characteristics, so it is suitable for the production of fans used in the chemical manufacturing industry.
• Stainless steel plate, which is also a very common raw material for fans, because it has many types, including austenitic, martensitic, ferritic, duplex steel, etc., so the use of the material to produce fans also have a variety of different properties.
• Some manufacturers will also use plastic as the main material, the general choice is PP, but because of the poor compressive properties of plastic, so the use of the material produced by the fan application range is small, the market is also relatively rare.

Of course, with the increasingly stringent requirements of customers, some of the use of polymer materials produced by the centrifugal fan also appeared on the market.

How Centrifugal Fan Noise is Generated?

Centrifugal fans are widely used in metallurgy, chemical industry, petroleum, machinery, cement, construction, and other key industries.

Centrifugal fans play a very positive role in speeding up industrial production.

All moving objects produce noise, and the noise generated by centrifugal fans during operation can affect the surrounding environment.

It will not only damage the hearing damage health, but also hinder the normal communication seminars and dialogue language, and bring a certain impact on the safety of production;

In fact, the centrifugal fan is a volumetric compressor, including a pair of mutually vertical engagement of the waist-shaped impeller relative to the high-speed rotation of the transported gas.

Centrifugal fan operation, aerodynamic noise is the main noise (i.e., airflow noise).

Transmission gear noise, motor noise and pressure regulating valve noise, and other components, will also generate noise, but the largest source of noise is pneumatic noise.

When operating under certain conditions, high-intensity noise is radiated from the fan inlet, outlet pipe, casing, and other areas.

Under actual conditions of use, the exhaust fan port is often connected to the air delivery pipe.

Therefore, the inlet noise is the most intense and the most disturbing to the environment.

Fans not only have high noise intensity but also have a complex and continuous frequency component.

In order to quantitatively describe the noise energy distribution over the entire frequency range, noise measurements with noise spectral analysis filters tested in eight octaves at frequencies from 800 Hz to 63 Hz, the noise spectral characteristic curve is obtained for the sound source, i.e., the sound pressure level of the octave in this frequency relationship curve.

First, the noise spectrum is wide, when the pressure is low, the load is small, usually at a lower frequency of 125 Hz peak frequency; when operating to rated pressure conditions, at a frequency of 500 Hz therefore a new noise peak will appear.

This indicates that the noise at medium and high frequencies increases significantly with the increase in operating pressure of the centrifugal fan.

The intensity of the noise and the static pressure of the fan presents size-related spectral characteristics, but also with the flow rate of the centrifugal fan, there is a strong relationship.

As the flow rate increases, the noise increases, when the speed doubles, the noise of the centrifugal fan can be increased by about 5 ~ 10 decibels, which has an important role in reducing the noise of high frequencies in the centrifugal fan.

What Issues Need to be Considered When Designing a Centrifugal Fan?

Centrifugal fans need to be designed with the following points in mind.

The reasonable choice of blade type:

In a common centrifugal fan at a certain speed, the pressure coefficient of the backward impeller is smaller, the impeller diameter is larger, and its efficiency is higher; for the forward impeller is the opposite.

Blade exit angle selection:

Blade exit angle is the design of the first to select one of the main geometric parameters.

In order to facilitate the application, usually classify the blade as strong back-bending blade, back-bending wing-shaped blade, back-bending straight blade, back-bending circular arc blade; radial exit blade, radial straight blade.

Selection of the number of blades:

In centrifugal fans, increasing the number of blades of the impeller increases the theoretical pressure of the impeller, because it reduces the influence of relative vortices.

Therefore, for each kind of impeller, there is an optimal number of blades.

Determine exactly how many blades, sometimes according to the experience of the designer

The choice of worm shell shape size:

volute shape size should be as small as possible.

A high ratio fan can be used to shorten the volute, for a low ratio fan generally choose the standard volute.

Selection of full pressure coefficient: When designing a centrifugal fan, the actual pressure is always pre-determined. At this time, the need to choose the full pressure coefficient.

How to Adjust the Air Volume of Centrifugal Fan?

Centrifugal fan air volume adjustment.

Adjustment method one.

Under the premise that the characteristics of the fan duct network system remain unchanged, the desired purpose is achieved by changing the rotational speed of the centrifugal fan to make the pressure, air volume, and power of the fan change.

Fan speed increases, then the fan air volume and pressure increase, and vice versa.

The main advantage of this method is that there is no additional energy loss, so its economic performance is relatively good.

Adjustment method two.

It is to change the characteristics of the pipe network system by adjusting the throttle valve, or by changing the opening degree of the insert plate.

In this case, the air volume is inversely proportional to the pressure, in addition to the degree of opening of the throttle valve or insert plate.