Overview of Fan Muffler
Fan silencer has the same form as exhaust duct silencer and blower-induced fan silencer. It adopts the principle of resistive sound absorption and noise reduction which has better effect on medium and high frequency broadband characteristics, noise resistance and noise reduction, microperforated muffler and impedance composite muffler with good effect on low, medium frequency and pulsation characteristics.
Brief Introduction of Fan Muffler
Resistive muffler is an absorption muffler. According to the different structure of airflow passage, it can be divided into straight tube type, sheet type, folded plate type, honeycomb type, acoustic flow type, labyrinth type and elbow type. Resistive muffler is a kind of muffler which converts sound energy into heat energy and dissipates it by means of friction and viscous resistance when sound wave propagates in porous sound-absorbing materials, so as to achieve the purpose of muffling and reducing sound. It is the most widely used type in all mufflers.
Reactive muffling is different from resistive muffler in the principle of noise reduction. It can not absorb sound energy directly. Instead, it uses abrupt interface or side resonant cavity on the pipeline to make some frequency sound waves propagating along the pipeline reflect and interfere at the abrupt interface, so as to achieve the purpose of noise reduction. It is divided into expansion chamber muffler and resonance muffler.
In practical noise control engineering, the noise is mostly in broadband, usually combine the Resistive sound absorption to reduce noise and Resistance to muffling to reduce the sound, to control high-intensity broadband noise.
Types of fan mufflers
Fan muffler is divided into centrifugal fan muffler, Roots fan muffler, blower muffler, axial flow fan muffler. Fan silencer is mainly used to reduce the aerodynamic noise of various fan tuyeres, air ducts and air intakes of closed machine rooms. According to the different structure of fan inlet and outlet, it can be divided into circular structure and rectangular structure.
(1) The circular structure is divided into two types: A and B. Both ends of A type are flanges, which are directly connected to the pipeline (i.e. pipe muffler). One end of B type is flange and the other end is direct atmospheric exhaust (rain-proof wind cap). It is only for the selection of the end of outdoor pipeline and the air intake of enclosed engine room.
(2) The resistive silencer in rectangular structure is generally 100 mm or 150 mm in thickness and 15-30 dB (A) in sound deadening capacity. Under the condition of 5-12 m/s wind speed, the applicable air volume is 1000-50000 m3/h. In its structure, impedance is used to eliminate high-frequency noise and low-frequency noise in order to maximize the bandwidth of noise elimination.
Fan muffler (GF type)
The GF type fan silencer series products produced by our company are used to control the aerodynamic noise caused by the fan to the environment.It is used for noise elimination of inlet and outlet ducts of various centrifugal and axial flow fans.
The muffler series products are impedance acoustic flow type. According to the spectrum characteristic data obtained from the actual test of noise sources of various types of fans in power plants, the main basis for designing sound absorber structure and fluid channel is used to determine which spectrum range needs how much noise reduction. At the same time, narrow rectangular channel with larger material finishes can be used to enhance the absorption effect.
When the noise source of the fan is at the maximum noise level, its spectrum values is often more than one, but for different spectrum bands, the requirement of noise reduction is also different. For this reason, the product adopts the resistance structure which can silence high and medium frequency noise and the resistance structure which can silence medium and low frequency noise. At the same time, two kinds of silencing areas of high frequency machine and low frequency are adopted in the resistance channel to maximize the silencing frequency band so as to achieve good silencing effect. After the user has installed the product as required, the limit noise level will not exceed 65-90 dB.
Description for the structure of main components of blower muffler (GF type)
The main structure of GF fan muffler is composed of 1 muffler body, 2 rain caps, 3 multi-channel mufflers, 4 flow control mufflers and other main components.
(1) Muffler body
The muffler body mainly consists of Q235 steel plate, which is rolled up to the design size by the veneer reeling machine, and then welded by splicing. Usually, double-sided welding process is adopted. Installation support, loading and unloading truck lifting lug and vertical installation lifting lug are installed on the outside of the muffler body. Before installation, the welding points of the lifting lug joint can be checked to ensure that the welding points are firm before installation.
(2) Rainfall cap
The rainproof cap is used to prevent the backfilling of foreign bodies such as rainwater in the production process and bring damage to the operating equipment. The distance of support of rainproof cap and muffler body is generally set between 300--700 mm. The support of rainproof cap is welded and strengthened after setting according to the site conditions to ensure the safe operation of the equipment.
(3) Multichannel muffler
The multi-channel silencer is rolled by galvanized orifice plate. The orifice plate is coated with glass fiber cloth, and the acoustic rock wool is added to the outside of the fiber cloth. The multi-channel silencer, also known as honeycomb silencer, is mainly used to reverse the pressure drop. The air volume and noise after split-flow will be absorbed by the external sound-absorbing material of the silencer to achieve the purpose of noise reduction.
The muffler is composed of porous sound absorption board, sound absorption glass fibre and muffled asbestos. It has multiple effects of good sound absorption effect, flow control to reduce pressure drop and noise, and check whether it is firm before installation.
Working principle and conditions of fan muffler
1) Working principle
The model is selected and muffler of fan is designed at earlier stage according to the exhaust volume of fan, the nature and temperature of exhaust gas. Compound muffler is mainly aimed at large flow of gas, which can reduce pressure drop and disperse airflow through a flow-control and grading for large flow gas. The impact and friction noise produced by high-speed and high-pressure gases are treated by a noise reduction process through the sound absorption material inside the flow control plate. After dispersing, the gas enters the secondary noise reduction process. The secondary noise reduction generally consists of honeycomb, flow control plate, sound absorption wall and other forms of flow control and sound absorption parts. According to customer requirements, different mufflers have different design and working principles, but they are mainly composed of flow control, shunt, sound absorption and so on.
The GF muffler is developed on the basis of the principle of silencing sound with soundproof film. The acoustic performance and aerodynamic performance of the muffler are excellent. The structure is reasonable and easy to install. It is a kind of high air resistance honeycomb muffler. The resistance section adopts the form of multi-chamber resistance rubber straight tube channel and cross-shaped sound absorber, which ensure adequate noise reduction in a wider band. The structure of GF muffler is composed of many parallel muffler tubes. The muffler tubes are filled with porous sound absorbing materials. Stiffeners shall be installed on the shell in order to reduce the radiated sound generated by the vibration of shell wall caused by airflow.
Based on the spectrum characteristic data obtained from the actual test of noise sources of various industrial fans, the main basis for designing sound absorbers and fluid channels is used to determine what noise reduction amount is needed for spectrum range. Meanwhile, a narrow rectangular channel with large sound absorption material is adopted to enhance the absorption effect. In addition, when the noise source of the fan is at the maximum noise level, its spectrum values is often more than one, and for different spectrum bands, the requirement for noise reduction is also different.
For this reason, the GF series ventilation duct muffler and the blower-induced fan muffler are all impedance acoustic flow type. A resistive structure is adopted to absorb and silence high and intermediate frequency noise, and anti-noise structure is adopted to suppress the noise of medium and low frequencies. At the same time, two kinds of sound absorption and muffling zones, high frequency and low frequency, are adopted in the resistance channel to maximize the muffling frequency band, so as to achieve a good effect of noise reduction and muffling.
GF series ventilation duct fan muffler and blower induced draft fan muffler are suitable for all kinds of centrifugal, axial flow, Roots fan and air compressor.
2) Working conditions
(1) The solid content in the air flow of the fan shall not exceed 10% per cubic meter.
(2) Gas discharged or inhaled, non-corrosive.
(3) The moisture contained in the gas is non-sticky or other non-corrosive liquid gas passing through the muffler.
Application Range of Fan Muffler
Mainly used for various series of high-pressure centrifugal fans, used to reduce aerodynamic noise such as inlet and outlet port. It is widely used in power, petroleum, chemical industry, metallurgy, municipal, textile, cement, environmental protection and other industries for efficient noise reduction. For example: high-pressure fan, centrifugal fan, axial fan, Roots fan, blower, induction/supply fan, fan, oblique fan, cross-flow fan and so on.
A. During hoisting, unloading and transportation, the outer packaging of the muffler can’t be damaged to prevent impurities from entering the muffler or blocking the small holes.
B. Check the specifications and models of mufflers according to the packing list, check whether the mufflers are in good condition, and check whether the technical data (including product qualification certificate, quality certificate, muffler completion drawings and use instructions) are complete.
C. Mufflers should be packaged and stored if they are not installed immediately after acceptance. Do not expose to air the muffler holes and nozzle grooves for a long time. Even if they are stacked on site for a short time before installation, they are not allowed to be exposed in places with mud or other impurities in order to avoid blocking the holes.
Instructions for ordering
1. Purposes (dust removal, intake and exhaust fans, workshop intake and exhaust outlets, noise control of other types of high and low pressure fans, etc.).
2. The installing types shall be explained for fan exhaust port, intake port, pipeline middle installation form, pipeline end installation form, vertical installation form, horizontal installation form and so on.
3. Emissions: m/h
4. Diameter and wall thickness of the original interface.
5.Our company can design and produce all kinds of silencers/mufflers as long as the technical parameters provided by users are complete.
Technical parameters of muffler
Muffler technical parameters means the type of working medium, working medium emission (m/h), working medium state before the valve, and the diameter and length of exhaust (gas) pipe (mm), which are the main basis for designing muffler specifications. The detail parameters, size and weight can be found in samples or random data.
Following is the data of muffler parameters of conventional fans for reference only. Our company can design and manufacture it according to the actual working conditions of customers.
|S/N||Model||Blowing rate(10000m3/h)||Nominal size||Weight||Examples of power boiler application (for order reference).|
|1||GF-5||4-6||1.2||1.6||1750||Air intake of feeder fan for N6 turbine and 35TH boiler.|
|2||GF-7||6-7||1.2||2.4||2400||Air intake of feeder fan for N12 turbine and 60TH boiler.|
|3||GF-10||8-12||1.6||2.4||2950||Air intake of feeder fan for N25 turbine and 120TH boiler.|
|5||GF-18||15-20||2.4||2.4||4400||Air intake of feeder fan for N50 turbine and 220TH boiler.|
|7||GF-23||20-25||2.0||4.0||5500||Air intake of feeder fan for N100,N670 turbine and 400TH, 410TH boiler.|
|10||GF-45||38-50||4.0||3.2||10500||Air intake of feeder fan for N100,N670 turbine and 400TH, 410TH boiler.|
|12||GF-60||50-70||5.0||4.0||14400||Air intake of feeder fan for N310 turbine and 1000TH boiler.|
1. The dimensions of the nozzles shall be changed if the size of exhaust nozzles are not in conformity with the tables.
2. As there are many kinds of steam emission items of thermal equipment values, our company will design and manufacture silencers of various specifications according to the amount of exhaust steam, steam pressure and nozzle size proposed by users.
Daily maintenance and attentions
1. Operators can’t desert their post jobs, shall pay attention to the operation of the equipment, and stop to check and it measures should be taken in time if abnormal condition is found.
2. Check the fastening condition of each component regularly, no loosening is allowed.
3. Check regularly whether the weld and support points are abnormal or not.
4. Observe whether the fan muffler flutters or not and tighten the flange in time when the leakage is serious.