Function of cylinder silencer, principle of cylinder silencer and precautions for selection

Cylinder silencer function


Noise includes mechanical noise, electromagnetic noise and aerodynamic noise. The sound produced by solid vibration is mechanical noise. In the electromagnetic coil, the vibration of the moving iron core caused by alternating current is electromagnetic noise. When gas flows, eddy currents or sudden changes in pressure occur, causing vibration of the gas, which is aerodynamic noise.



The compressed air on the exhaust side of the cylinder is usually discharged into the atmosphere through the exhaust port of the reversing valve. Due to the high residual pressure, the maximum exhaust speed is near the speed of sound, and the air expands rapidly, causing vibration of the gas, resulting in strong exhaust noise. The size of the noise is related to the exhaust speed, exhaust volume and shape of the exhaust channel.



The amount of noise is measured in decibels (dB). The noise in a general machine shop is 70~85dB, and the noise emitted by pneumatic tools such as air rivet guns is about 100 dB. According to international standards, when working eight hours a day, the allowed continuous noise is 90 dB;when the time is halved, the noise is allowed to increase by 3 dB, but 115 dB is the maximum limit. Any noise above 85 dB should be reduced.



People's perception of noise is also related to the frequency of the noise. The generally audible sound frequency range is 20~20000HZ, and the normal speaking sound frequency range is 500~2000HZ. High-frequency noise sounds much louder than low-frequency noise at the same decibel level.



On a gas tank with a volume of 24L and an internal pressure of 0.5MPa, a solenoid valve with an effective cross-sectional area of ​​48.5mm2 is installed. When the solenoid valve is opened to vent to the outside world, the general exhaust noise is 1m away from the outlet of the solenoid valve. 80~120dB.



Working in a noisy environment for a long time will make people feel tired and reduce work efficiency;it will also reduce people's hearing and affect human health. Therefore, corresponding measures to reduce noise must be taken.








Working principle of cylinder silencer


Good noise reduction performance means that there is a sufficient amount of noise reduction within the frequency range of the noise generated. Two silencing principles are introduced below:
1) Absorption type, which allows compressed air to pass through porous sound-absorbing materials and generate heat through the friction of air flow, so that the pressure energy of the gas is partially converted into heat energy, thereby reducing exhaust noise. Absorption mufflers have good performance in eliminating medium and high frequency noise. Generally, the noise can be reduced by more than 25 dB. Most sound-absorbing materials use polyvinyl chloride fiber, glass fiber, sintered copper beads, etc.



2) Expansion interference type, the diameter of this muffler is larger than the exhaust hole diameter. The airflow diffuses, collides, reflects, and interferes with each other inside, weakening the noise intensity, and is finally discharged into the atmosphere from the porous shell with a larger aperture. Mainly used to eliminate medium and low frequency noise.



Lead the gas discharged from some air valves to a main exhaust pipe with a sufficiently large inner diameter. An exhaust cleaner can be installed at the outlet of the main exhaust pipe, or the outlet of the exhauster can be located outdoors or in a trench to reduce the working environment. The noise inside is called the concentrated exhaust method. This method uses the principle of expansion interference to reduce noise.







Precautions for selection and use of cylinder silencer
1) The requirements for the muffler are to have good noise reduction effect within the noise frequency range and small exhaust resistance (that is, the effective cross-sectional area must be large), so as not to affect the reversing performance of the reversing valve. And the structure is required to be durable, that is, the holes are not easily blocked and easy to clean. The specifications of the muffler are usually selected based on the connection diameter of the reversing valve. If the holes are clogged, they must be cleaned or replaced. Otherwise, the flow rate will decrease, the actuator speed will gradually slow down, and the response performance will gradually deteriorate.


2) When the connector is made of resin material, although it has sufficient strength, the installation force should not be too large, and it should not bear lateral impact loads.


3) When the sound-absorbing material is PP, PE or PVF, it should not be used in situations where organic solvents exist.
4) It should be noted that the adiabatic expansion temperature drops during exhaust, which will cause the moisture contained in the compressed air to freeze on the cylinder muffler, causing the exhaust resistance to increase. Therefore, the moisture should be separated as much as possible in the pipeline before exhaust.






The above is an introduction to the function of the cylinder muffler, the principle of the cylinder muffler and the precautions for selection. If you want to know more relevant information, please log in to Sunway Pneumatic www.diancifa.cc.