Three steps for noise control in compressed air blow off and exhaust. Noise from compressed air can be very loud and damaging, so reducing noise is important.
Three steps should be taken where ever compressed air is exhausted, whether from cylinders or when used for blow-off and cooling applications.
- Mufflers and Engineered Nozzles: Compressed air used for exhaust, typically from a cylinder, should have exhaust mufflers. Compressed air used for blow-off or cooling should utilize engineered blow-off nozzles that reduce noise levels. There are a few different designs on the market claiming to be the best, but the ones that perform optimally tend to be those that use a Coanda profile to entrain surrounding air along with the compressed air released, basically converting pressure to flow. This does three things… pressure is converted rather than lost as pressure drops, noise levels fall dramatically, energy consumption is reduced, and a laminar flow is maintained at a greater distance than from an open pipe, tube or hole so the nozzle or other blow off device is effective at a much greater distance.
- Velocity: Sound level is proportional to the velocity of the compressed air flow exhausted. In fact, the sound level is proportional to velocity by a factor to the power of 8.
Sound Level ∞ Velocity8
Exhaust mufflers will take this into account. Once blow-off nozzles or other air-saving/noise reducing blow off products are installed, the velocity can be reduced by cutting back on the pressure at that location to the level where it accomplishes its job and then kept at the level. This minimizes noise levels and also saves energy. - On-Off Control: Finally, you should use one of the key advantages of compressed air – that it can be stored and used on demand. Utilizing PLCs that integrate sensors along a production line can turn the compressed air supply on and off as needed. When the air is not used, there is no noise, and further energy savings are realized.
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So next time you are in the factory – “listen” then “look”. Every exhaust can be addressed to reduce noise levels at a relatively low cost with a quick return on energy saving and improving your plant environment.
Nex Flow Air Products Corp. manufactures engineered nozzles and other blow-off products and can advise on the best item to use for any particular application and offer consultation for end-use noise and energy management.
