Noise from compressed air can be very loud and damaging so reducing the noise level 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 designs that use a Coanda profile to entrain surrounding air along with the compressed air released, basically converting pressure to flow. This does three things… because pressure is converted rather than lost as pressure drop, 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 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 make use of one of the key advantages of compressed air – the fact that it can be stored and used on demand. Utilizing PLC’s that integrate sensors along a production line can turn the compressed air supply on and off as needed. Obviously when the air is not used, there is no noise and further energy savings are realized.
So next time you are in the factory – “listen” then “look”. Every single exhaust can be addressed to reduce noise levels at relatively low cost with a quick return on energy saving, and improving your plant environment.
Nex Flow Air Products Corp. manufacturers 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.