PRODUCT SPOTLIGHT: CONTROLLING COMPRESSED AIR NOISE
John C. Dolehanty
Compressed air is a common and efficient source of energy for air motors, vacuums, pneumatic tools, painting etc. It plays such a large role that it is often referred to as industries ‘Fourth Utility’. One consequence of such prevalent use can be the introduction of excess noise when compressed air is used for cleaning, drying, cooling and part movement applications.
The noise generated by these processes alone is often loud enough to require employers to place affected employees into an on-going Hearing Conservation Program (HCP). This noise needs to be reduced as much as possible to minimize the risk of noise induced hearing loss.
There are several products readily available that are proven to reduce the noise associated with compressed air. These products are either nozzles that are applied to the end of open pipe for blowing, or silencers that are used to quiet pneumatic exhaust.
When the fast moving air stream from an open pipe comes into contact with the surrounding static air, turbulent air flow is generated. One of the resultant by-products is excess noise. Often a nozzle will be placed on the end of a open-pipe. In industry, the main purpose for adding an air nozzle is to modify the blowing pattern of the open-ended compressed air pipe. When using a silencer nozzle, it is desired that the nozzle also maintain the blowing force (thrust) while reducing the sound level. Modifying the air pattern can be accomplished through the use of a variety of nozzles. Keith Timmons, the Managing Partner of Silvent North America states, “most products like this in the market place do nothing more than dispense the air, there is no engineering into the nozzle; it’s just a machined piece of metal that the air passes through”. However, it takes a special type of nozzle to maintain the thrust and produce less sound and to use less energy (compressed air) at the same time.
Silvent is the leading supplier of engineered compressed air nozzles in the world. According to Mr. Timmons, Silvent products are developed “from the beginning to first and foremost reduce compressed air noise at the outlet of the nozzle. As a result, there is a lot of engineering that goes into the outlet orifices on the nozzle tip, as well as the size of the opening, positioning. Everything is designed to process the air through the nozzle tip so that noise is reduced. We break up the air into multiple high-velocity steams of air [via the multiple orifices] that reduce the turbulence, therefore reducing the noise”. Silvent makes nozzles that area able to provide an efficient blowing force from a fraction of an ounce to over 20 lbs. of blowing force.
WHY SHOULD YOU USE NOZZLES? There really are no good reasons NOT to use air nozzles. The proper nozzle application will:
The pictures below show an example of three different Silvent nozzle types. Each nozzle is engineered to reduce the sound level, maintain the thrust (compared to open pipe), consume less compressed air, and meet the OSHA 30 p.s.i. requirement.
Air Wands (Air Guns)
The first priority in eliminating an air wand with an open-ended compressed air pipe is the danger associated with compressed air coming in contact with skin. U.S. Federal O.S.H.A. does not allow sources of compressed air where the dead-end pressure (compressed air pressure that comes in contact against your skin) to exceed 30 p.s.i. All Silvent nozzles meet this requirement – even the nozzles that can produce up to 20 pounds of blowing force. According to Mr. Timmons, this is because “with each nozzle design, with its multiple orifices, it is impossible to dead end enough of the outlet ports with enough surface area to develop 30 p.s.i of pressure against the skin – there is always a relief somewhere”.
Pneumatic Exhaust Control (Mufflers)
Why Are Open Pipes Still In Use Today?
In a single word: Education. The use of compressed air to clean, dry, cool and move parts has been accepted for many, many years. However, the application of silencer nozzles and exhaust mufflers is relatively new. It is very common for employers or employees to assume that a quieter product is “less efficient” or “has less power”. With regards to compressed air, the opposite is true. The more noise generated means the less efficient the air flow. In the case of compressed air, less noise equals more power.
Silvent provides a small booklet entitled The Ten Truths of Blowing with Compressed Air that lays out in layman’s terms may of the daily compressed air truths we take for granted, and communicates and educates how controlling compressed air noise can be an advantageous endeavor.
For questions or information on compressed air nozzles and silencers you can contact Keith Timmons at Silvent (800) 263-5638 or visit their website at www.Silvent.com. Silvent products are available directly through the McMaster Carr supply catalog as well as the MSC Industrial Supply Company catalog.
Mr. Dolehanty is the President of Phase To, Inc., and has over 18 years of experience in hearing conservation and noise control. Mr. Dolehanty can be reached at (517) 886-9379 and at email@example.com.
Copyright © 2006
Phase To, Inc.