PORTSMOUTH, Virginia –
A Norfolk Naval Shipyard (NNSY) employee's idea has cut the noise generated by a common piece of shipyard industrial equipment, reducing risk to his coworkers and potentially workers at other shipyards.
Paul Foster is the continuous training and development subject matter expert for freeze seals at the shipyard and designed a noise attenuator for freeze seal equipment located in a compressed air trailer, where noise resonated as high as 108 decibels.
The Navy and Department of Defense occupational exposure limit for noise is 85 decibels, equivalent to a busy city. Noise at or above this level is considered hazardous. At 108 decibels, the sound was comparable to a semi-truck when it purges air, said Foster.
That level of noise meant employees were required to wear two layers of hearing protection in order to prevent short- and long-term effects from the exposure.
Dryer towers in the trailer are used to dry air required to make freeze seals, an ice plug used for primary or secondary isolation in a system where liquid flows. Because these dryers accumulate small drops of water, they require a purge valve, which is where the noise comes from.
Because Foster had experience as an insulator, he was familiar with sound-deadening material used on bulkheads (walls) in ships.
"Essentially, I created an enclosure for filters on the dryers and put the sound-deadening materials all the way around," said Foster. "When the loud, piercing sound goes into the material, it is then attenuated."
The device manipulates sound waves in a way similar to stealth technology that bounces radar waves in different directions.
"The more you can get the sound waves to hit the acoustic material, the better the attenuation of the sound will be," said Foster.
Foster worked with the shipyard's rapid prototype lab to help build a prototype attenuator using recommended material and specifications. Once the kinks were worked out, the final device developed was able to greatly reduce the noise.
Foster's attenuator reduced the noise to approximately 84 decibels -- four times less than what it had been and low enough that double hearing protection was no longer required near the equipment.
The best part is, the noise reduction doesn't stop at NNSY. These types of dryer towers are used throughout the Navy, so anyone can use the attenuators, said Foster.
Currently, the NNSY pipefitting shop is working with the engineering and planning department to continue to improve on Foster's design. Mechanics and engineers working on it there believe there is a good chance the noise level can be reduced even further.
Foster was recently recognized with a Beneficial Suggestion Award for his effort.
-NAVSEA-