Paint booth packages are often purchased with integral axial exhaust fans. The exhaust fans come with an estimated pressure loss, which may not be application-specific because the booth (s) location is not always determined at the time of order. Most Original equipment manufacturers (OEM) package booth suppliers select fans on airflow (CFM) and don’t consider pressure loss or noise levels. This project review offers an example of attenuation of excessive noise from three identical paint booths that are used by a manufacturer of damper control products.
Industrial plants have the risk of generating high levels of noise when operating. Long exposure can cause numerous issues for workers. In this case, the owner was concerned about his worker’s exposure to excessive noise levels because when subjected to high sound levels, health issues such as permanent hearing loss may result.
The client purchased three packaged paint booth systems. Each booth exhausted 8,000 CFM from their assigned assembly line. All booths included identical tube axial fans for ventilation. The design intent was to duct the booth exhaust air up through the roof and outside.
Fan inlet silencers on paint booth exhaust fans
Following the system installation, the customer was extremely concerned about the noise emitted as an individual paint booth was recorded at 95 dBA. When decibels are in harmony with adjacent fans, they increase the total dBA by three. With an understanding of synchronous noise, the estimated noise levels with three fans operating simultaneously were projected to be about 101 dBA. OEMs are not specialists in ventilation criteria like noise, airflow, static pressure, etc. As a result, these variables are often overlooked in packaged systems, causing issues like the one explained above. The end user approached SysTech for alternatives to address the needed noise attenuation.
Of the options discussed, most would have been “band-aid” solutions to the noise issues experienced. The typical solutions for the noise issue would be new fans or fan silencers. The end-user hesitated to purchase new fans because of the current fan issue, so inlet silencers were the solution. The silencers were sized based on the true fan noise and the customer’s noise requirements of 70 dBA at 10’ from the booth opening. To meet the criteria, we constructed a 72” long and 40” in diameter silencer that fulfilled the end user’s requirements.
The silencer installation project was a success, mostly because the parts on this order were rapid-build and shipped in 2 weeks. Because the booths were already installed, this quick shipment allowed the plant to get the booths back up and running in a timeline that did not heavily impact workflow.
A recent follow-up visit, to the site to ensure working order showed decreased dBA and high customer satisfaction. They could not believe how quiet it was. The new sound reading was between 65 and 70 dBA per booth. An exact reading was not possible as the outside plant noise was louder than the fans, skewing the readings.
