A Custom Silencer Case Study

Botterell Hall at Queen’s University

Botterell Hall at Queen’s University in Kingston, Ont., is home to the school’s Centre for Neuroscience Studies and plays host to advanced heart, stroke and cancer research. A decision was made to upgrade the mission-critical laboratory’s exhaust system, comprising four roof-mounted high plume exhaust fans situated on top of the 10-storey building. Soon after, it was discovered that commissioned sounds levels failed to comply with a key Ontario regulatory ordinance (MOECC NPC-300). A retrofit noise abatement solution was required.

University Lab Building

High Plume Exhaust Fan noise control

Using dissipative silencers and a modular acoustic barrier to mitigate noise from laboratory exhaust fans

The Project Facility
A University lab building located in a high traffic area

The Noise Source
Laboratory High Plume Exhaust Fan – Axial Fans with Discharge Dilution Nozzles

The Solution
PMA Circular HPF Silencers
PMA AcoustaMod Sound Barrier System

The Project Team
Owner – Queen’s University
General Contractor – Pomerleau
Acoustic Consultant – O2E Environmental Consultants

Reason for Mitigation:
Provincial ordinance; Compliance with local regulatory limits for exterior noise emissions

Project Challenges

Aero-acoustic Challenges

Noise emissions stemming from high plume fan arrangements are typically the greatest at the ‘exhaust tip’ of the equipment, requiring inline silencing between the fan and the dilution nozzle. This fan set required extensive acoustic mitigation, thereby requiring the aero-acoustic design to be made as efficient as possible.

Structural restrictions

In addition to the weight of the inline silencers (42” ID, 144” long), an independent structural support assembly was required to accommodate a full perimeter acoustic barrier. The acoustic barrier was needed to shield casing-radiated noise off of the fan casing. But doing so created excessive wind loads that needed to be transferred into the roof structure.

Site coordination

As a construction project with multiple active trades, site coordination was critical to get the job done safely and to the necessary specifications. Our team managed multiple site coordination considerations that were highly complex including road closures, while also coordinating with various project stakeholders.

Aesthetic and functional considerations

As one of the tallest buildings on campus and in clear view from street level, the acoustic solution needed to align aesthetically with the existing fan set and the building façade. Because the entire fan system required complete acoustic shielding, the final design needed to accommodate clear access for future maintenance.

Project Solution

Design

We supplied four inline bulleted silencers that were installed in between the fan discharge and the dilution nozzle. The core bullet was aerodynamically optimized to reduce pressure drop and introduce greater laminar flow through the body of the silencer. This resulted in zero impact to the vertical plume height created by the system.

Structural Restrictions

Our team worked with the base building engineer to come up with an independent support frame and stub column configuration that properly transferred the wind and dead-loads from the silencer/barrier system to the reinforced roof girders. A complete moment frame was developed to limit critical loads being transferred into the roof.

Installation

Precise installation was critical. So, we coordinated a 3D metrology team to assist with the stub column installation. A series of remote sensors were placed along the interior beam centre lines. Parklane’s 3D structural model was then traced on-site to ensure load transfer points were situated precisely over top of the roof beams.

Site coordination

We coordinated with the client, the general contractor and City of Kingston throughout the process to arrange trades on site, as well as managing crane and freight logistics, and necessary road closures/traffic control—all in a short time frame. The complete on-site installation and site coordination was completed by our in-house team.

Downtime Minimization

To drastically limit crane time on site, the entire structural and acoustic solution was designed in a modular fashion. The acoustic barrier system was pre-integrated to the new substructure to eliminate on-site field assembly. The circular silencers came pre-fabricated inside a support frame, which could then be hoisted as one piece to the roof and installed in a fraction of the time required using traditional methods.

Aesthetics

To ensure the final system blended into the existing building façade, the perimeter acoustic barrier was finished with an architectural cladding panel colour matched to a similar product used on the building penthouse. The silencers were factory painted to match the OEM fan set components.

Results

Despite difficult weather conditions and a demanding schedule, Parklane was able to deliver an acoustically compliant solution which adhered to the structural, mechanical, architectural and functional requirements of the system and the facility. We did it by leveraging our systems and process to ensure a high-precision installation process without error.

Read the full story

View our blog post for the full story of how we helped Queen’s University achieve full regulatory compliance at Botterell Hall.

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