Ductwork. Reduce fan-generated noise immediately
movement. Flexible couplings shall be provided at the
outside of any mechanical room wall by acoustically
bottom of pipe risers. Spreaders shall be used to separate
coating or wrapping the duct. The ductwork design shall
adjacent pipes, unless the distance is large enough to
appropriately consider and address airborne equipment
prevent contact in an earthquake. See Chapter 4:
noise, equipment vibration, ductborne fan noise, duct
Structural Engineering, SMACNA Seismic Restraint Manual
breakout noise, airflow generated noise and ductborne
and ASHRAE Application Handbook for more detailed
crosstalk noise. All ductwork connections to equipment
information.
having motors or rotating components shall be made with
Piping Supports. Provide channel supports for multiple
6-inch length of flexible connecters. All ductwork within
pipes and heavy duty steel trapezes to support multiple
the mechanical room or serving courtrooms shall be
pipes. Hanger and support schedule shall have
supported with isolation hangers.
manufacturer's number, type and location. Comply with
Piping Hangers and Isolation. Isolation hangers shall be
MSS SP69 for pipe hanger selections. Spring hangers and
used for all piping in mechanical rooms and adjacent
supports shall be provided in all the mechanical rooms.
spaces, up to a 15.2 m (50 ft) distance from vibrating
Noise Control in Duct Systems. System sound levels at
equipment. The pipe hangers closest to the equipment
maximum flow must be carefully evaluated to ensure
shall have the same deflection characteristics as the
acoustic levels required in Chapter 3. Duct noise control
equipment isolators. Other hangers shall be spring
shall be achieved by controlling air velocity, by the use of
hangers with 19 mm (0.75 in) deflection. Positioning
sound attenuators, by the use of double wall ductwork
hangers shall be specified for all piping 203 mm (8 in) and
with insulation in-between (only on courtroom return air
larger throughout the building. Spring and rubber
transfer grilles) and by not oversizing terminal units. Duct
isolators are recommended for piping 51 mm (2 in) and
liners are not permitted as a means of sound attenuation.
larger hung below noise sensitive spaces.
Terminal units shall be selected so that design air volume
Floor supports for piping may be designed with spring
is approximately three-quarters of the terminal box's
mounts or rubber pad mounts. For pipes subject to large
maximum capacity. Volume dampers in terminal units
amounts of thermal movement, plates of Teflon or
shall be located at least 1.8 m (6 ft) from the closest
graphite shall be installed above the isolator to permit
diffuser and the use of grille mounted balance dampers
horizontal sliding.
shall be restricted except for those applications with
accessibility problems.
Anchors and guides for vertical pipe risers usually must
be attached rigidly to the structure to control pipe
Noise Transmission Attenuation (Courthouses).
movement. Flexible pipe connectors shall be designed
Attenuate noise transmission to and from courtrooms,
into the piping before it reaches the riser.
judges' chambers, jury rooms, prisoner consulting rooms
and from prisoner detention areas.
Provisions for Piping in Earthquake Zones. In regions of
moderate and high seismicity, sleeves for pipes shall be at
least 25 mm (1 inch) larger than the pipe, to allow for
152 F A C I L I T I E S S T A N D A R D S
FOR THE
PUBLIC
BUILDINGS
SERVICE
5.14 Vibration Isolation, Acoustical Isolation, and Seismic Design for Mechanical Systems
Revised March 2005 PBS-P100
Previous Page
