PRODUCT SPECIFICATION GUIDE
MODEL:DUCT SILENCERS
DIVISION 23–HEATING, VENTILATING, AND AIR-CONDITIONING (HVAC)(PREVIOUSLY DIVISION 15)
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Specifier Notes: This product guide specification is written according to the Construction Specifications Institute (CSI) Format.
The section must be carefully reviewed and edited by the Engineer to meet the requirements of the project and local building code. Coordinate with other specification sections and the drawings.
Delete all "Specifier Notes" when editing this section.
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SECTION 233319
DUCT SILENCERS
PART 1 - GENERAL
1.1SECTION INCLUDES
A.Duct Silencers.
1.2RELATED SECTIONS
A.Section 230548 – Vibration and Seismic Controls for HVAC.
1.3REFERENCES
A.AMCA 1011 – Certified Ratings Program – Product Rating Manual for Acoustical Duct Silencers.
B.ANSI S12.51 – 2002/ISO 3741:1999 Acoustics-Determination of Sound Power Levels of Noise Sources Using Sound Pressure-Precision Method for Reverberation Rooms.
C.ANSI/ASHRAE 41.3 – Standard Method for Pressure Measurement.
D.ASHRAE Applications Handbook, Chapter “Noise and Vibration Control”.
E.ASTM A653 / A653M – Standard Specification for Steel Sheet, Zinc-Coated (Galvanized) or Zinc-Iron Alloy-Coated (Galvannealed) by the Hot-Dip Process.
F.ASTM E84 – Standard Test Method for Surface Burning Characteristics of Building Materials.
G.ASTM E413 – Classification for Rating Sound Insulation.
H.ASTM E477 – Standard Test Method for Measuring Acoustical and Airflow Performance of Duct Liner Materials and Prefabricated Silencers.
I.NFPA 90A – Standard for the Installation of Air-Conditioning and Ventilating Systems.
1.4SUBMITTALS
A.Comply with requirements of Section 013300 - Submittal Procedures.
B.Product Data: Submit manufacturer's product data indicating materials, dimensional data, pressure losses and acoustical performance at octave band center frequencies from 63Hz to 8,000Hz.
C.Shop Drawings: Submit shop drawings indicating assembly, thicknesses, dimensional data, pressure losses, acoustical performance, layout and connection details.
D.Design Data: Provide engineering calculations, referenced to specifications and standards, indicating that maximum room sound levels are not exceeded.
E.Test Reports: Submit laboratory acoustic test reports to indicate dynamic insertion loss and noise generated values of silencers meet or exceed specified values. Acoustic performance data must be submitted for octave band center frequencies from 63Hz to 8,000Hz.
F.Instructions: Indicate installation requirements, which maintain integrity of acoustic performance.
1.5QUALITY ASSURANCE
A.Manufacturer: Company specializing in manufacturing the products specified in this Section with a minimum 5 years experience.
B.Warranty Period: 5 years from the date of shipment.
PART 2 - PRODUCTS
2.1MANUFACTURER
A.Pottorff, 5101 Blue Mound Road, Fort Worth, TX 76106. Phone (817) 509-2300
2.2DUCT SILENCERS
A.General: Furnish and install factory pre-fabricated duct silencers of the types and sizes shown on the plans and/or listed in the schedule. Any change or exception to this specification must be submitted and approved in writing by the Engineer at least 10 days before the bid date.
B.Fire Performance: Combustion ratings for the acoustic fill shall not be greater than the following when tested in accordance with ASTM E84, NFPA Standard 255, or UL No. 723:
Flame Spread Classification – 25
Smoke Development Rating – 50
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Specifier Notes: Select product models according to project schedules and requirements.
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C.Rectangular Silencers including models RFN, RCN, RFP, RCP, RXFN, RXCN, RXFP, RXCP,and RNN: Outer casing shall be not less than ASTM A653/653M, 22 gauge, die-formed, type G60 galvanized lock former quality steel.
D.Rectangular Elbow Silencers including models EFN, ECN, EFP, ECP, EXFN, EXCN, EXFP, EXCP, and ENN: Outer casing shall be not less than ASTM A653/653M, 22 gauge, die-formed, type G60 galvanized lock former qualitysteel
E.Tubular Silencers including models CFN, CFP, CCN, CCP, CXFN, CXFP, CXCN, CXCP andCXNN: Outer casings shall be fabricated from type ASTM A653/653M, G60 galvanized lock former quality steel, in the following gauges:
12-36 inches: 22 gauge.
37-60 inches: 18 gauge.
F.Rectangular Silencers including models STC-40 and STC-45: Outer casing shall be constructed of an inner duct wall and an outer duct wall. The inner duct wall shall be not less than ASTM A653/653M, 22-gauge, die-formed, type G60 galvanized lock former quality steel. The outer duct wall shall be not less than 10-gauge type G60 galvanized steel High Transmission Loss (HTL) type casing.
G.Rectangular Silencers including model STC-50: Outer casing shall be constructed of an inner duct wall and an outer duct wall with not less than ASTM A653/653M, 18-gauge, die-formed, type G60 galvanized lock former quality steel. The thickness of the double wall duct section shall be 2” and filled with 2” thick inorganic glass fiber.
H.Interior partitions for rectangular silencers shall be fabricated from not less than ASTM A653/653M, 26 gauge, die-formed, type G60 galvanized lock former quality perforated steel.
I.Interior partitions for tubular silencers shall be fabricated from not less than ASTM A653/653M, 22 gauge, die-formed, type G60 galvanized lock former quality perforated steel.
J.Fill Material:
1.Dissipative and Film Lined silencers:
a.Models including RFN, RCN, RFP, RCP, RXFN, RXCN, RXFP, RXCP,STC-40, STC-45, STC-50, EFN, ECN, EFP, ECP, EXFN, EXCN, EXFP, EXCP, CFN, CFP, CCN, CCP, CXFN, CXFP, CXCN, and CXCP:
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Specifier Notes: Select one of the following.
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Fill material shall be of inorganic glass fiber of a proper density to obtain the specified acoustic performance and be packed under not less than 5% compression to eliminate voids due to vibration and settling. Materials shall be inert, vermin and moisture proof.
Fill material shall be recycled material made from post-industrial natural cotton fibers and treated with an EPA registered fungal inhibitor to actively resist the growth of mold, fungi and bacteria. Material shall not contain any formaldehydes or Volatile Organic Compounds (VOC’s) in order to prevent off-gassing.
Fill material shall be fiber free, open cellmelamine-based foam. ***Specifier Note: Not available for STC-40, STC-45, and STC-50***
2.No-Media silencers
a.Models includingRNN and CXNN: Duct silencershall not contain fill material of any kind. Sound attenuation shall be achieved with broadly tuned resonators.
3.Media Protection:
a.Dissipative silencers including RFF, RCF, RXFF, RXCF, EFF, ECF, EXFF, EXCF, CFF, CCF, CXFF and CXCF: Where indicated on the silencer schedule, fill material shall be encased in a fiberglass cloth to prevent erosion of fill materialinto the airstream.
b.Models including RFP, RCP, RXFP, RXCP, EFP, ECP, EXFP, EXCP, CFP, CCP, CXFP, CXCP,or where indicated on the silencer schedule: Fill material shall be encased and sealed with a thin layer of polymeric film membrane.
K.Construction:
1.Units shall be constructed in accordance with the ASHRAE Guide recommendations for high pressure ductwork. Seams shall be lock formed and mastic filled. Rectangular casing seams shall be in the corners of the silencer shell to provide maximum unit strength and rigidity. Interior partitions shall be fabricated from single piece, perforated sheets and shall have die-formed entrance and exit shapes so as to provide the maximum aerodynamic efficiency and minimum self-noise characteristics in the duct silencer. Blunt noses or squared off partitions will not be accepted.
2.Attachment of interior partitions to the casing shall be by means of an interlocking track assembly. Tracks shall be solid galvanized steel and shall be permanently attached to the outer casing. Attachment of the interior partitions to the tracks shall be such that a minimum of 4 thicknesses of metal exists at this location. The track assembly shall stiffen the exterior casing, provide a reinforced attachment detail for the interior partitions, and shall maintain a uniform airspace width along the length of the silencer for consistent aerodynamic and acoustic performance.
3.Interior partitions shall be additionally secured to the outer casing with permanently attached nose clips at both ends of the duct silencer.
4.The silencer side sheet casings shall be undersized in comparison to the height of the interior perforated acoustic splitters to maintain a tight seam between the splitters and the silencer casing.
5.Attachment of interior partitions for tubular silencers shall be secured with galvanized steel radial mounting brackets welded to the partition and the outer casing. The radial brackets shall be installed at 90 degree angles to each other to assure uniform spacing for consistent aerodynamic and acoustic performance.
6.All interior partitions shall be located to provide a minimum 1” perimeter clearance at both ends of the silencer shell so as to allow for the field installation of “duct-mate” or similar flanging when required.
7.Sound attenuating units shall not fail structurally when subjected to a differential air pressure of 8 inches water gauge from inside to outside the casing.
8.Airtight construction when required shall be provided by use of a duct sealing compound on the jobsite, material and labor furnished by the contractor.
9.Duct Transitions: When transitions are required to adapt silencer dimensions to connecting ductwork, they shall be furnished by the installing contractor.
2.3SOURCE QUALITY CONTROL
A.Acoustic Performance:
1.All silencer ratings shall be determined in a duct-to-reverberant room test facility, which provides for airflow in both directions through the test silencer in accordance with ASTM Specification E477.
2.The test set-up and procedure shall be such that all effects due to end reflection, directivity, flanking transmission, standing waves and test chamber sound absorption are eliminated.
3.Acoustic ratings shall include Dynamic Insertion Los (DIL) and Generated Noise (GN) Power Levels both for FORWARD FLOW (air and noise in same direction) and REVERSE FLOW (air and noise in opposite directions) with airflow of at least 2000fpm entering face velocity. Data for rectangular silencers shall be presented for tests conducted using silencers no smaller than the following cross sections: Rectangular, in. – 24 x 24, 24 x 30, or 24 x 36.
4.Data for acoustic performance shall include Dynamic Insertion Loss (DIL) and Generated Noise (GN) Power Levels for octave band center frequencies from 31.5Hz to 8,000Hz.
5.For Sound Transmission Class (STC) model silencers: Single-number Sound Transmission Class (STC) ratings determined based on one-third octave band Dynamic Insertion Loss (DIL) values from 125Hz to 4,000Hz shall not be less than:
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Specifier Notes: Select one of the following.
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STC-40 when rated in accordance with ASTM Specification 413.
STC-45 when rated in accordance with ASTM Specification 413.
STC-50 when rated in accordance with ASTM Specification 413
B.Aerodynamic Performance: Static pressure loss of silencers shall not exceed those listed in the silencer schedule at the airflow indicated. Airflow measurements shall be made in accordance with ASTM Specification E477 and in a NVLAP accredited laboratory. Tests shall be reported on the identical units for which acoustic data is presented. Static pressure loss measurements shall be taken in the same set-up and at the same time as DIL and GN.
PART 3 - EXECUTION
3.1INSTALLATION
A.Install duct silencers in accordance with manufacturer’s instructions.
B.Support duct silencers independent of ductwork.
END OF SECTION
Specification Guide for Duct SilencersDecember 2011
PottorffPage 1