SECTION 15889 DUCTWORK

This spec was part of the Des Plaines, IL River WRF project that bid Feb 26, 2015.


SECTION 15889 DUCTWORK
PART 1 - GENERAL

1.1 SUMMARY

A. Work Includes

1. Ductwork
a. Rectangular
1) Galvanized
2) Stainless Steel
b. Double Wall insulated ductwork – Outdoor Conditioned Air Applications

2. Duct cleaning.

1.2 REFERENCES

A. American Society for Testing and Materials (ASTM)

1. ASTM A90 Test Method for Weight of Coating on Zinc-Coated (Galvanized) Iron or Steel Articles

2. ASTM A167  Specification for Stainless and Heat-Resisting Chromium Nickel Steel Plate, Sheet and Strip

3. ASTM  A525  Specification  for  General  Requirements  for  Steel  Sheet,  Zinc- Coated (Galvanized) by the Hot Dip Process

4. ASTM A527 Specification for Steel Sheet, Zinc-Coated (Galvanized) by the Hot Dip Process, Lock-Forming Quality

5. ASTM  C553  Specification  for  Mineral  Fiber  Blanket  and  Felt  Insulation (Industrial Type)

B. Underwriters Laboratories Inc. (UL)

1. UL 181 Factory-Made Air Ducts and Connectors

C. National Fire Protection Association (NFPA)

1. NFPA 90A Installation of Air Conditioning and Ventilating Systems

D. Sheet Metal and Air Conditioning Contractors National Association (SMACNA)

1. SMACNA Low Pressure Duct Construction Standards

2. SMACNA High Pressure Duct Construction Standards

E. American   Society   of   Heating,   Refrigerating   and   Air   Conditioning   Engineers (ASHRAE):

1.
ASHRAE
Handbook Fundamentals; Chapter 33 - Duct Design
2.
ASHRAE
Handbook Equipment; Chapter 1 - Duct Construction

1.3 DEFINITIONS

A. Duct Sizes: Inside clear dimensions as shown on plans. For lined ducts, maintain sizes inside lining.

B. Low Pressure Ductwork: Up to 2 inch WG positive or negative pressure and velocities less than 2,500 FPM.

1.4 REGULATORY REQUIREMENTS

A. Construct ductwork to NFPA 90A.


PART 2 - PRODUCTS

2.1 MATERIALS

A. Comply with SMACNA's "HVAC Duct Construction Standards--Metal and Flexible" for acceptable materials, material thicknesses, and duct construction methods, unless otherwise indicated. Sheet metal materials shall be free of pitting, seam marks, roller marks, stains, discolorations, and other imperfections.

B. Reinforcement Shapes and Plates: Galvanized-steel reinforcement where installed on galvanized sheet metal ducts, Stainless Steel where installed on stainless steel ducts.

C. General: Non-combustible or conforming to requirements for Class 1 air duct materials, or UL 181.

D. Steel Ducts: ASTM A525 or ASTM A527 galvanized steel  sheet,  lock-forming quality, having zinc coating of 1.25 oz per sq ft for each side in conformance with ASTM A90.

E. Stainless Steel Ducts: ASTM A167, Type 304, 2 gauges heavier than standard galvanized ductwork. (In lieu of stainless steel, rigid fiberglass ductwork can be substituted pending approval of the engineer.)

F. Fasteners: Rivets, bolts, or sheet metal screws. Use  stainless  steel  fasteners  on stainless steel ducts.

G. Sealant: Non-hardening, water resistant, fire resistive, compatible with mating materials; liquid used alone or with tape, or heavy mastic.

H. Tie Rods: Galvanized steel, 1/4-inch minimum diameter for lengths 36 inches or less; 3/8-inch minimum diameter for lengths longer than 36 inches.

I. Hanger Rod: Steel, galvanized; threaded both ends, threaded one end, or continuously threaded. Stainless steel in areas where stainless steel duct is used.

2.2 SEALANT MATERIALS

A. Joint and Seam Sealants, General: The term "sealant" is not limited to materials of adhesive or mastic nature but includes tapes and combinations of open-weave fabric strips and mastics.

B. Joint and Seam Tape: 2 inches wide; glass-fiber-reinforced fabric.

C. Tape Sealing System: Woven-fiber tape impregnated with gypsum mineral compound and modified acrylic/silicone activator to react exothermically with tape to form hard, durable, airtight seal.

D. Water-Based Joint and Seam Sealant: Flexible, adhesive sealant, resistant to UV light when cured, UL 723 listed, and complying with NFPA requirements for Class 1 ducts.

E. Solvent-Based Joint and Seam Sealant: One-part, nonsag, solvent-release-curing, polymerized butyl sealant formulated with a minimum of 75 percent solids.

F. Flanged Joint Mastic: One-part, acid-curing, silicone, elastomeric joint sealant complying with ASTM C 920, Type S, Grade NS, Class 25, Use O.

G. Flange Gaskets:  Butyl rubber or EPDM polymer with polyisobutylene plasticizer.

2.3 HANGERS AND SUPPORTS

A. Building Attachments: Concrete inserts, powder-actuated fasteners, or structural-steel fasteners appropriate for construction materials to which hangers are being attached.

1. Use powder-actuated concrete fasteners for standard-weight aggregate concretes or for slabs more than 4 inches thick.

2. Exception: Do  not  use  powder-actuated  concrete  fasteners  for  lightweight- aggregate concretes or for slabs less than 4 inches thick.

B. Hanger Materials: Galvanized sheet steel or threaded stainless steel rod. Note: All Hanger material shall be either Galvanized or stainless steel. No bare steel hangers will be accepted.

1. Hangers Installed in Corrosive Atmospheres: Electrogalvanized, all-thread rods or galvanized rods with threads painted with zinc-chromate primer after installation.

2. Strap and Rod Sizes: Comply with SMACNA's "HVAC Duct Construction Standards--Metal and Flexible" for steel sheet width and thickness and for steel rod diameters.

3. Galvanized-steel straps attached to aluminum ducts shall have contact surfaces painted with zinc-chromate primer.

C. Duct Attachments: Sheet metal screws, blind rivets, or self-tapping metal screws; compatible with duct materials.

D. Trapeze and Riser Supports:  Steel shapes complying with ASTM A 36/A 36M.

1. Supports for Galvanized-Steel Ducts:  Galvanized-steel shapes and plates.

2. Supports for Stainless-Steel Ducts:  Stainless-steel support materials.

2.4 RECTANGULAR DUCT FABRICATION

A. Fabricate ducts, elbows, transitions, offsets, branch connections, and other construction according to SMACNA's "HVAC Duct Construction Standards--Metal and Flexible" and complying with requirements for metal thickness, reinforcing types and intervals, tie-rod applications, and joint types and intervals.

1. Lengths:  Fabricate rectangular ducts in lengths appropriate to reinforcement and rigidity class required for pressure class.

2. Deflection: Duct  systems  shall  not  exceed  deflection  limits  according  to SMACNA's "HVAC Duct Construction Standards--Metal and Flexible."

B. Transverse Joints: Prefabricated slide-on joints and components constructed using manufacturer's guidelines for material thickness, reinforcement size and spacing, and joint reinforcement.

1. Manufacturers:
a. Ductmate Industries, Inc.
b. Nexus Inc.
c. Ward Industries, Inc.

C. Formed-On Flanges: Construct according to SMACNA's "HVAC Duct Construction Standards--Metal and Flexible," Figure 1-4, using corner, bolt, cleat, and gasket details.

1. Manufacturers:
a. Ductmate Industries, Inc.
b. Lockformer.

2. Duct Size:  Maximum 30 inches wide and up to 2-inch wg pressure class.

3. Longitudinal Seams:  Pittsburgh lock sealed with noncuring polymer sealant.

D. Cross Breaking or Cross Beading: Cross break or cross bead duct sides 19 inches and larger and 0.0359 inch thick or less, with more than 10 sq. ft. of nonbraced panel area unless ducts are lined.

2.5 ROUND DUCT AND FITTING FABRICATION

A. Diameter as applied to flat-oval ducts in this Article is the diameter of a round duct with a circumference equal to the perimeter of a given size of flat-oval duct.

B. Round, Spiral Lock -Seam Ducts: Fabricate supply ducts of galvanized steel according to SMACNA's "HVAC Duct Construction Standards--Metal and Flexible."

C. Duct Joints:

1. Ducts up to 48 Inches in Diameter: Interior, center-beaded slip coupling, sealed before and after fastening, attached with sheet metal screws.

D. 90-Degree Tees and Laterals and Conical Tees: Fabricate to comply with SMACNA's "HVAC Duct Construction Standards--Metal and Flexible," with metal thicknesses specified for longitudinal-seam straight ducts.

E. Diverging-Flow Fittings: Fabricate with reduced entrance to branch taps and with no excess material projecting from fitting onto branch tap entrance.

F. Fabricate elbows using die-formed, gored, pleated, or mitered construction. Unless elbow construction type is indicated, fabricate elbows as follows:

1. Mitered-Elbow Radius and Number of Pieces: Welded construction complying with SMACNA's "HVAC Duct Construction Standards--Metal and Flexible," unless otherwise indicated.

2. Round Mitered Elbows: Welded construction with the following metal thickness for pressure classes from minus 2- to plus 2-inch wg:
a. Ducts 3 to 36 Inches in Diameter:  0.034 inch.

3. 90-Degree, 2-Piece, Mitered Elbows: Use only for supply systems or for material-handling Class A or B exhaust systems and only where space restrictions do not permit using radius elbows. Fabricate with single-thickness turning vanes.

4. Round Elbows 8 Inches and Less in Diameter: Fabricate die-formed elbows for 45- and 90-degree elbows and pleated elbows for 30, 45, 60, and 90 degrees only. Fabricate nonstandard bend-angle configurations or nonstandard diameter elbows with gored construction.

5. Round Elbows 9 through 14 Inches in Diameter: Fabricate gored or pleated elbows for 30, 45, 60, and 90 degrees unless space restrictions require mitered elbows. Fabricate nonstandard bend-angle configurations or nonstandard diameter elbows with gored construction.

6. Round Elbows Larger Than 14 Inches in Diameter and All Flat-Oval Elbows: Fabricate gored elbows unless space restrictions require mitered elbows.

7. Die-Formed Elbows for Sizes through 8 Inches in Diameter and All Pressures
0.040 inch thick with 2-piece welded construction.

8. Round Gored-Elbow Metal Thickness: Same as non-elbow fittings specified above.

2.6 GENERAL

A. Construct Ts, bends, and elbows with radius of not less than 1-½ times width of duct on centerline. Where not possible and where rectangular elbows are used, provide turning vanes. Where acoustical lining is indicated, provide turning vanes of perforated metal with glass fiber insulation.

B. Increase duct sizes gradually, not exceeding 15 degrees divergence wherever possible. Divergence upstream of equipment shall not exceed 30 degrees; convergence downstream shall not exceed 45 degrees.

C. Elbows and transformation pieces, etc., shall be one to two gauges heavier, depending on size. Ratio of width individual air passages to total width of elbow shall be one (1) to five (5).

D. Longitudinal joints in horizontal runs or in risers shall be made with grooved seams. In elbows and transformation pieces, they shall be made with Pittsburgh corner seams or double corner seams.

E. Bracing shall be galvanized steel or stainless steel angles as applicable and conform to SMACMA recommendations and standards.

F. All ductwork shall be constructed in accordance with SMACNA and ASHRAE Specifications Standards and in accordance with state and local code requirements. Ductwork to be sealed in accordance with SMACNA seal Class B.

G. Provide fire resistant neoprene or other approved flexible connections on the entering and leaving side of all air handling units, etc., and at the collection boxes of all roof fans, etc., or as shown on plans, equal to Ventfabric "Ventglas". Attach with metal collar frames to prevent air leakage.

H. Provide flexible connection for ducts of dissimilar metals to prevent galvanic action.

I. Use double nuts and lock washers on threaded rod supports.

2.7 DOUBLE WALL INSULATED DUCTWORK

A. All ductwork located outside the building envelope conveying conditioned air shall be of double wall insulated construction.

B. All panels shall be 2 inches thick or as shown on the Drawings with a galvanized steel exterior shell and a solid interior shell of material suitable for application or as noted on the Drawings.  Unless noted here – (Note:  Interior material shall be stainless steel).

C. The exterior and interior shells shall be tack or spot welded to perimeter and internal longitudinal steel channels and box-end internal closures in such a manner and spacing that no failure of the panel assembly will occur at the maximum operating loads in the structural performance section hereinafter specified.

D. The exterior shell material shall be a minimum 18 gauge and the interior shell material shall be a minimum 22 gauge or as noted for stainless steel above.

E. Perimeter and internal longitudinal steel channel members shall be ASTM Type A-446 structural quality galvanized steel and shall be a minimum 16 gauge steel thickness.

F. Steel panel surfaces, internal channels and trim items shall be fabricated from zinc- coated steel with a hot-dipped galvanized coating, resulting in a minimum G-90 coating class as determined by ASTM A-525 and shall meet requirements of ASTM A-526 for commercial quality galvanized carbon steel.

G. Each panel assembly shall be completely filled with acoustical/thermal insulation material that is non-combustible, inert, mildew resistant and vermin-proof. Insulation shall not settle within the panel assembly. No insulating materials shall be used that have a flame spread rating over 25 or a smoke developed rating of over 50 as determined by ASTM Standard E-84 (UL-723, NFPA 255) and as specified by ANSI/NFPA Standard 90A.

H. Panels shall be of tongue-and-groove construction, with adjacent panels held rigidly together by the use of an integral, longitudinally continuous, self-locking joint, effective on both the inside and outside of each panel joint interface.

I. Insulating materials used in prefabricated panel assemblies shall have thermal conductivity of 0.12 at a mean temperature of 75 degrees Fahrenheit.


PART 3 - EXECUTION

3.1 SERVICE

A. Ductwork systems serving and/or located in Class 1, Division 1 areas, high moisture and/or corrosive areas to be stainless steel and/or as noted on the drawings.

3.2 INSTALLATION

A. Provide openings in ductwork where required to accommodate thermometers and controllers. Provide pilot tube openings where required for testing of systems, complete with metal can with spring device or screw to ensure against air leakage. Where openings are provided in insulated ductwork, install insulation material inside a metal ring.

B. Locate ducts with sufficient space around equipment to allow normal operating and maintenance activities.

C. Suspended horizontal ductwork shall be securely and rigidly anchored and supported from the building structure by means of rod-angle iron or strap iron hangers. Rod hangers shall be threaded at both ends and equipped with nuts and washers. Angle and straphangers shall be attached to ducts by means of welds or sheet metal screws or by rivets. They shall be attached to suitable roof or ceiling structures through formed angles, by anchor screws and heavy, wide washers. If attached to floor slab, the bearing quality of slab material shall be checked and found capable of supporting weight of duct.

D. Vertical dust risers shall be rigidly supported as they pass through floors, ceilings or roofs by angle iron spanning the opening and firmly and securely attached to the building walls or columns. All ductwork shall be so installed as to be free from vibration under all normal operating conditions. Where required, suitable sound attenuators shall be incorporated with the anchors and/or supports. Finish openings in floors, walls and ceilings with 22 gauge sheet metal closures to give a neat appearance.

E. Where ducts pass through walls or floors, provide a suitable sheet metal angle around the periphery of the duct. Where ducts pass through exterior building construction, provide a suitable flashing and counterflashing to make a weathertight installation.

F. Where external insulated ducts pass through walls, floors or ceilings, suitable size openings shall be made to allow for the insulation through the opening. The insulation shall not be stopped on each side of the opening.

G. Connect diffusers to low pressure ducts with 5 feet maximum length of flexible duct. Hold in place with strap or clamp.

3.3 FIELD QUALITY CONTROL

A. Perform the following field tests and inspections according to SMACNA's "HVAC Air Duct Leakage Test Manual". Provide evidence of compliance upon request.

1. Disassemble, reassemble, and seal segments of systems to accommodate leakage testing and for compliance with test requirements.

2. Conduct tests at static pressures equal to maximum design pressure of system or section being tested. If pressure classes are not indicated, test entire system at maximum system design pressure. Do not pressurize systems above maximum design operating pressure.

3. Maximum Allowable Leakage: Comply with requirements for Leakage Class 3 for round and flat-oval ducts, Leakage Class 12 for rectangular ducts in pressure classes lower than and equal to 2-inch wg (both positive and negative pressures), and Leakage Class 6 for pressure classes from 2- to 10-inch wg.

4. Remake leaking joints and retest until leakage is equal to or less than maximum allowable.

3.4 ADJUSTING AND CLEANING

A. Clean duct system and force air at high velocity through duct to remove accumulated dust. To obtain sufficient air, clean half the system at a time. Protect equipment, which may be harmed by excessive dirt with temporary filters, or bypass during cleaning.

END OF SECTION