SECTION 233114 - MEDIUM PRESSURE DUCTWORK



This master should be used by designers working on Port of Portland construction projects and by designers working for PDX tenants (“Tenants”). Usage notes highlight a few specific editing choices, however the entire section should be evaluated and edited to fit specific project needs.

SECTION 233114 - MEDIUM PRESSURE DUCTWORK

GENERAL

1. DESCRIPTION

A. This section describes medium pressure ductwork and fittings, including round and oval, single and double wall, and rectangular steel.

2. RELATED WORK SPECIFIED ELSEWHERE

A. Section 230500, Common Work Results for HVAC

B. Section 230529, Hangers and Supports for HVAC Piping and Equipment

C. Section 230545, Seismic Restraints for HVAC Piping and Equipment

D. Section 230548, Vibration and Seismic Controls for HVAC Piping and Equipment

E. Section 230590, Pressure Testing of HVAC Systems

F. Section 230593, Testing, Adjusting, and Balancing

G. Section 230719, HVAC Insulation

H. Section 233300, Air Duct Accessories

I. Section 233600, Air Terminal Units

3. REFERENCES

A. NFPA: National Fire Protection Association

1. NFPA 90A: Standard for the Installation of Air-Conditioning and Ventilating Systems

B. SMACNA: Sheet Metal and Air Conditioning Contractors’ National Association

1. SMACNA HVAC Duct Construction Standards - Metal and Flexible

4. SUBMITTALS

A. For systems, equipment, and components specified herein, submit product/material data; shop drawings; as-constructed data; installation, startup, and testing manuals; and as-constructed drawings.

1. Rectangular Steel Ductwork: Include schedule of rectangular duct construction standards.

Use only if Commissioning Section 019100 is included in the project manual.

B. Commissioning Plans and Related Documentation: For systems, equipment, and components specified herein, submit commissioning plans and schedules; and checkout, startup, operational, functional and final acceptance test plans, procedures, checklists, and reports.

5. QUALITY ASSURANCE

A. Installer Qualifications: Work shall be performed by qualified, experienced mechanics, in accordance with SMACNA and these specifications.

B. Regulatory Requirements:

1. Entire ductwork system, including materials and installation, shall be installed in accordance with NFPA 90A.

2. Ductwork and components shall be listed as UL 181, Class I air duct; flame rating shall not exceed 25 and smoke rating shall not exceed 50.

PRODUCTS

1. HANGERS, SUPPORTS, ANCHORAGE, AND SEISMIC RESTRAINTS

A. Provide hangers, supports, anchorage, seismic restraints, and seismic control for products specified herein in accordance with the requirements of the contract documents and SMACNA “HVAC Duct Construction Standards - Metal and Flexible.”

2. GENERAL

A. Fabricate from galvanized steel, unless otherwise shown on the drawings.

B. Minimum gauge, duct construction, joint reinforcing, fittings, hangers, and supports in accordance with SMACNA “HVAC Duct Construction Standards - Metal and Flexible.”

C. Duct Classification: Ducts shall be considered medium pressure when design velocities exceed 2000 fpm and static pressure is 2-inch W.G. or greater positive. Construct ducts in accordance with minimum reinforcement requirements for static pressure class of 4 inches positive.

3. SINGLE WALL ROUND DUCT AND FITTINGS

A. Acceptable Manufacturers: United Sheet Metal; Semco; Streimers; Dee’s; Metco; Temp Control; Arrow; or equal.

B. Materials:

1. Medium pressure round ductwork up to 36-inch diameter spiral lock seam. Round ducts over 36 inches in diameter shall be either spiral lock seam or shop fabricated with longitudinal seams.

2. Takeoffs: Main and branch takeoffs similar to United Spiral Uniform Duct fittings type SRSTC, SRSTL, SRSPTC, or SRSPTL, typically. All fittings shall be continuously welded.

3. Transitions, Elbows:

a. Transitions of concentric type or eccentric type to maintain elevations detailed, with not more than 15-degree angle variation on sloped portion.

b. 90-degree elbows of five-piece design with centerline radius equal to 1 1/2 times duct diameter minimum, continuously welded. Mitered elbows will not be allowed.

c. 60-degree and 45-degree elbows of three-piece design with long radius.

d. Y-branch fittings similar to United Uniseal SRHY or SRHYR. Bull head tees will not be allowed.

4. SINGLE WALL OVAL DUCT AND FITTINGS

A. Acceptable Manufacturers: United Sheet Metal; Semco; Metco; Dees; or equal.

B. Materials:

1. Medium pressure oval ductwork through 24 inches minor axis (duct height) fabricated from spiral lock seam. Ducts with minor axis above 24 inches shall be fabricated from longitudinal seam ducts.

2. Takeoffs: Main and branch takeoffs shall be similar to United Uniseal fittings type SOSTC, SOSTL, SOSPTC, or SOSPTL, typically. Provide standing seam joints sealed with high pressure duct sealer, or provide welded joints, or provide spot welded joints sealed with high pressure duct sealer.

3. Transitions and Elbows:

a. Transitions of concentric type or eccentric type to maintain elevations detailed, with not more than 15-degree angle variation on sloped portion.

b. 90-degree elbows of pie stamped or five-piece design with centerline radius equal to 1 1/2 times duct diameter minimum. Mitered elbows will not be allowed.

c. 60-degree and 45-degree elbows of three-piece design with long radius.

d. Y-branch fittings similar to United Uniseal SOSYH or SOSYE. Bull head tees are not allowed.

5. DOUBLE WALL ROUND AND FLAT OVAL DUCTWORK

A. Acceptable Manufacturers: United Sheet Metal; Semco; Metco; Dees; or equal.

B. Materials:

1. Medium pressure double wall round and oval ductwork shall have outer pressure sheet from spiral lock seam up to 36-inch diameter round and 22-inch minor axis oval. Round ducts over 36-inch diameter and oval ducts over 22-inch minor axis shall have either spiral lock seam or longitudinal welded seams. Provide 1-inch-thick layer of fiberglass insulation having a k-factor of not less than 0.27 BTU/HR/SF/0 F at 75ºF ambient. Inner liner shall be perforated with not less than 23 percent free area.

2. Double wall fittings shall be similar to single wall fittings except they shall conform to double wall construction as specified above.

6. RECTANGULAR STEEL DUCTWORK

A. Fabricate from galvanized steel unless noted otherwise on the drawings.

B. Longitudinal seams shall be Pittsburgh type. Button punch snap lock may be used only if sheet metal screws are added on 24-inch centers.

C. Joining and reinforcement systems as manufactured by Ductmate, Roloc, TDC, or equal are acceptable. Ductmate 35 is equivalent to SMACNA “J” reinforcement and Ductmate 25 is equivalent to SMACNA “F.” Fasten to duct with sheet metal screws minimum of 6 inches on center.

D. Fittings:

1. Fabricate fittings for easiest airflow using radius elbows with centerline radius elbows equal to 1 1/2 times the duct dimension in the plane of the turn.

2. Transitions: Concentric or eccentric type to maintain elevations with not more than 15 degree angle variation on sloped portion.

3. Conical Taps: For branch takeoff to terminal unit, construct with inlet 4 inches wider than outlet and no raw edges inside.

E. Use of mitered elbows with turning vanes will not be accepted except where indicated on the drawings. Radius elbows with centerline radius less than 1.5D shall be vaned type and may be used only with the approval of the Port.

EXECUTION

1. MEDIUM PRESSURE ROUND AND OVAL DUCTWORK INSTALLATION

A. Install in accordance with the manufacturer’s instructions and with SMACNA “HVAC Duct Construction Standards - Metal and Flexible.”

B. Seal all traverse and longitudinal joints with high pressure duct sealer and wrap with duct sealer tape or hard cast with minimum 2-inch overlap.

C. Use slip-on connections for round ducts 36 inches in diameter and less, and for oval ducts with a 42-inch major axis and less not requiring additional reinforcement. Other ducts shall use flanged joint connections, fabricated and sealed in accordance with the manufacturer’s instructions.

D. Reinforce oval duct in accordance with SMACNA standards.

E. At connections to terminal units a maximum 5'-0" of flexible duct may be substituted for straight duct only.

2. MEDIUM PRESSURE ROUND AND OVAL DOUBLE WALL DUCT INSTALLATION

A. Install in accordance with the manufacturer’s instructions.

B. Seal all traverse and longitudinal joints with high pressure duct sealer and wrap with duct sealer tape or hardcast with minimum 2-inch overlap. Treat all welded seams with protective paint inside and outside.

C. Use slip-on connections for double wall round duct 34 inches in diameter and below, or 40-inch major axis on oval duct and below. Use flange connections on all other sizes.

3. MEDIUM PRESSURE RECTANGULAR DUCT INSTALLATION

A. Install duct, fittings, supports, and hangers in accordance with SMACNA “HVAC Duct Construction Standards - Metal and Flexible.”

B. Seal traverse and longitudinal joints with high pressure duct sealer and wrap with duct sealer tape or hard cast with minimum 2-inch overlap.

C. Provide supplementary steel for support of ductwork in shafts and between building structural members.

D. Make change in duct size or shape necessitated by interference by using rectangular equivalents of equal velocity.

Choose one of the following two articles. Use Commissioning if Section 019100 is included in the project manual; otherwise use Testing.

4. COMMISSIONING

A. Commission systems, equipment, and components specified herein.

B. Field Tests: Perform leakage tests in accordance with Section 230590, Pressure Testing of HVAC Systems.

5. TESTING

A. Check out, start up, and test systems, equipment, and components specified herein.

B. Field Tests: Perform leakage tests in accordance with Section 230590, Pressure Testing of HVAC Systems.

END OF SECTION 233114

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