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// CODE SNIPPET

506.3.2 Joints, Seams and Penetrations of Grease Ducts

2014 FBC - Mechanical, 5th edition > 5 Exhaust Systems > 506 Commercial Kitchen Hood Ventilation System Ducts and Exhaust Equipment > 506.3 Ducts Serving Type I Hoods > 506.3.2 Joints, Seams and Penetrations of Grease Ducts
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Joints, seams and penetrations of grease ducts shall be made with a continuous liquid-tight weld or braze made on the external surface of the duct system.

Exceptions:

  1. Penetrations shall not be required to be welded or brazed where sealed by devices that are listed for the application.
  2. Internal welding or brazing shall not be prohibited provided that the joint is formed or ground smooth and is provided with ready access for inspection.
  3. Factory-built commercial kitchen grease ducts listed and labeled in accordance with UL 1978 and installed in accordance with Section 304.1.

506.3.2.1 Duct Joint Types

Duct joints shall be butt joints, welded flange joints with a maximum flange depth of 1/2 inch (12.7 mm) or overlapping duct joints of either the telescoping or bell type. Overlapping joints shall be installed to prevent ledges and obstructions from collecting grease or interfering with gravity drainage to the intended collection point. The difference between the inside cross-sectional dimensions of overlapping sections of duct shall not exceed 1/4 inch (6 mm). The length of overlap for overlapping duct joints shall not exceed 2 inches (51 mm).

506.3.2.2 Duct-To-Hood Joints

Duct-to-hood joints shall be made with continuous internal or external liquid-tight welded or brazed joints. Such joints shall be smooth, accessible for inspection, and without grease traps.
Exception: This section shall not apply to:
  1. A vertical duct-to-hood collar connection made in the top plane of the hood in accordance with all of the following:
    1. The hood duct opening shall have a 1-inch-deep (25 mm), full perimeter, welded flange turned down into the hood interior at an angle of 90 degrees (1.57 rad) from the plane of the opening.
    2. The duct shall have a 1-inch-deep (25 mm) flange made by a 1-inch by 1-inch (25 mm by 25 mm) angle iron welded to the full perimeter of the duct not less than 1 inch (25 mm) above the bottom end of the duct.
    3. A gasket rated for use at not less than 1,500°F (815°C) is installed between the duct flange and the top of the hood.
    4. The duct-to-hood joint shall be secured by stud bolts not less than 1/4 inch (6.4 mm) in diameter welded to the hood with a spacing not greater than 4 inches (102 mm) on center for the full perimeter of the opening. All bolts and nuts are to be secured with lockwashers.
  2. Listed and labeled duct-to-hood collar connections installed in accordance with Section 304.1.

506.3.2.3 Duct-To-Exhaust Fan Connections

Duct-to-exhaust fan connections shall be flanged and gasketed at the base of the fan for vertical discharge fans; shall be flanged, gasketed and bolted to the inlet of the fan for side-inlet utility fans; and shall be flanged, gasketed and bolted to the inlet and outlet of the fan for in-line fans. Gasket and sealing materials shall be rated for continuous duty at a temperature of not less than 1500°F (816°C).

506.3.2.4 Vibration Isolation

A vibration isolation connector for connecting a duct to a fan shall consist of noncombustible packing in a metal sleeve joint of approved design or shall be a coated-fabric flexible duct connector listed and labeled for the application. Vibration isolation connectors shall be installed only at the connection of a duct to a fan inlet or outlet.

506.3.2.5 Grease Duct Test

Prior to the use or concealment of any portion of a grease duct system, a leakage test shall be performed. Ducts shall be considered to be concealed where installed in shafts or covered by coatings or wraps that prevent the ductwork from being visually inspected on all sides. The permit holder shall be responsible to provide the necessary equipment and perform the grease duct leakage test. A light test shall be performed to determine that all welded and brazed joints are liquid tight.

A light test shall be performed by passing a lamp having a power rating of not less than 100 watts through the entire section of ductwork to be tested. The lamp shall be open so as to emit light equally in all directions perpendicular to the duct walls. A test shall be performed for the entire duct system, including the hood-to-duct connection. The duct work shall be permitted to be tested in sections, provided that every joint is tested. For listed factory-built grease ducts, this test shall be limited to duct joints assembled in the field and shall exclude factory welds.

Related Code Sections


506.3.2 Exhaust Systems, Joints, Seams and Penetrations of Grease Ducts
Joints, seams and penetrations of grease ducts shall be made with a continuous liquid-tight weld or braze made on the external surface of the duct ...
2017 FBC - Mechanical, 6th edition > 5 Exhaust Systems > 506 Commercial Kitchen Hood Ventilation System Ducts and Exhaust Equipment > 506.3 Ducts Serving Type I Hoods > 506.3.2 Joints, Seams and Penetrations of Grease Ducts
506.3.2 Exhaust Systems, Joints, Seams and Penetrations of Grease Ducts
Joints, seams and penetrations of grease ducts shall be made with a continuous liquid-tight weld or braze made on the external surface of the duct ...
2020 FBC - Mechanical, 7th edition > 5 Exhaust Systems > 506 Commercial Kitchen Hood Ventilation System Ducts and Exhaust Equipment > 506.3 Ducts Serving Type I Hoods > 506.3.2 Joints, Seams and Penetrations of Grease Ducts
506.3.2 Exhaust Systems, Joints, Seams and Penetrations of Grease Ducts
Joints, seams and penetrations of grease ducts shall be made with a continuous liquid-tight weld or braze made on the external surface of the duct ...
2014 FBC - Mechanical, 5th edition > 5 Exhaust Systems > 506 Commercial Kitchen Hood Ventilation System Ducts and Exhaust Equipment > 506.3 Ducts Serving Type I Hoods > 506.3.2 Joints, Seams and Penetrations of Grease Ducts
506.3.2.1 Exhaust Systems, Duct Joint Types
Duct joints shall be butt joints, welded flange joints with a maximum flange depth of 1 / 2 inch (12.7 mm) or overlapping duct joints of either ...
2020 FBC - Mechanical, 7th edition > 5 Exhaust Systems > 506 Commercial Kitchen Hood Ventilation System Ducts and Exhaust Equipment > 506.3 Ducts Serving Type I Hoods > 506.3.2 Joints, Seams and Penetrations of Grease Ducts > 506.3.2.1 Duct Joint Types
506.3.2.2 Exhaust Systems, Duct-To-Hood Joints
Duct-to-hood joints shall be made with continuous internal or external liquid-tight welded or brazed joints. Such joints shall be smooth, accessible ...
2017 FBC - Mechanical, 6th edition > 5 Exhaust Systems > 506 Commercial Kitchen Hood Ventilation System Ducts and Exhaust Equipment > 506.3 Ducts Serving Type I Hoods > 506.3.2 Joints, Seams and Penetrations of Grease Ducts > 506.3.2.2 Duct-To-Hood Joints
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