A fastening member for joining together adjacent duct sections includes a head and a shank extending from the head, the shank having an unthreaded space adjacent to the head and a threaded portion extending from the unthreaded space, the threaded portion threadedly engaging a hole of an inserted corner plate positioned in flange of a first duct section. When the fastening member is fully inserted, the inserted corner plate positioned in the flange of the first duct section is retained within the unthreaded space.

A fastening member for joining together adjacent duct sections includes a head and a shank extending from the head, the shank having an unthreaded space adjacent to the head and a threaded portion extending from the unthreaded space, the threaded portion threadedly engaging a hole of an inserted corner plate positioned in flange of a first duct section. When the fastening member is fully inserted, the inserted corner plate positioned in the flange of the first duct section is retained within the unthreaded space.

A fastening member for joining together adjacent duct sections includes a head and a shank extending from the head, the shank having an unthreaded space adjacent to the head and a threaded portion extending from the unthreaded space, the threaded portion threadedly engaging a hole of an inserted corner plate positioned in flange of a first duct section. When the fastening member is fully inserted, the inserted corner plate positioned in the flange of the first duct section is retained within the unthreaded space.

A fastening member for joining together adjacent duct sections includes a head and a shank extending from the head, the shank having an unthreaded space adjacent to the head and a threaded portion extending from the unthreaded space, the threaded portion threadedly engaging a hole of an inserted corner plate positioned in flange of a first duct section. When the fastening member is fully inserted, the inserted corner plate positioned in the flange of the first duct section is retained within the unthreaded space.

A fire-rated exhaust duct system comprising a modular configuration or structure. The fire-rated exhaust duct system comprises a plurality of exhaust duct sections. Each of the exhaust duct sections is configured to be joined or connected with other exhaust duct sections in the field or at an installation site, e.g. in building housing a kitchen facility or a laboratory facility to form longer sections or runs for exhaust duct system.

A fire-rated exhaust duct system comprising a modular configuration or structure. The fire-rated exhaust duct system comprises a plurality of exhaust duct sections. Each of the exhaust duct sections is configured to be joined or connected with other exhaust duct sections in the field or at an installation site, e.g. in building housing a kitchen facility or a laboratory facility to form longer sections or runs for exhaust duct system.

A tubular duct member comprises a plurality of sheet metal panels 10, 12 joined along adjacent longitudinal edges by cooperating folded sheet metal catches 14, 16, the catches being pushed together such that respective detent surfaces 28, 30 on each catch engage behind one another to retain the edges of the sheets together. One of the catches 14 includes a body 36 of resilient material compressed between the catches and biasing the catches apart to maintain the detent surfaces 28, 30 bearing against one another.

A tubular duct member comprises a plurality of sheet metal panels 10, 12 joined along adjacent longitudinal edges by cooperating folded sheet metal catches 14, 16, the catches being pushed together such that respective detent surfaces 28, 30 on each catch engage behind one another to retain the edges of the sheets together. One of the catches 14 includes a body 36 of resilient material compressed between the catches and biasing the catches apart to maintain the detent surfaces 28, 30 bearing against one another.

A double wall round or oval duct system assembly having an outer duct connector, an inner duct connector and a closure ring is provided. The inner duct connector of the duct assembly has an adhesive applied on the transverse flange face of its transverse flange thus allowing a sealing connection between the inner and outer duct connectors upon compression with the closure ring. The double wall round or oval duct system assembly will improve the efficiency and will reduce or eliminate air leakage upon connection of two round or oval duct segments. A method of installing the assembly system is also provided.

A vertical Pittsburgh Seam closing apparatus having a base supporting surface, a track mechanism for moving a carriage assembly which holds seam forming members used to close a Pittsburgh Seam, a pair of upper and lower guide members for guiding the duct section into a proper vertical position, and upper and lower clamping members positioned inside the duct section and adjacent the inside portion of the Pittsburgh Seam to be closed, the upper guide members and clamping member being selectively movable and adjustable for accommodating different duct section lengths. In one embodiment, the seam forming assembly includes three roller members mounted in vertical arrangement to each other, one roller member being V-shaped in configuration and the other two roller members being substantially cylindrical in shape. The V-shaped roller member may also include one or more projecting members for forming dimples in the closing process to prevent shifting and/or slipping of the closed seam.