Patent Grant
12152802
The present invention relates to duct systems and more particularly, to a fire-rated ventilation duct system.
Various regulatory regimes require that buildings be designed and constructed to provide safe means of egress to enable the occupants to safely exit the building in case of fire. Typically, this involves constructing floors and walls in a building which are fire-rated and designed to prevent fire from spreading from one area, compartment, or floor, to another. To ensure the designated egress routes such as stairways are passable, fresh air is supplied to egress routes, so they are maintained under positive pressure, and contaminated air is exhausted from fire compartments. Such an arrangement is designed to prevent the contaminated air from migrating from the engaged fire compartment to the egress routes and/or other sections of the building.
In addition to ventilating the egress routes in a building, new buildings may be designed to utilize the fire rated ventilation ducts for the handling of other types of non-hazardous exhaust that pass through the interior sections and fire separations in the building before being exhausted outdoors. For instance, commercial kitchen dishwasher exhaust and swimming pool exhaust are two examples of exhaust systems that contain high moisture and mildly corrosive elements that benefit from the elimination of required fire dampers, and the associated costs for the inspection and maintenance of the fire dampers, in these types of duct systems.
To protect these ducts so they can continue to function when exposed to fire, building codes typically require a shaft type construction that is configured to enclose the duct and the duct supports. Shaft type construction typically requires multiple layers of gypsum board to be installed to metal framing members. Such installations typically require considerable space around the duct to accommodate the multiple layers of gypsum board. In addition, to the requirements for installation, there are limitations on the maximum span which limits the enclosable duct size, and the resultant fire ratings are typically limited to a 2-hour fire rating when enclosing horizontal ducts.
In the art, there are also known fire-rated wrap systems that utilize ceramic insulation. Such systems typically involve wrapping installed ventilation systems fabricated from sheet metal with one or two layers of ceramic insulation blankets that are enclosed in a foil scrim outer layer. Most systems require the end of each insulation wrap to be overlapped by the next wrap section along the duct's length and sealed with foil backed tape in order to create a seal. Typically, the end of each wrap around the duct typically overlaps the starting end of the wrap so there are no butt seams in the system, with the ends once again sealed with foil backed tape. Stainless steel bands are then wrapped and clamped around the outer insulation layer to hold the insulation in place during a fire.
While the outer foil scrim layer construction can be effective to provide the required fire resistance rating, the foil scrim layer is easily susceptible to physical damage. As a result, local regulatory regimes and/or building codes require that the “wrapped” systems also be encased or enclosed with an outer sheet metal casing to prevent damage to the foil scrim layer to thereby avoid reducing the fire-rating or fire resistance rating of the system.
It will be appreciated that “wrap type” fire-rated duct systems suffer from a number of drawbacks including:
In the art, there are also known fire-rated duct systems that utilize rigid fire-resistant insulating boards as cladding to make the duct systems fire resistant. Similar to ceramic insulation wrap systems, the fire-resistant insulating boards are installed after the duct (sheet metal) systems are first installed. Each system and board manufacturer typically have their own specific installation requirements. Typically, the installation of the board systems involves the placement of spacers, cut from the same board material as the outer enclosure, around the duct so that the fire-resistant enclosure boards can clear the duct's traverse duct connectors. Installation of the enclosure boards often involves applying mastic to the edges of abutting boards in order to provide a seal between the boards. This is followed by nailing, stapling or otherwise banding the boards together along their longitudinal edges to prevent them from separating in a fire. Some known systems also require additional boards to be installed over the transverse joints in the system to prevent the passage of heat though those joints.
It will be appreciated that known “board type” fire-rated duct system also suffer from a number of drawbacks including:
Accordingly, there remains a need for improvements in the art.
The present invention is directed to a fire-rated ventilation duct system and improvements therein.
According to an embodiment, the present invention comprises a fire-rated ventilation duct section comprising: an inner liner configured as conduit for air movement, said inner liner comprising a metallic material and having a first end and a second end, and said first end including a first connection section, and said second end including a second connection section; an outer casing configured for encasing said inner liner, said outer casing comprising a metallic material having a fire-rating, said outer casing having a first end and a second end, and said first end including a first duct connection section configured for joining one end of a second fire-rated ventilation duct, and said second end including a second duct connection section configured for joining one end of a third fire-rated ventilation duct; an insulation layer configured to provide a thermal insulation layer between said inner liner and said outer casing, and said first connection section of said inner liner further comprising a first liner spacer and said second connection section of said inner liner further comprising a second liner spacer, said first and said second liner spacers being configured to define a cavity for receiving and positioning said insulation layer between an outer surface of said inner liner and an inner surface of said outer casing; said first duct connection section of said outer casing being configured to attach to at least a portion of said first connection section of said inner liner, and said second duct connection section of said outer casing being configured to attach to at least a portion of said second connection section of said inner liner to form a sealed duct section.
According to another embodiment, the present invention comprises a fire-rated ventilation duct assembly comprising: a first duct module, said first duct module including, an inner liner configured as conduit for air movement, said inner liner comprising a metallic material and having a first end and a second end, and said first end including a first connection section, and said second end including a second connection section; an outer casing configured for encasing said inner liner, said outer casing comprising a metallic material having a fire-rating, said outer casing having a first end and a second end, and said first end including a first duct connection section and said second end including a second duct connection section, an insulation layer configured to provide a thermal insulation layer between said inner liner and said outer casing, and said first connection section of said inner liner further comprising a first liner spacer and said second connection section of said inner liner further comprising a second liner spacer, said first and said second liner spacers being configured to define a cavity for receiving and positioning said insulation layer between an outer surface of said inner liner and an inner surface of said outer casing; said first duct connection section of said outer casing being configured to attach to at least a portion of said first connection section of said inner liner, and said second duct connection section of said outer casing being configured to attach to at least a portion of said second connection section of said inner liner to form a sealed duct section; and a second duct module, said second duct module including, an inner liner configured as conduit for air movement, said inner liner comprising a metallic material and having a first end and a second end, and said first end including a first connection section, and said second end including a second connection section; an outer casing configured for encasing said inner liner, said outer casing comprising a metallic material having a fire-rating, said outer casing having a first end and a second end, and said first end including a first duct connection section and said second end including a second duct connection section, an insulation layer configured to provide a thermal insulation layer between said inner liner and said outer casing, and said first connection section of said inner liner further comprising a first liner spacer and said second connection section of said inner liner further comprising a second liner spacer, said first and said second liner spacers being configured to define a cavity for receiving and positioning said insulation layer between an outer surface of said inner liner and an inner surface of said outer casing; said first duct connection section of said outer casing being configured to attach to at least a portion of said first connection section of said inner liner, and said second duct connection section of said outer casing being configured to attach to at least a portion of said second connection section of said inner liner to form a sealed duct section; and said second duct connection section of said first duct module being configured for joining the first duct connection section of said second duct module, so that said first duct module and said second duct module are coupled together to form said fire-rated ventilation duct assembly.
According to another embodiment, the present invention comprises a fire-rated duct section comprising: an inner liner configured as conduit for air movement, said inner liner comprising a metallic material and having a first end and a second end, and said first end including a first spacer section, and said second end including a second spacer section; an outer casing configured for encasing said inner liner, said outer casing comprising a metallic material, said outer casing having a first end and a second end, and said first end including a first duct connection section configured for joining one end of a second fire-rated ventilation duct, and said second end including a second duct connection section configured for joining one end of a third fire-rated ventilation duct; an insulation layer configured to provide a thermal insulation layer between said inner liner and said outer casing, and said first and said second spacer sections being configured to define a cavity for receiving and positioning said insulation layer between an outer surface of said inner liner and an inner surface of said outer casing; and said first duct connection section of said outer casing being configured to attach to at least a portion of said first spacer section of said inner liner, and said second duct connection section of said outer casing being configured to attach to at least a portion of said second spacer section of said inner liner to form a sealed duct section.
According to another embodiment, the present invention comprises a fire-rated duct assembly comprising: a first duct module, said first duct module including, an inner liner configured as a conduit for air movement, said inner liner comprising a metallic material having a specified fire-rating, and having a first end and a second end, and said first end including a first connection section, and said second end including a second connection section; an outer casing configured for encasing said inner liner, said outer casing comprising a metallic material having a fire-rating specification, said outer casing having a first end and a second end, and said first end including a first duct connection section and said second end including a second duct connection section, said first duct connection section of said outer casing being configured to attach to at least a portion of said first connection section of said inner liner, and said second duct connection section of said outer casing being configured to attach to at least a portion of said second connection section of said inner liner to form a sealed duct section; said outer casing comprising a first duct connector at said first end, and a second duct connector at said second end, said first duct connector comprising a formed section having a J profile, and said second duct connector comprising a formed section having a J profile; and a second duct module, said second duct module including, an inner liner configured as a conduit for air movement, said inner liner comprising a metallic material having a specified fire-rating, and having a first end and a second end, and said first end including a first connection section, and said second end including a second connection section; an outer casing configured for encasing said inner liner, said outer casing comprising a metallic material having a specified fire-rating, said outer casing having a first end and a second end, and said first end including a first duct connection section and said second end including a second duct connection section, said first duct connection section of said outer casing being configured to attach to at least a portion of said first connection section of said inner liner, and said second duct connection section of said outer casing being configured to attach to at least a portion of said second connection section of said inner liner to form a sealed duct section; said outer casing comprising a first duct connector at said first end, and a second duct connector at said second end, said first duct connector comprising a formed section having a J profile, and said second duct connector comprising a formed section having a J profile; and said first duct connector of said first duct module being configured for coupling to said second duct connector of said second duct module, so that said first duct module and said second duct module are connected together to form said fire-rated ventilation duct assembly.
Other aspects and features of the present invention will become apparent to those ordinarily skilled in the art upon review of the following description of embodiments of the invention in conjunction with the accompanying figures.
Reference will now be made to the accompanying drawings which show, by way of example, embodiments of the present invention, and in which:
Like reference numerals indicate like or corresponding elements or components in the drawings.
Reference is made to
Reference is made to
According to an exemplary embodiment, the inner duct 210 is fabricated from a metal or metallic sheet, such as, galvanized steel, aluminized steel, stainless steel, or aluminum, or other types of sheet metals, as required by the ventilation system's intended application. The inner duct or duct liner 210 may be formed or fabricated with a number of cross-sectional shapes or profiles, for instance, square, rectangular, circular or oval. According to an exemplary implementation, the inner duct liner sections or tubes 210 can be formed from flat metal sheets or from continuous metal coils. In typical installations and applications, rectangular shaped or oval shaped tubes are generally utilized as they are easier to fit into the crowded or confined ceiling spaces typical in the buildings being constructed today.
The wall thickness of the inner duct liner 210 will vary and/or be dependent on the metal used to fabricate the inner liner, the specific metal type, the dimensions of the ducts and/or duct spans, and/or operating pressure of the duct system. In accordance with industry practice, the metal thickness should, at a minimum, meet the requirements of applicable industry standards or regulations, such as for example, the ASHRAE or SMACNA HVAC standards.
According to an exemplary implementation, the inner duct liner 210 may be fabricated in square, rectangular, circular or oval configurations in a similar manner according to a process comprising the following steps or operations:
As shown in
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According to another aspect and as shown in
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It will be appreciated that the sealant pockets 438 (and 448) provide an effective mechanism to seal the slip-on liner spacer sections 430 to the inner duct panels 211 and provide a sealed or airtight inner duct liner 210.
According to another aspect, the slip-on liner spacer sections 430, 440 to provide the capability to ‘field modify’ duct sections or modules 100. For instance, the inner duct liner 210 can be cut in the field, the slip-on liner spacer sections 430 reinstalled and the inner duct liner 210 connected to the outer casing 220. According to another aspect, the slip-on liner spacer sections can be configured to act as corner fillers to cover the portion of insulation that is exposed and provide a duct connection sealing surface where the insulation would be exposed at the corners of square and rectangular profile ducts, i.e. between the inner duct liner 210 and the outer casing 220.
It will be appreciated that the liner spacer sections 410, 420 formed as an integral component of the transverse edges of the inner duct panel 211 increases the structural integrity, i.e. stiffness, of the inner duct liner 210. However, for circular or oval duct profiles, the slip-on liner spacer sections 430, 440 may be preferred due to additional considerations for forming raised profiles on curved liner sections, as will be apparent to those skilled in the art.
According to another aspect and as shown in
According to another aspect, the liner spacer sections 212, 214 may be formed or fabricated with partially segmented and/or perforated configuration. The partially segmented and/or perforated liner spacers may be fabricated by removing or modifying some or all of the liner spacer's profile at required locations by notching, punching, drilling, slitting, or utilizing other metal fabrication techniques, as will be understood by those skilled in the art. Advantageously, partially segmented and/or perforated liner spacer sections provide weight savings while still maintaining the structural stiffness for the inner duct liner 210 and attachment points or surfaces for the connecting to the outer casing 220. In addition, the liner spacer sections 212, 214 having partially segmented and/or perforated provide a less-effective thermal bridge between the inner duct liner 210 and the outer casing 220 thereby reducing the amount of heat transferred between the inner duct liner 210 and the outer casing 220.
The inner duct liner 210 (
For mechanical joint fabrication, the longitudinal joint between adjacent panels or sheets 211 may comprise snap, acme, or Pittsburgh type mechanical lock for inner duct liners 210 comprising 16 ga or lighter metal. If a snap type mechanical lock is used, which is typically limited to 20 ga metal, the assembled joint may require reinforcement with the use of rivets, screws, tack welding, dimpling, or other mechanical fastening methods to lock the components of the male-female joint together to prevent the male leg of the joint from lifting out of the female pocket due to system design pressure or other loads on the inner duct liner 210.
For inner duct liners comprising 16 ga or heavier metals, welded longitudinal seams or spirally wound seams may be preferable over mechanical joint or lock mechanisms due to practical limitations of forming or rolling the heavier gauge metallic sheets. As will be understood by those skilled in the art, suitable welding techniques include continuous welded seams, lapped resistance welded seams, or stitch welding lap seams with sealing between the stitch welds. For heavier or thicker gauge panels, other mechanical joints, such as pocket locks or mechanically fastened laps seams, or welded joints may be utilized.
According to another embodiment, the inner duct liner 210 includes one or more internal stiffeners indicated generally by reference 213 as shown in
According to an exemplary implementation, the insulation layers, e.g. non-combustible boards, blanket or batts, 230 are installed, e.g. attached or affixed, to the respective sides of the inner duct panels 211, as depicted in
For an inner duct liner 210 having with a curved surface, e.g. a circular or oval cross-section, the insulation layer 230 will typically comprise a blanket or batt type insulation in order to facilitate attachment or installation to the outer surface(s) of the inner duct liner 210. According to another implementation, the insulation layer 230 may comprise a non-combustible board which meets the fire resistance requirements or specifications (e.g. thickness and/or fire-resistance rating) and is also flexible or bendable to conform to the curved surface(s) of the inner duct liner 210. According to another aspect, the insulation board(s) can be formed to match the curved profile of the inner duct liner 210 according to the oval or circular profile and attached directly to the outer surface. The non-combustible insulation layer 230 may also be temporarily held in place during the assembly of the inner duct liner 210 and the outer casing 220 with the use of weld or stick pins, adhesives, tapes, or friction fitted between the inner duct liner 210 and the inner liner spacer sections 212.
As described above, the inner duct liner 210 can be fabricated utilizing rolled or brake formed techniques. It will be appreciated that when roll formed mechanical locks are used to connect the pieces or sections of the inner duct liner 210 into a tube, the insulation layer 230 may be exposed at the corners of the inner duct liner 210 and the outer casing 220 due to the notching required to form profiles along each edge of the inner duct liner panel 211. It will be further appreciated that the exposed insulation material makes it difficult to seal the inner duct liner 210 of one duct section module to the inner duct liner 210 of an adjacent duct section module in the field without additional treatment or coverage. According to an exemplary implementation, the exposed insulation edges are factory or field coated with a high modulus mastic that seals the insulation surface and bonds the insulation and seal material to the edges and/or surfaces of the liner spacer sections 212. For lower density insulation layers 230, or for insulation materials without sufficient inherent strength to provide a sealed surface, corner sections 610 (indicated individually by references 610a, 610b, 610c and 610d in
As described with reference to
As described above, the outer casing 220 comprises the outer panels 222 for a rectangular profile or cross-section. The thickness of the metal used to fabricate the outer casing panels 222 will vary by the type of sheet metal used, the size of the duct being fabricated, the operating pressure for the duct system and/or the required fire-resistance rating. At a minimum the metal thickness of the outer casing panels 222 should meet ASHRAE or SMACNA HVAC guidelines.
The outer casing 220 is fabricated in a manner similar to the inner duct liner 210, for instance, as described above. However, the thickness of outer casing panels 222 and/or the connection techniques or mechanisms will vary, for instance, based on the size of the outer casing 220 and/or the difference in size or dimensions between the inner duct liner 210 and the outer casing 220. According to an exemplary implementation, the outer casing 220 may be fabricated in square, rectangular, circular or oval configurations according to a process comprising the following steps or operations:
The section connectors 224, 226 for the outer casing panels 222 are formed along the opposing transverse ends as shown in
Reference is made to
As shown in
According to an exemplary implementation, the outer casing section connector 226 (224) is roll-formed from the sheet metal piece as an integral component at each end of the outer casing panel 222 with the outer edge or leg-end of the J profile having an internal or external return formed on the outer edge. It will be appreciated that this configuration is similar to the connection profiles under SMACNA T-24, T-25a and/or T25b industry standard.
Reference is next made to
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According to another embodiment and as shown in
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According to another aspect, the slip-on casing connectors 530 provide the capability to ‘field modify’ a duct section. The field modification may comprise, for instance, cutting the outer casing panels 222 and then re-installing the slip-on connectors 530 and re-attaching the liner spacer connectors 212, 214 to reconnect the inner duct liner 210. According to another aspect the slip-on connectors 530 are configured to provide additional structural rigidity or integrity, and can reduce the need or the number of internal stiffeners, and/or allow for smaller outer liner section connectors 530, 212 or 214, for a given size duct and/or duct operating pressure.
As shown in
Once the outer casing 220 is assembled around the inner duct liner 210 and the insulation boards 230, the section connectors 212, 214 and 224, 226 (or if being utilized, the slip-on connectors are first installed), the section connectors are finished. For a rectangular or a square profile, the section connectors are finished with corner connectors 620, indicated individually by references 620a, 620b, 620c and 620d, in
To complete the fire-rate duct assembly, the liner spacer connectors 212, 214 are connected to the outer casing section connectors 224, 226. The inner duct liner 210 and the outer casing 220 are aligned on one end to ensure an even sealing surface exists when being installed on site. Once aligned, the outer casing section connectors 224, 226 are attached to the respective liner spacer connectors 212, 214, utilizing screws, rivets, mechanical clinching, or adhesive bonding. For duct sections or modules 100 that will not be modified in the field, the outer casing section connectors 224, 226 and the liner spacer connectors 212, 214 are joined or attached together, as described above.
Reference is next made to
To further strengthen (and seal) or prevent the connectors from potentially separating under high heat conditions, the joint or joining surfaces of adjacent duct sections 200 and 201 are strengthened or enhanced with additional retention mechanisms as shown in
For duct sections or modules having a circular or oval profile, the assembly process is modified and comprises the following steps. A fire resistant sealant or gasket is applied to the face of the liner spacer connectors, comprising a sealant as described above. The first and second duct sections are drawn together to align the outer casing connectors. Clamps are attached at the centers of the top and bottom flat sections as well as at the centers of the curved portions of the section connectors to temporarily hold the adjacent duct sections or modules in place. Fasteners, for example, self-drilling/self-tapping screws 822 are installed through the adjacent section connectors, positioned approximately on center and on an approximately 6″ to 8″ spacing.
The present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. Certain adaptations and modifications of the invention will be obvious to those skilled in the art. Therefore, the presently discussed embodiments are considered to be illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.
The present application is a continuation of U.S. patent application Ser. No. 16/829,782, filed Mar. 25, 2020, the entire content of which is incorporated herein by reference.
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| Number | Date | Country | |
|---|---|---|---|
| 20220268480 A1 | Aug 2022 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 16829782 | Mar 2020 | US |
| Child | 17743319 | US |
