Bus duct firestop system

A firestop system for fire stopping a bus duct that passes through an opening in a marine deck or a marine bulkhead includes a boot seal wrapped around the bus duct housing. The boot seal has a top end attached to the bus duct, and a bottom end attached to the division. The boot seal is made of flexible material to allow for movement of the bus duct relative to the division due to vibration. The boot seal may be made of a thermal barrier wrap or other high-temperature insulating mat materials to allow heat generated under normal condition to escape while providing firestopping and temperature resistance under fire exposure conditions. The firestop system may also have a gasket positioned between the bus duct and the boot seal to accommodate irregularities in the outside surface of the bus duct housing.

FIELD OF THE INVENTION

This disclosure relates to the field of firestop system and particularly firestop system for bus duct penetrating through fire-rated divisions.

DESCRIPTION OF THE PRIOR ART

In marine construction, a bus bar enclosure, or a bus duct needs to be firestopped to comply with the International Maritime Organization (IMO) Fire Test Protocol (FTP) Code. When a bus duct penetrates through a fire-rated division, such as bulkheads and decks, many existing firestopping methods fail due to the vibration of the vessel. For example, vibrations may cause the sealant used in traditional methods to crack. Further, because the bus duct is a metal housing that is made of copper or aluminum, it tends to get hot in a fire and existing firestop products tend to trap the heat inside the bus duct.

SUMMARY

A firestop system for fire stopping a bus duct that passes through an opening in a division includes a boot seal positioned to surround the bus duct. The boot seal has a first end positioned to surround and attach to the bus duct and a second end distal from the first end and positioned to surround the bus duct and attach to the division. The division may be a marine deck or a marine bulkhead. The boot seal is made of flexible materials to allow for movement of the bus duct relative to the division due to vibration. The boot seal is also made of materials that allow for heat to escape during ambient conditions while providing firestopping and temperature resistance under fire exposure conditions. For example, the boot seal may be made of a thermal barrier wrap, such as microporous insulation material including at least alumina trihydrate. The boot seal may also be made of high-temperature fiberglass.

In some scenarios, each of the first end and second end of the boot seal defines an opening and the opening of the second end is larger than the opening of the first end. The firestop system may also include a first bracket positioned to surround the bus duct and attach the first end of the boot seal to the bus duct. The firestop system may have a gasket positioned between the first bracket and the bus duct. The gasket may be made of substantially intumescent foam gasket material.

The boot seal may include a sealable split extending from the first end of the boot seal to the second end of the boot seal to allow the boot seal to open and wrap around the bus duct for installation. In some scenarios, the sealable split may be closeable with a zipper that is made of fire retardant materials. The boot seal may also include a toggle attached thereto proximate to the first end of the boot seal to secure the boot seal to the bus duct.

The firestop system may also include a cover plate having a central opening positioned to surround a cross-section of the bus duct and configured to attach the second end of the boot seal to the division. The cover plate can be made of steel. The firestop system may also include one or more weld tabs positioned to attach the cover plate to the division. Alternatively, and/or additionally, the firestop system may have one or more clamps, each having a corresponding bolt positioned to go through an opening in the cover plate and an opening in the division and thread into the clamp so that the cover plate is attached to the division.

Additionally, the firestop system may also include one of more bolt attachments installed on the cover plate and positioned to attach a flange of the second end of the boot seal to the cover plate. The firestop system may further include a duct seal placed on the cover plate and positioned to cover the opening of the cover plate around the bus duct. The duct seal may also be locked to the cover place by one or more lock tabs that are fixedly attached to the cover plate.

In some scenarios, the firestop system may also include a second bracket positioned to attach the second end of the boot seal to the division. The second bracket may have an L-shaped cross-section formed by a first portion positioned to be attached to the division and a second portion extending perpendicularly from the first portion and positioned to attach the second end of the boot seal thereto. Alternatively, and/or additionally, the firestop system may further include a sleeve attachable to the division. The sleeve may be positioned to pass through the opening in the division. The sleeve may also have an opening that allows the bus duct to pass through. When the sleeve is attached to the division, it allows the second bracket to attach thereto, which secures the second end of the boot seal to the division.

DETAILED DESCRIPTION

This disclosure is not limited to the particular systems, methodologies or protocols described, as these may vary. The terminology used in this description is for the purpose of describing the particular versions or embodiments only, and is not intended to limit the scope.

As shown inFIG. 1, a traditional bus duct firestop generally uses fire-resistant mineral wool batt insulation packing material16to fill in the space between the bus duct20and the fire-rated floor or wall12. The fire-rated floor or wall may be a deck or bulkhead in a maritime construction. The traditional bus duct firestop system also has a firestop sealant18on top of the insulation material16, and it may be covered by a steel cover plate14. This traditional firestop system, however, may not be suitable for marine applications, in which vibration often results from the movement of the vessel. In marine applications, the sealant18may be prone to cracking due to the vibration. Further, the insulation material16is required to achieve temperature ratings, i.e. insulate the bus duct and reduce temperature transmission from exposed to unexposed side. However, as the metal housing of the bus duct gets hot as result of a fire, the insulation material can prevent the heat from being released, and thus trap the heat built up in the bus duct. When this happens, the current carrying capacity of the conductors inside the bus duct is reduced or de-rated. As such, the traditional firestop system may even create a greater fire risk or de-rating of the electrical bus bar. The bus duct firestop system described in this patent disclosure is intended to solve the above mentioned issues and/or other issues.

As shown inFIG. 2, a firestop apparatus for fire stopping a bus duct22that passes through an opening in a division28, such as a floor or wall in maritime application, includes a boot seal24positioned to surround the bus duct22. The boot seal has a first (top) end positioned to surround and attach to the bus duct, and a second (bottom) end distal from the first end and positioned to surround the bus duct and attach to the division. In some scenarios, the division may be a marine deck or a marine bulkhead. Each end of the boot seal24has an opening to surround the bus duct, and the opening of the bottom end is larger than that of the top end.

The boot seal may be made of flexible materials to allow for movement of the bus duct relative to the division due to vibration. The boot seal may include an insulating material such as a thermal barrier wrap or a high-temperature glass fiber mat. These materials allow for heat to escape during ambient conditions while providing firestopping and temperature resistance under fire exposure conditions. The thermal barrier wrap is usually manufactured for use in large electrical panels and gas valve stations installed in fire-rated construction, and may provide up to two hours of electrical circuit integrity ensuring circuit performance even when consumed in flame. In one example, the thermal barrier wrap of the boot seal may comprise a microporous insulation material including at least alumina trihydrate. High-temperature fiberglass may be widely available in various industries, such as those made with high quality E-Glass that will not burn and will withstand continuous exposure to temperatures at about 1000° F. to 1500° F. (540° C. to 800° C.). The boot seal may also be made of silicone coated glass fabric, such as those manufactured by Alpha Associates, Inc.

As shown inFIGS. 3A and 3B, the firestop system may include a bracket32positioned to surround the bus duct30and attach the top end of the boot seal to the bus duct. For example, the bracket32may be positioned between the bus duct30and the boot seal34, allowing the boot seal to be fastened or screwed thereto. In some scenarios, the bracket32may have a shape that corresponds to the shape of the bus duct30to form a seal between the bus duct30and the bracket32. The firestop system may also include a sealing gasket36positioned between the first bracket and the bus duct to conform to irregularities on the outside surface of the bus duct housing, such as seams and other projections, and perform a seal function. In some scenarios, the sealing gasket36may be substantially of intumescent foam material or the like.

There can be various ways to attach the bottom end of the boot seal34to the division40. For example, the firestop system may also include an additional bracket38positioned to attach the bottom end of the boot seal34to the division40. The additional bracket38may have a L-shaped cross-section formed by a first (horizontal) portion positioned to be attached to the division and a second (vertical) portion extending perpendicularly from the first portion and positioned to attach the second end of the boot seal thereto.

As shown inFIG. 4, the firestop system may also include a sleeve54positioned to pass through the opening in the division, and the sleeve54may also have an opening that allows the bus duct42to pass through, where the sleeve is attachable to the division56. For example, the sleeve can be welded, or screwed, to the bulkhead or deck. The sleeve54may also be configured to allow the second bracket52to attach thereto so that the bottom end of the boot seal50is secured to the division56.

The above illustrated embodiments can vary. For example, in a preferred embodiment, as shown inFIGS. 5-7, the firestop system may include a boot seal60positioned to surround the bus duct58. The boot seal58has two ends: the top end66and the bottom end67distal from the top end66. The top end66is positioned to surround and attach to the bus duct58, whereas the bottom end67is positioned to surround the bus duct58and attach to the division72. The boot seal60can be made of flexible materials such that it allows for movement of the bus duct relative to the division due to vibration. In a marine construction, the division may be a marine deck or a marine bulkhead. The materials for the boot seal60can use the various embodiments illustrated above.

InFIG. 6, the boot seal60may include a sealable split62extending from the top end66of the boot seal60to the bottom end67of the boot seal60to allow the boot seal60to open and wrap around the bus duct58for installation. In some scenarios, the sealable split62may be a zipper made of fire retardant materials. The boot seal60may further include a toggle64attached thereto proximate to the top end66of the boot seal60. The boot seal60may be opened at the sealable split62, wrapped around the bus duct58, and sealed at the sealable split62. Then the toggle64may be engaged to tighten the top end of the boot seal60so that it is secured around the bus duct58. The attachment of the boot seal60to the division72will be further explained with reference toFIGS. 7A-7C.

InFIG. 7A, the firestop system may include a cover plate70, which has a central opening98positioned to surround a cross-section of the bus duct58. The cover plate70can be made of metal, such as steel, and it can be configured to attach the bottom end of the boot seal to the division, which will be explained further. The firestop system may further include one or more weld tabs90positioned to attach the cover plate70to the division72. In some scenarios, the weld tabs90may be welded to the division, and allow for the cover plate70to attach thereon. In other scenarios, the welded tabs90may be glued, screwed or attached using other means to the division72. The illustrated attachment of the cover plate70to the division72provides the benefits of vibration resistant and elimination the need for other attachments.

In order to be installed around the bus duct58, the cover plate70may be split into multiple sections that join together. For example, the cover plate70may include two halves, which will be installed separately and joined together surrounding the bus duct58. In some scenarios, the cover plate70may include one or more bolt attachments92, such as one or more bolts, to attach the bottom end of the boot seal to the cover plate70. In doing so, as shown inFIG. 5, the bottom end67of the boot seal60may have a base, such as a flange68, which has one or more holes aligned with the one or more bolts92of the cover plate70to allow attachment of the boot seal60to the division72with hex nuts screwed onto the bolts92. Other methods, such as using a bracket, as illustrated above, may also be used to attach the boot seal60to the division72.

Returning toFIG. 7A, to provide sufficiently strong support for attaching the boot seal, the cover plate70may include multiple metal plates stacked together. For example, the cover plate70may include two metal plates, which provide a total thickness of about 10 mm. The cover plate70can be attached to the division72using a clamp88. This attachment is further shown inFIG. 7B. InFIG. 7B, the cover plate70is attached to the division72using a locking bolt74and a clamp88. The locking bolt has a head86and is threaded to mate with a thread in an opening of the clamp74. The division72and the cover plate70are now sandwiched between the head86of the locking bolt74and the clamp88. The locking bolt74, when tightened, will toggle-lock the cover plate70to the division72. This attachment is simple and permanent. It is also vibration resistant. It may also accommodate a wide range of deck thickness depending on the bolt length. For example, the deck thickness may be in the range from 4 mm to 16 mm or more. The thickness of the cover plate may be in the range of 10 mm.

In case a cover plate70has multiple plates stacked together, all of the stacked plates may be sandwiched between the head of the locking bolt74and the clamp88. Alternatively, as shown inFIG. 7A, a stacked cover plate may have at least a bottom plate and a top plate. The bottom plate of the stack may be attached to the division with a clamp88, with a top plate on top, whereas the top plate leaves an opening93for the head of the locking bolt86. Similarly, the top plate may also have one or more holes aligned with the bolts92that are attached to the bottom plate, so that the top plate can be stacked on top of the bottom plate. When the boot seal is placed on top of the cover plate and bolted to the cover plate via the one or more bolts92(inFIG. 5), the top plate of the stacked cover plate will also be secured to the bottom plate and the division.

As shown inFIG. 7C, the firestop system may further include a duct seal78placed on the cover plate70and positioned to cover the opening (98inFIG. 7A) of the cover plate around the bus duct. The duct seal78may be attached to the cover plate70by one or more lock tabs94. In some scenarios, the duct seal78may be made of intumescent foam. In order to be installed surrounding the bus duct, the duct seal78may be split into multiple sections, which can be joined together. The duct seal78, when joined together, has an opening that corresponds to the shape of the bus duct so that when installed, will form a seal around the bus duct58.

The above illustrated various embodiments provide easy methods of installing the firestop system. For example, a method for installing the illustrated firestop system inFIGS. 5-7may include placing a bottom cover plate70over an opening of the division72and attaching the bottom cover plate to the division72with one or more clamps88. Alternatively, and/or additionally, the method may also include fixedly attaching one or more weld tabs90on the division72and attaching the bottom cover plate to the division72via the weld tabs90. The bottom cover plate may have a central opening98of any size to accommodate the opening of the division72, in which the bus duct58goes through. For example, the opening98of the cover plate70may have a diameter of 250 mm. The bottom cover plate may also be split into multiple sections that, when bolted to the division72, join together to form around the bus duct58. The method of installing may also include placing a top cover plate over the bottom plate. The bottom plate may have one or more bolt attachments92, such as threaded bolts, attached thereto, where the threaded bolts pass through openings in the top cover plate.

The method of installing may also include placing a split intumescent foam duct seal78around the bus duct58, pushing it down flush with top of cover plates, and engaging the foam seal onto one or more lock tabs94, which are fixedly attached to the cover plate70. Additionally, the method of installing may include wrapping a split boot seal60around the bus duct58, where the split boot seal has a sealable split62, such as a zipper. The method may further include engaging and closing the zipper62to secure the top end66of the boot seal60to the bus duct58housing. The method may further include engaging an optional toggle64attached proximate to the top end66of the boot seal60to further tightly secure the boot seal60to the bus duct58. In attaching the bottom end67of the boot seal60, the method may include passing the threaded bolts92on the cover plate70through openings at the bottom end67of the boot seal60(e.g. a base or a flange) and attaching the boot seal60to the cover plate70using hex nuts.

In the above illustrated embodiments, a boot seal and various other components are disclosed to provide firestopping between a bus duct and a division in which the bus duct goes through. These embodiments provide advantages in that the firestop system can withstand vibrations as result of movement of vessel in marine applications. One or more components are disclosed to attach the boot seal to the bus duct and the division. Specific materials are also disclosed for various components of the firestop system. For example, the boot seal is a thermal barrier wrap, such as microporous insulation loaded with alumina trihydrate, or high-temperature fiberglass mat, to allow for heat to escape during ambient conditions while providing firestopping and temperature resistance under fire exposure conditions. The gasket used for attaching the top end of the boot seal to the bus duct is an intumescent foam gasket to be able to accommodate irregularities of the bus duct surface and thus provide a seal between the bus duct and the top end of the boot seal. These disclosures provide the several advantages of the firestop system over traditional firestop system, particularly in marine applications. However, it should be noted that such materials are merely illustrative for achieving a desired performance in a desired application. As the application varies, other materials may be substituted.

Other advantages of the present invention can be apparent to those skilled in the art from the foregoing specification. Accordingly, it be recognized by those skilled in the art that changes or modifications may be made to the above-described embodiments without departing from the broad inventive concepts of the invention. It should therefore be understood that this invention is not limited to the particular examples and embodiments described herein, but is intended to include all changes, modifications, and all combinations of various embodiments that are within the scope and spirit of the invention as defined in the claims.