Abstract:
Systems, apparatus and methods for hot tapping into pressurized, coated duct systems for transporting corrosive substances are disclosed. A branch line may be installed in such systems without shutting down or depressurizing the system using the disclosed systems, apparatus and methods without compromising the system coating or resistance to corrosion from the transported substances. Cut edges created when ductwork is cut to install a branch line are captured and sealed between two gaskets, avoiding the need for recoating with difficult to apply corrosive protection materials such as fluoropolymer coatings.

Description:
RELATED APPLICATION DATA 
       [0001]    This application claims the benefit of priority of U.S. Provisional Patent Application Ser. No. 62/208,125, filed Aug. 21, 2015, and titled Hot Tap System and Method for Coated Ductwork, which is incorporated by reference herein in its entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present disclosure generally relates to pressurized duct systems for transporting corrosive substances and, more particularly, to a hot tap system and method for installing branch lines in such systems. 
       BACKGROUND 
       [0003]    Many different types of manufacturing plants operate around the clock without shutting down except for emergency situations or infrequent, scheduled, long-term maintenance. Reasons for continuous operation include cost of shut down and restart, and potential impacts on quality of products until steady state is reached after restart. Semiconductor fabricating plants are an example of such a typically continuously-operating manufacturing facility. Because of continuous operation, it can at times be difficult or costly to improve, modify or otherwise change configurations in such facilities. 
         [0004]    When a continuously-operating fabricating plant uses ducts or pipes for conveying flowable materials, which may include gases or liquids, sometimes modifications can be made by “hot tapping” into a pipe or duct to add a new branch line without the need to shut down. However, hot tapping in semiconductor fabricating plants presents special challenges due to the corrosive nature of the gases conveyed within the duct work and the properties of the corrosion-resistant materials, such as fluoropolymer coatings, used to protect the duct work. Difficulties include minimizing damage to the protective coating, the adhesion-resistant properties of the coatings and the fact that even with carefully controlled processes, hot tapping into a duct creates a cut edge of the duct exposed to the corrosive materials transported therethrough. 
         [0005]    Various solutions have been proposed in the art for hot tapping coated ductwork transporting highly corrosive materials, including applying new protective coating material to the cut edges created during the hot tap process. However, available solutions are not always satisfactory due to difficulties in applying new coatings under field operating conditions, while maintaining system pressure, often in awkward positions where visibility of the areas to be treated is limited or impossible. 
       SUMMARY OF THE DISCLOSURE 
       [0006]    In one implementation, the present disclosure is directed to a method for installing a branch line in a duct system. The method includes creating opening in a duct wall to communicate with the branch line, the opening exposing an edge of the duct wall; placing an inner flange inside the duct wall around the opening; placing an outer flange outside the duct wall around the opening, the outer flange adapted to connect with the branch line; and sealing the edge of the duct wall between inner and outer gasket members to isolate the edge from substances conveyed through the duct system, wherein the inner gasket member is compressed between the inner and outer flanges and the outer gasket member is compressed between the inner flange and the inside of the duct wall. 
         [0007]    In another implementation, the present disclosure is directed to a method for installing a branch line in a negative-pressure, internally-coated, duct system. The method includes locating an installation position in an existing duct in the duct system; marking a cut line on an outside wall of the existing duct at the installation position; cutting the wall of the existing duct at the cut line to form an opening in the duct wall with a cut edge; sliding a blanking plate over the opening during cutting to control pressure loss in the duct system; removing the cut portion of the duct wall and covering the opening with the blanking plate; positioning a glove box over the opening and blanking plate; placing an inner flange having inner and outer gasket members disposed thereon in the glove box and closing the glove box; removing the blanking plate to access the opening through the glove box; manipulating the inner flange through the opening to a position inside the duct against the inner duct wall around the opening with the cut edge of the duct wall positioned between the inner and outer gasket members; replacing the blanking plate over the opening under the glove box; removing the glove box; positioning an outer flange adapted for connection to the branch line over the blanking plate aligned with the inner flange; removing the blanking plate with the outer flange remaining in position; and securing the inner and outer flanges together to compress the inner gasket member between the inner and outer flanges and to compress the outer gasket member between the inner flange and inside of the duct wall. 
         [0008]    In still another implementation, the present disclosure is directed to a branch line connector for internally-coated duct systems. The branch line connector includes an inner flange shaped to mate with an inner surface of a duct wall surrounding an opening formed in the duct wall; an outer flange shaped to mate with an outer surface of the duct wall surrounding the opening formed in the duct wall, the other flange adapted to connect with the branch line; inner and outer gasket members configured and dimensioned to be disposed between the inner and outer flanges with an edge of the opening in the duct wall sealed between the inner and outer gasket members, wherein the inner gasket member is positioned to be compressed between the inner and outer flanges and the outer gasket member is positioned to be compressed between the inner flange and the duct wall when the flanges are installed on the duct wall; and means for securing together the inner and outer flanges on the duct wall around the opening. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0009]    For the purpose of illustrating disclosed embodiments, the drawings show aspects thereof. However, it should be understood that the disclosure is not limited to the precise arrangements and instrumentalities shown in the drawings, wherein: 
           [0010]      FIG. 1  is a schematic side-view diagram of a hot tap apparatus according to one embodiment disclosed herein. 
           [0011]      FIG. 2  is a perspective view of components of the hot tap apparatus shown in  FIG. 1 . 
           [0012]      FIG. 3  is a schematic, partial cross-section of the hot tap apparatus shown in  FIGS. 1 and 2 . 
           [0013]      FIGS. 4, 5, 6, 7, 8, 9, 10 and 11  are perspective views illustrating steps of a method using an embodiment of a hot tap system disclosed herein. 
           [0014]      FIG. 12  is a perspective view illustrating the interior of a duct with an installed hot tap apparatus according to an embodiment disclosed herein. 
       
    
    
     DETAILED DESCRIPTION 
       [0015]    Disclosed are systems, apparatus and methods for hot tapping into pressurized systems for conveying corrosive materials while protecting all surfaces of the tap and cut duct work against the corrosive environment. In one embodiment, the ductwork may comprise fluoropolymer coated stainless steel ductwork, but the disclosed systems and methods are also applicable to other similarly protected systems. As used herein, hot tapping refers to cutting into a live system to install a fitting for a branch line or other new service with minimal pressure loss within the system, which permits, for example, field installations without shutting off or pressure fluctuations to the system. 
         [0016]    Pressurized systems may include both systems with positive or negative pressure depending on application and circumstances of use of the disclosed systems, apparatus and methods. 
         [0017]    As shown in  FIGS. 1 and 2 , an exemplary hot tap apparatus  10  disclosed herein includes an outer assembly  12  and an inner flange  14 . In the sketch of this example, the cross-section of the ductwork on which apparatus  10  is installed is designated by “D”. Outer assembly  12  further includes outer flange  16  from which body  18  extends. Body  18  may be adapted as needed to connect to specific services, ducts, tools, etc. according to the purpose and need for creating the branch line. In this example, body  18  is provided with closure flange inner part  20  and closure flange outer part  22 , which may be held together by any suitable means, such as nuts, washers and bolts  24  in order to provide a necessary connection to a branch line or other equipment, or as in  FIG. 2 , to capture closure plate  34  until final connections are made. Inner flange  14  includes captured cap nuts  28 , which may be secured in a sealed manner to inner flange  14 , for example, by welding, to provide a blind, threaded hole opening to the outside surface of the inner flange, but completely sealed on the inside surface. Cap nuts  28  thus provide a sealed means for connection to outer flange  16  by receiving threaded socket studs  30 , which are further secured with nuts, washers and lock washers  32 . All inner surfaces of outer assembly  12  and all surfaces of inner flange  14  are coated with a coating that is the same as or is compatible with the protective coating on the inside of the ductwork to be hot tapped. As used hereinafter, “branch line” refers to any line or equipment connectable or to be connected to an existing duct system using apparatus or methods disclosed herein. 
         [0018]    As also shown in  FIG. 2 , inner flange  14  includes double gasket seal  26 . Double gasket seal  26  is positioned on the inner surface of inner flange  14  such that the cut edge of the duct is captured between the inner and outer gasket member to isolate it from corrosive materials transported within the duct D after final installation. The material of double gasket seal  26  is also selected from a material compatible with the materials transported in the duct and will be adhered to the inner surface of inner flange  14  with a suitable adhesive or adhesive-like material. It should be appreciated that the seal between inner flange  14  and duct D after assembly is achieved primarily by the pressure applied through threaded socket studs  30  received in captured cap nuts  28 . Thus, the primary purpose of the adhesive material holding double gasket seal  26  in place is to facilitate assembly until adequate pressure is applied. In some embodiments, particularly for use in semiconductor fabrication plant systems, double gasket seal  26  may comprise a fibrillated PTFE rope gasket with an adhesive coating and peel-off protective layer. 
         [0019]    The partial cross-section schematically depicted in  FIG. 3  illustrates further features of the disclosed systems and apparatus. When assembled over a cut hole in duct D, inner gasket  26   i  of double gasket seal  26  is positioned inside the cut edge CE of the duct in order to protect the cut edge from the corrosive environment. To accommodate the thickness of the duct wall, it is preferable if inner gasket  26   i  has a height H1 greater than the height H2 of outer gasket  26   o.  In some embodiments height H1 will be approximately three times the thickness of the duct wall, whereas height H2 will be approximately two times the thickness of the duct wall. For example, in a system using fibrillated PTFE rope gasket material as mentioned above, with a 16 gauge duct wall (thickness approximately 1/16 inch), the uncompressed height H1 of inner gasket  26   i  may be about 3/16 inch and the uncompressed height H2 of outer gasket  26   o  may be about ⅛ inch. Each gasket may have a width of about ¼ inch in such an exemplary embodiment. Persons of ordinary skill may devise other suitable relationships for H1/H2 dependent upon dimensions and materials in which the apparatus is to be used based on the teachings contained herein. It should be noted that relative dimensions as depicted in  FIG. 3  are exaggerated to facilitate illustration of the features represented. 
         [0020]    Systems and methods for installing hot tap apparatus as disclosed above are described below with reference to  FIGS. 4-12 . It will be noted that in each of  FIGS. 4-10 , a system pressure gage (G) is shown, which indicates the relative negative pressure in a test system during an actual installation process. Pressure in  FIG. 4  is indicated before any cut is made into the system. Thereafter, while minor leakage is indicated, it is not sufficient to have a meaningful effect on overall system pressure. But most importantly, the leakage is substantially constant at that initial low level throughout the installation process, without pressure spikes occurring at any point during the installation. 
         [0021]    As shown in  FIG. 4 , location and size for connection of a new branch line using the disclosed system is identified and traced using template  36 . The template defines the outline of the hole to be cut, and preferably, the template includes marker  38  for locating an indexing hole  44  (shown on  FIG. 5 ) to receive an indexing/retaining nut as further described below. Tracing around the template provides an indication of the location for cutting into the duct shape of the hole to be cut. Marker  38  may be located in a slight indent in the shape of the hole to be cut to accommodate the location of the indexing hole and threaded indexing member. In some embodiments, the hole will also have a somewhat oblong shape and inner flange  14  is shaped complimentarily so that it can be manipulated through the cut hole and still seat and seal properly. In one exemplary embodiment, the hole is defined by a circle projected onto a duct with the diameter of the host duct. Then a ⅜″ offset is applied to allow for the bolt circle on flange  14 . 
         [0022]    As illustrated in  FIG. 5 , blanking plate  40  is slid into place as the hole is cut in order to minimize pressure loss in the system. Preferably, blanking plate  40  has an indexing slot  46  (see  FIG. 8 ) on its leading edge and is custom rolled to match the outer diameter of duct D to ensure a tight fit to limit system pressure loss. Using a thin cutting tool, such as a saw compatible with the ductwork, blanking plate  40  may be manipulated around by hand closely following the cut. Blanking plate  40  is held against the outside of the duct by the negative pressure within the duct system. Indexing hole  44  also may be drilled as located by marker  38 . The cut piece of duct D to be removed is indicated at CD. 
         [0023]    Next, as shown in  FIG. 6 , once the marked hole is appropriately cut and cut piece CD removed, glove box  42  is placed over the hole area with blanking plate  40  still in place. Glove box  42  is large enough so that it can accommodate inner flange  14  and also be secured on edges with blanking plate  40  in place, but slideable for removal after the glove box is secured. Securing of glove box  42  to the duct D can be done with suitable tape. Before removing blanking plate  40 , the air-tight door of glove box  42  is opened and the inner flange  14  is placed in the box with retaining bolt  43  loosely threaded into one of captured cap nuts  28  as a threaded indexing member, located to correspond to the indexing hole  44  (see  FIG. 5 ) previously drilled. The door of glove box  42  is then locked shut. As will be appreciated by persons of ordinary skill in the art, use of the blanking plate and glove box as described herein is well-suited to negative pressure systems. 
         [0024]    The installer then places his/her hands in the gloves of glove box  42 , as shown in  FIG. 7 , and holds onto inner flange  14  to ensure it does not fall into the duct when the blanking plate is removed. Blanking plate  40  is then removed to allow access to the installation hole. Inner flange  14  is manipulated through the hole and positioned with the inner gasket  26   i  of double gasket seal  26  visible through the hole, while outer gasket  26   o  is positioned outside of the cut edge and generally not visible. During positioning, retaining bolt  43  is placed through indexing hole  44  to ensure proper positioning of inner flange  14 . After placement is confirmed, blanking plate  40  is then slid back in place as shown in  FIG. 8 , aligning indexing slot  46  on the leading edge of the blanking plate with retaining bolt  43 . When indexing slot  46  bottoms out on retaining bolt  43 , the retaining bolt is tightened to a snug fit by hand. With backing plate  40  in place, the system is sealed and glove box  42  removed. In  FIG. 8 , blanking plate  40  has been pushed in about half way, with indexing slot  46  visible just before it entirely covers inner flange  14  and the inner gasket of double gasket seal  26 . 
         [0025]    In one embodiment, retaining bolt  43  is configured to cooperate with the specific system components with which it is intended to be used. As show in the figures, retaining bolt  43  is a shoulder bolt with a threaded section that matches the threads of captured nuts  28 , but has a shoulder small enough in diameter to fit through the bolt holes in outer flange  16 , yet large enough in diameter to capture the edges of indexing slot  46  so as to support inner flange  14  before installation of outer assembly  12  as described below. Alternatively, instead of a specially-designed shoulder bolt, one of socket studs  30  may be used with a specifically configured thin-walled tubular retaining nut dimensioned substantially as described above for the shoulder of retaining bolt  43 . In each case, the shoulder of retaining bolt  43  or the tubular retaining nut may have an elongated shape to facilitate gripping and hand tightening with the gloves of glove box  42 . 
         [0026]    Once glove box  42  is removed, outer assembly  12  may be installed as shown in  FIGS. 9-11 . First, outer assembly  12  is placed onto the duct by aligning its indexing hole with the retaining bolt  43 . Note that the indexing hole for outer assembly  12  is simply one of the bolt holes in outer flange  16 , which is positioned to correspond to the location of indexing hole  44  in the final assembly. With outer assembly  12  properly positioned in place on the duct, blanking plate  40  is then slowly slid back to allow the installation of studs  30  into captured cap nuts  28  of inner flange  14 . Threaded socket studs  30  are provided with hex or other sockets at the outer end to receive a driving tool. After placement of studs  30 , flat washer, lock washer and nut  32  are assembled onto each stud  30 . This process is repeated until all studs are installed for all available holes. Once all other studs and washer/nut combinations are installed, retaining bolt  43  is removed and replaced with a stud/washer/nut combination as in the other flange holes. If a tubular retaining nut is used instead of retaining bolt  43 , as described above, then only the retaining nut is removed and the nuts/washers  32  are applied to the stud  30  already in place. In one exemplary embodiment, nuts  32  are torqued to about 30 lbft. 
         [0027]    As illustrated in  FIG. 12 , and as will be appreciated by persons of ordinary skill based on the teachings presented hereinabove, the entire inside surface of inner flange  14  may be coated with the same coating as the inside of duct D, for example with fluoropolymer matching the duct inner surface. The only non-coated area presented to corrosive environment within the duct may be the edge of outer gasket  26   o  of double gasket seal  26 , but that also comprises a suitable corrosion-resistant material. In this manner, the cut edge of the hole made for the branch line, which is not coated due to its being cut in service, is captured and sealed between the inner and outer gaskets of double gasket seal  26 . It will also be appreciated by persons of skill in the art that embodiments described herein may be used with uncoated ducting to also provide a convenient means and method for installing a branch line or other equipment in without shutdown or excessive pressure loss in the system. 
         [0028]    As will also be appreciated by persons of ordinary skill, while illustrative embodiments disclosed above are described in connection with negative pressure systems, embodiments may be readily adapted to positive pressure systems based without departing from the present disclosure. 
         [0029]    The foregoing has been a detailed description of illustrative embodiments of the invention. It is noted that in the present specification and claims appended hereto, conjunctive language such as is used in the phrases “at least one of X, Y and Z” and “one or more of X, Y, and Z,” unless specifically stated or indicated otherwise, shall be taken to mean that each item in the conjunctive list can be present in any number exclusive of every other item in the list or in any number in combination with any or all other item(s) in the conjunctive list, each of which may also be present in any number. Applying this general rule, the conjunctive phrases in the foregoing examples in which the conjunctive list consists of X, Y, and Z shall each encompass: one or more of X; one or more of Y; one or more of Z; one or more of X and one or more of Y; one or more of Y and one or more of Z; one or more of X and one or more of Z; and one or more of X, one or more of Y and one or more of Z. 
         [0030]    Various modifications and additions can be made without departing from the spirit and scope of this invention. Features of each of the various embodiments described above may be combined with features of other described embodiments as appropriate in order to provide a multiplicity of feature combinations in associated new embodiments. Furthermore, while the foregoing describes a number of separate embodiments, what has been described herein is merely illustrative of the application of the principles of the present invention. Additionally, although particular methods herein may be illustrated and/or described as being performed in a specific order, the ordering is highly variable within ordinary skill to achieve aspects of the present disclosure. Accordingly, this description is meant to be taken only by way of example, and not to otherwise limit the scope of this invention. 
         [0031]    Exemplary embodiments have been disclosed above and illustrated in the accompanying drawings. It will be understood by those skilled in the art that various changes, omissions and additions may be made to that which is specifically disclosed herein without departing from the spirit and scope of the present invention.