Abstract:
The invention provides a lightweight, temperature-resistant debris shield suitable for used within a closed vessel. The invention has no small parts, and can be readily assembled and disassembled in a confined space without tools after passing through a tight passage such as a pressure vessel manway.

Description:
FIELD AND BACKGROUND OF INVENTION  
         [0001]    There are many designs of barriers to control debris when working inside a large vessel such as a pressure vessel. Various types of barriers have been used to seal off the vessel in order to prevent debris and insulation from being introduced into undesirable areas during fabrication or repair.  
           [0002]    If a debris barrier is installed inside a completed vessel, it is normally made of many small parts in order to fit through conventional access openings. This is time-consuming, since parts must be assembled within the vessel and then disassembled for removal, and may release additional debris.  
           [0003]    In one approach, a metal diaphragm or disk is assembled from many small parts, like a jig saw puzzle, which are held together with nuts and bolts. The parts must be small so they can be inserted and removed through access manways that are typically only 16″ to 24″ wide. These many small parts can become loose and serve as another source of debris. The metal disk is heavy, and can easily damage sensitive components nearby. Another disadvantage is that, after exposure to stress relief temperatures of up to 1220 deg F, the structure becomes very difficult to disassemble. The bolts must usually be removed with a cutting torch, thus serving as yet another potential source of debris.  
           [0004]    In a second approach, insulation has been stuffed into a cavity as a barrier against debris. Removing the insulation is messy and difficult. Grinding dust and other debris that become trapped in the folds and cavities of the insulation are easily released back into the vessel during removal. The insulation is also friable and can serve as source of debris as it is removed.  
           [0005]    From the preceding discussion it is apparent that a lightweight, temperature-resistant debris barrier or shield that has few or no small parts, and can be assembled in a confined space without tools after passing through a tight passage, such as a pressure vessel manway, would be welcomed by industry.  
         SUMMARY OF THE INVENTION  
         [0006]    The present invention is generally drawn to a temporary, multi-function sealing debris barrier which can be configured either as a heat resistant shield or a non-heat resistant grinding shield, and more particularly to a removable debris shield to internally protect a portion of a vessel, such as a pressure vessel, during fabrication.  
           [0007]    Accordingly, it is an object of the invention to provide a removable debris shield, suitable for use in a cylindrical vessel.  
           [0008]    It is a further object of the invention to provide a removable debris shield, suitable for use in a closed vessel, which is lightweight.  
           [0009]    Another object of the invention is to provide a removable debris shield, suitable for use in a closed vessel, which has few or no small parts.  
           [0010]    Yet another object of the invention is to provide a removable debris shield, suitable for use within a confined space, which is easy to install and remove through conventional access openings and without the use of any tools.  
           [0011]    Accordingly one aspect of the invention is drawn to a removable shield for use within a vessel, comprising: pliant material sufficient to span a desired interior portion of the vessel, a hem located around the periphery of the material and having at least one opening, and a hoop, having a first end and a second end, removably inserted through the at least one opening into the hem to extend the material across the desired interior portion of the vessel.  
           [0012]    Another aspect of the invention is to provide a removable shield for use within a cylindrical pressure vessel having an inside diameter, comprising: pliant material having a span larger than the inside diameter of the vessel, a generally circular hem located around the periphery of the material and having at least one opening, a generally circular hoop with a diameter larger than the inside diameter of the vessel and having a first end and a second end, the hoop being removably inserted through at least one opening into the hem to extend the material across the inside diameter of the pressure vessel, and spreader bolt having a nut, and a threaded section and an unthreaded section with a shoulder therebetween, wherein the spreader bolt is removably inserted into the first and second ends of the hoop and the first and second ends of the hoop are spread apart from each other by adjusting the nut.  
           [0013]    Yet another aspect of the invention is a method of shielding an interior portion of a vessel having an access opening from debris, comprising: providing pliant material sufficient to span a desired interior portion of the vessel, the material having a hem located around the periphery and the hem having at least one opening, providing a hoop having a first end and a second end, inserting the material and the hoop through the access opening into the vessel, and inserting the hoop through at least one opening of the hem to extend the material across the diameter of the vessel.  
           [0014]    The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming part of this disclosure. For a better understanding of the present invention, and the operating advantages attained by its use, reference is made to the accompanying drawings and descriptive matter, forming a part of this disclosure, in which a preferred embodiment of the invention is illustrated. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]    In the accompanying drawings, forming a part of this specification, and in which reference numerals shown in the drawings designate like or functionally similar parts throughout the same:  
         [0016]    [0016]FIG. 1 is a plan view of the invention showing the debris barrier after assembly;  
         [0017]    [0017]FIG. 2 is a perspective view of the invention in use as a debris shield during a grinding operation within a pressure vessel;  
         [0018]    [0018]FIG. 3 is an enlarged cross-sectional view of a portion of the debris barrier illustrated in FIG. 1 viewed in the direction of arrows  3 - 3 ; and  
         [0019]    [0019]FIG. 4 is an enlarged perspective view of a spreader bolt used in one embodiment of the subject invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0020]    Referring to FIG. 1, a debris barrier generally designated  10  is constructed as follows. A generally circular disk  15  is cut from a length of fabric or other pliant material. For a cylindrical vessel, the diameter of the disk  15  is preferably selected so that the resulting disk  15  is slightly larger than the inside diameter of the vessel to be sealed. As shown in FIG. 1, if the material is not wide enough to span the desired interior portion of the vessel, sufficient material can be heat sealed, glued with adhesives, sewn, or otherwise joined together via seams  20  to provide a disk having the required width. A hem  30  is formed around the periphery of disk  15  at  40 , leaving at least one opening  50 , for example at the 12 o&#39;clock position. The hem may be formed by doubling back the border of the material and fixing it in place via heat sealing, adhesives, sewing or the like. The hem is preferably about three to four inches wide.  
         [0021]    A large hoop  60 , having a first and second end, is rolled to a diameter several feet larger than the diameter of the vessel. One end of the hoop  60  and disk  15  are placed within a vessel  70  through conventional access openings, such as manway  80  shown in FIG. 2. The hoop  60  is then inserted into the hem  30  via the opening  50 , and pushed through the hem  30  until the hoop  60  is inserted fully through the hem  30 , as shown in FIG. 3. While hoop  60  is shown as tubular in cross-section, the subject invention is not limited to a particular cross-section, and could be made, for example, from a rod or merely of a piece of flat steel.  
         [0022]    Inside the vessel, the hoop exerts an outward force when sprung into the vessel, and the spring action of the open hoop extends the fabric of the debris barrier and holds the debris barrier in place inside the pressure vessel, as shown in FIG. 2.  
         [0023]    The debris barrier is very versatile. A debris barrier of a given diameter can accommodate a wide variation in vessel diameter. The fabric can be selected to accommodate various temperature conditions. For example, for applications where heat resistance is important, a high temperature textile fabric, such as Nextel™ aerospace fabric, available from 3M Company, or preferably Siltemp® silica textile, available from AMETEK, Inc. can be used. The fabric can then be stitched together with a high temperature thread, such as Keviar® thread, available from Dupont Co., and the hoop would typically be made of heat-resistant tubing, such as rolled Inconel® tubing available from Special Metals Corporation. Where heat resistance is not important, for example for use as a grinding shield, the fabric of the debris barrier could be made of canvas.  
         [0024]    The following example is illustrative of the present invention:  
       EXAMPLE  
       [0025]    The subject invention was tested on a full size mock up of a horizontal, cylindrical pressure vessel. The vessel  70  had an inside diameter of approximately eleven feet (11′) with a single manway  80  approximately sixteen inches (16″) in diameter located at the top of the vessel.  
         [0026]    A tubular hoop  60  was passed in through the manway  80  in a fashion similar to threading a key onto a key ring. A fabric disk  15  was draped down through the manway  80  into the vessel. During installation, a first installer held the opening  50  of the hem  30  of the disk  15  outside the vessel to prevent the fabric disc from dropping inside the vessel  70 .  
         [0027]    From inside the vessel  70 , a second installer introduced an end of the hoop  60  into the opening  50  in hem  30 , and fed it around inside the hem  30  until it re-emerged from the opening  50  in the hem  30 . The second installer, still within the vessel  70 , temporarily supported the weight of the assembly while the first installer, still outside of vessel  70 , reached in through manway  80  to install an optional spreader bolt  100 , shown in FIG. 1 and FIG. 4, between each of the open ends of the tubular hoop  60 . Optional spreader bolt  100  was used to help ensure a better seal. The spreader bolt was adjusted to spread the hoop  60  to force it tightly against the walls of the vessel  70  effectively sealing off a portion of vessel  70 .  
         [0028]    The spreader bolt  100  used in this example was a custom-made, one-piece bolt, preferably made of stainless steel, with an approximate overall length of six inches. As shown in FIG. 4, the spreader bolt  100  has an unthreaded section  110  at one end that is sized to fit into the end of hoop  60 . The other end of spreader bolt  100  has a threaded section  120  that is similarly sized to fit into the end of hoop  60 , but is fully threaded up to shoulder  130 . Shoulder  130  is located approximately 2″ in from the end of the unthreaded section  110 , and separates the unthreaded section  110  from the threaded section  120 . A free running nut  140 , also preferably of stainless steel, is initially installed up to the shoulder  130 . The ends of the hoop  60  are adapted to receive the spreader bolt when it is used, and the diameters of both the shoulder  130  and the nut  140  are large enough so that they cannot be inserted inside the ends of the hoop  60 .  
         [0029]    To install the spreader bolt  100 , the longer threaded section  120  is inserted into the end of the hoop  60 . The ends of the hoop  60  are manually spread sufficiently to allow the short unthreaded section  110  of the spreader bolt to be inserted into the other end of the hoop  60 . The free running nut  140  is then adjusted until the hoop  60  exerts sufficient force to form a seal. Spreader bolt  100  thus allows the debris barrier to be adjusted so that it contacts the inside diameter of vessel  70 , firmly and removably holding the debris barrier in place.  
         [0030]    While specific embodiments and/or details of the invention have been shown and described above to illustrate the application of the principles of the invention, it is understood that this invention may be embodied as more fully described in the claims, or as otherwise known by those skilled in the art (including any and all equivalents), without departing from such principles. For example, the example above demonstrates the subject invention in use within a horizontal cylindrical vessel of a specific size. The invention, however, could also be applied to a vertical cylindrical vessel and, with some changes to the dimensions, to vessels of various sizes. Also the hoop need not be circular in cross-section.