Patent Publication Number: US-2017369236-A1

Title: Liners including corner reinforcement and methods and apparatus for providing additional protection and/or reinforcement at the corners of a liner

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part of U.S. patent application Ser. No. 15,059,685 filed Mar. 3, 2016, which, in turn, is a continuation-in-part of U.S. patent application Ser. No. 13/396,231 filed Feb. 14, 2012 (now U.S. Pat. No. 9,278,478), which, in turn, was a continuation-in-part of U.S. patent application Ser. No. 11/697,243 filed Apr. 5, 2007 (now U.S. Pat. No. 8,133,345). The entire disclosures of the above applications are incorporated herein by reference. 
    
    
     FIELD 
     The present disclosure generally relates to linings or liners (e.g., liners with corner reinforcement, etc.), methods of providing a liner or lining for a tank, and methods and apparatus for providing additional protection and/or reinforcement at the corners of a liner or lining. 
     BACKGROUND 
     This section provides background information related to the present disclosure which is not necessarily prior art. 
     Currently, contents such as acids and chemicals are stored in tanks usually in the form of process tanks. These tanks relate to immobile types that may be installed above or below the ground, but also for the transportable types that are part of the over-the-road semi-trailers. The tanks may also be used on or in marine vessels as well as railroad cars. The size of the tank is not material, but the larger process tanks typically hold 1,000 gallons or more. Moreover, process tanks are particularly adaptable for tanks intended for highly corrosive liquids, but also may be used in conjunction with other pourable materials such as grain and pellets. 
     Most process tanks of the type considered are steel tanks which, over a period of time, may become corroded as a result of the fluids stored therein, or because of the rusting action of the exterior elements (e.g., ground water, rain, etc.). If the material stored in such tanks is corrosive, the corrosive material can contact the tank. In this situation, the life expectancy of the tank is relatively short and thus it becomes not only extremely expensive for replacement, but also highly dangerous for people and the environment. Furthermore, there is danger in the event that the tanks leak or are ruptured, or somehow fail to retain the contents and leak the contents into the ground (if the tanks are subterranean). If they are above-the-ground storage tanks or if the tanks are over-the-road type, there is danger along the highways and to the passing public. Accordingly, many process tanks utilize a protective liner or protective lining. 
     One common type of liner is a pre-fabricated “drop-in” liner. While drop-in liners may be machine welded (radio frequency welding is commonly used for these liners), the drop-in liners have disadvantages with respect to a bonded lining. During the drop-in process, air is entrapped behind the liner, which can condense and cause the mild steel tank to rust. Furthermore, during the drop-in process, creases form in the liner sheet, which stresses the liner material and leads to premature cracking and failure. Additionally, a tank part may catch the crease or protruding wrinkle and cause tear damage to the drop-in liner. When the drop-in liner develops a leak, solution seeps behind the liner pushing it off the walls or bottom and causing the liner itself to move into the process tank area resulting in operational problems. Once solution is behind a drop-in liner, the liner is very difficult to repair, since it may be almost impossible to find the source of the leak. Replacing the drop-in liner creates significant downtime, especially for electroplating tanks with auxiliary equipment affixed to the tank rim, e.g., ventilation hoods, piping, anode and cathode bars, heat exchangers and probes, level control devices, etc. 
     Also commonly used are bonded-to-metal linings. As will be discussed, this type of lining uses manual “flat strip” welds on the butted side panels and “corner strip” welds on the vertical joining walls and side to bottom joints. 
     In current lining procedures, installation personnel prepare the interior of the surface of the tank  10  ( FIG. 1 ) to receive the lining  14 . This preparation includes surface blasting the interior of the tank  10  and subsequent cleaning of the interior of the tank  10 . 
     With respect to the lining  14 , the installer cuts sheets of lining  16  ( FIG. 2 ) from a roll of lining material. At the installation site, the installer applies an adhesive to the now cut sheets of lining  16 . Then, the installer manually applies the lining sheets  16  to the interior of the tank  10 . As known in the art, heat may be applied to the lining sheets  16  to assist in applying the lining sheets  16  to the tank wall. Tanks typically have protrusions such as tank welds that bond the tank walls to the tank bottom. These tank welds protrude into the interior of the tank  10 . Even careful placement of the sheets  16  will result in gaps between the sheets  16  that are placed over the protruding welds. In other words, the sheets  16  will lay over the protrusions further enhancing the gaps between the sheets  16 . 
     As shown in  FIG. 2 , current cutting procedures result in uneven and/or rough edges  18  for each lining sheet  16 . When the installer bonds the sheets  16  to the tank  10  and next to each other, the rough edges  18  of the sheets  16  do not evenly match thus resulting in gaps  20  forming between the sheets  16 . When the installer cuts relatively smooth edges  18 , installation gaps  20  still exist between the adjacent sheets  16  due to the difficult and labor intensive installation process ( FIG. 3 ). For example, the sheets  16  are heavy and difficult to manage as the installer handles the sheets  16  while positioned within the tight constraints of the process tank  10  which is a confined space with elevated temperatures. As such, the installer may apply adjacent sheets  16  in a non-uniform layout and/or with a distance between them, further enhancing the gaps  20  between the edges  18  of the sheets  16 . Applying the sheets  16  at a corner of the tank  10  is particularly troublesome due to the space and angle considerations of the corner of the tank  10 . 
     After applying the lining sheets  16 , the installer welds a weld strip  22  (known as a “cap over flat strip weld” or a “cap over corner strip weld”) along the interface between a pair of adjacent sheets  16  ( FIGS. 2 and 3 ). The installer manually welds the weld strip  22  to the adjacent lining sheets  16 . The welder used by the installer in this process heats the weld strip  22  to the sheets  16 . Similar to the application of the sheets  16 , hand welding the weld strips  22  is a labor-intensive process. Maintaining consistent pressure with the welder is difficult since the touch of the installer applies the pressure. Additionally, it is difficult with the hand welder to maintain a constant distance between the welding nozzle and the welding strip. Furthermore, the weld strip may melt faster than the sheet  16 , so the welding process must be done with special care. The sheets  16  must be heated to a glossy state, yet the weld strip or the sheets  16  cannot be charred, as that would result in a failed weld. 
     The installer typically welds from the top of the lining sheet  16  to the bottom. As the process tank  10  may have a height such as twelve feet, this height causes starts and stops as opposed to continuous welds with tightly controlled temperatures and consistency in both pressure and timing. In addition, welding occurs within the tight constraints of the process tank  10  such that the installer does not provide a constant weld over any length of time. The tedious and laborious process for strip welding not only applies to welding strips to corner sheets, but it also applies to welding strips for sheets applied to the walls of the process tank  10 . 
     The human element of welding the strips  22  leads to weak welds (inconsistency of temperature, pressure and timing—the critical variables for welds) and leads to voids or “pinholes”  24  within the weld that bonds the weld strip  22  to the sheets  16  ( FIG. 4 ). The pinholes  24  shown in  FIG. 4  are exaggerated for purposes of clarity. Although the welded strip  22  may pass a “spark test” commonly used in the art, these pinholes  24  lead to problems for the process tank  10  as will be discussed. Furthermore, the corner weld that bonds sides and the bottom of the process tank  10  further exaggerates the effects of the gaps  20  and the pinholes  24  since the sheet  16  must position over the corner weld of the process tank  10 . This corner weld or other obstacle leaves a void between the sheet  16  and the tank weld. 
     When the tank  10  is filled with fluid  12  ( FIG. 1 ) such as an acid, the pressure of the fluid forces the fluid through the pinholes  24 . Consequently, the fluid forces through the gaps  20  and disperses between the lining  14  and the tank  10 . This leaked fluid then corrosively attacks the tank wall. Additionally, this leaked fluid may also corrosively attack the bond or adhesive interface between the lining  14  and the tank wall resulting in the lining  14  pulling away from the tank wall. Accordingly, the gaps  20  and the pinholes  24  between the lining sheets  16  lead to adverse and dangerous conditions. When the installer repairs the welded strip, the heat from the repair welder draws the leaked fluid toward the interface of the adjacent sheets  16 , wherein this fluid further attacks the tank wall positioned behind the repaired weld strip. 
    
    
     
       DRAWINGS 
       The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure. 
         FIG. 1  is a front elevation view of a storage tank with a partial cross sectional view thereof illustrating a current bonded lining applied to the tank walls, and a fluid stored therein which fluid has seeped through the lining and is between the tank walls and the lining; 
         FIG. 2  is a partial perspective view of a corner of a current lining illustrating a pair of lining sheets, a welded strip weld between the pair of lining sheets, and gaps between the lining sheets; 
         FIG. 3  is a partial perspective view of a corner of another current lining illustrating a pair of lining sheets having smooth edges, a welded strip weld between the pair of lining sheets, and a gap between and along the length of the edges of the lining sheets; 
         FIG. 4  is a front perspective of the lining sheets, weld strip, and gaps shown in  FIG. 3 , and further illustrating pinholes formed in the weld that bonds the weld strip to the lining sheets; 
         FIG. 5  is a partial sectional front view of an exemplary embodiment of a lining within a tank, which lining is constructed in accordance with and embodying one or more aspects of the present disclosure; 
         FIG. 6  is a back perspective view of an exemplary embodiment of a pair of lining sheets constructed in accordance with and embodying one or more aspects of the present disclosure; 
         FIG. 7  is a plan view of the pair of lining sheets shown in  FIG. 6  with the sheets contacting each other to form a corner beveled region; 
         FIG. 8  is a plan view of an exemplary embodiment of a pair of butt welded side sheets constructed on a sheet butt welding machine in accordance with and embodying one or more aspects of the present disclosure; 
         FIG. 9  is a plan view of an exemplary embodiment of a pair of extrusion welded side sheets constructed in accordance with and embodying one or more aspects of the present disclosure; 
         FIG. 10  is a partial perspective view of an infused weld being applied to the corner of the lining according to an exemplary embodiment of the present disclosure; 
         FIG. 11  is a front perspective of the pair of lining sheets and associated infused weld shown in  FIG. 10  constructed in accordance with and embodying one or more aspects of the present disclosure; 
         FIG. 12  is a back perspective view of the contacting pair of lining sheets shown in  FIG. 10 , and further illustrating an infused weld joining the pair of lining sheets which infused weld is constructed in accordance with and embodying one or more aspects of the present disclosure; 
         FIG. 13  is a plan view of the infused welded pair of lining sheets shown in  FIG. 12 ; 
         FIG. 14  is a plan view of an infused weld of the present disclosure, and illustrating a portion of the infused weld extending beyond the beveled regions of the pair of lining sheets, wherein this portion of the weld is exaggerated for purposes of clarity; 
         FIG. 15  is front view of an exemplary embodiment of a corner insert (broadly, a corner attachment) constructed in accordance with and embodying one or more aspects of the present disclosure; 
         FIG. 16  is a partial perspective view illustrating the corner insert shown in  FIG. 15  extrusion welded to a corner of a lining; 
         FIG. 17  is a perspective view of an exemplary embodiment of a lining constructed in accordance with and embodying one or more aspects of the present disclosure; 
         FIG. 18  is a partial side view of an exemplary embodiment of the present disclosure illustrating a sacrificial layer and an intermediate layer bonded to a lining; 
         FIG. 19  is a front perspective view illustrating the lining and the sacrificial layer and intermediate layer bonded to the lining shown in  FIG. 18 ; 
         FIG. 20  is a partial side elevation view of an exemplary embodiment of the present disclosure illustrating a sacrificial layer bonded to a lining; 
         FIG. 21  is a front perspective view of illustrating the lining and the sacrificial layer bonded to the lining shown in  FIG. 20 ; 
         FIG. 22  is a flowchart illustrating welding steps of an exemplary embodiment of a method for lining a tank in accordance with and embodying one or more aspects of the present disclosure; 
         FIG. 23  is a partial perspective view of an exemplary embodiment of a liner that includes an outer shell, an inner lining in which infused welds join the sheets of the lining, and a corner insert is welded to a corner of the lining in accordance with and embodying one or more aspects of the present disclosure; 
         FIG. 24  is a partial side perspective view of an exemplary embodiment of a lining applied to walls of a tank, which lining includes sheets separated by a gap and joined by an infused weld that also fills the gap between the sheets in accordance with and embodying one or more aspects of the present disclosure; 
         FIG. 25  is a partial perspective view of an exemplary embodiment of a lining sheet applied to a wooden flooring member, and illustrating an infused weld joining the lining sheet to the flooring member in accordance with and embodying one or more aspects of the present disclosure; and 
         FIGS. 26 and 27  are partial perspective views of an exemplary embodiment of an exterior corner cap (broadly, a corner attachment) along an exterior corner of a liner in accordance with and embodying one or more aspects of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Example embodiments will now be described more fully with reference to the accompanying drawings. 
     As explained in the background above, the inventor hereof has identified various drawbacks with conventional methods for lining storage or process tanks. As recognized by the inventor hereof, process tanks with bonded linings should have a lining that eliminates gaps between edges of adjacent lining sheets or panels. The inventor further recognized that linings for process tanks should have machine quality consistent strong welds created with consistent pressure, temperature, and timing that effectively seals the tank from the contents that contact the lining. 
     Accordingly, the inventor hereof discloses exemplary embodiments methods of lining tanks in which sheets or panels of the lining are extrusion welded together by infusing molten thermoplastic material within the interfaces of adjacent sheets. Also disclosed herein are exemplary embodiments of linings, liners, and tanks that may be formed by sheets or panels extrusion welded together by infused thermoplastic material. For descriptive purposes only, the terms “liner” and “lining” may be used interchangeably herein. Also for descriptive purposes only, the term “liner” may also be used herein to refer to a free standing liner (e.g., drop-in liner, etc.) for a tank which liner will not be or is not bonded to a tank&#39;s surfaces. Additionally, the term “lining” may also be used herein to refer to a lining for a tank that will be or is bonded to a tank&#39;s surfaces. 
     An exemplary embodiment relates to a method of lining a tank having walls and a bottom that intersect at a corner of the tank. In this exemplary embodiment, the method includes bonding a bottom sheet to the bottom of the tank. The method also includes bonding a pair of sheets to adjacent walls of the tank above the bottom sheet. Each sheet of the pair of sheets has a first edge and a second edge such that the first edges of the pair of sheets are positioned at the intersection of adjacent walls of the tank. The pair of sheets is then extrusion welded together by infusing a molten thermoplastic material along the pair of sheets and within an interface between the pair of sheets. Additionally, the method includes extrusion welding the pair of sheets to the bottom sheet by infusing molten thermoplastic material along and between the pair of sheets and the bottom sheet. The infused thermoplastic material seals the pair of sheets and bottom sheet to thereby isolate the lined tank from the contents (e.g., contents being stored and/or processed, etc.) within the lined tanks, as the contents contact the pair of sheets and bottom sheet instead of the tank walls and bottom. 
     In exemplary embodiments, molten thermoplastic weld material flows into and fills gaps between adjacent pairs of lining sheets or panels, and also penetrates the joint to the substrate (e.g., the tank wall, etc.). An infused weld area is thus created that helps to eliminate channels, pinholes, gaps, etc. behind the weld seams, which, in turn, helps reduce the probability of leaks and helps increase the service life of the tank, pit, storage vessel, etc. in which the lining is used. If a leak happens, then the weld also helps block solution from flowing behind the lining. 
     With reference to the figures,  FIG. 5  illustrates an exemplary embodiment of a lining  26  applied to a tank  28 . As shown in  FIG. 5 , the tank  28  has walls  30 , a bottom  32 , and a top  34 . The walls  30  and bottom  32  intersect at corners  36  of the tank  28 . The tank  28  may also include a cover (not shown) and other components (not shown), such as a manhole access, access doors, and supply/drain valves. By way of example only, the tank  28  may comprise a steel process tank. But other exemplary embodiments may include a lining or liner (e.g., lining  26 , etc.) that is configured for differently configured tanks than what is shown in  FIG. 5 , such as tanks, pits, storage vessels, etc. formed from different materials (e.g., concrete, fiberglass, wood, etc.) and/or tanks shaped differently, etc. By way of further example, liners or linings disclosed herein may also be used for lining a floor in a process room, for lining a concrete floor and containment area, for lining outdoor or indoor containment pits, etc. The inventor&#39;s liners, linings, and welding techniques disclosed herein may be used with steel, wood, concrete, fiberglass, and other substrates that require corrosion protection. 
     An exemplary method for providing the lining  26  to the tank  28  will now be provided. In this example, installation personnel may prepare the tank  28  prior to applying the lining  26  to the tank  28 . For the surface preparation of the tank  28 , the material should preferably be free from physical imperfections and sharp edges on the interior of the tank  28  and should preferably be ground smooth. The thickness and weight per square foot should preferably comply and be within ASTM (American Society for Testing and Materials) tolerances and AISA (American Iron and Steel Institute) tolerances. Furthermore, welded parts of the tank  28  should preferably be fabricated in accordance with standardized commercial practices to obtain a practical and uniform quality. Rectangular open tanks, in particular, should preferably be properly reinforced with girth angles in accordance with accepted practices in order to provide adequate structural strength and prevent bulging. If welding is required on inside corners of the tank, the welds should preferably be smooth with no porosity, high spot lumps, or pockets. The size construction and location of outlets, openings, and/or valve sleeves should preferably be fabricated in accordance with standardized commercial practice. 
     During preparation, the installer removes sharp edges on the interior surface of the tank  28 . The installer then prepares the interior surface of the tank  28 , such as by blasting or grinding the interior of the tank  28  to be free from oil, grease, and chemicals. The installer may grit blast steel to a white metal finish in accordance with steel structures and painting standards. The installer may also clean the surface by using steam-cleaning procedures, for example to remove rust, scale, and dirt. After blasting or grinding, remaining debris may then be removed from the tank  28  via brushing or vacuuming. Furthermore, the installer may apply a primer to prevent oxidation of metal surfaces. 
     With respect to the lining  26 , an installer processes a plurality of sheets or panels  38  ( FIGS. 6 and 7 ) that eventually form the lining  26 . The installer may process the plurality of sheets  38  at the location of the tank  28  by cutting the sheets  38  from a roll of material. The installer may also process the plurality of sheets  38  from the roll of material at an offsite location. In an exemplary embodiment, the roll of material for the lining  26  comprises an extruded plasticized polyvinyl chloride (PVC) sheet membrane. One such material is sold under the brand name Koroseal® or High Performance Koroseal® manufactured by R.J.F. International Corporation. Other exemplary materials for the lining  26  include Amer-Plate® or T-Lock® or Arrow-Lock® from Ameron Protective Linings or Exceline from F.C. Witt Associates Ltd. In yet other embodiments, the lining  26  (or other linings and linings disclosed herein) may comprise various other materials, such as rigid PVC type 1, rigid PVC type 2, vinyl or specially formulated flexible PVC, chlorinated polyvinyl chloride (CPVC), polypropylene (PPL), copolymer polypropylene (CoPPL), fiberglass reinforced plastic (FRP), polytetrafluoroethylene (PTFE); ethylene chlorotrifluoroethylene copolymer (ECTFE), polyvinylidene fluoride (PVDF), rubber, a geomembrane, ethylene interpolymer alloy (EIA), etc. In some exemplary embodiments, the sheets  38  of the lining  26  may include full-size RF (radio frequency) welded high performance Koroseal® panels (e.g., Koroseal® flexible PVC sheets, etc.), which helps eliminate lining seams in tank walls and bottom. 
     During the cutting process, the installer pulls a portion of the lining material from the roll and places the portion over a cutting surface. In an exemplary embodiment, the height of the lining material is about eight to about ten feet and the width is about four to about eight feet. After the proper size of the length of the lining sheet  38  is determined and pulled from the roll of lining material, the installer then cuts off the portion from the roll material to form the plurality of sheets  38  ( FIGS. 6 and 7 ) of lining material. 
     In the illustrated embodiment shown in  FIG. 6 , the sheets  38  have a rectangular configuration. The installer cuts the sheets  38  in dimensions for use on the walls  30  and the bottom  32  of the tank  28  ( FIG. 1 ). The cut sheets are designated as corner pairs of sheets  40  ( FIGS. 6 and 7 ), side sheets  42  ( FIGS. 8 and 9 ), and bottom sheets  44  ( FIG. 10 ). The lengths and configurations for the bottom sheets  44  are cut according to the interior surface of the bottom  32  of the tank  28  to which the lining  26  is being applied. The sheets  38  may contract and expand slightly in width during installation operations and during use due to thermal expansion and contraction. Allowance for such dimensional changes may be made when cutting the sheets  38 . The installer may manually cut the sheets  38  from the roll of lining material. In an exemplary embodiment, the thickness of the sheets  38  is at least 3/32 inches. In another exemplary embodiment, the thickness of the sheets  38  is about 3/16 inches. These dimensions disclosed in this paragraph (as are all dimensions disclosed herein) are example in nature as other exemplary embodiments of a lining may be sized dimensionally larger or smaller depending on the tank to which they will be applied. 
     As shown in  FIGS. 6 and 7 , each corner sheet  40  of the plurality of sheets  38  has a first edge  46 , a second edge  48 , a top edge  50 , and a bottom edge  52 . The installer separates the corner pair of sheets  40  so that the installer may further process the first edge  46  of each sheet  40 . The installer may first process (cut or scrape) the first edge  46  of each sheet  40  in order to clear the edge from uneven surfaces. Next, the installer may then bevel the first edge  46 . The installer uses a cutting apparatus to bevel the edges  46  at an acute angle. In an exemplary embodiment, the installer bevels the first edge  46  at about a 45 degree angle. 
     The installer then processes, such as by cutting or grinding, the second edge  48  of the sheets  40  in a substantially straight configuration in order to remove uneven surfaces. The installer may also bevel the second edge  48  of the sheets  40 . In an exemplary embodiment, the installer bevels the second edges  48  at about a 45 degree angle. 
     The installer may also bevel the edges of the bottom sheet  44  at an acute angle. In an exemplary embodiment, the installer bevels these bottom edges at about a 45 degree angle. 
     For the sheets  38  that are not designated as corner sheets  40  or bottom sheets  44 , the installer may process the edges of these side sheets  42  to remove uneven surfaces. In an exemplary embodiment, the installer processes these edges as substantially straight in a non-beveled configuration ( FIG. 8 ). In another exemplary embodiment, the installer processes the edges of these sheets  42  in a beveled configuration ( FIG. 9 ). These processes may be shop fabricated. 
     At the tank site, the installer cleans and prepares surfaces of the tank  28  and the backside of the sheets  38  so that the installer can apply adhesive cement (or other suitable adhesive) to both the prepared surfaces of the tank  28  and the back sides of the sheets  38 . The installer, as part of the cleaning process, may swab the surface of the back of the sheets  38  with methyl ethyl ketone. In addition to, or alternatively to the adhesive cement, the installer may use double-sided adhesive tape between the tank  28  and sheets  38 . In an exemplary embodiment, 3M® VHB (very high bond) tape may be used between the tank  28  and sheets  38  to help hold the lining  26  and sheets  38  thereof in place relative to the tank  28 . 
     The installer may apply adhesive cement on the prepared surfaces of the tank  28  and the swabbed backsides of the sheets  38 . More than one coat of adhesive cement may be applied to the tank surface and the backside of the sheets  38 . When applying adhesive cement with a paint roller, for example, the installer may use a short roller in order to prevent excessive adhesive cement build up along the tank  28  surface and the backsides of the sheets  38 . In the event the sheets  38  cannot be applied to the prepared surface of the tank  28  for an extended period of time and the adhesive cement loses its tack, the adhesive cement surface shall be refreshed or re-tackified by applying one or more additional coats of adhesive cement. 
     After the surface of the tank  28  and the back sides of the sheets  38  have been properly adhesively cemented, the installer bonds the bottom sheet  44  of the plurality of sheets  38  to the bottom  32  of the tank  28 . The installer places the bottom sheet  44  against the prepared bottom  32  of the tank  28  and bonds the bottom sheet  44  to the bottom  32  of the tank  28 . For example, the installer may roll or pressure the bottom sheet  44  to the bottom  32  of the tank  28  to avoid trapping air between the bottom sheet  44  and the tank  28 . The bottom sheet  44  is bonded to the bottom  32  of the tank  28  making sure the bottom edges are positioned flush against the sidewalls  30  of the tank  28 . Additionally, the installer may press and roll the bottom sheet  44  into the corners  36  in such a manner as to prevent bridging. In rolling out the air during the placement of the bottom sheet  44 , the installer may roll from the center of the bottom sheet  44  and progressively from one end to the other to avoid pocketing air. 
     After bonding the bottom sheet  44 , the installer bonds the pair of sheets  40  of the plurality of sheets  38  to adjacent walls  30  of the tank  28  and above the bottom sheet  44  such that the first edges  46  of the pair of sheets  40  are positioned at the intersection of adjacent walls  30  at the tank corner  36  of the tank  28  such that there is an interface  54  ( FIG. 7 ) between the pair of sheets  40 . Since the first edges  46  of the adjacent corner sheets may be beveled, the pair of sheets  40  is positioned at the corner intersection of the adjacent walls  30  to position a beveled region  56  between the pair of sheets  40  ( FIG. 7 ). 
     The installer may then bond the pair of sheets  40  to the walls  30  of the tank  28  by rolling or by pressuring the pair of sheets  40  to the walls  30  of the tank  28  to avoid trapping air between the pair of sheets  40  and the walls  30  of the tank  28 . The pair of sheets  40  is bonded to the walls  30  of the tank  28  making sure the bottom edges of the pair of sheets  40  are positioned flush against the bonded bottom sheet  44 . The installer presses and rolls the pair of sheets  44  into the corners  36  in such a manner as to prevent overslipping. 
     After the corner pairs of sheets  40  and bottom sheet  44  are properly bonded to the tank  28 , the installer then activates a handle-held extrusion-welding device  58  ( FIG. 10 ). In this example, the welding device  58  is made up essentially of a hand-held drill serving as the drive system and removable attachment for this drill. In the attachment, a strand of thermoplastic material  60 , supplied via one or several feed channels from a feed device, is chopped up. The thermoplastic material  60  is heated in a conveying device usually in the form of a worm conveyor and a plastering device so that the chopped thermoplastic material  60  reaches a plastic state and is then expelled as welding material through a welding chute of the welding device  58 . The chute includes a degenerating device in the shape of an internal blower as well as a heating device. In exemplary embodiments, the thermoplastic material  60  may comprise permanent thermoplastic lining materials such as, but not limited to, plasticized polyvinyl chloride, flexible polyvinyl chloride (F-PVC), rigid polyvinyl chloride, chlorinated polyvinyl chloride (CPVC), polyethylene (e.g., high molecular weight polyethylene (HMWPE), high-density polyethylene (HDPE), low-density polyethylene (LDPE), etc.), polyurethane/PVC alloy, synthetic rubber, fluoropolymer (homopolymer, copolymers (e.g., Poly(vinylidene fluoride-co-hexafluoropropene) (PVDF-HFP), etc.) or alloys), ethylene-chloro-tri-fluoro-ethylene (Halar ECTFE), geomembrane, ethylene interpolymer alloy (EIA), laminations of thermoplastic materials such as above, etc. Accordingly, exemplary embodiments include extrusion welding that comprises heating and forcing out, under constant pressure and temperature, the thermoplastic material  60 . 
     Referring to  FIG. 10  and turning to  FIGS. 11-13  and  FIG. 22 , the installer extrusion welds the corner pair of sheets  40  together by infusing molten thermoplastic material  60  along the pair of sheets  40  and within the beveled region  56  of the pair of sheets  40 . Infusing molten thermoplastic material  60  comprises introducing the thermoplastic material  60  through and/or over and/or into the intersection (the beveled region  56 ) of the associated sheets (the pair of sheets  40 ). Since the first edges  46  of the adjacent pair of sheets  40  are beveled, this extrusion welding infuses molten thermoplastic material  60  within the gap, void, or beveled regions  56  separating the beveled edges of the pair of sheets  40 . Due to the uniformity of the beveled edges, the weld infuses within the beveled regions  56  to seal the pair of sheets  40  together. In welding the pair of sheets  40 , the installer typically welds from the top of the interface  54  between the pair of sheets  40  to the bottom of the interface  54 . The installer repeats the thermoplastic welding process for the other pair of sheets  40  bonded to the remaining corners of the tank  28 . 
       FIGS. 11 and 12  are respective front and back views of an infused weld  62  that seals the pair of sheets  40 . Additionally,  FIG. 13  shows a plan view of the infused weld  62  for the pair of sheets  40 . 
       FIG. 14  illustrates an exemplary embodiment in which thermoplastic material  60  may weld the beveled region  56  between the pair of sheets  40  and slightly infuse beyond the sheets  40 , for example, to further seal the tank  28 .  FIG. 14  exaggerates the amount of infused thermoplastic material  60  beyond the interface  54  for purposes of clarity. Since the weld infuses within the sheets  40 , the weld  62  may also fill voids that exist between the sheets  40  and the tank weld or other components of the tank  28 . Should the lining  26  shrink via interaction of the lining  26  with a particular content such as a chemical, then the infused weld  62  maintains the integrity of the lining  26  and maintains the sealing effect of the lining  26 . 
     Returning to  FIG. 10 , the installer extrusion welds each corner pair of sheets  40  to the bottom sheet  44  by infusing molten thermoplastic material  60  along and in between the pair of sheets  40  and the bottom sheet  44 . Accordingly, the infused material seals the pair of sheets  40  to the bottom sheet  44 . Infusing molten thermoplastic material  60  comprises introducing the thermoplastic material  60  through and/or over and/or into the intersection of (the gap or beveled region  56  between) the associated sheets (the pair of sheets  40 ). 
     In an exemplary embodiment in which the edges of the bottom sheet  44  and the bottom edges of the pair of sheets  40  are beveled, the extrusion welding infuses molten thermoplastic material  60  within the gap or beveled region  56  between the pair of sheets  40  and the bottom sheet  44 . In another exemplary embodiment in which the edges of the bottom sheet  44  and the bottom edges of the pair of sheets  40  are nonbeveled, the extrusion welding infuses molten thermoplastic material  60  within the interface between the pair of sheets  40  and the bottom sheet  44 . The extrusion welding preferably infuses molten thermoplastic material  60  for any combination of beveled and non-beveled edges for the pair of sheets  40  and the bottom sheet  44 . In welding the pair of sheets  40  to the bottom sheet  44 , the installer typically welds from the left to the right as shown in  FIG. 10  illustrating the installer extrusion welding the pair of sheets  40  to the bottom sheet  44 . 
     The extrusion weld  62  reinforces the material of the lining  26  from reduction of the physical properties of the lining material that may occur during the installation process. The extrusion weld  62  is different from other welds, such as the “cap over” flat strip weld or “cap over” corner strip weld previously discussed above in the background section. In exemplary embodiments in which the infusion of the thermoplastic material  60  is an automated process via the extrusion welder  58 , the thermoplastic material  60  is applied under controlled parameters, such as constant pressure and constant temperature over time, which, in turn, helps to minimize, reduce, or preferably eliminate pinholes. Also in exemplary embodiments, the extrusion welder  58  controls melt pressure and melt temperature with a display and control box for convenient operation and monitoring. Because of the controlled pressure and temperature, the extruded thermoplastic material  60  may thus fuse more material within the sheets  38  than other weld methods. With this automatic application of thermoplastic material  60  under controlled parameters, a thicker, deeper, and stronger extrusion weld  62  may be created while also reducing, minimizing, or preferably eliminating pinholes. 
       FIG. 15  illustrates an exemplary embodiment of a corner insert  64  (broadly, a corner attachment), which may be extrusion welded or attached otherwise to a corner of a lining ( FIG. 16 ). By way of example, the corner insert  64  may be welded to the corner of the liner by an extrusion weld material, a weld rod, and/or weld seam strip. An extrusion weld, a hot gas rod weld, and/or a seam strip weld may be used to attach the corner strip  64  to the corner of the liner. 
     Or, for example, the corner insert  64  may be adhesively attached or bonded to the one or more corners of the liner by a glue and/or a tape (e.g., 3M very high bond (VHB) double sided adhesive tape, etc.). 
     In the illustrated embodiment of  FIG. 15 , the insert  64  is configured (e.g., molded, etc.) to have a triangular shape. For example, the insert  64  may be generally hollow and have a truncated triangular pyramidal configuration (triangular pyramidal frustum). 
     The insert  64  may be made from a wide variety of materials. For example, the insert  64  may be made from the same material as the lining  26 . Or, for example, the insert  64  may be made from a different material than the lining  26 . By way of example, the insert  64  and/or lining  26  may be made from rigid polyvinylchloride, chlorinated polyvinyl chloride (CPVC), polyethylene, polypropylene, polyvinylidene fluoride (PVDF), Kynar® polyvinylidene fluoride (PVDF), ethylene interpolymer alloy (EIA), geomembrane, etc. 
     The insert  64  may vary in size. For example, the insert  64  may have a thickness within a range of about 3/16 inches to about ⅜ inches. The installer may position an insert  64  at one or more corners  66  of the lining  26 . For example, an insert  64  may be positioned at each corner  66  of the lining  26 . As shown in  FIG. 10 , a corner  66  is formed by the pair of sheets  40  and bottom sheet  44  of the lining  26 . 
       FIG. 16  illustrates a corner insert  64  after an installer has extrusion welded the insert  64  to the infused pair of sheets  40  and the bottom sheet  44 . As shown, extrusion welding the insert  64  to the lining corner  66  comprises infusing molten thermoplastic material  60  at a predetermined distance beyond the insert  64  and along the infused pair of sheets  40  and bottom sheet  44 . In this example, infusing molten thermoplastic material  60  comprises introducing the thermoplastic material  60  through and/or over and/or into the intersection (the beveled region  56 ) of the associated sheets and insert  64 . Thermoplastic material  60  is infused under the controlled parameters of constant pressure and constant temperature over time to help reduce, minimize, or preferably eliminate pinholes. This welding enhances the strength of the weld  68  between the insert  64  and the lining corner  66 . In an exemplary embodiment, the predetermined distance beyond the insert  64  has a range of about two inches to about four inches. The installer may then repeat the welding of inserts  64  to each of the remaining corners  66  of the lining  26 . 
     In exemplary embodiments, a lining (e.g., lining  26  ( FIG. 5 ), lining  226  ( FIG. 24 ), etc.) or liner (e.g., liner ( FIG. 23 ), a bag liner, etc.) may include corner attachments (e.g., molded corner inserts, exterior corner caps, etc.) at one or more corners (e.g., along each interior and/or exterior corner, etc.) to provide additional protection and/or reinforcement in the corners of the liner. Other exemplary embodiments include tanks having molded corner inserts and/or exterior corner caps (e.g., exterior corner cap  464  ( FIGS. 26 and 27 ), etc.) at one or more corners (e.g., at each interior and/or exterior corner, etc.), which tanks are formed similarly to the liner  26  such that the tank&#39;s walls and bottom are formed by sheets extrusion welded together by infused thermoplastic material. In exemplary embodiments, one or more corner attachments (e.g., molded exterior corner caps, etc.) may be positioned and attached along one or more exterior corners of a lining. In some exemplary embodiments, there may be corner attachments (e.g., molded exterior corner caps, etc.) along each of the exterior corners of a lining in addition to corner attachments (e.g., molded corner inserts  64 , etc.) along each interior corner of the lining, to thereby provide double reinforcement or addition protection in the corner. 
     With further reference to  FIG. 5 , the installer bonds other sheets  42  of the plurality of sheets  38  to the remaining surfaces of the tank  28 . After bonding sheets  42  to the remaining surfaces of the tank  28 , the installer welds contacting edges of any adjacent sheets  42  to any respective bonded sheet  38 . The installer bonds respective sheets  42  adjacent to the second edges  48  of each of the corner pair of sheets  40 . In particular, the installer bonds the edges of the other sheets  42  in contact with the second edges  48  of the pair of sheets  40 . In this position, the installer may extrusion weld the other sheets  42  to the adjacent second edges  46  of the pair of sheets  40 . For example,  FIG. 8  illustrates an exemplary embodiment in which the installer butt-welds the straight edges of adjacent sheets  40 ,  42 . 
     In the exemplary embodiment shown in  FIG. 9 , the installer extrusion welds between beveled edges of adjacent sheets  40 ,  42  such that an infused weld  62  is between the beveled edges. In this example, infusing molten thermoplastic material  60  comprises introducing the thermoplastic material  60  through and/or over and/or into the intersection (the beveled region  56 ) of the associated sheets. Also in this exemplary embodiment, thermoplastic material  60  is infused under the controlled parameters of constant pressure and constant temperature over time to help reduce, minimize, or preferably eliminate pinholes. 
       FIG. 5  generally illustrates welds (butt-weld/infused weld) that bond corner sheets  40  to side sheets  42 . Multiple side sheets  42  may be bonded and welded on any particular wall  30  of the tank  28  depending on the relative size of the tank  28  to the sheets  42 . As the tank  28  may have a substantially tall height, ascending rows of corner sheets  40  and side sheets  42  may be bonded and welded under the previously discussed processes. 
     Table 1 lists strength test results for a variety of weld locations for the welds of the present disclosure and prior art welds. The tests were conducted on an Instron Model 1122 1,000 lb. load cell, wherein the welds tested were used with Koroseal® material. In the table, the “base” refers to the stock material with no welds whatsoever. The “corner extrusion weld” position refers to a welding process of the present disclosure for welding a pair of side sheets. The “prior art weld” position refers to conventional or current welding processes, such as the strip weld process previously discussed above in the background section. The “butt weld” position refers to a welding process of the present disclosure as previously discussed and shown in  FIG. 8 . As shown in Table 1, welding processes of the present disclosure result in higher weld strengths than the prior art welds. 
     
       
         
           
               
               
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                   
                   
                   
                 Failure  
                 Weld  
               
               
                   
                   
                   
                 Load 
                 Strength 
               
               
                   
                 Material 
                   
                 pounds per 
                 pounds  
               
               
                 Weld 
                 Thickness 
                 Temperature 
                 inch 
                 per inch 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
            
               
                 Base 
                 3/32 inch 
                  70° F. 
                 233 
                 245 
               
               
                 Corner Extrusion 
                 3/32 inch 
                  70° F. 
                 228 
                 228 
               
               
                 Weld 
                   
                   
                   
                   
               
               
                 Prior Art Weld 
                 3/32 inch 
                  70° F. 
                 163 
                 165 
               
               
                 Base 
                 3/16 inch 
                  70° F. 
                 485 
                 414 
               
               
                 Corner Extrusion 
                 3/16 inch 
                  70° F. 
                 324 
                 317 
               
               
                 Weld 
                   
                   
                   
                   
               
               
                 Prior Art Weld 
                 3/16 inch 
                  70° F. 
                 306 
                 227 
               
               
                 Corner Extrusion 
                 3/16 inch 
                 180° F. 
                 135 
                 98 
               
               
                 Weld 
                   
                   
                   
                   
               
               
                 Prior Art Weld 
                 3/16 inch 
                 180° F. 
                 78 
                 54 
               
               
                 Butt Weld 
                 3/16 inch 
                  70° F. 
                 405 
                 397 
               
               
                   
               
            
           
         
       
     
       FIG. 17  illustrates an exemplary embodiment of a resulting lining  26  formed by a process of the present disclosure as disclosed herein. As illustrated, the lining  26  comprises the bottom sheet  44  and the pairs of sheets  40 . Each pair has the first edge  46  and the second edge  48  that may be beveled forming the beveled region  56  between each pair of sheets  40 . The lining  26  further comprises the infused weld  62  along and within the interface  54  between the corner sheets  40 . The infused weld  62  also fills the gap or void between the corner sheets  40 . The extrusion weld  62  seals the pair of sheets  40  to each other and to the bottom sheet  44  while preferably eliminating pinholes. 
     The lining  26  further comprises the insert  64  welded to the lining corner  66  ( FIG. 15 ), which corner  66  is formed by the pairs of sheets  40  and the bottom sheet  44 . As previously noted, the thickness of each sheet  40  may be at least 3/32 inches. The thickness of the insert  64  ( FIG. 16 ) may have a range of about 3/16 inches to about ⅜ inches. The lining  26  may also comprise intermediate side sheets  42  that may be welded to the second edges  48  of the pair of each of the sheets  40 . 
     Some contents stored or processed in tanks or pits become more reactive when in contact with ambient air. For example, chrome solutions become more reactive as the chrome solution contacts ambient air. PVC is particularly susceptible to attack by chrome solutions. Accordingly, process tanks may include a sacrificial layer of material at the top of the process tank, which is exposed to the ambient air. The reactive solution chemically attacks the sacrificial layer. When the sacrificial layer nears the end of its useful life, the installer may then remove the sacrificial layer and replace it with a new sacrificial layer. This replacement process for conventional linings or linings having a sacrificial layer, however, is an expansive and labor intensive process. Currently, sacrificial layers use a double thickness of bonded High Performance Koroseal®, which protects the bonded-to-metal lining beneath it for a period of time, such as one to six years. 
       FIG. 18  illustrates an exemplary embodiment of a lining or liner  26  having an intermediate layer  70  and sacrificial layer  72 . In this example, the intermediate layer  70  is bonded to the liner or lining  26 . In an exemplary embodiment, the intermediate layer  70  comprises a rigid PVC material although other materials may also be used. 
     Next, the sacrificial layer  72  is affixed to the intermediate layer  70 . In an exemplary embodiment, the sacrificial layer  72  comprises a polyvinylidene fluoride (PVDF) material commonly known as Kynar® PVDF. Other materials may also be used for a sacrificial layer or skirt, such as polytetrafluoroethylene (PTFE), etc. 
     The sacrificial layer  72  may be affixed along the length of the intermediate layer  70  by welding the sacrificial layer  72  to the intermediate layer  70  using, for example, a weld material that comprises a hybrid rod material known as JSR #1.  FIG. 19  illustrates the liner or lining  26  bonded with the intermediate layer  70 , and the sacrificial layer  72  affixed to the intermediate layer  70 . 
       FIG. 20  illustrates an exemplary embodiment in which a sacrificial layer  72  (e.g., PVDF, etc.) is directly affixed over a lining, liner, or corrosion barrier  26 . In this example, sacrificial layers  72  may be welded to the lining  26 , for example, by using the hybrid rod material known as JSR #2 (soft).  FIG. 21  illustrates the lining  26  welded to the sacrificial layer  72 . 
     In the exemplary embodiment illustrated in  FIGS. 18-21 , the heights of the intermediate and sacrificial layers  70 ,  72  may be adjustable to accommodate varying levels of corrosive solutions dispersed within the tank. In another exemplary embodiment, a sacrificial layer  72  may be affixed to an intermediate layer  70  or to a lining  26  in a loose or sliding arrangement so that the sacrificial layer  72  can handle thermal expansion and contraction as the sacrificial layer  72  heats and cools in response to chemical reactions. 
     In some tank applications, parts that are being processed may damage the bottom sheet due to the part&#39;s weight and configuration. For example, an operator may mishandle a part while lowering the part in the solution. As such, the part may rapidly and uncontrollably drop into the tank and tear the bottom sheet. As another example, a part may dislodge from its carrier and drop into the tank and tear the bottom sheet. Some current process tanks are protected by chemical resistant masonry sheathings (“acid brick”). While these brick linings are not hydrostatically tight as a tank lining, (in fact, these brick linings are porous), the brick linings do offer both thermal and mechanical protection to the bottom sheet of the liner or lining. Acid brick has a very high cost factor as it must be installed on site and must be removed and replaced if the tank needs eventual relining. For some applications (hard chrome plating, for example), the used brick layer is considered hazardous waste leading to increased risks for personnel and to increased disposal costs. 
     Accordingly, an exemplary embodiment of a lining further includes an absorption layer or impact absorbing bumper pad positioned over and/or bonded to the top of the bottom sheet. This impact protective layer may comprise a honeycomb, egg-crate, and/or laminate structure, such as a non-float (high specific gravity) thermoplastic. The structure may also comprise compressible material that absorbs impact from dropped parts. By being made of pieces of a size and weight easily handled by installation personnel, this structure is easily removed from the tank bottom if a lining repair on or near the bottom is required. 
       FIG. 23  illustrates an exemplary embodiment of a liner that may be positioned within or applied to a tank. For example, the liner may be used as a “drop-in” free-standing liner (e.g., foldable and/or flexible drop-in bag liner, etc.) that is positioned within a tank without bonding the liner to the tank&#39;s surfaces. In other exemplary embodiments, the liner shown in  FIG. 23  may be used instead as a lining, which is bonded to a tank&#39;s surfaces. In yet other exemplary embodiments, the liner shown in  FIG. 23  may be configured for use as a standalone tank. 
     As shown in  FIG. 23 , the liner includes an inner lining  126  and an outer shell  178 . The lining  126  includes sheets or panels  138  separated by gaps along their edges. The sheets  138  are joined by an infused weld  162  formed by extrusion welding, such that the infused weld  162  also fills the gaps  156  between the sheets  138 . During the extrusion welding, molten thermoplastic material  160  infuses within the gaps  156  separating the sheets  138 . As shown in  FIG. 23 , molten thermoplastic weld material  160  also fills gaps  181  defined by and/or adjacent walls of the outer shell  178 . 
     A corner insert or attachment  164  (e.g., molded triangular corner insert, etc.) is extrusion welded or otherwise attached to a corner of the inner lining  126 , which provides double protected corners. In other exemplary embodiments, a corner attachment (e.g., molded triangular exterior corner cap, etc.) may also or alternatively be extrusion welded or otherwise attached along one or more exterior surfaces. A skirt or sacrificial layer  172  is also provided, which may be formed from Teflon® polytetrafluoroethylene (PTFE) or other suitable material. 
     In this exemplary embodiment, double sided electrically-conductive adhesive tape or bonding adhesive  179  may be used between the lining  126  and shell  178 , which has a ground connection to allow for leak detection, permeation monitoring, DC spark testing, etc. Alternative electrically-conductive adhesives, coatings, mediums, etc. may also be used. 
     The liner shown in  FIG. 23  also includes a pre-leak checking tab  180  (e.g., metal “spark” test tab, etc.). The pre-leak checking tab  180  and electrically-conductive medium between the outer shell  178  and inner lining  126  allows pre-leak testing, such as by “spark” testing and/or by a testing method disclosed in U.S. Pat. No. 7,111,497 the entire contents of which is incorporated herein by reference. Prompt detection of leaks allows for repair before damage becomes extensive to the tank. 
     Various materials may be used for the lining&#39;s sheets  138 , thermoplastic material  160 , corner inserts  164 , and outer shell  178 , such as the exemplary materials referred to above. In an exemplary embodiment, the lining sheets  138 , thermoplastic material  160 , and corner inserts  164  may comprise plasticized polyvinyl chloride (e.g., Koroseal® material, etc.), while the outer shell  178  comprises a high-impact polyvinyl chloride shell. In other exemplary embodiments, the outer shell  178  may comprise polyvinyl chloride (PVC) (e.g., Seaboard™ PVC, PVC foam, rigid PVC type 1, rigid PVC type 2, etc.), and the lining sheets  138  may comprise polyvinylidene fluoride (PVDF) (e.g., Kynar® polyvinylidene fluoride (PVDF), etc.). 
     The thermoplastic material  160  may comprise permanent thermoplastic lining materials such as, but not limited to, plasticized polyvinyl chloride, flexible polyvinyl chloride (F-PVC), rigid polyvinyl chloride, chlorinated polyvinyl chloride (CPVC), polyethylene (e.g., high molecular weight polyethylene (HMWPE), high-density polyethylene (HDPE), low-density polyethylene (LDPE), etc.), polyurethane/PVC alloy, synthetic rubber, fluoropolymer (homopolymer, copolymers (e.g., Poly(vinylidene fluoride-co-hexafluoropropene) (PVDF-HFP), etc.) or alloys), ethylene-chloro-tri-fluoro-ethylene (Halar ECTFE), laminations of thermoplastic materials such as above, etc. By way of further example, the lining  126 , inserts  164 , and/or shell  178  may be made from rigid polyvinylchloride, chlorinated polyvinyl chloride (CPVC), polyethylene, polypropylene, copolymer polypropylene, polyvinylidene fluoride (PVDF), Kynar® polyvinylidene fluoride (PVDF), geomembrane, ethylene interpolymer alloy (EIA), etc. 
     Accordingly, the exemplary embodiment illustrated in  FIG. 23  may advantageously provide a double barrier protection via the inner lining  126  and outer shell  178 , such that there is triple protection or triple containment when the liner is within a tank. Depending on the particular contents to be stored and/or processed, the liner illustrated in  FIG. 23  may also be used as a tank itself for storing and/or processing contents without the liner having to be positioned within a tank. The exemplary embodiment illustrated in  FIG. 23  may advantageously have a relatively long service life, solid, strong, and fewer welds as compared to conventional liners. 
       FIG. 24  illustrates an exemplary embodiment of a lining  226  applied to walls  230  of a tank  228 . As shown, the lining  226  includes sheets or panels  238  separated by a gap  256 . The sheets  238  are joined by an infused weld  262  that also fills the gap  256  between the sheets  238 . During the extrusion welding, molten thermoplastic material  260  infuses within the gap  256  separating the sheets  238 . The infused thermoplastic material  260  seals the sheets  238  and isolates the lined tank  228  from contents (e.g., contents being stored and/or processed, etc.) within the lined tank  228 , as the contents contact the sheets  238  of the lining  226  instead of the tank walls  230 . 
     Molten thermoplastic weld material  260  flows into and fills the gap  256  between the sheets  238  and penetrates the joint to the tank wall  230 . As shown in  FIG. 24 , the thermoplastic weld material  260  also fills a gap  281  defined by and/or adjacent the tank wall  230 . An infused weld area  262  is thus created that helps eliminate channels, pinholes, gaps, etc. behind the weld seams, which, in turn, helps reduce the probability of leaks and helps increase the service life of the tank  228 . If a leak happens, then the weld  262  also helps block solution from flowing behind the lining  226 . 
     The sheets  238  may be attached to the tank walls  230  by double sided adhesive tape (e.g., 3M VHB tape, etc.). Alternatively, other suitable attachment means (e.g., adhesive cement, etc.) may be used for attaching the sheets  238  to and holding them in place relative to the tank walls  230  with the gap  256  between adjacent sheets  238 . In this exemplary embodiment and/or other exemplary embodiments disclosed herein, double sided electrically-conductive adhesive tape may be used between the lining  226  and tank  228 . The use of an electrically-conductive tape between the lining  226  and tank  228  allows pre-leak testing, such as “spark” testing and/or by a testing method disclosed in U.S. Pat. No. 7,111,497 the entire contents of which is incorporated herein by reference. Prompt detection of leaks allows for repair before damage becomes extensive to the tank. 
     Also in this embodiment (as in other embodiments disclosed herein), various materials may be used for the lining sheets  238  and thermoplastic material  260  including those materials referred to above. In an exemplary embodiment, the lining sheets  238  may be made out of plasticized polyvinyl chloride (e.g., Koroseal® material, etc.). The thermoplastic material  260  may comprise permanent thermoplastic lining materials such as, but not limited to, plasticized polyvinyl chloride, flexible polyvinyl chloride (F-PVC), rigid polyvinyl chloride, chlorinated polyvinyl chloride (CPVC), polyethylene (e.g., (high molecular weight polyethylene (HMWPE), high-density polyethylene (HDPE), low-density polyethylene (LDPE), etc.), polyurethane/PVC alloy, synthetic rubber, fluoropolymer (homopolymer, copolymers (e.g., Poly(vinylidene fluoride-co-hexafluoropropene) (PVDF-HFP), etc.) or alloys), ethylene-chloro-tri-fluoro-ethylene (Halar ECTFE), ethylene interpolymer alloy (EIA), geomembrane, laminations of thermoplastic materials such as above, etc. 
     Accordingly, the exemplary embodiment illustrated in  FIG. 24  may advantageously have a relatively long service life, have welds that are solid and strong (more tolerable to stresses), and have fewer welds as compared to conventional linings. The lining  126  may also include corner attachments (e.g., corner inserts  64  ( FIG. 16 ), exterior caps  464  ( FIGS. 26 and 27 ), etc.) as disclosed herein, which, in turn, provide double protected corners. 
       FIG. 25  illustrates an exemplary embodiment of a sheet or piece  338  of lining material applied to a wooden flooring member  390 . As shown, an infused weld  362  joins the liner sheet  338  to the flooring member  390 . During extrusion welding, molten thermoplastic material  360  infuses into a gap  356  (e.g., an inverted v-shaped notch, dovetail shaped notch, etc.) in the flooring member  390  to bond the piece or sheet  338  of lining material to the flooring member  390 . In other embodiments, liners or linings disclosed herein may also be used for lining non-wooden floors, such as a concrete floor in a containment area, etc. 
       FIGS. 26 and 27  illustrate an exemplary embodiment of an exterior corner cap  464  (broadly, a corner attachment) along an exterior corner of a liner or lining  426  (e.g., a flexible PVC or vinyl bag liner, etc.) in accordance with and embodying one or more aspects of the present disclosure. The exterior corner cap  464  may be configured to provide additional protection and/or reinforcement at the corner of the liner  426 . 
     The exterior corner cap  464  (e.g., molded triangular thermoplastic corner cap, etc.) may be attached to or along exterior surfaces of the side sheets  442  and bottom sheet  444  of the liner or lining  426 . By way of example, the exterior corner cap  464  may be welded to the corner of the liner  426  by an extrusion weld material, a weld rod, and/or weld seam strip. Accordingly, an extrusion weld, a hot gas rod weld, and/or a seam strip weld may be used to attach the exterior corner cap  464  to the corner of the liner  426 . Or, for example, the exterior corner cap  464  may be adhesively attached or bonded to the corner of the liner  426  by a glue and/or a tape (e.g., 3M very high bond (VHB) double sided adhesive tape, etc.). 
     In the illustrated embodiment of  FIGS. 26 and 27 , the exterior corner cap  464  is configured (e.g., molded, etc.) to have a triangular shape. For example, the exterior corner cap  464  may be generally hollow and have a truncated triangular pyramidal configuration (triangular pyramidal frustum). 
     The exterior corner cap  464  may be made from a wide variety of materials. For example, the exterior corner cap  464  may be made from the same material as the lining  426 . Or, for example, the exterior corner cap  464  may be made from a different material than the lining  426 . By way of example, the exterior corner cap  464  and/or lining  426  may be made from rigid polyvinylchloride, chlorinated polyvinyl chloride (CPVC), polyethylene, polypropylene, polyvinylidene fluoride (PVDF), Kynar® polyvinylidene fluoride (PVDF), ethylene interpolymer alloy (EIA), geomembrane, etc. 
     The exterior corner cap  464  may vary in size. For example, the exterior corner cap  464  may have a thickness within a range of about 3/16 inches to about ⅜ inches. The installer may position an exterior corner cap  464  at one or more exterior corners of the lining  426 . For example, an exterior corner cap  464  may be positioned at each exterior corner of the lining  426  formed by adjacent pair of sheets  442  and bottom sheet  444  of the lining  426 . 
     In an exemplary embodiment, a tank liner generally includes a shell and a plurality of sheets coupled to the shell and defining an internal volume usable for storage of materials. Extrusion weld material is infused within a first gap defined by and/or adjacent at least one wall of the shell. A pair of adjacent sheets of the plurality of sheets is joined by extrusion weld material infused within a second gap along an interface between the pair of adjacent sheets. 
     The shell may comprise polyvinyl chloride (PVC) (e.g., PVC foam, etc.). The plurality of sheets may comprise polyvinylidene fluoride (PVDF). The extrusion weld material comprises thermoplastic material. The first gap may be defined entirely or at least partially in the at least one wall of the shell. The first gap may be between the at least one wall of the shell and at least one sheet of the plurality of sheets. The extrusion weld material may be infused within the first gap such that the extrusion weld material contacts or penetrates to the at least one wall of the shell. 
     Electrically-conductive material may be disposed between at least one sheet of the plurality of sheets and at least one wall of the shell. The electrically-conductive material with a ground connection may allow for leak detection, permeation monitoring, and/or spark testing. 
     The pair of adjacent sheets may be joined by the extrusion weld material without a filler rod in the second gap. Each sheet of the pair of adjacent sheets may include a beveled edge such that the second gap is defined between the beveled edges of the pair of adjacent sheets. 
     The plurality of sheets may comprise a bottom sheet and a plurality of side sheets. A triangular insert may be extrusion welded at a corner formed by the bottom sheet and a pair of adjacent side sheets. The pair of adjacent sheets is adhesively attached to the shell. The shell and the plurality of sheets may be configured for use as a drop-in liner for a tank and/or for use as a standalone tank. 
     Other exemplary embodiments relate to methods of providing a tank liner that includes a shell and a plurality of sheets defining an internal volume usable for storage of materials. In an exemplary embodiment, a method generally includes infusing extrusion weld material within a first gap defined by and/or adjacent at least one wall of the shell and within a second gap along an interface between a pair of adjacent sheets of the plurality of sheets. The pair of adjacent sheets may be joined by the extrusion weld material infused within the second gap. 
     The method may include infusing the extrusion weld material within the first gap. After infusing the extrusion weld material within the first gap, the method may also include positioning the pair of adjacent sheets adjacent each other to form the second gap and then infusing the extrusion weld material within the second gap. 
     The method may include extrusion welding along the first gap to infuse the extrusion weld material within the first gap. After extrusion welding along the first gap, the method may also include coupling the pair of adjacent sheets to the shell such that the second gap is formed and then extrusion welding along the second gap to infuse the extrusion weld material within the second gap. 
     The shell may comprise polyvinyl chloride (PVC) foam. The plurality of sheets may comprise polyvinylidene fluoride (PVDF). The extrusion weld material may comprise thermoplastic material. 
     The first gap may be at least partially defined in the at least one wall of the shell. The extrusion weld material may be infused within the first gap such that the extrusion weld material contacts the at least one wall of the shell. The pair of adjacent sheets may be joined by the extrusion weld material without a filler rod in the second gap. Each sheet of the pair of adjacent sheets may include a beveled edge such that the second gap is defined between the beveled edges of the pair of adjacent sheets. 
     As disclosed herein, exemplary embodiments include welds that are formed with extrusion welding machines such that the welds are preferably designed to eliminate gaps resulting from imperfect hand welded seams. Exemplary embodiments may further include molded corner inserts for double protection in the corners. In some exemplary embodiments in which a liner or lining is intended for a large tank, a liner or lining may include full-size RF (radio frequency) welded high performance Koroseal® panels (e.g., Koroseal® flexible PVC sheets, etc.) to eliminate lining seams in tank walls and bottom. For example, if a tank is very large, a lining may include large sub-panels joined by skived edges with overlapped extrusion welds. This, in turn, may help avoid entrapped air, similar to rubber lining joints, and eliminate hand welds with seam strips in immersion service. 
     The inventor has developed and discloses herein hot gas/hot air extrusion welding machine techniques that overcome disadvantages that are characteristic of hand-welding, such as channels, pinholes, and gaps that can form behind hand welded seams and allow the solution in a tank or pit to flow behind the lining and corrode the substrate if a leak occurs. As disclosed herein, the inventor&#39;s techniques modify the preheating process and delivery of the weld material. For example, and as disclosed herein for exemplary embodiments, a welding machine extrudes a high-performance, plasticized PVC weld material that infuses into the substrate&#39;s pores and voids as well as joins the PVC sheet linings. Rather than extending the sheet linings on a sidewall and bottom of a tank or pit so that they meet at a 90-degree joint, the sheet linings are configured or shortened to leave a relatively small gap at the joint. This allows molten thermoplastic weld material to flow into and fill the gap between the lining sheets and penetrate the joint to the substrate (e.g., the tank wall, etc.). An infused weld area is thus created that helps eliminate channels, pinholes, and gaps behind the weld seams, which, in turn, helps reduce the probability of leaks, and helps increase the service life of the tank, pit, storage vessel, etc. Should a leak happen, the weld helps block solution from flowing behind the lining. 
     Also with the inventor&#39;s hot gas/hot air extrusion welding machine techniques the welding rod may be fully melted, which results in a homogenous weld with fewer stresses. The weld may be formed in a single pass, further reducing stresses introduced by the multiple passes common in traditional hand welding. The inventor&#39;s extrusion welding is faster and is less sensitive to surface oxidation. 
     As recognized by the inventor hereof, the inner bottom corners where three intersecting lining sheets must be joined are typical problem areas and a frequent source of early leaks and premature lining failures with conventional linings in that it is difficult to perform a high-quality weld in a corner. This is because high-quality welds need the right speed, temperature, and pressure as the welding machine is moved along the joint. But at a corner, the lining sheets can&#39;t be preheated because the welding machine stops. To address this problem, the inventor hereof has disclosed exemplary embodiments of molded thermoplastic corner inserts (broadly, corner attachments), which enable the welding machine to weld continuously in the corners without having to stop at the corners. 
     Exemplary embodiments of linings and liners disclosed herein may be used with virtually any type of (e.g., for different uses, formed from different materials (e.g., steel, fiberglass, rubber, lead, plastic, etc.) different shapes and sizes, etc.) process tank, indoor or outdoor containment pit, other storage or liquid containment vessels, etc. Exemplary embodiments may also be configured as relatively rigid “drop-in” thermoplastic liners which possess superior perimeter machine welds which are mechanically anchored to the tank or to a framework for placement into the tank in a manner such that the liner does not float in the tank. 
     Also disclosed are exemplary embodiments of methods of providing additional protection and/or reinforcement at one or more corners of a liner including a bottom and one or more sides defining an internal volume usable for storage of materials. In an exemplary embodiment, a method generally includes positioning and attaching one or more corner attachments at the one or more corners of the liner that are formed between the bottom and the one or more sides of the liner. The one or more corner attachments may be configured to provide additional protection and/or reinforcement at the one or more corners of the liner. 
     The method may include positioning and attaching the one or more corner attachments along one or more inner surfaces of the liner that define one or more interior corners of the liner. Additionally, or alternatively, the method may include positioning and attaching the one or more corner attachments along one or more exterior surfaces of the liner that define one or more exterior corners of the liner. 
     The method may include welding the one or more corner attachments at the one or more corners of the liner by using an extrusion weld material, a weld rod, and/or a weld seam strip; and/or gluing or taping the one or more corner attachments at the one or more corners of the liner. 
     The one or more corner attachments may comprise molded thermoplastic material having a generally triangular shape. The bottom and the one or more sides of the liner may comprise polyvinylidene fluoride (PVDF), ethylene interpolymer alloy (EIA), or a geomembrane. The one or more corner attachments may comprise polyvinylidene fluoride (PVDF), ethylene interpolymer alloy (EIA), or a geomembrane. 
     The liner may be configured for use as a flexible or foldable drop-in bag liner, for use a drop-in liner for a tank and/or for use as a standalone tank. 
     The method may include positioning and attaching the one or more corner attachments along one or more inner surfaces of a tank, and installing the liner within the tank such that the one or more corners of the liner are aligned with and coupled to the one or more corner attachments previously attached along the one or more inner surfaces of the tank. 
     The method may include installing the liner within a tank; and positioning and attaching the one or more corner attachments along one or more inner surfaces of the liner that define one or more interior corners of the liner previously installed within the tank. 
     Also disclosed are exemplary embodiments of liners or liners including corner reinforcement or reinforced corners. In an exemplary embodiment, a liner generally includes a bottom and one or more sides defining an internal volume usable for storage of materials. The liner further comprises one or more corner attachments positioned and attached at one or more corners of the liner that are formed between the bottom and the one or more sides of the liner. The one or more corner attachments are configured to provide additional protection and/or reinforcement at the one or more corners of the liner. 
     The one or more corner attachments may comprise one or more corner inserts along one or more inner surfaces of the liner that define one or more interior corners of the liner. Additionally, or alternatively, the one or more corner attachments may comprise one or more exterior corner caps along one or more outer surfaces of the liner that define one or more exterior corners of the liner. 
     The one or more corner attachments may be welded to the one or more corners of the liner by an extrusion weld material, a weld rod, and/or weld seam strip. An extrusion weld, a hot gas rod weld, and/or a seam strip weld may be used to attach the one or more corner attachments to the one or more corners of the liner. Or, the one or more corner attachments may be adhesively attached or bonded to the one or more corners of the liner by a glue and/or a tape. 
     The one or more corner attachments may comprise molded thermoplastic material having a generally triangular shape. The bottom and the one or more sides of the liner may comprise polyvinylidene fluoride (PVDF), ethylene interpolymer alloy (EIA), or a geomembrane. The one or more corner attachments may comprise polyvinylidene fluoride (PVDF), ethylene interpolymer alloy (EIA), or a geomembrane. 
     The liner may be configured for use as a flexible or foldable drop-in bag liner, for use a drop-in liner for a tank and/or for use as a standalone tank. 
     In some exemplary embodiments, a liner may generally include a bottom and one or more sides welded to the bottom by a pre-existing weld material to thereby define an internal volume usable for storage of materials. The liner may further comprise an extrusion weld material extrusion welded over the pre-existing weld material to thereby reinforce and/or strengthen a weld joint between the bottom and the one or more sides. 
     The liner may comprise a flexible and/or foldable bag liner including one or more corners formed between the bottom and the one or more sides. The pre-existing weld material may be disposed along the one or more corners. The extrusion weld material may be extrusion welded over the pre-existing weld material along the one or more corners to thereby reinforce and/or strengthen a weld joint along the one or more corners. 
     The liner may comprise a cylindrical liner. The pre-existing weld material may be disposed along a bottom annular portion of the cylindrical liner between the one or more sides and the bottom. The extrusion weld material may be extrusion welded over the pre-existing weld material along the bottom annular portion to thereby reinforce and/or strengthen the weld joint along the bottom annular portion. 
     Exemplary embodiments are also disclosed of methods of reinforcing and/or strengthening a weld joint between a bottom and one or more sides of a liner defining an internal volume usable for storage of materials. In an exemplary embodiment, a method generally includes extrusion welding an extrusion weld material over a pre-existing weld material forming the weld joint between the bottom and the one or more sides of the liner. The method may include extrusion welding the extrusion weld material over the pre-existing weld material after the liner has been previously installed within a tank. 
     Exemplary embodiments are also disclosed of apparatus for providing additional protection and/or reinforcement at one or more corners of a liner including a bottom and one or more sides defining an internal volume usable for storage of materials. In an exemplary embodiment, an apparatus generally includes one or more corner attachments configured to be positioned and attached at the one or more corners of the liner that are formed between the bottom and the one or more sides of the liner. The one or more corner attachments are configured to provide additional protection and/or reinforcement at the one or more corners of the liner. The one or more corner attachments may comprise molded thermoplastic material having a triangular shape, and/or the one or more corner attachments comprise polyvinylidene fluoride (PVDF), ethylene interpolymer alloy (EIA), or a geomembrane. 
     Example embodiments are provided so that this disclosure will be thorough, and will fully convey the scope to those who are skilled in the art. Numerous specific details are set forth such as examples of specific components, devices, and methods, to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, that example embodiments may be embodied in many different forms (e.g., different materials may be used, etc.) and that neither should be construed to limit the scope of the disclosure. In some example embodiments, well-known processes, well-known device structures, and well-known technologies are not described in detail. 
     Specific dimensions, specific materials, and/or specific shapes disclosed herein are example in nature and do not limit the scope of the present disclosure. The disclosure herein of particular values and particular ranges of values for given parameters are not exclusive of other values and ranges of values that may be useful in one or more of the examples disclosed herein. Moreover, it is envisioned that any two particular values for a specific parameter stated herein may define the endpoints of a range of values that may be suitable for the given parameter (i.e., the disclosure of a first value and a second value for a given parameter can be interpreted as disclosing that any value between the first and second values could also be employed for the given parameter). Similarly, it is envisioned that disclosure of two or more ranges of values for a parameter (whether such ranges are nested, overlapping or distinct) subsume all possible combination of ranges for the value that might be claimed using endpoints of the disclosed ranges. 
     The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting. As used herein, the singular forms “a”, “an” and “the” may be intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms “comprises,” “comprising,” “including,” and “having,” are inclusive and therefore specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. It is also to be understood that additional or alternative steps may be employed. 
     When an element or layer is referred to as being “on”, “engaged to”, “connected to” or “coupled to” another element or layer, it may be directly on, engaged, connected or coupled to the other element or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly engaged to”, “directly connected to” or “directly coupled to” another element or layer, there may be no intervening elements or layers present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between” versus “directly between,” “adjacent” versus “directly adjacent,” etc.). As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. 
     Although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms may be only used to distinguish one element, component, region, layer or section from another region, layer or section. Terms such as “first,” “second,” and other numerical terms when used herein do not imply a sequence or order unless clearly indicated by the context. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the example embodiments. 
     Spatially relative terms, such as “inner,” “outer,” “beneath”, “below”, “lower”, “above”, “upper” and the like, may be used herein for ease of description to describe one element or feature&#39;s relationship to another element(s) or feature(s) as illustrated in the figures. Spatially relative terms may be intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the example term “below” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly. 
     The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements, intended or stated uses, or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.