Patent Publication Number: US-11644247-B2

Title: Apparatus and method to prevent splitting or rupture in fluid coils

Description:
CROSS-REFERENCE TO RELATED APPLICATION DATA 
     This application claims the benefit of and priority to Provisional U.S. Patent Application Ser. No. 62/949,219, filed Dec. 17, 2019, titled Apparatus and Method to Prevent Splitting or Rupture in Fluid Coils, the disclosure of which is incorporated herein in its entirety. 
    
    
     BACKGROUND 
     The present disclosure relates to an apparatus and method to prevent fluid coils from splitting or rupturing due to the thermal expansion of liquid, such as water, in freezing conditions and steam condensing to water and subsequently freezing. 
     It is well-known that during a phase change of water from liquid to solid, its volume expands as much as 10% or more (volumetric thermal expansion). In fluid systems, thermal expansion can exert immense stresses and pressure on equipment and structures. In the field of heating, ventilation, and air-conditioning (HVAC), finned tube heat exchangers or HVAC coils are often used for heating and cooling of air in which a fluid such as water (liquid) or steam (gas) is circulated inside a closed loop of coils to transfer heat between the fluid and the air. Coils carrying water that are exposed to ambient air at or below the freezing point of water (e.g., 0° C. or 32° F.) for a sufficient amount of time may freeze up causing extreme pressures within the coil system that can damage the coil assemblies. Likewise, in steam coils, water may condense and then freeze which can subject the coils to extreme pressures. Subsequent to freezing and upon thawing of ice, water can leak out through breaks or split areas in the coils, at, for example, return bends. Leakage can cause flooding, which may damage the HVAC systems, as well as other equipment and areas of buildings in the vicinity of the flooded zones. This can result in expensive repairs or equipment replacement, in addition to service downtime suffered from the freezing/flooding event. 
     To prevent freezing and damage to systems, freeze plugs, expansion relief headers with pressure relief valves, and other devices are known. For example, it is known to use pressure relief devices at return bends or headers that blow out in the event of a freeze event to prevent damage to coils. However, these devices are limited in providing maintenance-free service upon the aftermath of the blow-out of the plugs due to excessive pressures caused by tube freezing. Indeed, the pressure relief device once blown out require replacement and maintenance, and water can bleed through tube cracks and flood the surrounding areas even before it is realized that damage has occurred. 
     Another device uses expansion relief headers with pressure relief valves in conjunction with pressure and temperature sensors to detect dropping temperature and rising pressure around selected values in a freeze event. These assemblies then release an appropriate volumetric amount of water to prevent damage to the tubes and return bends. While these devices require less maintenance, they are costly and bulky due to the various sensors and valves added to the expansion relief headers. 
     In another device, round, hollow tubular inserts are affixed in a central position using guides within pressurized water pipes and water mains. The insert is constructed of a thin-walled, flexible material that is capable of being deformed, thereby absorbing expansion pressures exerted by the water in a frozen state. However, this device only functions in a conduit conveying or containing water that does not involve heat transfer between inner and outer environments of the conduit. Moreover, if used in fluid coils in HVAC applications, such inserts severely degrade the thermal-hydraulic performance of the coils. In addition, leaching of the flexible material into the fluid is also a concern when in direct contact with non-potable water that may carry various chemical impurities. 
     A similar device for freeze protection in fluid transport passages uses an annular passage formed between an insert made of a compressible elastomeric material and a rigid conduit. The device also introduces a substantially liquid impermeable membrane preferably disposed in substantially adjacent relationship with the insert. Such a device also fails in heat transfer applications as it directly adds an interference with a large thermal resistance inside the water conduit. In addition, although a liquid impermeable membrane is used to separate the insert from the fluid, the presence of the membrane reduces the hydraulic performance of the fluid system. 
     In still another system, an apparatus and method utilize a freeze protection material consisting of a closed cell, expanded polymeric material with specific properties that is configured to protect fluid systems. Although these materials can be free of zinc, silicon, sulfur, sodium, potassium, or halogens, so as not to interfere with chemical reactions in sensitive fluid systems through leaching of these elements into the surrounding fluids, it is possible that other chemical additives, such as chlorine, in water treatment systems for high temperature HVAC systems can accelerate leaching. 
     As such, many of the known freeze prevention devices and systems are disadvantageous for fluid coils in HVAC applications due to their limited capabilities in treated water systems, in exposure to a wide range of working temperatures, and in systems that use chemical additives. Moreover, many of these systems reduce the thermal-hydraulic performance due to, for example, direct contact of compressible materials with the working fluid in a fluid passage. In addition, some known freeze protection methods and devices/systems for fluid coils require either labor-intensive maintenance with potential flooding and/or large, expensive sensor systems that can complicate construction. 
     Accordingly, there is a need for a device to prevent fluid coils from splitting or rupturing due to the thermal expansion of liquid, such as water in freezing conditions or in steam coils when the steam condenses to water and subsequently freezes. Desirably, such a device can be used in treated water systems, without the cooling system and device materials interacting with one another in deleterious ways. More desirably still, the device compresses to absorb the expansion volume of water in the system as it freezes to ice, and once the ices thaws, it returns to it pre-compressed state. 
     SUMMARY 
     In one aspect, a fluid coil includes a tube bundle having a series of straight tubing runs and a series of return bends extending between and fluidically connecting ones of the straight tubing runs, an expansion header fluidically connected to at least some of the return bends, and a polymeric material disposed in the expansion header. The polymeric material has an initial shape and is compressible to repeatedly expand and contract between a first volume in which water is present in the tube bundle and a second volume in which the water undergoes a phase change. The phase change can be from water to ice or from steam to water (by condensation in steam coils) and then to ice. 
     Contraction of the polymeric material absorbs an increase in volume as the water undergoes a phase change to ice to prevent stressing and rupture of the tube bundle, and upon a phase change from ice to water, the polymeric material returns to its initial shape. 
     In an embodiment, a suitable polymeric material is resilient and hydrophobic and can have a closed cell structure. The material can have a working temperature in a range of about −40° F. to about 250° F., and a Shore A hardness of about 50 to 90. 
     In an embodiment, the polymeric material is chemically resistant and non-reactive to chemicals used for corrosion control and/or microbial control. Suitable materials include, but are not limited to, an elastomer, a fluorocarbon, a perfluoroelastomer, ethylene-propylene, and tetrafluoroethylene/propylene, and combinations thereof. 
     In an embodiment, the fluid coil includes a fin pack and support members, such that the tube bundle and fin pack are mounted within the support members. In some embodiments the fluid coil includes a first plurality of return bends on a first side of the tube bundle and a second plurality of return bends on a second side of the tube bundle. The first plurality of tube bends extends between and fluidically connects ones of the straight tubing runs on the first side of the tube bundle and the second plurality of tube bends extends between and fluidically connects ones of the straight tubing runs on the second side of the tube bundle. 
     In embodiments, the fluid coil includes two expansion headers, a first expansion header fluidically connected to the first plurality of return bends and a second expansion header fluidically connected to the second plurality of return bends. In such an embodiment, an expansion header can be associated with each of the pluralities of return bends. 
     In embodiments, the polymeric material is a pressurizable bladder. The pressurizable bladder can be a tube, and can further include caps at ends of the tube to close off the tube. One of the caps can include a fitting for introducing a compressed gas into the tube. 
     One suitable material for the tube is EPDM rubber. The bladder can be pressurized to about 120 psi to 150 psi. 
     A system to prevent the rupture of a tube bundle in a fluid coil, which the fluid coil has a tube bundle having a series of straight tubing runs and a series of return bends extending between and fluidically connecting ones of the straight tubing runs, includes an expansion header fluidically connected to at least some of the return bends and a polymeric material disposed in the expansion header. The polymeric material has an initial shape and is compressible to repeatedly expand and contract between a first volume in which water is present in the tube bundle and a second volume in which the water undergoes a phase change to ice. 
     In embodiments, the compressible material is a pressurizable bladder. The bladder can be, for example a tube. The tube can include caps at ends of the tube to close off the tube. The tube can be affixed to the caps by clamps to seal the tube. One of the caps can include a fitting for introducing a compressed gas into the tube. One suitable material is formed from EPDM. The bladder can be is pressurized to about 120 psi to 150 psi. 
     Contraction of the polymeric material absorbs an increase in volume as the water undergoes a phase change to ice so as to prevent stressing and rupture of the tube bundle, and, upon a phase change from ice to water, the polymeric material returns to its initial shape. It will be appreciated that in steam coils, the steam may condense to water and then undergo a phase change to ice. 
     A method to prevent the rupture of a tube bundle in a fluid coil, which fluid coil has a tube bundle having a series of straight tubing runs and a series of return bends extending between and fluidically connecting ones of the straight tubing runs, and an expansion header fluidically connected to at least some of the return bends, includes disposing in the expansion header a polymeric material having an initial shape, which material is compressible to repeatedly expand and contract between a first volume in which water is present in the tube bundle and a second volume in which the water undergoes a phase change to ice. In methods, contraction of the polymeric material absorbs an increase in volume as the water undergoes a phase change to ice to prevent stressing and rupture of the tube bundle, and, upon a phase change from ice to water, the polymeric material returns to its initial shape. 
     In methods, wherein the polymeric material is a pressurizable bladder. The pressurizable bladder can be a tube, and can including caps at ends of the tube to close off the tube. One of the caps can include a fitting for introducing a compressed gas into the tube. The tube can be formed from EPDM. In methods, the bladder is pressurized to about 120 psi to 150 psi. 
     Since the apparatus has no pressure relief valves, the fluid is kept inside the expansion headers without bleeding to the outside environment, which adds another level of protection to avoid system flooding. The apparatus may also provided without expensive sensors, so the cost is reduced significantly. The apparatus is equipped with an end cap that is threaded to the end of the expansion header for easy repair and maintenance, should the material need to be inspected or replaced. 
     Further understanding of the present disclosure can be obtained by reference to the following detailed description in conjunction with the associated drawings, which are described briefly below. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       Various embodiments of an apparatus or system and method to prevent the splitting or rupturing of fluid-carry coils are disclosed as examples and are not limited by the figures of the accompanying drawings, in which like references may indicate similar elements and in which: 
         FIG.  1    is an isometric front view of an embodiment of a fluid coil having a system to prevent splitting or rupturing of the coil bundle in the event of a thermal event such as freezing, the illustrated fluid coil being a four-row fluid coil; 
         FIG.  2    is a sideview of the fluid coil; 
         FIG.  3    is an isometric rear view of the fluid coil; 
         FIG.  4    is a top view of the fluid coil; 
         FIG.  5    is a front view of the fluid coil; 
         FIG.  6    is a partial cross-sectional view of the expansion header of  FIG.  5   , the expansion header shown filled with a compressible polymeric material; 
         FIG.  7    is a rear view of the fluid coil; 
         FIG.  8    is a partial cross-sectional view of the expansion headers of  FIG.  6   , the expansion headers shown filled with a compressible polymeric material; 
         FIG.  9    illustrates another embodiment of the system to prevent splitting or rupturing of the coil bundle, showing the expansion header; 
         FIG.  10    is a sectional view of the expansion header of  FIG.  9   ; 
         FIG.  11    is a partial section view of the upper portion of the expansion header of  FIGS.  9  and  10   ; and 
         FIG.  12    is an illustration of a feed and control system for the apparatus to prevent fluid coils from splitting or rupturing due to the thermal expansion of liquid. 
     
    
    
     DETAILED DESCRIPTION 
     While the present disclosure is susceptible of embodiments in various forms, there is shown in the drawings and will hereinafter be described a presently preferred embodiment with the understanding that the present disclosure is to be considered an exemplification and is not intended to limit the disclosure to the specific embodiment illustrated. 
     A novel apparatus or system and method are disclosed to prevent the splitting or rupturing of fluid-carry coils in, for example, an HVAC system, due to the thermal expansion of water in freezing conditions for a fluid coil, or the phase change from steam to water (condensation) and subsequently from water to ice. The present disclosure provides an apparatus or system, and method that protect fluid coils from splitting or rupturing when such a freeze event occurs. The present system and method reliably and repeatedly protect fluid coils from splitting or rupturing due to excessive stresses and pressure caused by expansion during a phase change of water to ice inside such coils. 
     Referring to the figures there is shown a fluid coil  10  having a tube bundle  12  and a fin pack  14  mounted and secured to support members  16  by fasteners  18 . The tube bundle  12  has an inlet header  20  with an inlet piping connection  22 , an outlet header  24  with an outlet piping connection  26 , and expansion headers  28 , as will be discussed in more detail below. The inlet header  20  and outlet header  24  are connected to the tube bundle  12  by pipe extensions  30 . An air vent  32  is located on an upper side of the outlet header  24  and a water drain  34  is located on the lower side of the inlet header  20 . 
     The tube bundle  12  has a series of return bends  36  extending between and connecting straight tubing runs  38 . In the illustrated fluid coil  10  there are two series of return bends  36   a ,  36   b  on one side of the bundle  12  and one series of return bends  36   c  on an opposite side of the bundle  12 . 
     The expansion headers  28  are connected to their respective return bends  36  in each series of return bends  36 . The expansion headers  28  are connected to the return bends  36  by header connectors  40 . For example, in the illustrated fluid coil  10 , expansion header  28   a  is connected to return bends  36   a  by header connectors  40   a , expansion header  28   b  is connected to return bends  36   b  by header connectors  40   b , and expansion header  28   c  is connected to return bends  36   c  by header connectors  40   c.    
     For purposes of the present disclosure, the expansion headers  28   a ,  28   b  an  28   c  are referred to collectively by reference number  28 , the return bends  36   a ,  36   b  and  36   c  are referred to collectively by the reference number  36  and the header connectors  40   a ,  40   b  and  40   c  are referred to collectively by reference number  40 . 
     In an embodiment, the expansion headers  28  are closed at their ends  42  by caps  44 . The caps  44  can be removable to inspect, repair or replace material  46  disposed in the expansion headers  28 , which material  46  is described in more detail below. In embodiments the end  44  caps are threaded onto the expansion headers  28 . 
     It is to be understood that reference to “connection” or “connected” in the present disclosure means fluidically connected so as to permit flow between and among the connected elements. 
     Referring now to  FIGS.  6  and  8   , to absorb the expansion and contraction within the tube bundle  12 , a high-quality, compressible material  46  is disposed in the expansion headers  28 . The material  46  expands and contracts within a minimum volume and a maximum volume. The material  46 , when contracted by the excessive expansion pressure caused by the phase change of water, e.g., freezing, allows the fluid (and ice) to volumetrically expand into a predetermined volume of the material  46  as the material  46  compresses, thus reducing the stresses and pressure on the tube bundle  12  to prevent splitting or rupturing of the tube bundle  12 . 
     The material  46 , upon thawing of the ice, expands to regain its original volume within a predetermined space of the expansion header  28 . It is anticipated that the material  46  has an appropriate hardness so that in a normal liquid state of water, the material  46  maintains its original shape within the confined space of the expansion header  28 . The material  46  also has an appropriate compression set property to reliably and repeatedly protect the fluid coil  12  from splitting or rupturing when the ambient air temperature is at or below the freezing point and water in the coil freezes (or in steam coils, when steam in the coil condenses to water and subsequently freezes). 
     The material  46  must be able to achieve the required expansion and contraction in freeze and thaw conditions and the ability to retain its original shape following repeated expansions and contractions. That is, the material  46  is sufficiently resilient to return to its original shape with minimal or no deformation. 
     One suitable material  46  is a polymeric material that is water resistant or hydrophobic, and has a closed cell structure. To function well in the HVAC environment, the material  46  should have a working temperature in a range of about −40° F. to about 250° F. It should be resilient and be able to withstand reliably and repeatably expand and contract for long and short periods of time. And, when expanded, the material  46  should return to its original shape and volume. 
     The material  46  should also be sufficiently hard so that it maintains its shape when in contact with water at temperatures up to at least about 250° F. and a working pressure of up to about 250 pounds per square inch (psi) beyond which it will deform. A presently contemplated, suitable hardness is a Shore A hardness of about 50 to 90. 
     The material  46  should also be chemically resistant and/or non-reactive when, for example, used in water cooling/heating systems. Such systems may use a variety of chemicals to, for example, control corrosion, such as sulfites, orthophosphates, nitrites, molybdates, silicates, zinc, polyphosphates, phosphonates, triazoles, azoles and others. Systems may also use a variety of chemicals for microbial control, such as oxidizing biocides (e.g., chlorine, bromine, chlorine dioxide, glutaraldehyde liquid micro biocides, and ozone), and non-oxidizing biocides (e.g., isothiazolin, glutaraldehyde, dibromo-nitrilopropionamide (DBNPA), carbamate, quaternary amines, and terbuthylazine). In addition, the material  46  should be chemically compatible with such chemistry/chemicals to reduce leaching concerns. Other chemicals/chemistry for use in water cooling/heating systems will be recognized by those skilled in the art. 
     Some suitable materials  46  include, for example, elastomers such as fluorocarbons, such as VITON® (commercially available from DuPont Performance Elastomers), FLUOREL® (commercially available from 3M Company) and TECHNOFLON® (commercially available from Solvey Solexis, USA), perfluoroelastomers such as CHEMRAZ® (commercially available from Green, Tweed &amp; Co.), KALREZ® commercially available from DuPont Performance Elastomers, and TECHNOFLON PFR® (commercially available from Solvey Solexis, USA), ethylene-propylene such as NORDEL® (commercially available from Dow Chemical), KALTAN® (commercially available from DSM Elastomers), and ROYALENE® (commercially available from Chemtura Corporation), and tetrafluoroethylene/propylene, such as ALFAS®, (commercially available from Asahi Class Co., Ltd.), and TBR® (commercially available from DuPont Performance Elastomers). Other classes of materials  46  and materials that provide the desired operational and performance characteristics will be recognized by those skilled in the art and are within the scope and spirit of the present disclosure. 
     It is also anticipated that the material  46 , at room temperature and pressure, will fill the expansion headers  28 , although there may be some embodiments in which an air or fluid space is present in the headers  28  when the material  46  is disposed in the headers  28 . 
     It is also anticipated that in some embodiments monitoring systems are incorporated into the fluid coil  10 . For example, thermistors, such as NTC thermistors or other temperature sensing devices can be mounted in, on or to the fluid coil  10  at, for example, the caps  44 . Other monitoring and/or sensing devices can likewise be incorporated in the fluid coil  10 . 
     It will be appreciated that because some embodiments of the apparatus or system does not require the use of pressure relief valves, fluid is kept inside the fluid bundle  12  (and the expansion headers  28 ) without bleeding to the outside environment, which adds another level of protection to avoid system and surrounding area flooding. 
     Another embodiment of a system  110  to prevent the rupture of a tube bundle  12  in a fluid coil  10  is illustrated in  FIGS.  9 - 12   . Similar to the system of  FIGS.  1 - 8   , the system  110  is used to prevent the splitting or rupturing of fluid-carry coils in, for example, HVAC systems, due to the thermal expansion of water in freezing conditions. The system  110  includes one or more expansion headers  112  that are connected to return bends in the coil  10  by header connectors  114 . The headers  112  include a compressible member  116 , and in an embodiment, a pressurizable, expandable bladder  118 . In an embodiment the bladder  118  is a polymeric tube  120 , for example an ethylene propylene diene monomer (EPDM) rubber tube  120 . The tube  120  is formed from a material that is compatible with the fluid system in which it is used. Other materials will be recognized by those skilled in the art. 
     The tube  120  is sealed at both ends  122 . In an embodiment tube caps  124 , such as copper tube caps are positioned in the tube ends  122 . A clamp  126  is positioned on each tube end  122  overlying the tube  120  and the tube cap  124  to seal each end  122 . The tube caps  124 , sealed to the tube  120  define an interior pressurizable volume  128 . 
     In an embodiment, one end  129   a  of the header  112  is sealed and the other end  129   b  is closed by a header cap  130 . In an embodiment, the header cap  130  is a steel cap, such as a galvanized cap, so as to minimize any galvanic interaction between or among the materials. The header cap  130  encloses the bladder  118 , tube caps  124  and clamps  126  in the header  112 . 
     To pressurize the bladder  118 , a fitting  132 , such as a gas fitting, is positioned through the header cap  130  and its adjacent tube cap  124 , and extends into the pressurizable volume  128 . The fitting  132  can be mounted to the tube cap  124  by, for example brazing and the like. The fitting  132  can be, for example, a threaded pipe nipple. Other methods to mount the fitting  132  to the tube cap  124  will be recognized by those skilled in the art. A seal  134 , such as an O-ring, can be positioned about the fitting  132 , between the tube cap  124  and the header cap  130 . A fitting  136 , such as a push to connect fitting can be mounted to fitting  132  to which tubing  144  can be connected. 
     It is contemplated that the bladder  118  is pressurized to a predetermined pressure to function to accommodate the expanded volume as the water freezes to ice (or, for example, in the case of steam coils as the steam condenses to water and subsequently freezes to ice). It is anticipated that the bladder  118  will be pressurized or charged to about 120 to about 150 psi. As the water in the coil  10  assembly freezes, it will expand into the expansion header  112  and compress the bladder  118  externally—that is the ice will expand into the space between the header  112  and the bladder  118 . The bladder  118  compresses (thus reducing its volume) and the pressure in the bladder  118  increases to accommodate the decrease in the bladder&#39;s volume (the differential volume of ice and water) during a freezing event. As the ice thaws, the bladder  118  will return to its original volume by forcing the lower volume water back into the coil assembly  10 . 
     A system  140  to pressurize the bladder  118  is illustrated in  FIG.  12   . The system  140  includes a source  142  of compressed gas, such as compressed air. In the illustrated system  140 , a compressor and storage tank are illustrated. It will be appreciated that other sources  142  of compressed gas can be used and are within the scope and spirit of the present disclosure. 
     The system  140  includes flow conduits  144 , such as tubing, between the source  142  and the fitting  132 . In an embodiment, a pressure regulator  146  is positioned downstream of the source  142  and feeds the compressed air to a manifold  148 . In an embodiment, a one way valve  150 , pressure sensor  152 , preferably a wireless pressure sensor, and a pressure relief valve  154  are positioned in line from the manifold  148  to each of the header bladders  118 . In this manner, pressure to each header bladder  118  is monitored and relief, for example in the event of over-pressurization, is provided. The various fittings and the like necessary to provide gas-tight connection between the pressurized air source  142  and the bladder inlet, e.g., the fitting  132 , will be recognize by those skilled in the art. 
     A method to prevent the rupture of a tube bundle  12  in a fluid coil  10 , which fluid coil  10  has a tube bundle  12  having a series of straight tubing runs  38  and a series of return bends  36  extending between and fluidically connecting ones of the straight tubing runs  38 , and an expansion header  28  fluidically connected to at least some of the return bends  36 , includes disposing or positioning in the expansion header  28 , a polymeric material  46  having an initial shape. The polymeric material  46  is compressible to repeatedly expand and contract between a first volume in which water is present in the tube bundle  12  and a second volume in which the water in the tube bundle  12  undergoes a phase change to ice. 
     Contraction of the polymeric material  46  absorbs an increase in volume as the water undergoes the phase change to ice so as to prevent stressing and rupture of the tube bundle  12 , and, upon a phase change from ice to water, the polymeric material  46  returns to its initial shape. 
     A suitable polymeric material  46  can be resilient and hydrophobic, and can have a closed cell structure. In methods, the polymeric material  46  has a working temperature in a range of about −40° F. to about 250° F. and a Shore A hardness of about 50 to 90. 
     In methods, the polymeric material  46  is chemically resistant and non-reactive to chemicals used for corrosion control and microbial control. Suitable polymeric materials  46  include, but are not limited to, an elastomer, a fluorocarbon, a perfluoroelastomer, ethylene-propylene, and tetrafluoroethylene/propylene, and combinations thereof. 
     In another method, a pressurizable, expandable bladder  118  is positioned in the header  112 . The bladder  118  can be a polymeric tube  120 , for example an ethylene propylene diene monomer (EPDM) rubber tube  120 . The method includes sealing the tube  120  at both ends  122 . The tube  120  can be sealed by tube caps  124 , such as copper tube caps that are positioned in the tube ends  122  with a clamp  126  positioned on each tube end  122  overlying the tube  120  and the tube cap  124  to seal each end  122 . In the method, the tube caps  124  sealed to the tube  120  define an interior pressurizable volume  128 . 
     The method can include sealing one end  129   a  of the header  112  and closing the other end  129   b  of the header  112  by a header cap. The header cap can be, for example, a steel cap, such as a galvanized cap, so as to minimize any galvanic interaction between or among the materials. The method includes enclosing the bladder  118 , tube caps  124  and clamps  126  in the header  112  with the header cap  130 . 
     The method further includes pressurizing the bladder  118  through, for example, a fitting  132 , such as a gas fitting, that is positioned through the header cap  130  and its adjacent tube cap  124 , and extends into the pressurizable volume  128 . The method can include mounting the fitting  132  to the tube cap  124  by, for example brazing and the like. The fitting  132  can be, for example, a threaded pipe nipple. Other methods to mount the fitting  132  to the tube cap  124  will be recognized by those skilled in the art. Further, the method can include sealing the fitting  132  at, the header cap  130  using a seal  134 , such as an O-ring between the tube cap  124  and the header cap  130 . 
     In a method, the bladder  118  is pressurized to a predetermined pressure so that it functions to accommodate the increased volume of ice as the liquid water freezes (or in steam coils, as the steam condenses to water and the water subsequently freezes). It is anticipated that the bladder  118  is pressurized or charged to about 120 to about 150 psi so that as the water, it expands into the expansion header  112  and pressurizes the bladder  118  externally, in the space between the header  112  and the bladder  118 . In this method, the bladder  118  compresses and the pressure in the bladder  118  increases as it accommodates the increase in volume of ice during freezing, and as the ice thaws, the bladder  118  returns to its original volume and pressure by forcing the lower volume water back into the coil assembly  10 . 
     The method can include using a system  140  to pressurize the bladder  118  that includes a source of compressed gas  142  and flow conduits  144  such as tubing between the source  142  and the fitting  132 . The method includes regulating the pressure to the bladder  118  downstream of the source  142 . The method can further include feeding the compressed air to a manifold  148  and, feeding the compressed air from the manifold  148  to the bladder  118  through a series of valves and other components, such as a one way valve  150 , a pressure sensor  152 , preferably a wireless pressure sensor, and a pressure relief valve  154 . In this manner, the system  140  allows for monitoring the pressure to each header bladder  118 , and providing relief, for example in the event of over-pressurization. The method may include other fittings and the like necessary to provide gas-tight connection between the pressurized air source  142  and the bladder  118  inlet, e.g., fitting  132 . 
     It will be appreciated that although the presently disclosed apparatus and method to prevent fluid coils from splitting or rupturing due to the thermal expansion of liquid is described based on a water-based system, such a description is presented as an example only, and that the present apparatus and method may be used in a wide variety of fluid and gaseous systems to prevent coils from splitting or rupturing due to thermal expansion. It will be understood that such other fluid and gaseous systems are within the scope and spirit of the present disclosure. 
     In the present disclosure, the words “a” or “an” are to be taken to include both the singular and the plural. Conversely, any reference to plural items shall, where appropriate, include the singular. All patents and published applications referred to herein are incorporated by reference in their entirety, whether or not specifically done so within the text of this disclosure. 
     It will also be appreciated by those skilled in the art that any relative directional terms such as sides, upper, lower, top, bottom, rearward, forward and the like are for explanatory purposes only and are not intended to limit the scope of the disclosure. 
     From the foregoing it will be observed that numerous modifications and variations can be made without departing from the true spirit and scope of the novel concepts of the present disclosure. It is to be understood that no limitation with respect to the specific embodiments illustrated is intended or should be inferred.