Abstract:
Reinforced corrugated tubing comprising corrugated tubing having peaks and valleys and a reinforcement material disposed in the valleys. A method of reinforcing corrugated tubing comprises disposing a reinforcement material in valleys of the corrugated tubing.

Description:
TECHNICAL FIELD  
         [0001]    This disclosure relates generally to corrugated tubing and in particular to corrugated tubing with pressure reinforcement, vibration attenuation and high cycle life.  
         BACKGROUND  
         [0002]    Corrugated tubing or metal hose provides an alternative to rigid piping systems as a conduit for transporting fluids such as natural gas. The corrugated tubing can be easily installed and is useful in many system applications. Corrugated tubing allows for simpler more cost-effective installation due to its uniquely flexible structure and relatively high strength. The same flexibility has inherent limitations. As the internal pressure of the working fluid inside the tubing is increased the corrugated tubing structure reacts to the pressure. The typical corrugated tubing structure begins to spread and expand along its length when the internal pressure overcomes the strength of the tubing material. The higher pressures of the working fluid cause the corrugations to expand. The corrugation expansion results in a distortion of the tubing out of its original shape and size.  
           [0003]    In order to meet higher operating pressure ranges, conventional corrugated tubing is sleeved with a wire braid. The braid is fixed at opposite ends of the corrugated tubing. The braid reinforces the corrugated tube structure thereby resisting the expansion of the corrugations when the internal pressure is increased. The braid is effective in the function of resisting the expansion of the corrugated tubing thereby increasing operational pressure capability. However, the braid covering the corrugated tubing outer diameter is subject to relative motion with the corrugated tubing that it covers. The tubing and the braid move relative to each other along the length of the corrugated tubing. In applications that plumb the corrugated tubing to mechanical equipment that create vibration translated to the tubing, the relative motion causes abrasion between the inside of the braid and the outer surface of the tubing. The abrasion between the tubing outer surface and the braid inner surface creates failure mechanisms that compromise the integrity of the corrugated tubing structure. The braid saws and rubs off the outer surface material of the corrugated tubing until the tubing pressure boundary fails and subsequently leaks the working fluid.  
           [0004]    Conventional corrugated tubing also may include a topically applied jacket that serves to protect the tubing from its external environment. The jacket also provides a surface to apply marking such as pressure ratings, manufacturer, etc. These topically applied jackets, however, do not provide pressure reinforcement and are not intended to do so.  
         SUMMARY  
         [0005]    The drawbacks and deficiencies of the prior art are overcome or alleviated by a reinforced corrugated tubing system. Reinforced corrugated tubing is disclosed comprising corrugated tubing and a reinforcement material deposited between the corrugations of the tubing. A method of reinforcing corrugated tubing is also disclosed comprising disposing a reinforcement material in the corrugations.  
           [0006]    The above discussed and other features and advantages of the reinforced corrugated tubing will be appreciated and understood by those skilled in the art from the following detailed description and drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]    Referring now to the drawings wherein like elements are numbered alike in the several FIGURES:  
         [0008]    [0008]FIG. 1 is a cross-sectional side view of reinforced corrugated tubing;  
         [0009]    [0009]FIG. 2 is a side partial cross-sectional view of a fitting attached to the reinforced corrugated tubing.  
     
    
     DETAILED DESCRIPTION  
       [0010]    [0010]FIG. 1 is a cross-sectional side view of reinforced corrugated tubing  10 . The reinforced corrugated tubing  10  comprises corrugated tubing  12  which, in the embodiment of FIG. 1, is annular tubing. It is understood that the reinforcement material may be applied to other types of corrugated tubing such as helical tubing. The corrugated tubing  12  has an exterior surface  14  and an interior surface  16 . The interior surface  16  typically is exposed to the working fluid. The corrugated tubing  12  comprises a structure that has varying diameters or convolutions that form peaks  18  and valleys  20  in alternating series along the length of the corrugated tubing  12 . The exterior surface  14  is used as the reference for the peak  18  and valley  20  as opposed to the interior surface  16 . The peak  18  consists of the convolution with the larger outside diameter and the valley  20  consists of the convolution with the smaller outside diameter.  
         [0011]    A reinforcement material  22  is disposed on the exterior surface  14  of the corrugated tubing  12 . The reinforcement material  22  substantially fills the valleys  20  and covers the peaks  18  on the exterior surface  14 . The reinforcement material  22  is disposed along the length of the corrugated tubing  12 . The material makeup of the reinforcement material  22  has properties that resist forces that distort the material such as tension and shear forces. As a result, when the internal pressure of a working fluid increases and acts to spread apart the corrugated tubing  12  the reinforcement material  22  disposed in the valleys  20  of exterior surface  14  resists the forces that are created. The reinforcement material  22  inhibits the expansion or spreading of the corrugated tubing  12  such that the corrugated tubing  12  does not significantly distort either in the linear dimension or the diameter of the corrugated tubing  12 . The reinforcement material  22  supports each convolution of the corrugated tubing  12 . The material makeup of the reinforcement material  22  is also resilient and flexible. As the corrugated tubing  12  is bent and flexed along its length, the reinforcement material  22  bends and flexes with the corrugated tubing  12 . The reinforcement material  22  allows the corrugated tubing  12  to flex, and in some embodiments the reinforced corrugated tubing  10  can be flexed into a knot.  
         [0012]    The thickness of the reinforcement material  22  can be varied to enhance resistance to tube expansion or to provide more or less flexibility to the corrugated tubing  12 . A variety of pressure ratings can be met by changing the thickness of the reinforcement material  22 . A direct relationship exists between the thickness of the reinforcement material  22  and the pressure rating of the corrugated tubing  12 . Applying a reinforcement material  22  to the corrugated tubing  12  increases the pressure rating of the corrugated tubing  12  above the pressure rating of the corrugated tubing  12  without a reinforcement material  22 . The reinforcement material  22  also increases the number of flex cycles required to create metal fatigue failure in the corrugated tubing  12  and attenuates vibration to reduce failure of corrugated tubing  12  due to vibration fatigue.  
         [0013]    In one embodiment, the reinforcement material comprises medium density polyurethane. The material composition of the reinforcement material  22  can be any material that has the physical properties to resist deformation as well as be compatible with the metallic materials of the corrugated tubing  12 . Other materials are contemplated that possess both resistance to distortion forces such as shear and tension and possess flexibility as well as adhesive properties. The material of the reinforcement material  22  can be compatible with any metallic corrugated tubing such as 300 series stainless steel corrugated tubing  12 . The reinforcement material  22  can also protect the material of the corrugated tubing  12  from degradation as a result of exposure to harsh environments; the same protection provided by conventional jackets. Co-polyesters, polyethylene, stabilized polymers, non-chlorinated polymers and non-halogenated polymers and in general polymers can be used.  
         [0014]    The reinforcement material  22  can be extruded into the corrugations of corrugated tubing  12 . The use of other manufacturing processes can be employed to dispose the reinforcement material  22  onto the exterior surface  14  of the corrugated tubing  12 . In one embodiment, the reinforcement material  22  is driven into the valleys  20  to substantially fill valleys  20  and covers peaks  18 . As the reinforcement material  22  is extruded it is substantially molten and flows down into the corrugations of the corrugated tubing  12 . The molten reinforcement material  22  cools on the corrugated tubing  12 . The molten reinforcement material substantially fills the valleys  20  and covers the peaks  18 . In an alternate embodiment, a polymer reinforcement material  22  is extruded down into the corrugations and then cured (e.g., through heat).  
         [0015]    The reinforcement material  22  may be applied so that the reinforcement material  22  bonds to substantially the entire exterior surface  14 . The optional bonding of the reinforcement material  22  to the exterior surface  14  can be mechanical bonding or chemical bonding such that reinforcement material  22  substantially adheres to the exterior surface  14  of the corrugated tubing  12 . Also, by being located in the valleys  20 , the reinforcement material  22  mechanically blocks the deformation of the corrugated tubing  12  as a result of the material properties of the reinforcement material  22 . With the reinforcement material  22  applied such that there is an adhesion between the reinforcement material  22  and the surface of the corrugated tubing  12 , there is no relative motion between the reinforcement material and the surface of the corrugated tubing  12 . Having eliminated the relative motion between the reinforcement material  22  and the exterior surface  14 , the abrasive wear mechanism is substantially eliminated while still providing pressure reinforcement.  
         [0016]    [0016]FIG. 2 is a side view, in partial cross-section, illustrating the field attachable installation of a fitting  24  onto the reinforced corrugated tubing  10 . The fitting  24  can have a nut  26  disposed on a body  28 . The fitting  24  can have a locating sleeve  30 . Included with the fitting  24  is at least one split ring washer  32 . The body can comprise many materials including brass and brass alloys as well as many carbon steels, such as C12L14 carbon steel.  
         [0017]    The fitting  24  can be field mounted as follows. The reinforcement material  22  disposed on the corrugated tubing  12  is removed sufficiently enough to expose at least a valley  20  of a convolution. The corrugated tubing can be cut at that valley  20  with a pipe cutter on the exterior surface  14 . The nut  26  is placed over the corrugated tubing  12  and two split ring washers  32  are placed in the first valley  20  adjacent to the cut end. The locating sleeve  30 , which is connected to the body  28 , can be placed in the corrugated tubing  12 . The locating sleeve  30  ensures that the central axis of the body  28  is aligned with the central axis of the corrugated tubing  12 . The nut  26  is then tightened on a first threaded end of the body  28 . As the nut  26  is tightened, the corrugated tubing  12  at the outside of the split ring washers  32  (e.g. near the cut end of the corrugated tubing  12 ) is folded upon itself and flared outwardly by a tapered portion  34  of the body  28 . The corrugated tubing  12  is compressed between the tapered portion  34  and the split ring washers  32  and a leak proof seal is achieved. With the fitting  24  coupled to the reinforced corrugated tubing  10 , the reinforced corrugated tubing  10  can be coupled with other reinforced corrugated tubing  10  or devices. The fitting  24  can also be coupled to the corrugated tubing  12  by welding techniques. The welding attachment can be pre-fitted. With the fitting  24  welded to the corrugated tubing  12  certain elements can be eliminated from the fitting  24  such as the nut  26  and the split ring washers  32 .  
         [0018]    A sleeve  36  is shown in FIG. 2 disposed on the fitting  24  and the reinforcement material  22  over the corrugated tubing  12 . The sleeve  36  provides a strain relief between the interface of the fitting  24  and the corrugated tubing  12 . Strain relieving provides additional reinforcement to the interface between the corrugated tubing  12  and fitting  24 . The strain relief redistributes the stresses away from the interface or attachment area of the fitting  24  and the corrugated tubing  12  out to the fitting  24  and the corrugated tubing  12 . The additional reinforcement allows the corrugated tubing  12  with the fitting  24  to operate at higher service pressures. The sleeve  36  also provides an additional boundary around the corrugated tubing  12  inhibiting the exposure to harsh environments. The sleeve  36  can comprise plastic in one embodiment, but any material that can provide structural support for the fitting  24  and the reinforced corrugated tube  12  may be utilized. The sleeve  36  made of a metal is also contemplated. The sleeve  36  can be applied by use of heat shrinking in one embodiment, and in another the sleeve is welded to the fitting  24 . The sleeve  36  is disposed so that a sufficient coverage of both the fitting  24  and the reinforcement material  22  is achieved.  
         [0019]    While preferred embodiments have been shown and described, various modifications and substitutions may be made thereto without departing from the spirit and scope of the invention. Accordingly, it is to be understood that the reinforced corrugated tubing has been described by way of illustration and not limitation.