Abstract:
An end fitting ( 200 ) for terminating an end of a hose comprising a tubular body of flexible material arranged between inner and outer helical wires, characterized in that the end fitting comprises: an inner member ( 202 ) adapted to be disposed at least partially within the hose; and a hose engaging member ( 208 ) adapted to press against the inner member  202  to retain the hose between itself and the inner member ( 202 ). The end fitting also includes a separate means for retaining one or more layers of the hose, the retaining means comprising an outer retaining member ( 232 ) adapted to press against an inner retaining member ( 230 ) to retain the or each layer of the hose between the outer and inner retaining members ( 232, 230 ) of the retaining means.

Description:
This invention relates to hose, and more particularly relates to hose which can be used in cryogenic conditions. More specifically the invention relates to hose end fittings. 
     BACKGROUND OF THE INVENTION 
     Typical applications for hose involve the pumping of fluids from a fluid reservoir under pressure. Examples include supplying of domestic heating oil or LPG to a boiler; transporting produced oilfield liquids and/or gases from a fixed or floating production platform to the cargo hold of a ship, or from a ship cargo hold to a land-based storage unit; delivering of fuel to racing cars, especially during refuelling in formula 1; and conveying corrosive fluids, such as sulphuric acid. 
     It is well known to use hose for the transport of fluids, such as liquefied gases, at low temperature. Such hose is commonly used to transport liquefied gases such as liquefied natural gas (LNG) and liquefied propane gas (LPG). 
     In order for the hose to be sufficiently flexible, any given length must be at least partially constructed of flexible materials, i.e., non-rigid materials. 
     The structure of such hose generally comprises a tubular body of flexible material arranged between an inner and outer helically wound retaining wires. It is conventional for the two wires to be wound at the same pitch, but to have the windings displaced by half a pitch width from one another. The tubular body typically comprises inner and outer layers with an intermediate sealing layer. The inner and outer layers provide the structure with the strength to carry the fluid therein. Conventionally, the inner and outer layers of the tubular body comprise fabric layers formed of a polyester such as polyethylene terephthalate. The intermediate sealing layer provides a seal to prevent the fluid from penetrating the hose, and is typically a polymeric film. 
     The retaining wires are typically applied under tension around the inside and outside surfaces of the tubular body. The retaining wires act primarily to preserve the geometry of the tubular body. Furthermore, the outer wire may act to restrain excessive hoop deformation of the hose under high pressure. The inner and outerwires may also act to resist crushing of the hose. 
     A hose of this general type is described in European patent publication no. 0076540A1. The hose described in this specification includes an intermediate layer of biaxially oriented polypropylene, which is said to improve the ability of the hose to resist the fatigue caused by repeated flexing. 
     Another hose is described in GB-2223817A. The hose described in this publication is a composite hose comprising an inner helical metallic core, a plurality of layers of plastics material fibres and films wound on the core, at least one layer of glass cloth and at least one layer of aluminium foil disposed adjacent one another and wound onto the plastics material, and an outer helical metallic former. This hose is said to be suitable for transporting flammable fuels and oils. 
     Another hose is described in GB-1034956A. 
     SUMMARY 
     The invention is especially applicable to the hose described in WO01/96772. We have made some improvement to the end fitting of the hose described in this application. These improvements may be used with any combination of the features of the end fitting described in WO01/96772. They may also be used with any combination of the features of the end fitting described in WO01/96772. 
     The first feature relates to the hose engaging member. Thus, according to one aspect of the invention there is provided an end fitting for terminating an end of a hose comprising a tubular body of flexible material arranged between inner and outer gripping members, characterised in that the end fitting comprises: an inner member adapted to be disposed at least partially within the hose; and a hose engaging member adapted to press against the inner member to retain the hose between itself and the inner member, and a separate means for retaining one or more layers of the hose, the retaining means comprising an outer retaining member adapted to press against an inner retaining member to retain the or each layer of the hose between the outer and inner retaining members of the retaining means. 
     Preferably, the inner and outer retaining members are ring-shaped. More preferably the inner and outer retaining members are preferably provided in the form of a ring, preferably with the outer retaining member being disposed concentric with the inner retaining member. More preferably, the first and second members are split rings, to facilitate assembly. 
     In a preferred embodiment, the outer retaining member which comes into contact with the or each layer of the hose is provided with gripping formations to facilitate gripping of the or each layer of the hose. The surface of the inner retaining member may be provided with corresponding formations. 
     In a preferred embodiment, the adjacent surfaces of the inner and outer retaining members are provided with gripping formation to facilitate gripping of the or each layer of the hose therebetween. 
     There may be any convenient number of inner and outer retaining members. In the simplest embodiment, there is one outer retaining member and one inner retaining member. It is possible to provide two or more outer retaining members with one inner retaining member. It is possible to provide two or more inner retaining members with one outer retaining member. And it is possible to provide two or more outer retaining members with two or more inner retaining members, preferably so that each outer retaining member has a corresponding inner retaining member. 
     The hose engaging member is preferably ring-shaped. The hose engaging member is preferably in the form of a ring, more preferably a split ring. The hose engaging member preferably clamps all the layers of the hose securely between itself and the inner member of the end fitting. 
     In a preferred embodiment, the inner retaining member of the retaining means is integral with the hose engaging means. In this embodiment the hose engaging means comprises a first part of a first cross-sectional thickness (i.e. diameter, when ring-shaped), and the integral inner retaining member comprises a second part of a second cross-sectional thickness (i.e. diameter, when ring-shaped), the second thickness being less than the first thickness. The outer retaining member may have a third cross-sectional thickness (i.e. diameter, when ring-shaped), and the second and third cross-sectional thicknesses may be equal. Preferably, the sum of the second and third cross-sectional thicknesses is substantially the same as the first cross-sectional thickness. 
     When the inner retaining member is integral with the hose engaging member, it is preferable that the hose engaging member is L-shaped, so that the inner retaining member extends from the body of the hose engaging member, and the outer retaining member can be receiving in the recess of the L-shape. 
     When the inner retaining member is integral with the hose engaging member, the inner surface of the inner retaining member may also function to clamp the hose fixedly between the hose between itself and the inner member, i.e., it may contribute to the hose engaging function. 
     The second feature relates to the provision of a bend stiffener. The inner member used in the invention can in some circumstances cause a discontinuity in the bending stiffness at near the end of the hose making it prone to localisation of curvature, i.e. overbending, thereby disturbing the hose carcass formed by the helical wires of the hose. 
     In an embodiment, the load transmitting member comprises a cylindrical member having a first recess for receiving a part of the hose engaging member and a second recess for receiving part of the end member, whereby loads applied to the hose engaging member can be transferred to the end member via the cylindrical load transferring member. 
     Preferably, the bend stiffener is integral with the load transmitting member. 
     According to another aspect of the invention, the end fitting further includes an elongate tubular bend stiffener adapted to fit around the hose on the opposite side of the hose engaging member to the end member. The bend stiffener is preferably a polymeric material, most preferably polyurethane. Preferably the bend stiffener is tapered, such that the thickness decreases in a direction away from the end of the hose; the degree of the taper may be optimised for each particular application. Preferably the tip of the bend stiffener (i.e. the part furthest from the end of the hose) is provided with a shoulder against which any outer mechanical protection on the hose may be run. An example of such outer mechanical protection is described in our copending UK patent application number 0226271.5. 
     The third feature relates to the way the load transferring means is secured to the inner member. In WO01/96772 the end member of the load transferring means was shown bolted to the inner member. We discovered that while this arrangement was satisfactory, the fatigue resistance of the connection could be improved by making the end member an integral part of the inner member. Therefore, according to another aspect of the invention the end member of the load transferring means is integral with the inner member. The integral arrangement can be machined from a single forging or a block of welded components. 
     According to another aspect of the invention there is provided an end fitting for terminating an end of a hose comprising a tubular body of flexible material arranged between inner and outer gripping members, the end fitting comprising a load transferring means which includes a hose engaging member adapted to grip the hose, a load transmitting member, and an end member, the arrangement being such that the hose engaging member and the end member are connected through the load transmitting member, whereby loads applied to the hose engaging member can be transferred to the end member via the load transferring member, characterised in that the load transmitting member comprises a cylindrical member having a first recess for receiving a part of the hose engaging member and a second recess for receiving part of the end member. 
     The end member is preferably integral with the inner member. 
     The end fitting preferably also comprises an elongate tubular bend stiffener adapted to fit around the hose on the opposite side of the hose engaging member to the end member, wherein the bend stiffener is integral with the load transmitting member. 
     According to another aspect of the invention there is provided an end fitting for terminating an end of a hose comprising a tubular body of flexible material arranged between inner and outer helical wires, characterised in that the end fitting comprises: an inner member adapted to be disposed at least partially within the hose; and a hose engaging member comprising at a first member adapted to press against the inner member to retain the hose between the first member and the inner member, and a second member adapted to press against the first member to retain the hose between the second member and the first member. 
     According to another aspect of the invention there is provided a combination of a hose with an end fitting as described above. 
     The hose preferably comprises a tubular body and an axial reinforcing braid disposed between inner and outer gripping members, wherein the tubular body comprises inner and outer reinforcing layers and a sealing layer disposed between the inner and outer reinforcing layers. 
     The hose preferably further comprises a protective and/or insulative layer wrapped around said hose, wherein said protective and/or insulative layer has an end portion which is adapted to be received in the first recess of the cylindrical load transferred member. 
     Although more than one layer of the hose may be retained by the retaining means of the end fitting, it is particular preferred that the braid alone of the hose is retained between the inner and outer retaining members of the retaining means. 
     As mentioned above the hose and end fitting can be provide with any combination of the features of the hose and end fitting described in WO01/96772 and in UK patent application number 0226271.5. 
     The hose according to the invention can be provided for use in a wide variety of conditions, such as temperatures above 100° C., temperatures from 0° C. to 100° C. and temperatures below 0° C. With a suitable choice of material, the hose can be used at temperatures below −20° C., below −50° C. or even below −100° C. For example, for LNG transport, the hose may have to operate at temperatures down to −170° C., or even lower. Furthermore, it is also contemplated that the hose may be used to transport liquid oxygen (bp −183° C.) or liquid nitrogen (bp −196° C.), in which case the hose may need to operate at temperatures of −200° C. or lower. 
     The hose according to the invention can also be provided for use at a variety of different duties. Typically, the inner diameter of the hose would range from about 2 inches (51 mm) to about 24 inches (610 mm), more typically from about 4, 6 or 8 inches (203 mm) to about 16 inches (406 mm). In general, the operating pressure of the hose would be in the range from about 500 kPa gauge up to about 2000 kPa gauge, or even up to about 4000 kPa gauge, or higher. These pressures relate to the operating pressure of the hose, not the burst pressure (which must be several times greater). The volumetric flow rate depends upon the fluid medium, the pressure and the inner diameter. Flowrates from 1000 m 3 /h up to 12000 m 3 /h are typical. 
     The hose according to the invention can also be provided for use with corrosive fluids, such as strong acids. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Reference is now made to the accompanying drawings in which: 
         FIG. 1  is a perspective view of a hose with which the end fitting according to the invention may be used; 
         FIG. 2  is a schematic cross sectional view of a first embodiment of an end fitting for a hose, according to the invention; 
         FIG. 3  is a schematic cross sectional view of a second embodiment of an end fitting for a hose, according to the invention; 
         FIG. 4  is a schematic cross sectional view of a third embodiment of an end fitting for a hose, according to the invention; 
         FIG. 5  is enlarged schematic cross sectional view of part of a hose engaging member of the end fitting according to the invention before assembly; 
         FIG. 6  is enlarged schematic cross sectional view of part of a hose engaging member of the end fitting according to the invention after assembly. 
     
    
    
     DETAILED DESCRIPTION 
     The type of hose to which this invention applies is described in detail in WO01/96772.  FIG. 1  shows the hose  100  in more detail. 
     Briefly, the hose  100  comprises inner and outer gripping members  102 ,  104 , which are preferably arranged in a helical form, and are preferably wires. Between the gripping members  102 ,  104  are arranged a tubular body  106  and an axial reinforcing braid  108 , which surrounds the tubular body  106 . The tubular body comprises an inner reinforcing layer  110 , and outer reinforcing layer  112  and a sealing layer  114  arranged between the inner and outer reinforcing layers  110 ,  112 . An outer protective/insulative layer  116  surrounds the braid  108 . As mentioned above the hose  100  is described in greater detail in WO01/96772, the contents of which are incorporated herein by reference. 
     The ends of the hose may be sealed using the end fitting  200  shown in the figure. The hose has not been shown in the figure, in order to improve the clarity. The end fitting  200  comprises a tubular inner member  202  having a hose end  202   a  and a tail end  202   b . The end fitting  200  further includes a sealing member which comprises a sealing ring  204 , which is typically based on a polymeric resin such as PTFE, and a stainless steel split ring  206  around the sealing ring  204 . 
     The end fitting  200  further includes a load transferring means comprises a hose engaging member  208 , a load transferring member  210  and an end member in the form of a disk-shaped plate  212 . The plate  212  is integral with the tail end  202   b  of the inner member  202 , as illustrated at  212   b . The load transferring member comprises a disk-shaped plate  214  and at least one load transferring rod  216 . In the figure there are two of the rods  216 , but it is preferable to provide three or more of the rods  216 , and it is preferable that the rods are equi-spaced around the circumference. A tightening nut  218  is provided on each rod  216 . The plates  212  and  214  have apertures  212   a  and  214   a  respectively for receiving the rods  216 . 
     The hose engaging member  208  is provided with an inner helical recess in the form of grooves  208   a  which are adapted to receive the outer wire of the hose therein. The inner member  202  is provided with an outer helical recess in the form of grooves  202   d  which are adapted to receive the inner wire therein. The grooves  208   a  and  202   d  are spaced by half a pitch length p, where p is the pitch length of the gripping wires of the hose (not shown). 
     The hose engaging member  208  also includes a retaining means for retaining the braid  108  of the hose  100 . The retaining means comprises an inner retaining member  230  which is integral with the rest of the hose engaging member, and a separate outer retaining member  232 . The outer  232  is capable of clamping the braid  108  of the hose  100  between itself and the inner member  230 . The outer member  232  has gripping formations on the inner surface thereof to facilitate gripping the braid  108  between the outer member  232  and the inner member  230 . The gripping formations are preferably circumferential but can take other patterns. 
     The member  202  is provided with two circumferential projections  202   e  which are located under the sealing ring  204 . The projections  202   e  serve the improve the sealing of the tubular member between the inner member  202  and the sealing ring  204 , and help to prevent the tubular member from inadvertently being pulled out of position. 
     The end fitting  200  is also provided with a polymeric bend stiffener  240  which has apertures  242  through which the rods  216  may be received. One end of the bend stiffener  240  abuts the plate  214 . 
       FIG. 3  shows an end fitting which is similar to the end fitting shown in  FIG. 2 , and the same reference numerals have been used to designate the parts. The differences are: the bend stiffener is not provided in the design shown in  FIG. 2 , although it could be, if desired; the plates  212  and  214  have a smaller diameter, so that the structure is more compact. 
       FIG. 4  shows an end fitting which is similar to the end fitting shown in  FIG. 2 , and the same reference numerals have been used to designate the parts. In  FIG. 4  the load transferring rod has been replaced by a load transferring member  250  which has recesses  250   a  and  250   b  adapted to receive the edges of plates  212  and  214  respectively. 
     The recess  250   b  also receives and end portion  260   a  of a protective and/or insulative layer  260  provided on the outer surface of the hose  100  (i.e. provided outside the gripping member  104 . The layer  260  may be the same sort of layer as described in our copending international patent application number PCT/GB2003/004932. This comprises an elongate profiled member which is wrapped helically around the outside of the hose  100 . 
     Reference is now made to  FIGS. 5 &amp; 6 . For the axial reinforcing braid  108  to function most effectively, it should be securely anchored at the end fitting  200 . The outer member  232  mates with the inner member  230  to provide this anchor. This interface is designed to reduce to zero the tension in the braid  108 , caused by hose pressure and tension, in order to help prevent the braid  108  from being pulled from the anchor. 
     When the braid  108  is pulled axially it tries to reduce its radius, owing to the braid structure. If it is prevented from reducing its radius then a contact pressure is generated equal to the local tension times the local curvature. To illustrate the concept of local curvature, consider a string were wrapped around a cylinder, where the local curvature is the reciprocal of the cylinder radius. This contact force times the local friction coefficient anchors the braid  108  (this is the so called “capstan” effect). The frictional force is non-linear because of the undulating formations  230   a  and  232   a  on the members  230  and  232 —it would be linear if it were straight plates. Non-linear decay is more effective. 
     The braid folds back out of the hose body around a filleted front edge  230   b  of the member  230 . The filleted edge  230   b  prevents large stress concentrations being induced in the braid  108  as a result of the contact of the braid  108  with the member  232  under tension. This radius controls the contact pressure generated by the tension in the braid  108 . The drop in tension is a non-linear function of the product of the angle of contact the braid makes with the radius and the local friction coefficient. In the case shown, where the radius of the fillet is constant, the non-linear function is exponential. 
     When the outer member  232  is fully mated against the inner member  230  the profiled surfaces  230   a  and  232   a  of the first and second members respectively mate closely thus forcing the braid  108  to pass through a series of undulations. Each undulation acts as a capstan and so reduces the tension in the braid as described earlier. 
     The hose is secured to the end fitting  200  as follows. The inner member  202  is threaded into the end of the hose, so that the hose lies close to the plate  212 . The inner wire of the hose is received in the grooves  202   d  and the outer wire of the hose is received in the grooves  208   a . The inner and outer wires are cut back so that they do not extend along the inner member  202  beyond the grooves  202   d  and  208   a . Any insulation of the hose is also cut back to this point. The inner reinforcing layer of the hose is also cut back at this point, or at some point before it reaches the sealing ring  204 . This means that the sealing layer of the hose directly engages the outer surface of the inner member  202 . The rest of the tubular body of the hose is allowed to extend along the inner member  202  between the inner member  202  and the sealing ring  204 . 
     The hose engaging member  208  is then tightened to cause it to clamp down on the hose bring it into firm engagement with the hose. The nuts  218  are then tightened, which induces some axial tension in the hose, thereby taking up any play in the system. These forces are transmitted from the hose engaging member  208 , to the plate  214 , to the rod  216 , to the plate  212 , and to the tail end  202   b  of the inner member  202 . The tubular member is pulled back over the upper surface of the hose engaging member  208 , and between the outer member  232  and the inner member  230 . The second outer  232  and the inner member  230  clamp the braid  108  firmly in place. 
     The tubular body  106  of the hose  100  extends under the sealing ring  204 . After the hose engaging member  208  and the nuts  218  have been tightened, the split ring  206  is tightened in order to increase the force applied on the tubular body by the sealing ring  204 . 
     The end fitting  200  is then cooled to a low temperature by liquid nitrogen. This causes the sealing ring  204  to contract relatively more than the split ring  206 , whereby the compressive force applied on the sealing ring  204  by the split ring  206  is reduced. While the split ring  206  and the sealing ring  204  are at a relatively low temperature, the split ring  206  is again tightened. The temperature is then allowed to rise to ambient conditions, whereby the compressive force on the sealing ring increases by virtue of the greater expansion of sealing ring  204  relative to the split ring  206 . 
     It will be appreciated that the invention described above may be modified. For example, the inner retaining member  230  could be separate from the rest of the hose engaging member. Furthermore, additional inner and outer retaining members  230  and  232  may be provided.