GB2366348A

GB2366348A - Hose incorporating an improved sealing layer

Info

Publication number: GB2366348A
Application number: GB0109013A
Authority: GB
Inventors: Matthew Vernon Ridolfi; Eric Joseph Davis; Gerard Anthony Hall; Simon Peter Alexander Thorp; Joel Aron Witz; Raymond Nicholas Burke
Original assignee: BHP Petroleum Pty Ltd
Current assignee: BHP Petroleum Pty Ltd
Priority date: 2000-06-12
Filing date: 2001-04-10
Publication date: 2002-03-06
Anticipated expiration: 2021-04-10
Also published as: GB2366348B; GB2366345A; GB0109013D0; GB0014353D0

Abstract

A hose 10 comprises a tubular body 12 of flexible material arranged between inner and outer helically wound wires 22,24. The tubular body 12 comprises a sealing layer 18 sandwiched between an inner and an outer reinforcing layer 14,16. The sealing layer 18 comprises at least two polymeric films 18<U>a</U>,18<U>b</U> , one of the films being made of a first polymer and another of the films being made of a second polymer different from the first polymer. One of the films, preferably the outer film, is stiffer than the other film, thereby producing a differential yield strain in the material properties. The sealing layer 18 further includes at least one layer partially or entirely made of metal. The first polymer is preferably a polyolefin and the second polymer is preferably a fluoropolymer. The hose is preferably used in the transfer of cryogenic fluids.

Description

2366348 HOSE INCORPORATING AN IMPROVED SEALING LAYER This invention

relates to hose. More particularly, the invention relates to hose incorporating an improved sealing layer. The invention is especially concerned with hose which can be used in cryogenic conditions.

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 outer wires 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.

We have now found a way to improve the sealing layer in hose of the type described above, According to one aspect of the invention there is provided a hose comprising a tubular body of flexible material arranged between inner and outer gripping members, the tubular body comprising a sealing layer sandwiched between an inner and an outer reinforcing layer, characterised in that the sealing layer comprises at least two polymeric films, one of the films being made of a first polymer and another of the films being made of a second polymer different from the first polymer.

In an especially advantageous embodiment, one of the polymeric films is stiffer than the other of the films, whereby a differential yield strain is present in the material properties at the operating temperature and pressure. Preferably the outer film is stiffer than the inner film. The effect of this is that in the unfortunate occurrence of a hose burst, there is a controlled failure of the sealing layer such that the stiffer outer polymer fails while the more ductile polymer holds the internal pressure for a finite time, allowing the pressure gradually to dissipate.

In the preferred embodiment, the maximum strain at failure is in excess of 100% at ambient temperature for the more ductile layer, and is at least 20% less for the other layer.

Each polymeric film of the sealing layer is preferably a polyamide, a polyolefin or a fluoropolymer.

When the polymeric film of the sealing layer comprises a polyamide, then it may be an aliphatic polyamide, such as a nylon, or it may be an aromatic polyamide, such as an aramid compound.

We prefer that one of the polymeric films of the sealing layer is a polyolefin and that another of the polymeric films of the sealing layer is a fluoropolymer.

Suitable polyolefins include a polyethylene, polypropylene or polybutylene homopolymer, or a copolymer or terpolymer thereof. Preferably the polyolefin film is monoaxially or biaxially oriented. More preferably, the polyolefin is a polyethylene, and most preferably the polyethylene is a high molecular weight polyethylene, especially ultra high molecular weight polyethylene. This is described in greater detail below.

Since the sealing layer is intended to provide a sealing function, the sealing layer should be provided in the form of a film which is substantially impermeable to the transported fluids.- Thus, the highly oriented UHMWPE needs to be provided in a form which has satisfactory sealing properties. These products are usually provided in the form of a solid block which can be further processed in order to obtain the material in the required form. The film may be produced by skiving a thin film off the surface of the solid block. Alternatively the films may be blown films of UHMWPE.

Suitable fluoropolymers include polytetrafluoroethylene (PFTE); a fluorinated ethylene propylene copolymer, such as a copolymer of hexafluoropropylene and tetrafluoroethylene (tetrafluoroethyleneperfluoropropylene) available from DuPont Fluoroproducts under the trade name Teflon FEP; or a fluorinated hydrocarbon perfluoralkoxy - available from DuPont Fluoroproducts under the trade name Teflon PFA. These films may be made by extrusion or by blowing.

Preferably, the sealing layer comprises a plurality of layers of each of the polymeric films. In an embodiment, the layers may be arranged so that the first and second polymers alternate through the thickness of the sealing layer. However, this is not the only possible arrangement. In another arrangement all the layers of the first polymer may be surrounded by all the layers of the second polymer, or vice versa.

We prefer that the polymeric films of the sealing layer are formed of a sheet of material which has been wound into a tubular form by winding the sheet material in a helical manner. Each polymeric film may comprise a single continuous sheet which is wrapped around the inner reinforcing layer from one end of the hose to the other. However, more usually (and depending on the length of the hose) a plurality of separate lengths of the polymeric film would be wound around the inner reinforcing layer, each length of film covering a part of the length of the hose. If desired the sealing layer may comprise at least two heat shrinkable sealing sleeves (i.e. tubular in form) which are arranged over the inner reinforcing layer. At least two of the sleeves should be made of a different material.

The sealing layer comprises at least two different films and these are preferably arranged in an overlapping relationship. It is preferred that the sealing layer comprises least 5 overlapping layers, more preferably at least 10 overlapping layers. In practice, the sealing layer may comprise 20, 30, 40, 50, or more overlapping layers of film. The upper limit for the number of layers depends upon the overall size of the hose, but it is unlikely that more than 100 layers would be required. Usually, 50 layers, at most, will be sufficient, The thickness of each layer of film would typically be in the range 50 to 100 micrometres. The layers will be made up of at least two different types of polymeric film.

It will, of course, be appreciated that more than one sealing layer may be provided.

Preferably, the sealing layer further comprises at least one layer partially or entirely comprising a layer. Thus, the metal layer may be a layer of metallic film, or a polymer coated metallic film or a metallised polymer film. We prefer that the metal layer is a polymer coated metallic film. The metal may be, for example, aluminiurn oxide. The polymer may be, for example, a polyester.

Suitable polymer coated metal films include the films available from HiFi Industrial Film, of Stevenage, England, under the trade names MEX505, MET800, MET800B and MET852; MET800B is preferred.

A further metal layer may be disposed outwardly of the first metal layer. Preferably, the further metal layer is disposed between the tubular body and the outer wire. Rockwool layers may also be provided here to improve the thermal insulation. The aim of this is to create a thermal annulus between the two metal layers.

According to another aspect of the invention there is provided a hose comprising a tubular body of flexible material arranged between inner and outer gripping members, the tubular body comprising a sealing layer sandwiched between an inner and an outer reinforcing layer, characterised in that the sealing layer comprises an UHMWPE.

In this aspect of the invention, if the sealing layer is formed of heat shrinkable sleeves, it is not essential for the sleeves to be made of different materials, but they must be made of UHMWPE.

In the most advantageous embodiment of the invention, the sealing layer comprises at least two polymeric films of different materials, and at least one of the films comprises an ultra high molecular weight polyethylene.

The main purpose of the reinforcing layers is to withstand the hoop stresses which the hose is subjected to during transport of fluids therethrough. Thus, any reinforcing layer which has the required degree of flexibility, and which can withstand the necessary stresses, will be adequate. Also, if the hose is intended for transporting cryogenic fluids, then the or each reinforcing layer must be able to withstand cryogenic temperatures.

We preferthat the or each reinforcing layer is formed of a sheet of material which has been wound into a tubular form by winding the sheet material in a helical manner. This means that the or each reinforcing layer does not have much resistance to axial tension, as the application of an axial force will tend to pull the windings apart. The or each reinforcing layer may comprise a single continuous layer of the sheet material, or may comprise two or more single continuous layers of the sheet material. However, more usually (and depending on the length of the hose) the or each layer of the sheet material would be formed of a plurality of separate lengths of sheet material arranged along the length of the hose.

In the preferred embodiment each reinforcing layer comprises a fabric, most preferably a woven fabric. The or each reinforcing layer may be a natural or synthetic material. The or each reinforcing layer is conveniently formed of a synthetic polymer, such as a polyester, a polyamide or a polyolefin. The synthetic polymer may be provided in the form of fibres, or a yarn, from which the fabric is created.

When the or each reinforcing layer comprises a polyester, then it is preferably polyethylene terephthalate.

When the or each reinforcing layer comprises a polyamide, then it may be an aliphatic polyamide, such as a nylon, or it may be an aromatic polyamide, such as an aramid compound. For example, the or each reinforcing layer may be a poly-(pphenyleneterephthalamide) such as KEVLAR (registered trade mark).

When the or each reinforcing layer comprises a polyolefin, then it may be a polyethylene, polypropylene or polybutylene homopolymer, or a copolymer or terpolymer thereof, and is preferably monoaxially or biaxially oriented. More preferably, the polyolefin is a polyethylene, and most preferably the polyethylene is a high molecular weight polyethylene, especially UHMWPE.

The UHMWPE used in the present invention would generally have a weight average molecular weight above 400,000, typically above 800,000, and usually above 1,000,000. The weight average molecular weight would not usually exceed about 15,000,000. The UHMWPE is preferably characterised by a molecular weight from about 1,000,000 to 6,000,000. The UHMWPE most useful in the present invention is highly oriented and would usually have been stretched at least 2-5 times in one direction and at least 10-15 times in the other direction.

The UHMWPE most useful in the present invention will generally have a parallel orientation greater than 80%, more usually greater than 90%, and preferably greater than 95%. The crystallinity will generally be greater than 50%, more usually greater than 70%. A crystallinity up to 85-90% is possible.

UHMWPE is described in, for example, US-A-4344908, US-A-4411845, USA4422993, US-A-4430383, US-A-4436689, EP-A-183285, EP-A-0438831, and EPA0215507.

It is particularly advantageous that the or each reinforcing layer comprises a highly oriented UHMWPE, such as that available from IDSM High Performance Fibres BV (a Netherlands company) under the trade name DYNEEMA4 or that available from the US corporation AlliedSignal Inc. under the trade name SPECTRAJ Additional details about DYNEEMA are disclosed in a trade brochure entitled "DYNEEMA; the top performance in fibers; properties and application" issued by IDSM High Performance Fibers BV, edition 02/98. Additional details about SPECTRA are disclosed in a trade brochure entitled "Spectra Performance Materials" issued by AlliedSignal Inc., edition 5/96. These materials have been available since the 1980s.

Preferably, the sealing layer further comprises at least one polymer coated metallic film or a metallised polymer film.

According to another aspect of the invention there is provided a hose comprising a tubular body of flexible material arranged between inner and outer gripping members, the tubular body comprising a sealing layer sandwiched between an inner and an outer reinforcing layer, characterised in that the sealing layer comprises at least one polymer coated metallic film.

The metallic film is reflective and therefore reduces heat loss or heat gain - this is especially useful for cryogenic applications. In addition the metallic film can have good barrier properties, thereby reducing vapour transmission - this is useful to prevent material loss transporting gases.

In the aspects of the invention described above, is preferred that the hose is also provided with an axial strengthening means as described in our United Kingdom patent application of even date entitled "Hose".

The gripping members typically each comprise a helically wound wire. The helices of the wires are typically arranged such that they are offset from one another by a distance corresponding to half the pitch of the helices. The purpose of the wires is to grip the tubular body firmly therebetween to keep the layers of the tubular body intact and to provide structural integrity for the hose. The inner and outer wires may be, for example, mild steel, austenitic stainless steel or aluminium. If desired, the wires may be galvanised or coated with a polymer.

It will be appreciated that although the wires making up the gripping members may have a considerable tensile strength, the arrangement of the wires in coils means that the gripping members can deform when subjected to relatively small axial tension. Any significant deformation in the coils will quickly destroy the structural integrity of the hose.

When the hose is intended for cryogenic applications, then it is desirable to provide insulation over the tubular body. The insulation could be provided between the outer wire and the tubular member and/or outside the outer wire. The insulation may comprise material conventionally used to provided insulation in cryogenic equipment, such as a synthetic foam material. One suitable form of insulation is described in our copending United Kingdom patent application of even date entitled "Hose Having improved Flexing Capabilities".

The hose according to the invention can be provided for use in a wide variety of conditions, such as temperatures above 1 OO'C, temperatures from OOC to 1 OOOC and temperatures below OOC. With a suitable choice of material, the hose can be used at temperatures below -20 OC, below -500C or even below -1 OO'C. For example, for LNG transport, the hose may have to operate at temperatures down to -1700C, or even lower. Furthermore, it is also contemplated that the hose may be used to transport liquid oxygen (bp -1 83'C) or liquid nitrogen (bp -1 96'C), in which case the hose may need to operate at temperatures of -2000C 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 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 possibly up to about 2500 kPa gauge. 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 m3/h up to 12000 m3/h are typical.

The hose according to the invention can also be provided for use with corrosive materials, such as strong acids, Reference is now made to the accompanying drawings, in which:

Figure 1 is a schematic diagram showing the principle stresses to which the hose according to the invention may be subjected in operation; Figure 2 is a schematic cross-sectional view of a hose according to the invention; and Figure 3 is a sectional view showing the a sealing layer of a hose according to the invention.

Figure 1 shows the stresses to which a hose H is normally subjected to during use. The hoop stress is designated by the arrows HS and is the stress that acts tangentially to the periphery of the hose H. The axial stress is designated by the arrows AS and is the stress which acts axially along the length of the hose H. The flexing stress is designated FS and is the stress which acts transverse to the longitudinal axis of the hose H when it is flexed. The torsional stress is designated TS and is a twisting stress which acts about the longitudinal axis of the hose. The crushing stress is designated CS and results from loads applied radially to the exterior of the hose H.

The hoop stress HS is generated by the pressure of the fluid in the hose H. The axial stress AS is generated by the pressure of the fluid in the hose and also by the combination of the weight of the fluid in the hose H and by the weight of the hose H itself. The flexing stress FS is caused by the requirement to bend the hose H in order to position it properly, and by movement of the hose H during use. The torsional stress TS is caused by twisting of the hose.

The present invention is primarily concerned with improving the resistance of hose to the flexing stress FS and the hoop stress HS. In Figure 2 a hose in accordance with the invention is generally designated 10. In order to improve the clarity the winding of the various layers in Figure 2, and in the other Figures, has not been shown.

The hose 10 comprises a tubular body 12 which comprises an inner reinforcing layer 14, an outer reinforcing layer 16, and a sealing layer 18 sandwiched between the layers 14 and 16.

The tubular body 12 is disposed between an inner helically coiled wire 22 and an outer helically coiled wire 24. The inner and outer wires 22 and 24 are disposed so that they are offset from one another by a distance corresponding to half the pitch length of the helix of the coils.

An insulation layer 26 is disposed around the outer wire 24. The insulation layer may be a conventional insulating material, such as a plastics foam, or may be a material described in our copending United Kingdom patent application entitled "Hose Having Improved Flexing Capabilities".

The inner reinforcing layers 14 and 16 comprise woven fabrics of a synthetic material, such as aramid fibres. The inner reinforcing layer 14 is made up of a plurality of individual sheets of fabric which have been wound around the inner helical wire 22. The outer reinforcing layer 16 is made up of a plurality of individual sheets of fabric which have been wound around the sealing layer 18.

The sealing layer 18 is shown in greater detail in Figure 3. The sealing layer 18 comprises a plurality of layers 18a of a film made of a first polymer (such as a highly oriented UHMWPE) interleaved with a plurality of layers 18b of a film made of a second polymer (such as PFTE or FEP). The layers 18a and 18b have been wrapped around the outer surface of the inner reinforcing layer 14 to provide a fluid tight seal between the inner and outer reinforcing layers 14 and 16. As mentioned above, the layers 18a and 18b do not necessarily have to be arranged in an alternative fashion. For example, all the layers 18a could be arranged together, and all the layers 18b could be arranged together.

The hose 10 can be manufactured by the following technique. As a first step the inner wire 22 is wound around a support mandrel (not shown), in order to provide a helical arrangement having a desired pitch. The diameter of the support mandrel corresponds to the desired internal diameter of the hose 10. The inner reinforcing layer 14 is then wrapped around the inner wire 22 and the support mandrel.

A plurality of layers of the plastics films 18a, 18b making up the sealing layer 18 are then wrapped around the outer surface of the inner reinforcing layer 14. Usually, the films 18a and 18b would have a length substantially less than the length of the hose 10, so that a plurality of separate lengths of the films 18a and 18b would have to be wound around the inner layer 14. The films 18a and 18b are preferably arranged in an alternating fashion through the thickness of the sealing layer 18. Typically there might be five separate layers of the films 18a and 18b through the thickness of the sealing layer.

The outer reinforcing layer 16 is then wrapped around the sealing layer 18. The outer wire 24 is then wrapped around the tubular body 12, in order to provide a helical arrangement having a desired pitch. The pitch of the outer wire 24 would normally be the same as the pitch of the inner wire 22, and the position of the wire 24 would normally be such that the coils of the wire 24 are offset from the coils of the wire 22 by a distance corresponding to half a pitch length; this is illustrated in Figure 2, where the pitch length is designated p. The insulation layer 26 may then be applied around the outer wire 24 and the tubular body 12.

The ends of the hose 10 may be sealed by crimping a sleeve onto an insert inside the hose 10. This termination is generally applied after the hose 10 as been removed from the mandrel. An improved technique for sealing the ends of the hose 10 is disclosed in our copending United Kingdom patent applications of even date entitled "End Fitting for a Hose" and "End Fitting Having Improved Sealing Capabilities". copending United Kingdom patent applications of even date entitled "Apparatus for Sealing the End of Hose" and "Sealing Member for Sealing the End of Hose".

It will be appreciated that the invention described above may be modified. For example, one or more of, or even all of, the sealing layers 18a may be a polymer coated metallic film. Similarly, one or more of, or even all of, the sealing layers 18b may be a polymer coated metallic film.

Claims

CLAIMS:

1 A hose comprising a tubular body of flexible material arranged between inner and outer helically wound wires, the tubular body comprising a sealing layer sandwiched between an inner and an outer reinforcing layer, characterised in that the sealing layer comprises at least two polymeric films, one of the films being made of a first polymer and another of the films being made of a second polymer different from the first polymer, wherein one of the films is stiffer than the other film, whereby a differential yield strain is present in the material properties at the operating temperature and pressure, and wherein the sealing layer further includes at least one layer partially or entirely comprising a metal.

2. A hose according to claim 1, wherein the outer film is stiffer than the inner film.

3. A hose according to claim 1 or 2, wherein the polymeric films comprise a polyester, a polyamide, a polyolefin or a fluoropolymer.

4. A hose according to claim 1, 2 or 3, wherein one of the polymeric films comprises a polyolefin and the other of the polymeric films comprises a fluoropolymer.

5. A hose according to claim 3 or 4, wherein the polyolefin comprises a highly oriented ultra high density polyethylene.

6. A hose according to claim 3, 4 or 5, wherein,the fluoropolymer comprises a copolymer of hexafluoropropylene and tetrafluoroethylene.

7. A hose according to any preceding claim, wherein the sealing layer comprises a plurality of layers of each of the polymeric films, the layers being arranged so that the first and second polymers alternate through the thickness of the sealing layer.

8. A hose according to any preceding claim, wherein the metal layer is a layer of metallic film, or a polymer coated metallic film or a metallised polymer film.

9. The use of a hose according to any preceding claim, to transport fluids at cryogenic temperatures therethrough.

10. A hose substantially as herein described with reference to and as shown in the accompanying drawings.