GB2610818A

GB2610818A - Pipe in pipe

Info

Publication number: GB2610818A
Application number: GB2113160.2A
Authority: GB
Inventors: Lachlan Ivett Jonathon
Original assignee: Flexigas UKC Ltd
Current assignee: Flexigas UKC Ltd
Priority date: 2021-09-15
Filing date: 2021-09-15
Publication date: 2023-03-22
Also published as: GB202113160D0

Abstract

A pipe for gas pipe installation, the pipe comprising a corrugated stainless steel tubing (CSST) 110, the CSST having a protective cover 112, and an outer sleeve layer configured over the CSST, comprising an inner sub-layer 200 and an outer 2nd gas tight cover 202. Embodiments include: A method of manufacturing a pipe for gas installations, the method comprising the steps of: providing a CSST to carry the gas, the CSST having a protective cover; configuring, using a tool, or by hand, a sub layer over the protective cover; and configuring an outer cover over the sub layer; wherein the sub layer and the outer cover are configured such that the CSST is free to move axially within the sub layer and the outer cover. The sub layer is configured over the CSST such that there is a small radial clearance between the CSST and the sub layer. An outer cover is provided that engages with the sub layer such that the two form an outer sleeve layer and remain together as the CSST is axially moved (slidable) in relation with the outer cover.

Description

PIPE IN PIPE

TECHNICAL FIELD

100011 The present disclosure relates to a tubing for gas fuel lines. In particular, the present disclosure relates to a pipe in pipe that provides protection against leakage in enclosed spaces, where there is no ventilation to the outside environment, and additionally, meets the requirement of gas installation codes in respect of a slidable sleeve.

BACKGROUND

[0002] Background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.

[0003] Around the world, corrugated stainless steel tubing (CSST) has become popular for use in plumbing gas fuel lines, primarily in gas pipelines provided for domestic applications. Corrugated stainless steel tubing, on account of its flexibility, is well suited for plumbing gas lines, and include a corrugated stainless-steel tubing and a yellow protective cover to protect the corrugated stainless steel tubing (hereinafter, the corrugated stainless steel tubing as well as the corrugated stainless steel tubing with the protective cover are referred to as corrugated stainless steel tubing / CS ST).

[0004] However, like all tubes, including rigid tube, they are susceptible to a leak on occasion. For example, a manufacturing defect or mishandling of the tube during transport or installation may result in an undetectable leak in the tube. Such undetectable leaks are usually quite safe as gas tubing is typically installed such that there is advantageous ventilation, so that any minor gas leak from the tubing gets naturally vented to the outside environment and a dangerous build-up of gas is avoided.

100051 In many gas installation codes, or local requirements, there are specific requirements intended to ensure that gas tubing always has some level of ventilation surrounding it. For example, in the UK, when gas tubing passes through an unvented void, for example an enclosed space in which there is no ventilation to the outside environment, gas tubing must be placed inside a specifically built duct or sleeve, which at one or both ends is open to the outside environment, or to a vented area, i.e., an area that in turn is open to the outside environment. Furthermore, the UK gas installation code defines a "sleeve" as an "annulus through which CSST tubing can be inserted and withdrawn".

[0006] This is usually achieved by positioning the gas tubing inside a readily available sleeve or conduit, usually made from a plastic but can also be metallic, for the part of the installation that passes through any unvented voids, as shown in FIG. IA, where the gas tubing 102 is installed within a sleeve 104 through the length of the unvented void 106. The sleeve 104 in turn opens to a ventilated area 108. The gas tubing 102 is inserted by hand through the sleeve 104, on site, by the gas installer.

[0007] To meet the requirement, and so that gas installers do not have to insert the gas tubing into a sleeve themselves by hand, different manufacturers have started marketing products that meet the above requirement in place of installation of the sleeve 104 through the void 106, and thereafter inserting the gas tubing 102 through the sleeve 104. Typically, these products are marketed as a "pre sleeved" or "pipe in pipe" products.

[0008] One such product, as shown in FIG. 1B, consists of the traditional CS ST 102 (that is corrugated stainless steel tubing 110 with lx protective yellow cover 112) and a secondary cover 120, which includes internal ribs 122 and its inside and is extruded over the first yellow cover 112 of the CSST 102. The secondary cover 120, due to the internal ribs 122, creates a very small gap between the first and second covers. These products claim that the gap between the yellow cover 112 (Also referred to as a Pt cover) and the ribbed secondary cover (also referred to as 2nd or outer cover) constitutes a "duct" or "sleeve", meeting the requirement of the UK gas installation code BS 6891 in respect of plumbing of gas pipelines through unvented voids. These products also often include a draw string 124, that can be used to remove the outer cover 120.

[0009] However, the above product suffers from a number of drawbacks. For example, when the tube is bent, the channels created by the ribs have a tendency to get closed and prevent any gas escape through the ribbed channels. Besides, the 2nd cover is thin, and is highly unlikely to protect the tube from mechanical damage, such as a nail or screw, as it is not made from a resilient material. However, the main drawback of this product is that as the 2s cover 120 is extruded onto the Pt cover 112, it is not slidable or movable axially vis a vis the 1st cover. I.e, over long distances, the 2nd 120 cover is stuck to the I " cover 112 and cannot move up and down the CSST 102 due to friction. This product therefore does not meet the requirements of some parts of the UK gas installation code..

[0010] Another product that is marketed by some manufacturers includes a normal CSST 102, i.e. the corrugated stainless steel tubing 110 with lx protective yellow cover 112, which is placed inside a traditional gas conduit 104, such as corrugated PVC, at the manufacturing location, as shown in FIG. IC, so that the installer does not have to do it on site.

[0011] This product overcomes some of the above stated problems, as the large gap 130 between the Pt cover 112 and the 21 cover / sleeve 104 allows the 2ral cover 104 to be slidable over the 1st cover. However, the product is bulky, and not favoured by installers as it takes up too much space inside a service shaft. Additionally, as the gap between the 1st cover 112 and the 2nd cover 104 is so big, the inner tube is not sufficiently supported to be used in riser shafts, which is another requirement of the UK installation code. Finally, the outer corrugated shape of the sleeve is not practical, as it tends to grab and get caught on obstructions when being pulled through a building site.

[0012] Evidently, the reason why existing products either consist of: 1) a secondary cover / sleeve typically attached to the Pt cover, or 2) a secondary cover / sleeve, made of a resilient material, that remains independent and slidable vs. the 1" cover, but incorporates a large gap 117 between the 1" and 21 covers, is that it is quite difficult to extrude or manufacture a secondary cover / sleeve, made of a resilient material, in close proximity to the Pt cover, without having the 2"d cover / sleeve attaching to the I " cover in some form, i.e., it is impossible to extrude a resilient secondary corrugated PVC sleeve onto the first cover in close proximity, and also maintain a small annulus between the 1" and 2nd covers. In the experience of this applicant, a significant radial clearance or gap between the 1s1 cover and the 2"d cover / sleeve is required, before the 2"d cover / sleeve can be configured over the top, if the sticking of the two layers is to be avoided. Additionally, it is difficult to "pull through-long lengths of CSST into standard PVC gas conduit where there is only a small anulus / radial clearance between the 1" cover and the 2"(I cover / sleeve. In practical terms, due to friction, the max length, where the radial clearance is 2.5mm or less, that may be pulled through is about 10-15m.

[0013] There is therefore a need in the art for a solution to the above stated problems and requirement to provide a pre-manufactured pipe in pipe solution to meet the requirement of gas pipe installations in unventilated locations, where the gap between the internal diameter of the 2"d cover / sleeve, and the outside diameter of the 1 protective cover is minimized, but where the 2" cover / sleeve still remains slidable over the 151 cover.

[0014] All publications herein are incorporated by reference to the same extent as if each individual publication or patent application were specifically and individually indicated to be incorporated by reference. Where a definition or use of a term in an incorporated reference is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply.

[0015] In some embodiments, the numbers expressing quantities of ingredients, properties such as concentration, reaction conditions, and so forth, used to describe and claim certain embodiments of the invention are to be understood as being modified in some instances by the term "about." Accordingly, in some embodiments, the numerical parameters set forth in the written description and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by a particular embodiment. In some embodiments, the numerical parameters should be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of some embodiments of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as practicable. The numerical values presented in some embodiments of the invention may contain certain errors necessarily resulting from the standard deviation found in their respective testing measurements.

[0016] As used in the description herein and throughout the claims that follow, the meaning of "a," "an," and "the" includes plural reference unless the context clearly dictates otherwise. Also, as used in the description herein, the meaning of "in" includes "in" and "on" unless the context clearly dictates otherwise.

[0017] The recitation of ranges of values herein is merely intended to serve as a shorthand method of referring individually to each separate value falling within the range. Unless otherwise indicated herein, each individual value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g. "such as") provided with respect to certain embodiments herein is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention otherwise claimed. No language in the specification should be construed as indicating any non-claimed element essential to the practice of the invention.

[0018] Groupings of alternative elements or embodiments of the invention disclosed herein are not to be construed as limitations. Each group member can be referred to and claimed individually or in any combination with other members of the group or other elements found herein. One or more members of a group can be included in, or deleted from, a group for reasons of convenience and/or patentability. When any such inclusion or deletion occurs, the specification is herein deemed to contain the group as modified thus fulfilling the written description of all Markush groups used in the appended claims.

OBJECTS OF THE INVENTION

100191 A general object of the present disclosure is to provide a solution that overcomes problems associated with installation of gas pipes in unventilated locations.

[0020] An object of the present disclosure is to provide a pipe that meets the requirement of gas installation codes related to installation of gas pipes in unventilated locations.

[0021] Another object of the present disclosure is to provide a pipe in pipe for installation in unventilated locations that minimizes space required by the pipe.

[0022] Yet another object of the present disclosure is to provide a pipe in pipe that has an outer sleeve/duct as close to the inner pipe as possible without compromising flow of leaked gas under all possible situations.

100231 Still another object of the present disclosure is to provide a pipe in pipe wherein the inner pipe is slidable within the outer pipe.

100241 Yet still another object of the present disclosure is to provide a pipe in pipe that is based on readily available materials, thereby resulting in corresponding cost advantage.

SUMMARY

[0025] Aspects of the present disclosure relate to a pipe for installation of gas fuel supply lines. In particular, the present disclosure relates to a pipe in pipe configuration for installation of gas fuel lines in unventilated locations. More particularly, the present disclosure provides a pipe in pipe configuration that meets the requirements of gas installation codes related to installation of gas pipes in unventilated locations by allowing venting of any leaked gas to a vented area. An aspect of the present disclosure relates to a method for manufacturing gas tubing destined to be used in an unventilated location.

[0026] In an aspect, a pipe for gas pipe installation is disclosed having a corrugated stainless steel tubing, the corrugated stainless steel tubing having a protective cover; and an outer sleeve layer configured over the corrugated stainless steel tubing. In an aspect, the outer sleeve layer is configured such that the corrugated stainless steel tubing is free to move axially within the outer sleeve layer.

[0027] In an embodiment, the outer sleeve layer can include an outer cover and a sub layer configured within the outer cover around the corrugated stainless steel tubing. The sub layer and the outer cover are dimensioned such that the sub layer engages with the outer cover for the sub layer and the outer cover to remain together as the corrugated stainless steel tubing is moved axially within the outer cover.

100281 In an embodiment, the sub-layer can be dimensioned such that radial clearance between the sub layer and the protective cover is 2.5mm or less.

[0029] In an embodiment, the outer cover can be configured to provide fluidic connectivity between two ends of outer cover, thereby venting any leakage from the corrugated stainless steel tubing to a ventilated area.

[0030] In an embodiment, the sub layer can be configured to prevent sticking of the sub layer over the protective cover.

[0031] In an embodiment, the sub layer can be a corrugated tubing having a longitudinal slit, wherein the corrugated tubing can be made of PVC.

[0032] In an embodiment, the sub layer can be a corrugated tubing, wherein the corrugated tubing can be made of PVC, and is arranged over one longer length of CSST in 2 more smaller pipe segments before the outer cover is applied.

[0033] In an embodiment, the longitudinal slit can be dimensioned such that, when the sub layer is squeezed, two sides of the longitudinal slit abut each other to ensure that the 30 radial clearance between the sub layer and the protective cover does not go below a desired clearance, thereby allowing free longitudinal movement.

[0034] In an embodiment, the radial clearance of the annulus between the protective cover of the CSST and the sub layer, is less than 1/2 width of the sub layer wall, width of the sub layer wall being defined as half of difference between inner and outer diameters of the PVC corrugated tubing sub layer.

[0035] In an embodiment, the sub layer can be an elongate strip of a resilient material extending between two ends of the outer cover configured over a substantial portion of an outer circumferential surface of the corrugated stainless steel tubing.

[0036] In an embodiment, longitudinal sides of the elongate strip can include a plurality of laterally disposed fingers such that when the elongate strip is configured around the corrugated stainless steel tubing, the fingers of the opposite sides at least partially overlap each other.

[0037] in an embodiment, the longitudinal sides of the elongate strip can include a plurality of fingers such that, when the elongate strip is configured around the corrugated stainless steel tubing, the fingers of the opposite sides interlock with each other.

[0038] In an embodiment, the elongate snip can be preformed to a substantially cylindrical shape with an inner diameter such that, when the elongate strip is positioned around the corrugated stainless steel tubing, the radial clearance between the sub layer and the protective cover of the corrugated stainless steel tubing is ensured.

[0039] in an embodiment, the elongate strip can be preformed to a helical shape with an inner diameter such that, when the helical shaped elongate strip is positioned over the corrugated stainless steel tubing, the radial clearance between the sub layer and the protective cover of the corrugated stainless steel tubing is ensured.

[0040] in an embodiment, the sub layer can be a square mesh.

[0041] in an embodiment, the outer cover of the sleeve layer can be an extruded PE layer having smooth surface. An aspect of the present disclosure relates to a method for manufacturing a pipe for gas installations in unventilated locations. The method including the steps of; providing a corrugated stainless steel tubing to carry the gas, the corrugated stainless steel tubing having a protective cover over an outer surface of the corrugated stainless steel tubing; configuring, using a tool, a sub layer over the protective cover; and configuring an outer cover over the sub layer.

[0042] In an aspect, the sub layer and the outer cover are configured such that the corrugated stainless steel tubing is free to move axially within the outer cover.

[0043] In an embodiment, the method can include the step of: configuring the sub-layer around the corrugated stainless steel tubing such that radial clearance between the protective cover of the corrugated stainless steel tubing and the sub layer is less than 2.5mm.

[0044] In an embodiment, the method can include the step of configuring the sub layer and the outer cover with dimensions such that the sub layer engages with the outer cover for the sub layer and the outer cover to remain together as the corrugated stainless steel tubing is moved axially within the outer cover.

[0045] In an embodiment, the method can include the step of: configuring the outer cover to provide fluidic connectivity between two ends of outer cover, thereby venting any leakage from the corrugated stainless steel tubing to a ventilated area.

[0046] In an embodiment, the method can include the step of: configuring the sub layer to prevent sticking of the sub layer over the protective cover of the corrugated stainless steel 15 tubing.

100471 In an embodiment, the method can include the step of: configuring a plastic or PVC corrugated tube as the sub layer, the corrugated tube having a longitudinal slit.

[0048] In an embodiment, the method can include the step of: configuring a plastic or PVC corrugated tube as the sub layer, the corrugated tube not having a longitudinal slit, but 20 made up of 2 or more segments, arranged over one longer length of CSST.

[0049] In an embodiment, the method can include the step of: configuring the longitudinal slit such that, when the sub layer is squeezed, two sides of the longitudinal slit abut each other to ensure that the radial clearance between the sub layer and the protective cover does not go below a desired clearance, thereby allowing free longitudinal movement of the sub layer and the outer cover.

[0050] In an embodiment, the method can include the step of: using an elongate strip of a resilient material as the sub layer by preforming the elongate strip to a circular shape with inner diameter such that, when the elongate strip is positioned around the corrugated stainless steel tubing, the radial clearance between the protective cover of the CSST and the sub layer is ensured.

[0051] In an embodiment, the method can include the step of: providing a plurality of laterally extending fingers along longitudinal sides of the elongate strip such that when the elongate strip is configured around the corrugated stainless steel tubing, the fingers of the opposite sides at least partially overlap each other.

[0052] In an embodiment, the method can include the step of: configuring the plurality of laterally extending fingers such that, when the elongate strip is configured around the corrugated stainless steel tubing, the fingers of the opposite sides interlock with each other.

[0053] In an embodiment, the method can include the step of: using an elongate strip of a resilient material as the sub layer by preforming the elongate strip to a helical shape with inner diameter such that, when the elongate strip is positioned around the corrugated stainless steel tubing, the radial clearance between the protective cover of the CSST and the sub layer is ensured.

[0054] in an embodiment, the method can include the step of: preforming the elongate strip to the helical shape such that the elongate strip is positioned over the corrugated stainless steel tubing, a gap exists between two adjacent sides of the strip, which gap ensures that when the sub later is squeezed, the radial clearance between the protective layer and the sub layer is ensured.

[0055] In an embodiment, the method can include the step of using square mesh of a resilient material as the sub layer by preforming the mesh to a circular shape with inner diameter such that when the mesh is positioned around the corrugated stainless steel tubing, the radial clearance between the protective cover of the CSST and the sub layer is ensured.

[0056] An aspect of the present disclosure relates to a method for manufacturing a pipe for gas installations in unventilated locations. The method including the steps of providing a corrugated stainless steel tubing to carry the gas, the corrugated stainless steel tubing having a protective cover over an outer surface of the corrugated stainless steel tubing; assembling a corrugated PVC tubing as a sub layer over the protective cover of the corrugated stainless steel tubing the in close radial proximity; and configuring an outer cover over the sub layer.

[0057] Various objects, features, aspects and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like components.

BRIEF DESCRIPTION OF THE DRAWINGS

[0058] The accompanying drawings are included to provide a further understanding of the present disclosure, and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the present disclosure and, together with the description, serve to explain the principles of the present disclosure.

[0059] FIG. IA shows the conventional methodology adopted for installation of gas fuel tubing in an unventilated location.

[0060] FIGs. 113 and I C show conventional pipe-in-pipe products for installation of gas fuel tubing in an unventilated location.

[0061] FIGs. 2A to 2D illustrate exemplary views of the disclosed pipe having a sublayer with laterally extending fingers on two opposite sides of a strip of resilient material that overlap with each other, in accordance with the first embodiment of the present disclosure.

100621 FIGs. 2E illustrates a tool for configuring sub layer of FIGs. 2A-2D over the CSST, in accordance with the first embodiment of the present disclosure.

100631 FIG. 2F illustrates the sub layer of FIG. 2A-2D being assembled / configured over the CSST using the tool of FIG. 2E, in accordance with the first embodiment of the present 20 disclosure.

[0064] FIGs. 3A to 3C illustrate exemplary views of the disclosed pipe haying a sublayer with laterally extending fingers on two opposite sides of a strip of resilient material that interlock with each other, in accordance with the first embodiment of the present disclosure.

[0065] FIGs. 4A to 4C illustrate exemplary views of the disclosed pipe haying a sublayer of a corrugated PVC pipe with a slit, in accordance with the first embodiment of the present

disclosure.

100661 FIG. 4D illustrates a corrugated tube with a longitudinal slit for use as a sub layer, in accordance with the first embodiment of the present disclosure.

100671 FIG. 4E illustrates a tool for configuring sub layer of FIG. 4D over the CSST in accordance with the first embodiment of the present disclosure.

[0068] FIG. 4F illustrates he sub layer of FIG. 4D being extruded over the CSST using the tool of FIG. 4E, in accordance with the first embodiment of the present disclosure.

[0069] FIG. 4G illustrates longitudinal sides of the sub layer of FIG. 4D abutting each other, when squeezed to maintain a minimum radial clearance between the CSST and the sub layer, in accordance with the first embodiment of the present disclosure.

[0070] FIG. 4H illustrates a final pipe in pipe product based on the sub layer of FIG. 4D, in accordance with the first embodiment of the present disclosure.

[0071] FIG. 41 illustrates a sub-layer being assembled with multiple sub-layer segments being configured over one length of CSST.

[0072] FIGs. SA to 5D illustrate exemplary views of the disclosed pipe having a sublayer of helically formed strip of a resilient material, in accordance with the first embodiment of the present disclosure.

[0073] FIGs. 6A to 6C illustrate exemplary of the disclosed pipe having a sublayer of square mesh, in accordance with the first embodiment of the present disclosure.

[0074] FIG. 7 illustrate an exemplary method flow diagram for the disclosed method for manufacture of a pipe-in pipe for installation in an unventilated location, in accordance with the second embodiment of the present disclosure.

DETAILED DESCRIPTION

[0075] The following is a detailed description of embodiments of the disclosure depicted in the accompanying drawings. The embodiments are in such detail as to clearly communicate the disclosure. However, the amount of detail offered is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present

disclosure as defined by the appended claims.

[0076] Each of the appended claims defines a separate invention, which for infringement purposes is recognized as including equivalents to the various elements or limitations specified in the claims. Depending on the context, all references below to the "invention" may in some cases refer to certain specific embodiments only. In other cases it will be recognized that references to the "invention" will refer to subject matter recited in one or more, but not necessarily all, of the claims.

[0077] Various terms are used herein. To the extent a term used in a claim is not defined, it should be given the broadest definition persons in the pertinent art have given that term as reflected in printed publications and issued patents at the time of filing.

[0078] Embodiments disclosed herein relate to a pipe for installation of gas fuel supply lines, specifically for installation in unventilated locations or locations that typically require a sleeve, and a method for manufacturing a pipe in pipe product that can be used for installation of gas pipelines in unventilated locations. Specifically, embodiments of the present disclosure provide a pipe that meets the requirements of gas installation codes related to installation of gas pipes in unventilated locations, such as venting of any leaked gas to a ventilated area, and ability to easily withdraw and insert a gas carrying tubing within an outer cover that prevents leaked gas from entering the unventilated area by venting it to the ventilated area.

[0079] In an aspect, the disclosed pipe in pipe for gas fuel installations is based on a sub layer configured over a protective cover of a corrugated stainless steel tubing (CSST), the sub-layer provides a structure that can be attached during the manufacturing process to the CSST, in very close proximity to the 1" protective cover of the CSST, but remains slidable over the Pt protective cover. A secondary outer cover or sleeve is then provided over the sub layer. The secondary cover provides fluidic connectivity between two ends of the outer cover so that any leakage of gas is vented to ventilated area to which the any or both ends of the outer cover may open. The sub layer also prevents direct contact between the protective cover of the CSST and the outer cover, which would prevent smooth and sliding between the CS ST and the outer cover. The sub layer is also configured such that it remains loosely held over the CSST to allow its sliding over the protective cover of the CSST. As the secondary outer cover is configured onto the sub layer in such a way that it adheres to and bonds with the sub layer, a secondary cover can therefore be extruded in very close proximity to the V protective cover, without it getting stuck to / adhered to bonded with the V inner protective cover.

[0080] In an aspect, the sub layer is configured to allow flow of any leaked gas from the CSST to towards the outer cover to be prevented from moving to outside unventilated environment and moved towards any or both end of the outer cover that open to ventilated 30 area.

[0081] In different embodiments, the sub layer can be a preformed elongate strip of a resilient material or a square mesh. In application, the elongate strip of resilient material can be preformed to a cylindrical shape, and can be with or without a plurality of laterally extending fingers provided on two opposite longitudinal sides of the strip. The fingers can be configured to overlap with fingers on the opposite side or interlock with fingers on the opposite side. In alternate embodiment, the elongate strip of resilient material can be preformed to a helical shape.

[0082] In the preferred embodiment, the sub layer can be made of a plastic corrugated tubing having circumferential corrugations consisting of circumferential valleys or troughs.

To aid in assembly of the sub-layer over the CSST, advantageously, the sub layer may include a cut longitudinal slit extending from one end of the sub layer to the other. This cut slit allows the sublayer to be attached to the CSST in close proximity, i.e., with low radial clearance, to the I st protective cover, without the sub layer sticking to the 1" protective cover, over long distances, such as more than 15m. Advantageously, diameters may be chosen such that the radial clearance between the 1" protective cover, and the inner side of the sub layer, is less than 50% the width of sub layer wall itself. For example, if the width of the sub layer wall is 5mm (i.e. the height of the plastic corrugation from peak to trough was 5mm), then advantageously, the radial clearance would be 2.5mm or less.

[0083] in application, readily available materials of suitable size and shape, such as Helawrap®, or spiral protective/binding sleeves, or split corrugated PVC, typically used for cables may be used as a sub layer.

[0084] Referring to FiGs. 2A to 2D where an embodiment of the sub layer for the disclosed pipe in pipe is disclosed, the disclosed pipe can include a corrugated stainless steel tubing 102 having a protective cover (also referred to as inner cover or l' cover) I I 2 over a corrugated tubing 110, a sub layer 200 positioned over the protective cover 112 of the CSST 102, and an outer cover or 2"d cover 202. As shown, the sub layer 200 can be an elongate strip formed to a cylindrical shape. Opposite longitudinal sides of the elongate strip can include a plurality of fingers, such as fingers 204 and 206, such that in the cylindrically formed sub layer the fingers 204, 204 of the opposite sides overlap with each other.

[0085] The exemplary elongate strip shown in in FIG.s 2A to 2D is a readily available product called Helawrap®. However, any other product from a range of similar products primarily used for cable organisation can be used as a sub layer 200. A Helawrap® with a diameter can be selected such that its inner minimum diameter 250 after installation is in close proximity to outer diameter 252 of the protective 1 s' cover 112. For example, if the outer diameter 252 of the protective r cover is 23mm, then a Helawrap® sub layer 200 could be chosen with a min diameter 250 after installation of 25mm, such that after installation, there is a 1mm gap or radial clearance 240 and a small annulus is created between the 1st cover 112 and the sub layer 200.

[0086] The Helawrap® and other similar products are designed to be attached over long lengths of cable, and therefore can be easily installed over long lengths of CSST 102, using a small hand tool 270, shown in FIG 2E, typically provided by the manufacturer of these products. Such tools include features, such as a through shaft 271 for receiving the CSST tube / cable 102, and a conical shape 272 for splitting the elongate strip / Helawrap product. It also includes a handle 273, for pulling the hand tool along the CSST cable.

[0087] As the hand tool 270 is pulled along the CSST tubing, as in FIG. 2F, the Helawrap® sub layer 200 splits apart as it enters the cone shape 272 of the hand tool. As the hand tool 270 is pulled along the CSST 102 in one direction, the Helawrap® sub layer closes in back to its original diameter, but is now installed around the CSST 102, and in "close proximity" or close radial clearance to the p1 protective cover 112. Thus, using the hand tool 270, the sub layer 200 can be installed around the CSST 102 over long distances.

[0088] An outer cover 202 can then be configured over the sub layer 200. The outer cover 202 makes a gas tight structure around the sub layer 200 and the 1st cover I 12, and any gas leaking from the CSST 102 can move axially along the annulus 240 between the I st cover 112 and the sub layer 200 towards open end of the outer cover 202, which can be located in a ventilated location. Thus, the outer cover 202 and the sub layer 200 together form an outer sleeve layer as mandated by codes for installation of gas pipelines in unventilated locations.

[0089] Advantageously, the outer cover 202 can be extruded or manufactured onto the sub layer 200 in such a way that it engages with the sub layer 200, such that the sub layer and the outer cover 202 function like one outer sleeve layer. Since the sub layer 200 is slidable over the CSST 102 (while maintaining a close radial clearance) before the outer cover 202 is extruded or manufactured onto the sub layer 200 is, the combined outer cover 202 and the sub-layer 200 thus remains slidable over. the CSST 102.

[0090] FIGs. 3A and 3B show a different product used for cable organisation used as a sub layer 300, wherein the fingers 302 and 304 of the opposite sides overlap with each other. As can be understood, the sub layer 300 can be selected to meet the above described criteria in respect of radial clearance between the CSST 120 and the sub layer 300, and like the sub layer 200, the sub layer 300 can also be positioned over the CSST 102 using a corresponding tool.

[0091] FIGs. 4A to 4H show another embodiment of the sub layer that is based on a corrugated PVC tube / conduit of a resilient material having a longitudinal slit. As shown therein, the pipe can include a CSST 102 with a protective cover 112, a corrugated tube shown in FIG. 4D, used as a sub layer 400, which includes a longitudinal slit 402. An outer cover 202 is extruded over the sub layer 400. An inner diameter 450 of the corrugated PVC tube sub layer 400 can be chosen so that after the corrugated PVC tube has been configured over the CSST 102, radial clearance between the protective cover 112 and the sub layer 400 is 2.5mm or less. As can be appreciated, for this, inner diameter 450 of the corrugated tube sub layer 400 can be about 0-5mm bigger than the outer diameter 252 of the protective cover 112, so that there is a small annulus or radial clearance 440 (refer to FIG. 4G) between the inside of the sub layer 400 and the outer diameter of the protective cover 112.

[0092] In an embodiment, an attaching tool, shown in FIG. 4E, can be used to configure the corrugated PVC tube sub layer 400 over the CSST 102. The attaching tool 470 can be configured to split the PVC tube 450 and wraps it around the CSST 102. The tool 470 includes features, such as a through hollow shaft 471 for receiving the CSST tube 102, and a conical shape 472 for splitting the corrugated PVC tube 400. It also includes a handle 473, for pulling the hand tool 470 along the CSST 102. Advantageously, the attaching tool can be configured such that it is optimised for attaching split PVC to CSST. The through shaft 471 can be configured, such that it is 0-5mm larger than the CSST diameter 252, and the conical shape 472, can be configured such that it's diameter / width closely matches the CSST diameter 252, and is between 0-10mm larger than the CSST diameter.

[0093] It is to be appreciated that while the exemplary tool 470 shown in FIG 4E is a hand tool, it is possible to have a tool that has a similar shape and function, and which can be mounted in an assembly line, to facilitate easy splitting of the PVC tube 400 at the slit 402, as the CSST 102 is fed to be covered by the PVC tube 400 as the PVC tube 400 closes back over the CSST 102.

[0094] FIG. 4F illustrates the sub layer of FIG. 4D being assembled over the CSST 102 using the tool 470 of FIG. 4E. As shown, the corrugated PVC tube sub layer 400 splits apart as it enters the cone shape 472 of the tool 470. As the tool 470 is pulled along the CSST 102, the PVC tube 400 closes back to its original diameter, but is now installed around the CSST 102, and in "close proximity", i.e., with close radial clearance, to the V protective cover I 12. Thus, using the hand tool 470, the sub layer 400 can be installed around the CSST 102 over long distances, in close radial proximity to the 1st protective cover 112, and importantly, without adhering to it in any way, and thus remaining slidable over the CSST 102 despite being assemble close radial proximity to it..

[0095] in an embodiment, the sub layer 400, can be configured such that when the PVC tube 400 is squeezed, for example by being passed through an extruding machine to apply the outer cover 202, the radial clearance between the sub layer 400 and the CSST 102 does not go below the desired value. For this, the slit 402 can be sized such that when the sub layer 400 is squeezed, the longitudinal sides of the sub layer 400 come in contact with and abut each other, as shown in FIG. 4G by an arrow, thereby preventing further squeezing and maintaining a minimum radial clearance 440 between the CSST 102 and the sub layer 400.

[0096] Advantageously, the radial clearance of the annulus 440 is less than 1/2 (or <50%) the width of the split PVC layer sub layer wall 400. For example, if the width of the sub layer wall was 5mm (i.e. the height of the plastic corrugation from peak to trough was 5mm), then the radial clearance, or the gap 440 (all around the circumference of the annulus, would be 2.5mm or less. Advantageously, the split PVC sub layer is therefore well supported by the CSST as it passes through the extruding machine when the outer cover 202 is being applied.

This will ensure that the sub layer 400 is not damaged by the caterpillar track, that often pulls tubing through extrusion machines. It will also prevent one side of the split PVC sub layer 400, from "tucking inside" the other, and will ensure that the two sides continue to abut each other as the CSST plus sub layer are pulled through the extruder, and that the annulus 440 between the sub layer and CSST is maintained.

[00971 FIG. 4H shows the finished pipe having the sub layer 400, which is based on the corrugated PVC pipe sub layer. The pipe includes CSST 110 with 1s1 protective cover 112 and an outer sleeve layer, which includes a sub layer 400, and outer cover 202, wherein radial clearance between the protective cover 112 and the sub layer 400 is minimized without compromising on free axial sliding movement of the CSST 102 within the outer cover 202.

[0098] It is to be appreciated that although this embodiment depicts a PVC sub layer 400 with a longitudinal split, several other manufacturing methods could be used to configure a PVC sub layer in close radial proximity to the CSST layer, without employing a longitudinal slit. For example, smaller lengths (smaller than the CSST length) of a PVC sub layer could be slid over longer lengths of CSST in segments, so that the combined friction of each segment does not impede sliding of the sub layer into position. For example, separate PVC sub layer pipe segments of 5m each could be slid into position over I 00m of CSST -and this would require 20x separate PVC sub-layer segments. Additionally, a caterpillar machine or rope pulley device could be employed to pull through CSST 102, despite large amounts of friction on longer lengths, however such a method would likely damage the PVC sub layer. It is to be further appreciated that this embodiment seeks to cover all methods of assembling a PVC corrugated sub layer into close radial configuration over the CSST 102, but despite the method chosen the split corrugated PVC tube 450 is unlikely to be gas tight or aesthetically neat after being configured over the CSST, and thus a secondary PE outer cover 202 will need to be extruded over the top of the PVC sub layer.

[0099] FIG. 41 shows two shorter (shorter than the length of CSST 102 over which they are being configured) segments 490 of the sub layer 400, being slid together by hand, in the direction of the two arrows indicated, and being configured over a longer length of CSST 102. The annulus / radial clearance 440 is small enough that longer lengths of PVC conduit (such as >I5m per segment) cannot practically be pulled along the CSST due to friction. Advantageously, the radial clearance 440 is 2.5mm or less. After being configured, several methods could be applied to join the two segments 490 of the sub-layer together 400, such as tape, or a clip, or preferably an internal barb union, attached on the inside of the pipe segment 491. After the separate PVC pipe segments 490 are joined together, the outside cover 200 can be extruded over the entire length of the longer lengths of CSST plus multiple smaller PVC pipe segments. The outer cover 200 seals the gap between the PVC pipe segments 490, and creates a gas tight environment along the annulus 440, and between different PVC pipe segments 490.

[00100] FIGs. 5A to 5D show yet another embodiment of the sub layer that is based on an elongate strip of resilient material formed to cylindrical shape. In the fourth embodiment, the elongate strip, which forms sub layer 500, is formed to a helical shape such that when the helical shaped sub layer 500 is positioned over the CS ST 102, a gap 502 exists between two adjacent sides of the strip. As can be understood, the gap 502 shall be of helical shape. As with other embodiments of the sub layer, there can be small radial/annular gap between the protective cover 112 and the sub layer 500 to allow the helical shaped sub layer 500 to axially slide over the CSST 102.

[00101] in application, easily available readily available materials of suitable size and shape, such as Helawrap®, PVC split conduit, or spiral protective/binding sleeves, typically used for securing a bunch of cables may be used as a sub layer 200, 300, 400 and 500. Known tools used to position these protective sleeves over a bunch of cables can also be used, with or without any modifications, for positioning these protective sleeves over the CSST 102. [00102] In all the above embodiments of the sub layer, i.e, sub layers 200, 300, 400 and 500, inner diameter of preformed elongate strip of resilient material can be greater than than the outer diameter of the CSST 102, and when the sub layer 200, 300, 400 or 500 is positioned over the CSST 102, such as using a suitable tool, the sub layer 200, 300, 400 or 500 can be in loose contact with the CSST 102 to enable its sliding over the CSST 102. However, in the above embodiments, the sub layer, i.e. sub layers 200, 300, 400 and 500 can be configured such that they are in close proximity to the protective cover 112 with minimized radial clearance between the two, such that only a very small annulus exists between the sub layer 200, 300, 400 or 500 and the CSST 102 after assembly.

[00103] As can be understood, the sub layer 200, 300, 400 or 500 can also provide additional protection to the CSST 102 from objects such as nails, screws etc. that may pierce through the outer cover 202.

[00104] FIGs. 6A to 6C show yet another embodiment of the sub layer that is based on an square mesh. The sub layer 600 formed of the square mesh, like the sub layers 200, 300, 400 and 500 can be formed to cylindrical shape and positioned over the CSST 102 in a loose configuration with the outer surface of the CSST 102, such that it remains slidable vis a vis the CSST 102, and such that when a gas tight outer cover 202 is extruded, the outer layer, i.e., the Sub-layer and the outer cover, remain slidable over the CSST layer.

[00105] As is evident, the sub layers 200, 300, 400, 500 and 600 can prevent direct contact between the outer cover 202 and the protective cover 112 of the CSST 102, which avoids any resistance to free sliding between the CSST 102 and the outer cover 202, such as what might occur if an outer cover were extruded directly onto the CSST 102.

[00106] The outer cover 202 may be made from any kind of plastic material that forms a gas tight cylindrical tube, and which bonds / adheres to the sub layer. Preferentially, it is made from an extruded PE layer.

[00107] In an embodiment, difference between outer diameter of radial clearance between sub layer 200, 300, 400, 500 or 600, after the sub layer 200, 300, 400, 500 or 600 has been positioned over the CSST 102 and outer diameter of the ist protective cover 112 can be less than 4mm, i. e., the annulus / gap / radial clearance between the 1st protective cover and the inner diameter of the sub layer, is 2mm or less.

[00108] Referring to FIG. 7, where a method flow diagram for the disclosed method for manufacturing a pipe for gas installations in unventilated locations is disclosed, the method 700 can include at step 702 providing a corrugated stainless steel tubing, such as the CSST 102 shown in FIGs. 2A -6C, to carry the gas. The CSST 102 can include a protective cover, such as the protective cover 112 shown in FIGs. 2A -6C, over an outer surface of the corrugated stainless steel tubing 110. Step 704 of the method 700 can be to configure, using a tool, such as hand tool shown in FIGs. 2E and 4E, a sub layer, such as sub layer 200 shown in FIGs. 2A-2D, or sublayer 300 shown in FIGs. 3A-3C, or sublayer 400 shown in FIGs. 4A-4C, or sublayer 500 shown in FIGs, 5A-5C, or sublayer 600 shown in FIGs. 6A-6C, over the over the protective cover 112 of the CSST 102. Step 706 of the method 700 can be to configure an outer cover, such as outer cover 202 shown in FIGs. 2A to 6C, over the sub layer 200/300/400/500/600.

[00109] In an aspect, the sub layer 200/300/400/500/600 and the outer cover 202 are configured such that the CS ST 102 is free to move axially within the outer cover 202 and the sub layer.

[00110] The method 700 can further include the step of: configuring the sub-layer 200/300/400/500/600 over the CSST 102 such that radial clearance between the protective cover 112 and the sub layer 200/300/400/500/600 is 2.5mm or less.

[00111] In an embodiment, the method 700 can include the step of: configuring the sub layer 200/300/400/500/600 and the outer cover 202 with dimensions such that the sub layer 200/300/400/500/600 engages with the outer cover 202 for the sub layer 200/300/400/500/600 and the outer cover 202 to remain together as the CSST 102 is moved axially within the outer cover 202 [00112] In an embodiment, the method 700 can include the step of configuring the outer cover 202 to provide fluidic connectivity between two ends of outer cover, thereby venting any leakage from the CSST 102 to a ventilated area.

[00113] in an embodiment, the method 700 can further include the step of: configuring the sub layer 200/300/400/500/600 to prevent sticking of the sub layer over the protective cover 112.

[00114] in an embodiment, the method 700 can further include the step of: configuring a corrugated PVC tube, such as corrugated PVC tube shown in FIG. 4D, as the sub layer, the corrugated tube having a longitudinal slit, such as slit 402 shown in FIGs, 4A -4D.

[00115] In an embodiment, the method 700 can further include the step of: configuring the hand tool, such that its dimensions are optimised for configuring split PVC over CSST, with the through shaft having a diameter 0-5mm larger than the CSST diameter, and the conical shape having a diameter 0-10mm larger than the CSST diameter.

[00116] in an embodiment, the method 700 can further include the step of: configuring separate segments of a plastic or PVC corrugated tube, which does not have a longitudinal slit, over a longer length of CSST, by hand, such that 2 or more PVC sub layer segments are configured over one longer length of CSST.

[00117] in an embodiment, the method 700 can further include the step of j oi ning separate plastic corrugated tube segments together, once assembled over the CSST, for example by using tape, or a clip, before an outer cover is extruded on top.

[00118] In an embodiment, the method 700 can further include the step of: configuring the longitudinal slit 402 such that, when the sub layer 400 is squeezed, sides of the longitudinal slit abut each other to ensure that the radial clearance between the sub layer 400 and the protective cover 112 of the CSST does not go below a desired clearance, thereby allowing free longitudinal movement of the sub layer 400 and the outer cover 202.

[00119] In an embodiment, the method 700 can further include the step of: using an elongate strip of a resilient material as the sub layer by preforming the elongate strip to a circular shape with inner diameter such that, when the elongate strip is positioned over the corrugated stainless steel tubing, the radial clearance between the protective cover of the CSST and the sub layer is ensured [00120] In an embodiment, the method 700 can further include the step of providing a plurality of laterally extending fingers along longitudinal sides of the elongate strip such that when the elongate strip is configured over the corrugated stainless steel tubing, the fingers of the opposite sides at least partially overlap each other.

[00121] in an embodiment, the method 700 can further include the step of: configuring the plurality of laterally extending fingers such that, when the elongate strip is configured over the corrugated stainless steel tubing, the fingers of the opposite sides interlock with each other.

[00122] In an embodiment, the method 700 can further include the step of: using an elongate strip of a resilient material as the sub layer by preforming the elongate strip to a helical shape with inner diameter such that, when the elongate strip is positioned over the corrugated stainless steel tubing, the radial clearance between the protective cover of the CSST and the sub layer is ensured.

[00123] in an embodiment, the method 700 can further include the step of: preforming the elongate strip to the helical shape such that the elongate strip is positioned over the corrugated stainless steel tubing, a gap exists between two adjacent sides of the strip, which gap ensures that when the sub later is squeezed, the radial clearance between the protective cover of the CSST and the sub layer is ensured.

[00124] in an embodiment, the method 700 can further include the step of: using square mesh of a resilient material as the sub layer by preforming the mesh to a circular shape with inner diameter such that when the mesh is positioned over the corrugated stainless steel tubing, the radial clearance between the protective cover of the CSST and the sub layer is ensured.

[00125] Thus, the present disclosure provides a pipe in pipe for installation of gas fuel lines in unventilated locations. Additionally, the present disclosure provides a pipe in pipe for installation of gas fuel lines, where an outer sleeve layer comprising an outer cover and a sub layer, performs the functions of a sleeve, as described by UK gas installation standards. The disclosed pipe in pipe overcomes drawbacks of conventional methodology used for such installations by reducing size of the outer cover and by allowing free and easy sliding of the CSST within the outer protective cover layer.

ADVANTGES OF THE INVENTION

[00126] The present disclosure provides a solution that overcomes problems associated with installation of gas pipes in unventilated locations.

[00127] The present disclosure provides a pipe that meets the requirement of gas installation codes related to installation of gas pipes in unventilated locations.

1001281 The present disclosure provides a pipe in pipe for installation in unventilated locations that minimizes space required by the pipe.

1001291 The present disclosure provides a pipe in pipe that has an outer sleeve/duct as close to the inner pipe as possible without compromising flow of leaked gas under all possible situations.

[00130] The present disclosure provides a pipe in pipe wherein the inner pipe is slidable within the outer pipe.

[00131] The present disclosure provides a pipe in pipe that is based on readily available materials, thereby resulting in corresponding cost advantage

Claims

I claim: 1. A pipe for gas pipe installation, the pipe comprising: a corrugated stainless steel tubing, the corrugated stainless steel tubing having a protective cover; and an outer sleeve layer configured over the corrugated stainless steel tubing, comprising an inner sub-layer, and an outer 2nd gas tight cover
2. The pipe as claimed in claim 1, wherein the outer sleeve layer is configured such that the corrugated stainless steel tubing is free to move axially within the outer sleeve layer.
3. The pipe as claimed in claim 2, wherein the sub-layer is dimensioned such that radial clearance between the sub layer and the protective cover of the corrugated stainless steel tubing is 2.5mm or less.
4. The pipe as claimed in claim 3, wherein the outer cover is configured to provide fluidic connectivity between two ends of outer cover, thereby venting any leakage from the corrugated stainless steel tubing to a ventilated area.
5. The pipe as claimed in claim 3, wherein the sub layer is configured to prevent sticking of the sub layer over the protective cover of the corrugated stainless steel tubing irrespective of length of the pipe.
6. The pipe as claimed in claim 4, wherein the sub layer is a corrugated tubing having a longitudinal slit.
7. The pipe as claimed in claim 5, wherein the corrugated tubing is made of PVC.
8. The pipe as claimed in claim 5, wherein the longitudinal slit is dimensioned such that, when the sub layer is squeezed, two sides of the longitudinal slit abut each other to ensure that the radial clearance between the sub layer and the protective cover does not go below a desired clearance, thereby allowing free longitudinal movement.
9. The pipe as claimed in claim 3, wherein the sub layer is an elongate strip extending between two ends of the outer cover configured over a substantial portion of an outer circumferential surface of the protective cover of the corrugated stainless steel tubing.
10. The pipe as claimed in claim 9, wherein longitudinal sides of the elongate strip include a plurality of laterally disposed fingers such that when the elongate strip is configured around the corrugated stainless steel tubing, the fingers of the opposite sides at least partially overlap each other.
11. The pipe as claimed in claim 9, wherein longitudinal sides of the elongate strip include a plurality of fingers such that, when the elongate strip is configured around the corrugated stainless steel tubing, the fingers of the opposite sides interlock with each other.
12. The pipe as claimed in claim 9, wherein the elongate strip is made of a resilient material.
13. The pipe as claimed in claim 9, wherein the elongate strip is preformed to a substantially cylindrical shape with an inner diameter such that, when the elongate strip is positioned around the corrugated stainless steel tubing, the radial clearance between the sub layer and the protective cover pf the corrugated stainless steel tubing is ensured.
14. The pipe as claimed in claim 9, wherein the elongate strip is preformed to a helical shape with an inner diameter such that, when the helical shaped elongate strip is positioned around the corrugated stainless steel tubing, the radial clearance between the sub layer and the protective cover of the corrugated stainless steel tubing is ensured.
15. The pipe as claimed in claim 2, wherein radial clearance between the sub layer and the protective cover is less than half of a width of the sub layer.
16. The pipe as claimed in claim 2, wherein the outer cover of the sleeve layer is smooth.
17. The pipe as claimed in claim 2, wherein the outer cover of the sleeve layer is an extruded PE layer.
18. The pipe as claimed in claim 2, wherein the outer sleeve layer comprises an outer cover and an inner sublayer, wherein the sub layer and the outer cover are manufactured such that the sub layer engages with the outer cover, and for the sub layer and the outer cover to remain together as one, as the corrugated stainless steel tubing is moved axially within the outer sleeve layer.
19. The pipe as claimed in claim 3, wherein the sub layer is a square mesh.
20. The pipe as claimed in claim 1, wherein the sub-layer is made from 2 or more separate segments, configured over one longer length of CSST.
21. The pipe as claimed in claim 21, wherein the 2 or more separate sub-layer segments are joined together, before the outer cover is applied.
22. A method for manufacturing a pipe for gas installations in unventilated locations, the method comprising the steps of; providing a corrugated stainless steel tubing to carry the gas, the corrugated stainless steel tubing having a protective cover over an outer surface of the corrugated stainless steel tubing; configuring, using a tool, or by hand, a sub layer over the protective cover; and configuring an outer cover over the sub layer; wherein the sub layer and the outer cover are configured such that the corrugated stainless steel tubing is free to move axially within the sub layer and the outer cover.
23. The method as claimed in claim 22, comprising the step of configuring the sub-layer around the corrugated stainless steel tubing such that radial clearance between the protective cover and the sub layer is less than 2.5mm.
24. The method as claimed in claim 23, comprising the step of configuring the sub layer and the outer cover with dimensions such that the sub layer engages with the outer cover for the sub layer and the outer cover to remain together as the corrugated stainless steel tubing is moved axially within the outer cover.
25. The method as claimed in claim 24, comprising the step of. configuring the outer cover to provide fluidic connectivity between two ends of outer cover, thereby venting any leakage from the corrugated stainless steel tubing to a ventilated area.
26. The method as claimed in claim 25, comprising the step of configuring the sub layer to prevent sticking of the sub layer over the protective cover of the corrugated steel tubing.
27. The method as claimed in claim 26, comprising the step of: configuring a plastic corrugated tube as the sub layer, the corrugated tube having a longitudinal slit.
28. The method as claimed in claim 26, comprising the step of: configuring a plastic corrugated tube as the sub layer, the corrugated sub layer not having a longitudinal slit, and the corrugated sub-layer being made up of 2 or more segments over 1 single CSST length.
29. The method as claimed in claim 28, comprising the step of: joining two or more plastic corrugated pipe segments together, before extruding the outer cover.
30. The method as claimed in claim 27 comprising the step of: configuring the longitudinal slit such that, when the sub layer is squeezed, two sides of the longitudinal slit abut each other to ensure that the radial clearance between the sub layer and the protective cover does not go below a desired clearance, thereby allowing free longitudinal movement of the sub layer and the outer cover.
31. The method as claimed in claim 25, comprising the step of: using an elongate strip of a resilient material as the sub layer by preforming the elongate strip to a circular shape with inner diameter such that, when the elongate strip is positioned around the corrugated stainless steel tubing, the radial clearance between the protective cover of the corrugated steel tubing and the sub layer is ensured.
32. The method as claimed in claim 25, comprising the step of: providing a plurality of laterally extending fingers along longitudinal sides of the elongate strip such that when the elongate strip is configured around the corrugated stainless steel tubing, the fingers of the opposite sides at least partially overlap each other.
33. The method as claimed in claim 32, comprising the step of configuring the plurality of laterally extending fingers such that, when the elongate strip is configured over the corrugated stainless steel tubing, the fingers of the opposite sides interlock with each other.
34. The method as claimed in claim 23, comprising the step of: using an elongate strip of a resilient material as the sub layer by preforming the elongate strip to a helical shape with inner diameter such that, when the elongate strip is positioned over the corrugated stainless steel tubing, the radial clearance between the protective cover and the sub layer is ensured.
35. The method as claimed in claim 34, comprising the step of: preforming the elongate strip to the helical shape such that the elongate strip is positioned over the corrugated stainless steel tubing, a gap exists between two adjacent sides of the strip, which gap ensures that when the sub later is squeezed, the radial clearance between the protective cover and the sub layer is ensured.
36. The method as claimed in claim 21, comprising the step of: using square mesh of a resilient material as the sub layer by preforming the mesh to a circular shape with inner diameter such that when the mesh is positioned over the corrugated stainless steel tubing, the radial clearance between the protective cover and the sub layer is ensured.
37. A pipe for gas pipe installation, the pipe comprising: a corrugated stainless steel tubing, the corrugated stainless steel tubing having a protective cover; and an outer sleeve layer configured over the corrugated stainless steel tubing; comprising an inner corrugated plastic layer, and a gas tight outer cover of extruded plastic material.
38. The pipe as claimed in claim 37, wherein the inner corrugated layer and the outer cover are configured such that the corrugated stainless steel tubing is free to move axially within the outer sleeve.
39. The pipe as claimed in claim 38, wherein radial clearance between the corrugated stainless steel tubing and the outer sleeve layer, is 2.5mm or less.
40. The pipe as claimed in claim 37, wherein the corrugated plastic layer and the outer cover are manufactured such that the corrugated plastic sub layer engages with the outer cover, and for the corrugated plastic sub layer and the outer cover to remain together as one, as the corrugated stainless steel tubing is moved axially within the outer sleeve layer.
41. The pipe as claimed in claim 37, wherein the corrugated plastic layer consists of 2 or more separate segments, arranged over one single length of CSST.
42. The pipe as claimed in claim 41, wherein the corrugated plastic layer segments are joined together before the outer cover is extruded.