Termination for Sheathed Tubing with Leak Containment and Detection Provisions

Abstract

A fitting for an end of a length of corrugated tubing with an outer sheath includes an engagement ring for gripping the tubing adjacent to an endmost corrugation of the tubing to preclude axial displacement of the retainer on the tubing. The fitting also includes an end plug having at least one threaded surface and a hollow cylindrical part sized to admit and engage with the engagement ring. The end fitting also includes a nut having a threaded portion complementary with the threaded surface of the end plug and an inner surface that defines an inner cavity. An annular groove extends from the inner surface. A vent extends through the sidewall and is disposed between the threaded surface and the groove. A gasket is disposed in the annular groove and a portion of the gasket extends into the inner cavity and is configured to sealingly engage the sheath.

Claims

1. A method of terminating a length of corrugated tubing with an outer sheath, the method comprising the steps of: cutting the tubing, thereby forming an endmost corrugation; cutting the sheath, thereby exposing a portion of the tubing; inserting the tubing into an engagement ring having a ridge placed axially adjacent to the endmost corrugation of the tubing; and engaging a threaded portion of a nut with a threaded surface of an end plug to cause the ridge to securely grip the tubing, wherein the nut has a sidewall with an inner surface defining an inner cavity and an annular groove extending from the inner surface and a vent extending through the sidewall and disposed between the threaded surface and the annular groove and wherein a gasket is disposed in the annular groove such that a portion of the gasket extends into the inner cavity and sealingly engages the sheath.

2. The method of claim 1, wherein the gasket comprises an elastomeric material.

3. The method of claim 1, wherein the nut is an integral structure.

4. The method of claim 1, wherein the nut further includes an annular ring adjacent an end of the engagement ring.

5. The method of claim 4, wherein the annular ring divides a first portion of the nut from a second portion, and wherein the threaded portion is on the first portion and the annular groove is on the second portion.

6. The method of claim 1, wherein the end plug and the engagement ring sealingly engage the corrugated tubing to form a sealed annular volume whereby a potential leakage path between the corrugated tubing and the sheath is confined to emit at the vent.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Aspects of the present disclosure are best understood from the following detailed description when read with the accompanying figures. It is noted that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion.

[0012] FIG. 1 is a section view showing a fitting, tubing, and sheath according to one embodiment of the present disclosure.

[0013] FIG. 2 is an isometric exploded view of the fitting, tubing, and sheath of FIG. 1.

[0014] FIG. 3 is an external side elevation view of the fitting, tubing, and sheath of FIG. 1 and including a generally illustrated complementary termination such as an appliance connection.

[0015] FIG. 4 is a cross section along line 4-4 through the fitting nut shown in FIG. 3.

[0016] FIG. 5 is a cross-sectional view of a nut according to one aspect of the present disclosure.

DETAILED DESCRIPTION

[0017] The following disclosure provides many different embodiments, or examples, for implementing different features of the subject matter. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed.

[0018] Further, spatially relative terms, such as beneath, below, lower, above, upper and the like, may be used herein for ease of description to describe one element or feature's relationship to another elements) or feature(s) as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The apparatus may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may likewise be interpreted accordingly.

[0019] The fittings described herein provide for confinement of contents leaking from CSST using a simple arrangement. A nut of the termination fitting includes a cylindrical skirt part that is elongated back from the termination, over a proximal part of the tubing approaching a termination. The cylindrical skirt encloses over a portion of a sheath enveloping the tubing. The nut is preferably part of a clamping structure. One or more gaskets such as O-rings are provided within the cylindrical skirt part, preferably captive in an annular groove inside the skirt part, and is compressed between the outer surface of the sheath and the inner surface of the cylindrical skirt part. A vent opening can be provided in the skirt part for detecting or dissipating gas leaking along a flow path between the CSST and the sheath, from some indefinite point at which the CSST may have been damaged or breached.

[0020] In FIG. 1 a tubing termination fitting 100 is shown attached to a distal end 102b of a section of tubing 102, for example corrugated stainless steel tubing. A sheath 104 envelops a portion of the tubing 102. In some embodiments, the sheath 104 completely envelops the tubing 102 between two fittings, The sheath 104 has been stripped from a portion 102a of the tubing 102 near the distal end 102b of the tubing 102. This allows engagement with a portion of the fitting 100, as will be described further herein.

[0021] The tubing 102 has corrugations, namely spatially periodic regular variations in diameter forming successive ridges and valleys around the axis of the tube, ranging between a maximum diameter and a minimum diameter. The corrugations proceed along the longitudinal (axial) extension of the tubing 102. Tubing 102 may be cut from a longer length using a hand tool such as a hardened wheel tubing cutter or a hacksaw, for example. A power tool such as a radial arm or pivoting chop saw can be used. The tubing end is advantageously cut off square (i.e., on a plane normal to the longitudinal axis of the tubing 102).

[0022] The sheath 104 can be formed of any appropriate material that can provide secondary containment of gasses or liquids. For example, the sheath may be constructed of polyethylene (PE), EFEP or Nylon.

[0023] It should be understood that the fitting 100, tubing 102, and sheath 104 shown in FIG. 1 can form only a portion of a gas or liquid passageway. The remainder of the gas or liquid passageway could comprise an additional fitting coupling to a further length of tubing. Additionally or alternatively, the gas or liquid passageway can include a threaded fitting or nipple configured to couple to an appliance or to a gas supply pipe as shown in FIG. 3.

[0024] In the illustrated embodiment, the fitting 100 includes an end plug 106, an engagement ring 108, and a nut 110. In the stripped portion 102a, the tubing 102 is bare to be engaged by the fitting 100. In embodiments in which tubing 102 is corrugated tubing, the engagement ring 108 and/or the end plug 106 can engage the corrugations at the end of the tubing 102, or at least the endmost corrugation, and compress the corrugation(s) to achieve a hermetic seal between the tubing 102 and the fitting 100 as a whole. There are a number of specific ways in which the hermetic seal can be achieved, for example as disclosed in U.S. Pat. Nos. 7,055,868 and 6,877,781, which are incorporated herein by reference.

[0025] As shown in FIG. 2, the end plug 106 includes a hollow cylindrical part 111 sized to admit and engage with the engagement ring 108. In addition, the end plug 106 includes at least one threaded surface 112. The end plug 106 can also include a recess 114 sized and configured to receive a tubing gasket 116, as shown in FIG. 1. The tubing gasket 116 is configured to engage a portion of the tubing 102 to provide a hermetic seal, as will described further herein. The end plug 106 can also have a second threaded surface 118 which can be used to connect the fitting 100 to a further portion of the gas or liquid passageway.

[0026] As best seen in FIG. 5, the nut 110 has a sidewall 120 with a faceted, hexagonal outer surface which allows for engagement with, a spanner wrench for tightening. The sidewall 120 of the nut 110 includes a threaded portion 122 which is complementary to the threaded surface 112 of the end plug 106 and configured to engage therewith as will be described herein. The inner surface of the sidewall 120 defines an inner cavity 124 of the nut 110. Additionally, an annular groove 126 is defined in the sidewall 120. A sheath gasket 128 is disposed in the annular groove 126 and extends into the inner cavity 124 as will be described further herein. The nut 110 can further include an annular ring 130 extending into the inner cavity 124 and separating the nut 110 into a first portion 132 and a second portion 134. The first portion 132 includes the threaded portion 122 and the second portion 134 includes the annular groove 126. The second portion 134 can be in the form of a cylindrical skirt forming a cylindrical inner cavity 124. The nut 110 further defines a vent 136 through the sidewall 120. In at least one embodiment, the nut 110 is an integral structure. In such embodiments, the nut 110 can be formed of a unitary component, for example by metal casting, injection molding, additive manufacturing (e.g., 3-D printing), machining, or other appropriate process. An integral nut 110 can also be formed by fixedly attaching multiple components to one another, for example by welding or other appropriate procedure.

[0027] The sheath gasket 128 can be formed of any material that is able to form a seal between the nut 110 and the sheath 104. In one embodiment, the sheath gasket 128 is constructed of an elastomeric material, such as EPDM rubber. In one embodiment, the sheath gasket 128 can be an o-ring sized to contact both the nut 110 and the sheath 104 when the tubing 102 and sheath 104 are disposed in the fitting 100. In some embodiments, the inner surface of the nut 110 defines more than one annular groove and a sheath gasket is disposed in each and configured to engage the sleeve. Such embodiments may provide redundancy in the event that one sheath gasket is damaged, worn, or ineffective.

[0028] Returning to FIG. 1, when assembled and engaged with tubing 102, a first end of the engagement ring 108 abuts, or is adjacent to, the annular ring 130 of the nut 110. An opposite end of the engagement ring 108 abuts, or is adjacent to, the end plug 106 and/or tubing gasket 116. The engagement ring 108 has annular ridges 114a that correspond to the valleys of the corrugations. As the nut 110 is rotated with respect to the end plug 106, and advances in the distal direction (axially), the engagement ring 108 is compressed radially inwardly to grasp the corrugations (i.e., peaks and valleys) of the tubing 102. In addition, the distal end 102b of the tubing 102 is forced against the tubing gasket 116. As a result, the end plug 106 and the nut 110 pinch the tubing 102 and obtain a gas-tight seal. This engagement also prevents axial displacement of the tubing 102 with respect to the fitting 100. In addition, an o-ring 138 or other sealing element can be positioned between end plug 106 and nut 110 to provide additional sealing and prevent inadvertent relative rotation of these components.

[0029] The unsheathed portion 102a of the tubing 102 extends longitudinally beyond the sheath 104 enveloping the tubing 102. Thus, when the endmost corrugations of the tubing 102 are hermetically sealed by the fitting 100, there is an annular gap between the tubing 102 and the inside of the nut 110. This annular gap communicates with the vent 136, shown as a threaded opening in the nut 110. The vent 136 is located in the second portion 134 of nut 110.

[0030] The second portion 134 of the nut 110 also includes the annular groove 126 in which the sheath gasket 128 resides and bears radially between the nut 110 and the outside of the sheath 104, achieving a seal. To achieve such a seal, the natural inner diameter of the sheath gasket 128 may be less than the outer diameter of the sheath 104. Hence, the sheath gasket 128 fully engages the sheath 104 around its circumference. This seal prevents any uncontrolled leaking of the contents of the tubing 102. For example, if the tubing 102 should be damaged at some point along its proximal length 102c (e.g., between two fittings), for example due to crushing or undue bending of the tubing 102, the sheath 104 will confine any gas or other material leaking from inside the tubing 102 to the zone within the sheath 104. Any gas leakage between the tubing 102 and the sheath 104 is confined and contained within the sheath 104 by the sheath gasket 128. As a result, the leakage is not able to escape from the sheath 104 in the area between the sheath gaskets of two fittings. Hence, the sheath 104 prevents leakage in the areas between end fittings.

[0031] In addition, within the fitting 100, a sealed annular volume is formed between the tubing 102 and inner surface of the nut 110, with contents only being able to exit through the vent 136. Any breakage or damage of the stripped portion 102a of the tubing 102 which allows gas to escape from the tubing 102 is confined at one end by the hermetic seal between the distal end 102b of the tubing 102 and the tubing gasket 116. The gas is further confined by the seal between the sheath gasket 128 and the sheath 104. Hence, any leaking gas or pressure is directed to the vent 136. The vent 136 can couple to a leak detection pressure sensor (not shown) or in appropriate instances can couple to a venting conduit that conveys the gas to a safe point of discharge.

[0032] FIG. 3 is a side elevation view that additionally illustrates coupling of the fitting 100 to a complementary termination 200, for example the supply coupling to an appliance 202.

[0033] FIG. 4 is a section along lines 4-4 and shows the sealing engagement between the sheath gasket 128, the nut 110, and the sheath 104. The sheath gasket 128 bears radially inwardly against the outside of the sheath 104 to provide a sealing engagement, as described above. This arrangement confines any leakage between the tubing 102 and the sheath 104 to the volume inside the nut 110 and directs contents to the vent 136.

[0034] The benefits of containing any leakage between the tubing 102 and its sheath 104 are achieved in a direct and efficient manner, by extending the usual structure of the nut 110 of the fitting 100 for a distance in the proximal direction, back from the end of the terminal end, and sealing the inside of the extended nut 110 using a sheath gasket 128 in an annular groove 126. The outer surface of the nut 110 can have the usual hexagonal or similar cross section as shown in FIG. 4, enabling the assembler to apply a spanner wrench when tightening the corrugation clamping mechanism.

[0035] In other embodiments, a method for terminating a length of corrugated tubing with an outer sheath are provided. The method includes the step of cutting the tubing, thereby forming an endmost corrugation. The method also includes the step of cutting the sheath, thereby exposing a portion of the tubing. The tubing is then inserted into an engagement ring having a ridge placed axially adjacent to the endmost corrugation of the tubing. A threaded portion of a nut is then engaged with a threaded surface of an end plug to cause the ridge to securely grip the tubing. Additionally, a gasket disposed in an annular groove of the nut sealingly engages the sheath.

[0036] The fittings described herein are effective and not unduly expensive. The components are small and compact and require less assembly time. Because the nut houses the gasket that engages the sheath, extra components are not required to form a sealed volume. That leakage may be contained at the end of the tubing and sheathing or vented appropriately to the open air is particularly advantageous in sections of underground tubing installations.

[0037] The foregoing outlines features of several embodiments so that those skilled in the art may better understand the aspects of the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions, and alterations herein without departing from the spirit and scope of the present disclosure.