Flame-resistant heat shrink assemblies for trace heating cables

An end cap for a heat shrink kit having a heat shrink tubing, wherein the end cap includes a tubing portion sized to be inserted into the heat shrink tubing and an end portion configured to prevent at least a portion of a flame from reaching the heat shrink tubing.

BACKGROUND

During construction or repair of electrical systems, it may be necessary to join two or more cables together, or to properly terminate a single cable. Heat shrink kits that utilize heat shrink tubing can be used to join the two cables together or terminate the single cable. Heat shrink kits can include splice connection kits, tee splice kits, cold-lead kits, and/or end seal kits. Splice connection kits (which can also be referred to as splice kits) can include any components used to properly connect two ends of electric heat trace cables together. Splice kits can utilize soldering, welding, twisting, and/or mechanical connectors to connect two identical cables. Tee splice kits (which may also be referred to as tee connection kits) can include any components such as mechanical connectors used to properly connect three ends of electric heat trace cables together. Cold-lead kits can include electrically-insulated wiring that connects heating conductors to branch circuit wiring, and can be designed to not produce appreciable heat. End seal kits seal off the end of a single cable, and can include any components used to properly terminate the end of an electric heat trace cable that is not wired to power. There may be exposed wires or mechanical connectors in between insulated sections of the cable(s). The exposed section can be covered with heat shrink tubing, which can provide a barrier against moisture as well as electrical insulation.

Heat shrink tubing can include an adhesive lining. Adhesive lined heat shrink tubing is ubiquitous, and is an effective moisture sealer and electrical insulator. However, being polymeric in construction, the heat shrink tubing's resistance to flammability is limited, even when the tubing contains flame retardants. In many applications, resistance to flammability is of great concern. For example, certain heat shrink kits may be required to pass flammability tests such as CSA standard C22.2 No. 130-16.

Certain splice kits or cold-lead kits may be used to provide flammability protection to a tee connection (i.e. where three heating cable are joined together), while end seal kits can be used to provide flammability protection to an end of a cable (i.e. the end of a single heating cable). Kits used to protect tee connections or an end of a cable may have a sealed or pinched portion at the end of the heat shrink tubing, where the tubing is crimped during installation, before or after heat is applied to shrink the tubing. The pinched portion has been shown to be less resistant to flame than other parts of the heat shrink kit, in certain flammability tests. For example, CSA standard C22.2 No. 130-16 allows a flame to be provided anywhere along the heat shrink kit, including at the sealed or pinched portion at the tee connection or the end of the cable; if the flame applied to the pinched portion causes the sealed area to open up, the adhesive may ignite and burn for longer than the allowed duration per the test standard.

SUMMARY

The invention addresses the need for a cost effective and easy-to-use method to improve flammability protection for tee connection kits, splice kits with vertically aligned heating cables, and end seal heat shrink kits and overcome the drawbacks listed above. According to an aspect of the disclosure, a splice kit for providing environmental protection to a splice of electric heating cables includes: a length of heat shrink tubing having a pre-shrunk inner diameter and a shrunk inner diameter; and, an end cap made of a flame-resistant material. The end cap includes: a tubing portion having an inner surface, an outer surface, and one or more projections extending outward from the outer surface, the tubing portion sized to fit within the pre-shrunk inner diameter and to be larger than the shrunk inner diameter; an end portion integral with the tubing portion and wider than the tubing portion, the end portion configured to prevent at least a portion of a flame from reaching the heat shrink tubing; and, an interior space defined by the inner surface of the tubing portion, the interior space being configured to receive conductors of the heating cables that are connected together at the splice.

In one aspect, the end cap can be cylindrical, and the one or more projections can include a first rib extending entirely around a circumference of the outer surface. The tubing portion can have an outer diameter measured at the outer surface, and the end portion has an outer diameter that is greater than the outer diameter of the tubing portion. In another aspect, the tubing portion and the end portion can be prismatic. The tubing portion can include grooves formed into the outer surface to define the one or more projections. The projections can be formed at each of a plurality of corners of the tubing portion. The end portion can include a front surface and a rear surface opposite the front surface, the rear surface cooperating with the inner surface of the tubing portion to define the interior space. The interior space of the end cap can have a tapering width; the tapering width can include a maximum width at a distal end of the tubing portion opposite the end portion, and a minimum width approximate the end portion. The heat shrink tubing can be selected relative to a size of the end cap to allow the splice protected by the splice kit to pass a vertical flame flammability test. The splice kit can further include a first mastic layer configured to be applied over an interface between the end cap and the heating cables before the heat shrink tubing is placed over the splice and then shrunk.

According to other aspects of the disclosure, an end cap for a heat shrink kit having a heat shrink tubing is provided. The heat shrink kit can be a tee connection kit, an end seal kit, or another splice kit. The end cap includes a tubing portion sized to be inserted into the heat shrink tubing and an end portion configured to prevent at least a portion of a flame from reaching the heat shrink tubing.

According to another aspect of the disclosure, an end cap for a heat shrink kit having a heat shrink tubing is provided. The end cap includes a tubing portion sized to be inserted into the heat shrink tubing. The end cap is configured to allow the heat shrink kit to pass a vertical flame flammability test.

According to yet another aspect of the disclosure, an end cap for a heat shrink kit having a heat shrink tubing is provided. The end cap includes a tubing portion sized to be inserted into the heat shrink tubing and having a first diameter and an end portion having a second diameter, the second diameter being larger than the first diameter.

DETAILED DESCRIPTION

Before the present invention is described in further detail, it is to be understood that the invention is not limited to the particular aspects described. It is also to be understood that the terminology used herein is for the purpose of describing particular aspects only, and is not intended to be limiting. The scope of the present invention will be limited only by the claims. As used herein, the singular forms “a”, “an”, and “the” include plural aspects unless the context clearly dictates otherwise.

It should be apparent to those skilled in the art that many additional modifications beside those already described are possible without departing from the inventive concepts. In interpreting this disclosure, all terms should be interpreted in the broadest possible manner consistent with the context. Variations of the term “comprising”, “including”, or “having” should be interpreted as referring to elements, components, or steps in a non-exclusive manner, so the referenced elements, components, or steps may be combined with other elements, components, or steps that are not expressly referenced. Aspects referenced as “comprising”, “including”, or “having” certain elements are also contemplated as “consisting essentially of” and “consisting of” those elements, unless the context clearly dictates otherwise. It should be appreciated that aspects of the disclosure that are described with respect to a system are applicable to the methods, and vice versa, unless the context explicitly dictates otherwise.

Numeric ranges disclosed herein are inclusive of their endpoints. For example, a numeric range of between 1 and 10 includes the values 1 and 10. When a series of numeric ranges are disclosed for a given value, the present disclosure expressly contemplates ranges including all combinations of the upper and lower bounds of those ranges. For example, a numeric range of between 1 and 10 or between 2 and 9 is intended to include the numeric ranges of between 1 and 9 and between 2 and 10.

Existing approaches to splicing or terminating an electric trace heating cable include covering the splice or cable end with heat shrink tubing to protect it from the environment. The heat shrink tubing of a splice kit can be a single- or dual-layer heat shrink tubing and typically has an adhesive layer on its inner surface. The heat shrink tubing can be made from polyolefin, a fluoropolymer such as FEP, PTFE or Kynar, PVC, neoprene, silicone elastomer, Viton, or any other appropriate material that can shrink after heat is applied in order to provide a moisture barrier and/or electrical insulation. A splice kit for a cable splice can include solder and/or mechanical connectors[MA1]that connect two or more cables together. A splice kit for a cold-lead splice can include a mechanical connector and/or other appropriate components to join two lengths of cable together without the use of heat.

During installation of existing heat shrink kits, the heat shrink tubing is crimped or pinched to form a seal over the splice or at the end of the cable(s). This can form a pinched portion in which the adhesive may only be in contact with other adhesive, or with the heat shrink tubing, or with a component to which the adhesive does not well adhere. The pinched portion can be created by positioning a portion of the heat shrink tubing away from components of the cable and/or other components of the heat shrink kit, and crimping the portion with a tool such as needle nose pliers. The adhesive layer of the heat shrink tubing may keep the pinched portion in place and prevent the pinched portion from becoming uncrimped during service. The heat shrink tubing can then be shrunk. Alternatively, the pinched portion can be created by crimping the heat shrink tubing after heat has been applied to shrink the heat shrink tubing by pinching it with a tool such as a needle nose plier.

Crimping the heat shrink tubing to create the pinched portion can electrically insulate the cable as well as provide protection from moisture, but the pinched portion becomes a focal point of the overall flammability protection afforded by the heat shrink kit. The present disclosure provides apparatuses and installation methods for a heat shrink kit including a splice kit and a heat shrink assembly that overcomes the drawbacks of existing heat shrink kits by eliminating the pinched portion that remains after installation.

FIGS. 1A-Dillustrate steps of using an example splice kit in accordance with this disclosure. The splice kit can include a tee connection kit10for electrically connecting the conductors14of multiple cables16. In these Figures, the tee connection kit10is shown without a heat shrink assembly of the splice kit, which fits over and obscures the tee connection kit10. In some embodiments, including the illustrated example, the cables16can be self-regulating heating cables each including two conductors14A,14B and a core15of positive temperature coefficient (PTC) material that form a resistive heating circuit; a corresponding mechanical connector12mechanically and electrically couples together the conductors14of each cable16that are carrying the electric current in the same direction. In addition to the conductors14, the cables16may include a layer of insulation18, and a jacket20, and in some embodiments a braided layer22having one or more braided wires for grounding the cable16.

Each cable16can be prepared for splicing by exposing a suitable length of the conductors14. For example, as shown inFIG. 1Athe jacket20can be stripped back, and the braided wires of the braided layer22twisted into one or more bundles that can be easily moved aside; then, a portion of exposed insulation18can be stripped from the core15, which in turn can be cut or stripped away from the conductors14A,B. One or more adhesive layers, such as mastic strips30,32, can be applied to parts of the cable16. For example, a first mastic strip30can be adhered to the remaining exposed insulation18, and a second mastic strip32can be adhered to the jacket20. The adhesive layers later adhere to the unshrunk heat shrink tubing, to hold the latter in place; the adhesive layers can also adhere to other cables16, and/or to other adhesive layers of cables16being spliced together. Adhesive layers such as mastic can also be flame-retardant, increasing the flame resistance of the completed splice. Finally, a mastic strip30or other adhesive layer can extend a length D beyond the end of the exposed insulation18and core16; after the mastic strip30is wrapped around the cable16, the excess extending beyond the end of the cable can be pinched together between and around the conductors14A, B to seal the core15from liquid ingress.

As shown inFIG. 1B, for a three-cable tee splice, the cables16can be aligned and then coupled together. For example, the adhesive layers can be used to align and then adhere the cables16to each other, so the corresponding conductors can be twisted together. In some embodiments, one or more zip-ties34or other fasteners can be used to couple together the cables16. Referring toFIG. 1C, the braided layers22of the cables16can be coupled together and then secured to the bundle of cables. For example, the twisted bundles of braided wires can be twisted together and secured by an insulating end cap40, which in turn can be secured against the jackets20with fabric tape50.

Referring toFIG. 1D, the tee connection kit10can include one or more mechanical connectors12, which can be coupled to one or more conductors14of each of the cables16. The mechanical connectors12may be a push in wire fitting, crimp cap, or any other mechanical connector to join two or more lengths of wire or cable together without the use of heat. As illustrated, the corresponding conductor of each of the cables can be twisted together, and then secured using one of the mechanical connectors12. In an alternate embodiment of splice-type tee connection kits, corresponding conductors14of each of the cables16may be soldered together and the mechanical connectors12may be omitted. Heat shrink tubing can be placed around the cables16and connectors and shrunk using a heat applicator such as a heat gun or a torch, as described further below. The heat shrink tubing may provide electrical insulation as well as flammability protection.

Referring now toFIGS. 2A and 2B, a perspective view and a cross-sectional view are shown of an example embodiment of an end cap400. The end cap400can be made from a flame retardant material such as unfilled or glass filled polyphenylene sulfide (PPS) or polyetherimide (PEI) as described above. The end cap400may have a tubing portion402and an end portion404. The tubing portion may be inserted into a heat shrink tubing. At least a portion of the tubing portion402may be in contact with an inner surface of the heat shrink tubing. The end portion404may prevent a flame applied during a flammability test from reaching an adhesive of the heat shrink tubing and thereby provide flammability protection for the heat shrink tubing, as will be explained in detail below.

The tubing portion402can be sized to fit inside heat shrink tubing as shown inFIG. 3. Specifically, an outer diameter408can be sized to allow tubing portion402to fit inside the heat shrink tubing; further, an inner diameter406can be sized to allow one or more components of a cable and/or heat shrink kit to fit inside the tubing portion402. In accordance with some embodiments, the heat shrink tubing should be chosen based on an appropriate minimum expanded inside diameter and a maximum recovered (i.e. shrunk) inside diameter after a shrinking process. An appropriate heat shrink tubing can be chosen by selecting a heat shrink tubing which fits a kit dimension (i.e. fits around and/or over a heat shrink kit) before a shrinking process and nearly fully recovers after the shrinking process. If a heat shrink tubing does not nearly fully recover, it may shrink further and potentially split during the flammability testing. To reduce likelihood of splitting during the test, the maximum recovered inside diameter of the heat shrink tubing can be selected to be approximately equal to or slightly smaller than the outer diameter or equivalent outer diameter (i.e perimeter divided by pi). For example, a heat shrink tubing with a high shrink ratio and a recovered inner diameter significantly smaller than the outer diameter408may burst during flammability testing as the heat shrink tubing may further contract around the end cap400and potentially rupture.

The tubing portion402may include one or more ribs410extending laterally outward from the outer surface and thus being wider than the outer diameter408of the tubing portion402. If the outer diameter408is smaller than the minimum expanded (i.e. unshrunk) inner diameter of the heat shrink tubing, the heat shrink tubing can be easily slid over the end cap and the ribs410may allow the end cap400be retained more tightly by friction fit than an end cap without ribs410. When the heat shrink tubing is shrunk, the ribs410may also allow the heat shrink tubing to be better coupled to the end cap400. The ribs410can prevent the end cap400from being moved along the length of the shrunk heat shrink tubing. Additionally, the ribs410may allow a heat shrink tubing without an adhesive lining to be used in the heat shrink kit by providing a friction fit with the heat shrink tubing and thus retaining the heat shrink tubing.

The end portion404may have an end cap diameter412that can be larger than the outer diameter408. Furthermore, the end cap diameter412may be larger than the diameter of the heat shrink tubing after the heat shrink tubing is stretched and/or shrunk over the tubing portion. When the end cap diameter412is larger than the diameter of the stretched and/or shrunk heat shrink tubing, the end cap400can prevent at least a portion of a flame applied during a vertical flame test from reaching an adhesive of the heat shrink tubing, prevent at least a portion of the adhesive from igniting, and allow the heat shrink kit to pass the flammability test.

Referring now toFIG. 3, an example embodiment of an end cap300, such as the end cap400illustrated inFIGS. 2A-B, is shown. The end cap300is inserted into a heat shrink tubing302of a heat shrink kit304for cables310of a tee connection. As shown, the heat shrink kit304is for a tee connection, although it is understood the end cap300may be used with a splice kit for two cables or an end seal heat shrink kit. If the end cap300is used with a splice kit for two cables, the two cables may be arranged on top of each other and/or vertically aligned, similar to the arrangement shown inFIG. 1without a third cable. The heat shrink tubing302has been shrunk using a heat applicator. The end cap300can be made from a flame retardant plastic material such as unfilled or glass filled polyphenylene sulfide (PPS) or polyetherimide (PEI). The material of the end cap300can be chosen to be a similar color as the heat shrink tubing, which can improve the aesthetics of the heat shrink kit304.

The end cap300may be inserted into the heat shrink tubing302in order to provide flammability protection for the heat shrink kit304. In some embodiments, the end cap300can include a tubing portion306that fits within the heat shrink tubing302, and an end portion308that is attached to or integral with the tubing portion306and that does not fit within the heat shrink tubing302. The end cap300may only be inserted far enough into the heat shrink tubing302so that at least a portion of a tubing portion306is in direct contact with the heat shrink tubing302, but an end portion308is not in direct contact with the heat shrink tubing302. When the heat shrink tubing302is not in direct contact with the end portion308, the end cap300may protect an adhesive of the heat shrink tubing302from direct impingement with a flame applied during a vertical flame test. Additionally, the end portion308may have an outer diameter308A that exceeds the outer diameter306A of the heat shrink tubing302when the heat shrink tubing302is stretched over the tubing portion306. In this arrangement the end portion308may at least partially protect the heat shrink tubing302from encroaching flame, by preventing at least a portion of the flame from reaching the adhesive and/or heat shrink tubing302. The end cap300can also provide an insulation barrier to prevent at least a portion of the heat from the flame from being conducted to the heat shrink tubing302and/or the adhesive.

The end cap300can simplify the installation of the heat shrink kit304. The end cap300can prevent the need to seal the heat shrink tubing by crimping the heat shrink tubing. A user may only need to insert the end cap into the heat shrink tubing302and apply heat to the heat shrink tubing302. The end cap300may be installed by an unskilled worker. The end cap300can also reduce the required size of the heat shrink tubing302as compared to prior heat shrink kits. Prior kits require heat shrink tubing long enough to cover one or more cables and any connection components (i.e. mechanical connectors) as well as enough excess length to allow a worker to crimp the heat shrink tubing and create a sealed area. Heat shrink kits with an end cap may only need heat shrink tubing long enough to cover the cables and any connections (e.g. soldering points, mechanical connectors, etc.) of the heat shrink kit because the end cap can eliminate the need for crimping and/or sealing the heat shrink tubing.

The synergy between a flame-retardant end cap and an appropriate heat shrink tubing provides a configuration to improve a flammability performance of end seal heat shrink kits. The end cap protects the integral component of a kit once a flame is applied at the bottom portion of heat shrink kit. Furthermore, a heat shrink tubing with appropriate dimension (i.e. recovered inside diameter) can prevent the heat shrink tubing from splitting during the flammability testing once a flame is provided anywhere along the heat shrink tubing.FIG. 4illustrates the results of applying a vertical flame test to the heat shrink kit304and end cap300as installed inFIG. 3. The end cap300prevented excess damage to the heat shrink tubing302, and allowed the heat shrink kit304to pass the vertical flame test.

In a vertical flame test, a 460 mm long sample of a trace heater (i.e. the cables310) with any integral component (i.e. the heat shrink kit304and/or end cap300) shall be supported in a vertical position. A gas burner is mounted on a 20° angle block. A test flame is 125±10 mm long with an inner blue cone 40±2 mm high. A tip of an inner blue cone of the flame impinges on the outer surface of the sample (it can be anywhere on the sample). A strip of gummed kraft paper 12.5±1 mm wide is attached 254 mm above the flame application point. This paper strip is to extend out 20 mm from the opposite side where the flame is applied. The distance of lower clamp to point of flame application shall be at least 50 mm. Likewise, the distance of upper clamp to paper indicator shall be at least 50 mm. Underneath the test setup may or may not be a cotton layer depending on the standard of testing. The test shall be conducted where all drafts of air are excluded. The flame is applied for 15 seconds then removed for 15 seconds for a total of five times. The flame-retardant properties of the trace heater or surface heater shall be such that the exterior surface will neither support combustion for more than 60 s after five 15 s applications of a standard test flame (the period between applications of the flame being 15 s) nor convey flame either during or after the five applications of the test flame, and no cotton of the optional underlaying cotton layer igniting. A test sample shall be considered to have conveyed flame if more than 25% of the extended portion of the indicator is burned.

In the vertical flame test conducted with the heat shrink kit304and end cap300, the results of which are shown inFIG. 4, the flame was applied directly at the end cap300in order to test the effectiveness of the end cap300. The sample including the end cap300, heat shrink kit304, and cables310were determined to pass the vertical flame test according to the above criteria.

FIGS. 5-12illustrate another embodiment of an end cap500for the present splice kit, which is prismatic instead of cylindrical. With equivalent composition, length, and wall thicknesses, the prismatic end cap500has demonstrated superior impact stresses to the cylindrical end cap400mostly at cold impact testing. The end cap500can be made from a flame retardant material such as unfilled or glass filled polyphenylene sulfide (PPS) or polyetherimide (PEI) as described above. The end cap500may have a tubing portion502attached to or integral with an end portion504. An outer surface of the tubing portion502may define a series of projections510and/or grooves512; that is, in some embodiments, grooves512may be formed into the outer surface, creating projections410therebetween, or projections410may be attached to or integral with the tubing portion502and project away from the outer surface. The projections510and/or grooves512, or a combination thereof, provide a friction fit with the heat shrink tubing, in the manner described above with respect to the ribs410of the end cap400ofFIGS. 2A-B. Thus, projections510or grooves512can in some embodiments extend entirely or substantially around the perimeter of the outer surface; in other embodiments, as depicted, the projections510can be “teeth” formed along one, some, or all of the edges between the top, sides, and bottom of the tubing portion502. When the heat shrink tubing is shrunk, the projections510and grooves512allow the heat shrink tubing to be better coupled to the end cap500, preventing the end cap500from being moved out of place when the spliced cable(s) is/are installed or reinstalled. Additionally, the projections510and grooves512may allow a heat shrink tubing without an adhesive lining to be used in the heat shrink kit by providing a friction fit with the heat shrink tubing and thus retaining the heat shrink tubing.

An end506of the tubing portion502opposite the end portion504defines an aperture to the interior space508of the end cap500. In some embodiments, the interior space508can have a shape and volume defined by an inner surface520of the tubing portion502and a rear surface542of the end portion504. The tubing portion502may be inserted into a heat shrink tubing, and/or may be disposed over a wire splice or cable termination and then the heat shrink tubing pulled over the end cap500, such that at least a portion of the tubing portion502is in contact with an inner surface of the heat shrink tubing and the spliced or terminated conductors are inside the interior space508. The end portion504, having a front surface540facing outward from the cable(s), may prevent a flame applied during a flammability test from reaching an adhesive of the heat shrink tubing and thereby provide flammability protection for the heat shrink tubing, as well as all other components of the cables that would be exposed at the splice.

Referring toFIGS. 7-10, the tubing portion502can be sized to fit inside heat shrink tubing (i.e., as shown inFIGS. 3 and 15). Specifically, the tubing portion502can be sized along a minor width700(FIG. 7) and a major width900(FIG. 9) to allow tubing portion502to fit inside the heat shrink tubing before shrinking. Further, the interior space508can be sized to allow one or more components of a cable and/or heat shrink kit to fit inside the tubing portion502. The interior space508can have a uniform width along its length, or the interior space508can taper along the interior surface520of any or all of the top, bottom, left side, and right side of the tubing portion502. For example, as shown in the rear view ofFIG. 9and the cross-sections ofFIGS. 11 and 12, both the major width and the minor width of the interior space508can taper from maximum widths910,920at or approximate (i.e., when a lip of the aperture is rounded as illustrated) the end506of the tubing portion502, to minimum widths912,914at or approximate the rear surface542of the end portion504.

The end portion504may have a minor width710and a major width810that are both larger than the corresponding outer widths of the tubing portion502. Furthermore, the widths710,810may be larger than the diameter of the heat shrink tubing after the heat shrink tubing is stretched and/or shrunk over the tubing portion. In this arrangement, the end cap500can prevent at least a portion of a flame applied during a vertical flame test from reaching an adhesive or an inner surface of the heat shrink tubing, prevent at least a portion of the adhesive from igniting, and allow the heat shrink kit to pass the flammability test.

FIGS. 13-15show the steps of installing the heat shrink assembly of the present splice kit on the tee connection splice of three cables16, prepared as described and illustrated inFIGS. 1A-D. Referring toFIG. 13, an end cap130, which can be the end cap400, or the end cap500as illustrated, or another end cap in accordance with this disclosure, is fitted over the spliced conductors (i.e., by inserting the mechanical connectors12into the interior space508). Optionally, one or more adhesive layers132,134can then be applied. For example, a proximal mastic layer132can be wrapped over the interface between the end cap130and the cables16(i.e., over the pinched ends of the mastic layers30and over the distal end of the tubing portion136, sealing the interface against liquid, fire, and smoke ingress. A distal mastic layer134can also be applied, over any part of the cables16that have been modified for the splice and remain exposed (e.g., the insulation18and drain layers22at the stripped end of the jacket20).

Referring toFIGS. 14 and 15, a heat shrink tubing140is then pulled over the splice, either from the distal (unspliced) ends of the cables16, or over an end portion138of the end cap130; once the tubing140is in place, heat is applied to the heat shrink tubing140to shrink the heat shrink tubing140against the cables16and the other components of the splice kit, completing the splice. In accordance with some embodiments, the heat shrink tubing should be chosen based on an appropriate minimum expanded inside diameter and a maximum recovered (i.e. shrunk) inside diameter after a shrinking process. An appropriate heat shrink tubing can be chosen by selecting a heat shrink tubing which fits a kit dimension (i.e. fits around and/or over a heat shrink kit) before a shrinking process and nearly fully recovers after the shrinking process. If a heat shrink tubing does not nearly fully recover, it may shrink further and potentially split during the flammability testing. To reduce likelihood of splitting during the test, the maximum recovered inside diameter of the heat shrink tubing can be selected to be approximately equal to or slightly smaller than the outer diameter or equivalent outer diameter (i.e perimeter divided by pi). For example, a heat shrink tubing with a high shrink ratio and a recovered inner diameter significantly smaller than the perimeter of the tubing portion132may burst during flammability testing as the heat shrink tubing may further contract around the end cap130and potentially rupture.