CZ20012244A3 - Cable system intended for use in hazardous environment - Google Patents

Abstract

A method of forming a seal between a tubular cable outlet projecting from a joint enclosure (1) and a cable (21) passing through the cable outlet into the enclosure (1) in which a heat-recoverable sleeve (11) is shrunk around the cable (21) and the cable outlet (7, 8, 9); an electrically conductive, guard sleeve (13) is placed around the heat-recoverable sleeve (11) so that it substantially surrounds it and extends beyond each of its ends. The cable (21) sealed to the joint enclosure (1) can be used within a zone 1 hazardous environment, for example in a sewer. The guard sleeve (13) is preferably of stainless steel, so as to resist attack by rodents as well as enabling the joint enclosure (1) to meet zone-1 explosion-resistance requirements when the cable includes power supply conductors, for instance for powering electronic communication equipment within the enclosure (1).

Description

The present invention relates to a cable system for use in hazardous environments. In particular, the present invention is directed to a method of forming a seal between a cable and a junction box outlet for use in a hazardous environment and to forming a sealed joint in a hazardous environment.

BACKGROUND OF THE INVENTION

Hazardous environment means areas in which the atmosphere can become explosive. An explosive atmosphere is defined as a mixture of flammable substances in the form of gases, vapors or mixtures with air attaining critical atmospheric proportions of these mixtures under atmospheric conditions, as a result of which high temperatures, electrical shorts or sparks can cause an explosion. According to “Elex V, DIN VDE 0165-1991”, hazardous areas are classified into zones according to the probability of occurrence of hazardous air showing a tendency to explosion. The present invention is directed to use in a so-called hazardous area zone. According to ”Elex V, DIN VDA 0165-1991”, Zone 1 ”of an explosive atmosphere is a zone in which the explosive mixture may be present under normal operating conditions. Examples of Zone 1 ”hazardous areas include sewers, petrochemical production and processing plants, and pumping stations.

In connection with the existing sewer infrastructure, it has previously been proposed to use these walkways for routing cables such as communication cables or power lines. As mentioned in the previous paragraph, the sewer environment is classified as zone 1 ”of the hazardous environment. General items intended for use in Zone 1 "hazardous areas shall comply with the requirements of European Standard EN 50014: 1997". Specifically, it is important for any articles intended for use in such an environment that, under normal conditions of use, maintenance and cleaning, there is no risk of ignition and subsequent ignition due to electrostatic discharges, thereby averting the risk of potential explosions.

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The objects to be said should also be designed so that the maximum surface temperature does not exceed the specified temperature, which is the ignition temperature of the gases, liquids or solids present. The value of the specified maximum temperature depends on the exact nature of the environment, and this temperature is in the range of 85 ° C to 450 ° C for the "Zone 1" hazardous area. In addition, items used in Zone 1 ”hazardous areas shall be UV resistant, chemically inert and resistant to bending, even when the temperature is above the maximum specified temperature, which usually corresponds to the ignition temperature of gases, liquids or solids present in the environment. Especially if the "zone 1" is a hazardous central sewer system, any item used in such an environment must be resistant to rodent attacks.

Cables that are currently known include fiber optic or copper core cables, both of which are used for communication purposes, power distribution, and also composite cables containing both optical fibers and copper conductors. Regardless of the cable system, it can be stated that a commonly used network system comprises junction boxes that are installed at different points in the network. These junction boxes comprise means for connecting, terminating, interrupting, cable branching, etc., which are used in application of the methods and are well known to the skilled person in the art. If the intention is to place the cable network within an existing distribution system, it is generally assumed that easy access to the cable junction boxes is provided. For example, if cable networks are to be distributed in an existing collecting system, the junction boxes are usually placed immediately below the manhole manhole covers for ease of access. Where cable systems are to be introduced into "zone 1" of hazardous environments such as sewers, protection against aggressive conditions shall be ensured not only for the cable sheath and the outer surface of the junction box, but also for each junction point where the cable enters some junction box.

SUMMARY OF THE INVENTION

In order to achieve the above requirements, we have invented a sealing method and sealing system for use in hazardous environments.

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In accordance with a first feature of the present invention, there is provided a method of forming a seal between a cable outlet in the form of a tube protruding from a junction box and a cable passing through the cable outlet into a box, the method comprising the steps of: (i) positioning the thermoformable sleeve around and heating the housing such that one portion of the sleeve is conformably formed into a sealing fit with the outlet and another portion into a sealing fit with the cable; and (ii) positioning the electrically conductive protective sleeve around the thermoformable sleeve so as to generally surround the thermoformable sleeve and extend over each end of the thermoformable sleeve so that the junction box with such sealed cable can be used in "zone 1" hazardous environment .

Steps (i) and (ii) are typically performed outside the hazardous environment, and the method comprises the additional step of (iii) placing the junction box in the hazardous environment together with a cable that is sealed on the cable outlet of said junction box and protected by a protective sleeve. One type of hazardous environment is the collecting system. Throughout this patent specification, attention will be focused on the operation of cable networks in the sewer system. However, it is perfectly understood that the content of this patent specification is equally applicable to any other kind of "zone 1" hazardous environment.

In accordance with a second feature of the present invention, a sealed cable system is provided that is installed in a "zone 1" hazardous environment (preferably in a sewer system), and the cable system comprises (i) a cable junction box from which a cable outlet projects; (ii) a cable passing through the cable outlet to the junction box; (iii) a thermoformable sleeve that is shaped such that a portion of the sleeve conforms to a sealing fit with the cable outlet and the other portion of the sleeve conforms to a sealing fit with the cable; and (iv) an electrically conductive protective sleeve that is positioned around the thermoformable sleeve so as to generally surround said thermoformable sleeve and extend over each end of the thermoformable sleeve.

Both the sealing method and the sealed cable system of the present invention include the use of a thermoformable sleeve. Thermoformable sleeves are well known in the art, and are sleeves that change in size due to heat. It is usually preferred, and in this case also for the purposes of the present invention, that the thermoformable reel shrinks radially under the effect of heat. In accordance with the preferred method of the present invention, the heat evolves in accordance with the present invention in accordance with the present invention. using a hot air gun. An alternative heat source may be a burner. The thermoformable sleeves may be randomly made of polymeric materials such as a crosslinked polyolefin material, in particular crosslinked polyethylene. The cheapest heat-forming sleeves that are commercially available exhibit mostly electrically insulating properties. Typically, heat-insulating sleeves are used in the present invention to isolate electricity but to use electrically conductive sleeves.

It is preferred that the heat-forming sleeves used in the present invention are coated with an adhesive to improve their sealing ability. The sleeves are preferably coated with hot melt adhesive during hot forming of the sleeve. Thermoformable sleeves that are coated with an adhesive are known in the art.

Although the thermoformable sleeve is surrounded by a protective sleeve, gases and liquids may enter the space between the thermoformable sleeve and the protective sleeve. For example, in a sewer system, the cable system may be wholly or partially immersed in contaminated water and / or exposed to gases such as methane flown in the sewer causing corrosion. Therefore, the material of the thermoformable sleeve and its adhesive coating is preferably selected such that the material is chemically inert in relation to the corrosive effects occurring in the collecting system, such as the corrosive effect of contaminated water or corrosive gases occurring in the collecting system. The material for the thermoformable material is also preferably ultraviolet (UV) resistant. A particularly preferred material for making the thermoformable sleeves is crosslinked polyolefin, especially crosslinked polyethylene, most preferably medium or high density crosslinked polyethylene, or mixtures thereof.

It is necessary for the thermoformable sleeves to conform conformably to a sealing fit with the cable outlet and to the outer surface of the cable over a range of a certain length, preferably at least 75 mm, more preferably at least 100 mm, and particularly preferably at least 150 mm, to create a reliable seal. For example, in a sewer system, this length provides assurance that contaminated water or gases will not enter the junction box through the space between the cable and the cable outlet.

The method of sealing and the sealed cable system of the present invention comprises the use of an electrically conductive, protective sleeve. The protective sleeve is preferably electrically conductive to such an extent that its insulating electrical resistance does not exceed 1 Gohm at (23 ± 2) ° C and (50 ± 5)% relative humidity as measured according to European Standard 23.4.7,8. EN 500014: 1997. It is preferred that the protective sleeve comprises metal. A particularly preferred metal is steel, especially stainless steel. Other metals useful in this regard include aluminum, cast iron, galvanized steel, bronze and brass. A polymer material with adequate electrical conductivity can be used as a metal substitute.

The electrically conductive protective sleeve of the present invention is configured to generally surround the thermoformable sleeve and extend over both ends of the thermoformable sleeve. This technical measure makes sense in that it is practically impossible to accumulate electrostatic charges on the insulating surface of the thermoformable sleeve, since the sleeve is surrounded by a mass of conductive material.

The protective sleeve as a whole may continuously surround the thermoformable sleeve. In one embodiment, the protective sleeve is in the form of a generally continuous, cylindrical part, which can be made, for example, by casting metal into molds or made from rolled flat metal. In another embodiment, the protective sleeve may have an open structure, such as a metal mesh. Both the continuous and open structure of the protective sleeve will perform its basic function, which prevents the build-up of electrostatic charge on the insulating surface of the heat-moldable sleeve.

The protective sleeve is advantageously resistant to bending, even at elevated temperatures, in particular at temperatures above 85 ° C. This advantageous property of the protective sleeve protects the thermoformable sleeve surrounding the protective sleeve from damage from an object that pushes the sleeve in a hazardous environment. The preferred polyolefin hot-melt sleeve would typically soften at temperatures of about 85 ° C, and therefore, in the absence of a substantially stiffer protective sleeve that surrounds the hot-melt sleeve, it would be damaged by the pressure of the abutting article.

When the present invention is used in a sewer system, account should be taken of the requirement of sufficient strength of the protective sleeve, which must be resistant to rodent attacks. In this connection, it is noted that a continuous cast steel cylinder sleeve having a thickness of 2 mm or a flat stainless steel rolled part in the form of a continuous cylinder

-6 having a thickness of 1 mm, should meet such requirements. Preferably, the protective sleeve has a thickness of at least 0.4 mm.

The protective sleeve is generally tubular. Its cross-section may be continuously closed or non-closed, which means that it may consist of two partial shells which are held together under operating conditions. These parts can be mechanically or otherwise held together, or they can simply be placed in a mutual or non-sequential relationship.

The protective sleeve material is also selected to be chemically non-flowable and to exhibit UV resistance. Most metals meet these requirements. Stainless steel is particularly preferred. Cast iron, galvanized steel, aluminum and brass can also be used.

The combination of a thermoformable (preferably polymer) sleeve with a substantially stiffer, conductive protective sleeve thus creates a good UV-resistant and chemical-resistant seal between the cable outlet and the cable (using the formable sleeve means) while providing assurance that the system is impossible accumulation of static charge and subsequent explosions, prevents the destructive activity of rodents and protects against damage from leaning objects (based on the function of protective sleeve devices). Thus, the thermoformable sleeve and the protective sleeve cooperate to form an effective system in the "zone 1" hazardous environment.

The cable used in the sealing method and the sealed system according to the present invention may carry optical fibers or electrical conductors (e.g. copper), optionally both optical fibers and electrical conductors. In one embodiment of the present invention, the cable carries optical fibers and electrical wires to power so-called "active electronics" within the junction box. Electrical wires can power directional connection fields of telephone networks or similar devices located in junction boxes.

The junction box as a whole is typically in the form of a closed box with one or more tubular outlets that protrude and serve to introduce cables into its interior. The box may include a base body and a lid that may be detached to provide access to the connection area within the box for making connections within the network. The tubular cable entry outlets may have different shapes in cross-section, but usually these cross-sectional shapes are generally circular or oval. It is typical that the outlets that • • · · · · φ • • • φ φ φ φ φ φ φ φ φ φ φ φ φ φ φ φ φ ··

Having a circular cross-sectional shape, individual cables are introduced, while the outlets having an oval cross-sectional shape receive a cable loop which is intended to take a branch.

The junction box will generally comprise directional junction boxes of telephone networks, optical fiber binder boxes, electronic printed links, etc., depending on the purpose of the cables to be connected and the associated necessary connections within the junction box.

In the foregoing, the sealing method steps and features of the sealed system have been described with particular reference to forming a seal between the cable and the cable outlet into which the cable is introduced. However, if the cable is damaged somewhere along the cable at some distance from the cable to the junction box, gases, water, or other liquids may leak through unfilled cables (either fiber optic cables or electrical cables) into the junction box. The above-described seal between the outside of the cable and the cable outlet cannot prevent these fluids from penetrating through the inside of the cable itself. Therefore, a preferred embodiment of the sealing method according to the present invention further comprises sealing the inside of the cable, which can be considered as an additional technical measure to form a seal between the tubular cable outlet and the cable. The step of sealing the interior of the cable is preferably performed by pouring the ptyskyrice into the interior of the cable. The resin is preferably poured into the cable at the bottom of the cable and cable outlet after the forming step of the thermoformable lead. If a plurality of cable outlets protrude from the splice box, for example from the splice box lid, the cable sealing step is accomplished by simply pouring the resin mass into the splice box lid. The required amount of resin flows into the cable and some amount of resin enters the annular space between the cable and the cable outlet. Due to the fact that the resin is poured after the thermoforming sleeves have been previously formed, no resin will escape from the cable and the box. In general, the resin pouring step is performed before the cable is split into individual strands for the purpose of forming joints in the junction box. A useful resin is a two-component, curable, polyurethane or epoxy resin.

As mentioned above, the surrounding mass of electrically conductive material around the thermoformable sleeve substantially prevents the build-up of static electricity on the surface of the thermoformable sleeve. The outer surface of the main cable guide length in a hazardous environment, such as the cable length in the range of the sewer pipe, is generally made of polymeric material. This outer surface of the cable protects • 9 9 9 9 9 9 9 9 9 9 9

-8 before accumulating a static charge so that it connects to zero electrical potential at regular distances. For the purpose of attaching the cable to the inner surface of the drain pipe, for example, clips may be used which are placed every two meters. The junction box itself is made of metal or other conductive parts as a whole so that static electricity cannot accumulate on the junction box itself.

Overview of the drawings

Reference will now be made to exemplary embodiments of the present invention with reference to the accompanying drawings, in which:

Fig. 1 is a perspective view of a cable splice box from which a plurality of tubular cable outlets protrudes, and of thermoformable sleeves and protective sleeves designed to form seals on the cable outlets;

Fig. 2 is a cross-sectional view showing one of the thermoformable sleeves and the corresponding protective sleeve sealed to one of the cable outlets of Fig. 1.

DETAILED DESCRIPTION OF THE INVENTION

Giant. 1 shows a stainless steel junction box 1 comprising a fiber optic binder box and electronic printed circuit boards (not shown). The metal box 1 has a metal body part 3 and a lid 5 that can be detached to provide access to the interior of the box when making connections and the like. Six cable outlets 7, 8 having a generally circular cross-sectional shape and one cable outlet 9 having an overall oval cross-sectional shape protrude from the cover 5 of the cable junction box 1. Some outlets 7 having a circular cross-sectional shape and oval terminal 9 are free for cable entry. Other round outlets 8 are sealed. They can be removed during service life for the purpose of making the required changes within the cable network. Typically, each outlet protrudes to a distance of approximately 300 mm.

For the purpose of sealing each cable outlet 7, 9, adhesive-coated, heat-shrinkable polyethylene sleeves 11 are provided with appropriate dimensions. These sleeves have

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9 9 9

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9 before being heated some play around the terminals 7, 9. The reels 11 are in the form of tubes with a closed cross-sectional shape which are threaded to the end of the cable before the cable is introduced into the respective cable outlet 7. The heat-shrinkable polymer reels 11 are typically 350 mm. For the purpose of covering the shrinkable sleeves 11, the corresponding protective sleeves 13 and 15 are formed of stainless steel. These protective sleeves 13, 15 are tubular and longer than the shrink sleeves 11. The protective sleeve 15 for the cable outlet 9, whose cross section is oval, has an open cross-sectional shape and consists of two shell halves of the same shape and function. The protective sleeve 13 for the cable outlet 7 having the cross-sectional shape has a generally closed cross-sectional shape. The closed cross-sectional protective sleeve 13 must be threaded onto the end of the cable 21 before it is introduced into the respective cable outlet 7. The open cross-sectional protective sleeve 15 may be placed on the sealed assembly at a later time.

Each protective sleeve 13, 15 has a wider end 19 that is closest to the junction box 1, while the narrower end 17 is spaced from the junction box 1 depending on the length of the protective sleeve 13, 15 itself.

According to the sealing method of the present invention, the heat-shrink sleeve 11 and protective sleeve 13 are threaded onto the end of the cable 21, and then the cable 21 is inserted into a cable outlet 7 protruding from the lid 5 of the junction box. adaptively shrinking this reel 11 to conform to the outlet 7 over a length of about 150 mm and the outer sheath of the cable over a length of about 150 mm. Giant. 2 shows the seal structure after shrinking of the reel 11 and the placement of the stainless steel protective sleeve 13.

After shrinking the reel 11 on the cable outlets 7 and 9, the lid is turned (so that the cable outlets protrude downward from the lid 5) and a thermosetting resin (not shown) is poured into the lid to flow into the cables 21 and into the circular spaces between cable 21 and reels Π. The fact that this thermosetting material seals the reel on each cable outlet makes it impossible for it to penetrate into its own junction box. The resin cools and solidifies and ultimately prevents the penetration of any gases that can cause corrosion in such cases where they would enter damaged cables along the length of their conduit and enter the junction box through the cables.

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The next step concerns splitting the cables 21 into strands for connection inside the junction box 1.

Placing the reels 11 and sleeves 13, 15 and splitting the cables into the strands, as well as the interconnecting work inside the junction box, are performed outside the sewer using access to the sewer through the inlet shaft. Then, the assembled system with the sleeves 11 and sleeves 13, 15 installed is introduced into the sewer. The junction box 1 connects to zero electrical potential and the stainless steel protective sleeve 13, which generally surrounds the polymer sleeve 11, provides assurance that no static electricity will accumulate on the insulating surface of the sleeve 11. The protective sleeves 13, 15 also protect the sleeves 11 from damage caused by rodent attacks and, in addition, protect the sleeves 11, which soften when the shape changes, from damage to the objects that support the formed seal. The sleeve 11 itself provides a fluid-tight seal that prevents the penetration of liquids or gases between the outer surface of the cable and the cable outlet into which the cable is introduced.

Claims (18)

CLAIMS 1. A method of forming a seal between a tubular cable outlet extending from a junction box and a cable extending therethrough into a box, comprising the steps of (i) placing a thermoformable sleeve around the cable and cable outlet and heating the housing so that one part the sleeves conformably matched to the outlet and the other portion of the sleeve matched to the cable; and (ii) positioning the electrically conductive protective sleeve around the thermoformable sleeve such that the protective sleeve generally surrounds the thermoformable sleeve and extends over each end of the thermoformable sleeve; thus, the junction box with the cable sealed in this way can be used in the "zone 1" hazardous area. A method of forming a seal according to claim 1, wherein steps (i) and (ii) are carried out outside the zone 1 ^K hazardous environment system and that the method comprises the additional step (iii) of placing the cable junction box in the "zone 1". “Of a hazardous environment together with a cable which is sealed on the cable outlet of said junction box and protected with a protective sleeve. Method of forming a seal according to claim 1 or 2, characterized in that the "zone 1" of the hazardous environment is a collecting system. Method of forming a seal according to any one of claims 1 to 3, characterized in that the heat-forming sleeve is a heat-shrinkable polymeric sleeve, which is preferably coated with an adhesive. A method of forming a seal according to claim 4, wherein the heat-shrinkable reel has an electrically insulating surface. Method of forming a seal according to any one of the preceding claims, characterized in that the protective sleeve is made of metal. • 9 · 9 · 9 9 9 9 ♦ 9 • * 9999 999 A method of forming a seal according to any one of claims 1 to 6, characterized in that the protective sleeve is made of stainless steel. A method of forming a seal according to any one of claims 1 to 7, wherein the protective sleeve has a continuous outer surface. A method of forming a seal according to any one of claims 1 to 7, wherein the protective sleeve is made of mesh. A method of forming a seal according to any one of claims 1 to 9, wherein the protective sleeve is made of steel having a thickness of at least 0.4 mm. A method of forming a seal according to any one of the preceding claims, characterized in that it comprises the step of sealing the interior of the cable by pouring resin into the cable. A method of forming a seal according to claim 11, wherein the junction box comprises a lid from which a plurality of cable outlets protrudes, the method comprising the step of adjusting the lid to the position where the cable outlets are pointing downward and pouring resin into the lid so that the resin flows into the cables. 13. A sealed cable system that is installed in a " zone 1 " hazardous environment, comprising (i) a cable junction box from which a cable outlet extends; (ii) a cable passing through the cable outlet to the junction box; (iii) a thermoformable sleeve that is shaped such that one portion of the sleeve is conformably formed into a sealing fit with the cable outlet and another portion into a sealing fit with the cable; and (iv) an electrically conductive protective sleeve, which is disposed around the thermoformable sleeve so as to generally surround said thermoformable sleeve and extend over each end of the thermoformable sleeve. • · • • • ·· « • • • · * • · • Φ • • »» • • • • • • • • ··· ·· · * ·· ·· ♦ ·· 14. The sealed cable system of claim 13 wherein said hazardous environment is a sewer system. A sealed cable system according to claim 13 or 14, characterized in that the cable comprises optical fibers. A sealed cable system according to claim 13, 14 or 15, characterized in that the cable comprises or additionally comprises electrical conductors. A method of forming a seal between a tubular cable outlet that extends from a junction box and a cable that extends through a cable outlet to a junction box generally as described with reference to the illustration. 18. Cable system in general as described with reference to the drawings.