WO2011037445A1

WO2011037445A1 - A method of extracting a cable from a sheath

Info

Publication number: WO2011037445A1
Application number: PCT/MY2009/000220
Authority: WO
Inventors: Boon Keat Chong; Choi Hee
Original assignee: Inno-X Sdn Bhd
Priority date: 2009-09-28
Filing date: 2009-12-30
Publication date: 2011-03-31

Abstract

A method of extracting cable cores (104) from an outer cable sheath (101) that the cable cores (104) are soaked within matrix of greasy material (105) enclosed by an inner cable sheath (.103) followed by an intermediate cable sheath (102) and the outer cable sheath (101) comprises the steps of liquefying greasy material (105) partially or completely contained within the inner cable sheath (103); or dissolving greasy material by. injecting a solvent into the inner cable sheath (103); and pulling at least fraction of the cable cores (104) at one end from the inner cable sheath (103) to remove the cable cores (104), wherein each of the cable cores (104) enclosing a metal wire. A method of removing. cable cores (104) from an outer cable sheath (101) wherein the cables are free of greasy material within the inner cable sheath (103) is also disclosed. The removal comprises the steps of injecting a flowable medium into the inner cable sheath (103) to reduce friction in between the cable cores (104) and the inner cable sheath (103) as well as among the cable cores (104); and pulling at least fraction of the cable cores (104) at one end from the inner cable sheath (103) to remove the cable cores (104).

Description

A METHOD OF EXTRACTING A CABLE FROM A SHEATH

FIELD OF INVENTION

The present invention relates to a method of extracting or replacing cable cores enclosed within a cable sheath. In more specific, the present invention discloses an effective way to extract old underground cables, without the need to conduct much earth work to unearth the cables either direct buried underground, installed in an underground cable ducting or installed in a utility ducting within a building, yet the disclosed method allow replacement of the old cables with new? one.

BACKGROUND OF THE INVENTION

Rapid development in the field of computing and telecommunication has tremendously enhanced the rate of data transmission over the telecommunication line. However, copper-made cables still constitute majority of the telecommunication line laid underground at present that these cables have shown limited capability in high rate data transmission. Therefore, continuous effort has been dedicated to replace these old copper cables with much efficient fiber cable network. Conventional approach to completely unearth the old cables requires the ground to be excavated in order to remove the old buried copper cable, followed by substituting with new fiber cables not only costly but also time-consuming that such approach can be considered less efficient. In addition to the high costs, the work requires complex planning, permission from local authorities & is disruptive to traffic. Consequently, various approaches have been disclosed along these years to improve the operation of cable replacement. Eichenseher et al. discloses a method to recover the metal conductor from a telecommunication cable laid in earth. According to their method, the earth is excavated at spaced intervals of 20 to 50 meters to expose the cable then at least one end of the exposed cable is severed to reveal the metal conductor which later is subjected to pulling force to be retrieved from the cable sheath. Since there is no lubrication supplied and the friction in between the cable sheath and the conductor is high resulting the resistance to the relative movement increases, the claimed method only able to recover conductor of length not exceed 50 meters.

Another method to remove the conductor from the cable sheath is provided in the United States patent application no. 4197628. The claimed method attaches a sleeve at one end of the unearthed cable to introduce a lubricant into the cable sheath to establish sufficient amount of lubricant between the cable sheath and the conductor then subsequently withdraws the conductor at one end in the presence of the lubricants. Method of similar principle is further modified in another United States patent application no. 20041 17964 which claims a method specifically providing a fiowable medium into the annular space in between the inner envelop and the outer cable sheath for lubrication prior to withdrawing the conductor. However, these mentioned methods are not feasible for cables packed with grease or greasy material to avoid seepage of ground water into the cable. Further, underground cables may tend to be perforated under long term pressure and the lubricant introduced probably leak out from the perforated area that sufficient lubrication may not be able to achieve.

International patent application no. WO82/00388 also describes different approach can be used for replacing new conductors into cable sheath of existing cables. The claimed method aims to rid off electric insulating material such as polypropylene washer or papers presented in the co-axial cable sheath to free up the space for removing and replacing the existing conductor in the cables. The method provided in this application is expensive and time consuming and not useful for grease-filled cables too.

SUMMARY OF THE INVENTION

The present invention aims to provide a method of extracting cable cores from cable sheath of a fully grease-filled cable, or semi grease-filled or non grease-filled which is particularly buried underground or installed in an underground ducting. Specifically, the grease or greasy material contained within the cable is liquefied to serve as lubricant that ease withdrawal of the cable cores away from the cable sheath. Further object of the present invention is to offer an effective yet inexpensive method to replace cable cores of. an underground cable with a new high speed data transmission cable such as cable made of fiber optic, while the existing cable cores are being withdrawn.

At least one of the preceding objects is met, in whole or in part, by the present invention, in which one of the embodiments of the present invention includes a method of extracting cable cores from an outer cable sheath that the cable cores are soaked within matrix of greasy material enclosed by an inner cable sheath followed by an intermediate cable sheath and the outer cable sheath comprising the steps of liquefying greasy material partially or completely contained within the inner cable sheath; and pulling at least fraction of the cable cores at one end from the inner cable sheath to remove the cable cores, wherein each of the cable cores enclosing a metal wire.

Further aspect of the disclosed method comprises the step of fixing a replacement cable at another end of the cable cores prior to the pulling step, wherein the replacement cable is threaded through the inner cable sheath when the cable cores are being pulled. Accordingly, the disclosed method may have to expose partial of the cable cores at one end prior to the pulling.

To liquefy the greasy material, heat may be supplied through applying electric current or electrical potential to the wires to generate sufficient heat energy to melt the surrounding greasy material. Another embodiment to liquefy the greasy material includes the step of passing heated air and steam through the inner cable sheath to melt the greasy material. Preferably, the greasy material is none other than the filling composition specified in fully-filled telecommunication cables which similar to a gel or jelly composition made of Microcrystalline wax, paraffin wax, bees wax, mineral oil, polyethylene or any others chemical elements as stated in their respective formula. Another major embodiment involves a method of removing cable cores from an outer cable sheath that the cable cores are soaked within matrix of greasy material enclosed by an inner cable sheath followed by an intermediate cable sheath and the outer cable sheath comprising the steps of dissolving greasy material partially or completely contained within the inner cable sheath by injecting a solvent into the inner core; and pulling at least fraction of the cable cores at one end from the inner cable sheath to remove the cable cores, wherein each of the cable cores enclosing a metal wire. Likewise, a replacement cable is preferably fixed at another end of the cable cores prior to the pulling step, wherein the replacement cable is threaded through the inner cable sheath when the cable cores are being pulled. Preferably, the solvent is any one or combination of hexane, pentane, chloroform, benzene, xylene, diethyl ether, ethanol, methyl isobutyl ketone or polar or non polar solvent with proper amount of surfactant. Another major aspect of the present invention includes a method of removing cable cores from an outer cable sheath that the cable cores enclosed by an inner cable sheath followed by an intermediate cable sheath and the outer cable sheath comprising the steps of injecting a flowable medium into the inner cable sheath to reduce friction in between the cable cores and the inner cable sheath as well as among the cable cores: and pulling at least fraction of the cable cores at one end from the inner cable sheath to remove the cable cores, wherein each of the cable cores enclosing a metal wire.

In further aspect, the disclosed method also further comprises the step of detecting availability of perforated area along the inner cable sheath, intermediate cable sheath and/or outer cable sheath to avoid leakage of the injected flowable medium. Positive air pressure may be applied into the inner cable sheath at one end and the air pressure is measured at another end to ascertain presence perforated area.

Likewise, the flowable medium is a lubricant made of palm oil & its by-products. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a cross-sectional view of the cables with an outer cable sheath, an intermediate sheath, an inner sheath and a plurality of cable cores; and

Figure 2 shows the basic equipment set up for carrying out one embodiment of the disclosed method.

DETAILED DESCRIPTION OF THE INVENTION

The present invention consists of certain novel features and a combination of parts hereinafter fully described and illustrated in the accompanying drawings and particularly pointed out in the appended claims; it being understood that various changes in the details may be without departing from the scope of the invention or sacrificing any of the advantages of the present invention.

The cable mentioned hereinafter preferably refers to conventional telecommunication cables as illustrated in figure 1. The cables (100) mainly composed of an outer cable sheath (101) made of PVC or polyethylene, an intermediate sheath or screen (102) made of metal, inner sheath (103) which is oil soaked paper and cable cores (104) which are insulated copper or ferrous wires. Within the inner sheath (103), grease or greasy material (105) normally covers the void among the cable cores (104) to prevent seepage of water into the cable cores (104) if the cable sheaths are broken.

In accordance with the preferred embodiment, the present invention includes a method of removing cable cores (104) from an outer cable sheath (101) that the cable cores (104) are soaked within matrix of greasy material (105) enclosed by an inner cable sheath (103) followed by an intermediate cable sheath (102) and the outer cable sheath (101) comprising the steps of liquefying greasy material (105) partially or completely contained within the inner cable sheath (103); and pulling at least fraction of the cable cores (104) at one end from the inner cable sheath (103) to remove the cable cores, wherein each of the cable cores (104) enclosing a metal wire. Furthermore, , as illustrated in Figure 2, the disclosed method may include a step of fixing a replacement cable (11 1) at another end of the cable cores (104) prior to the pulling step, wherein the replacement cable (111) is threaded through the inner cable sheath (103) when the cable cores (104) are being pulled. Through the disclosed method, the existing cable cores (104) within the cable sheath can be easily replaced without the need to conduct much strenuous earth work to recover the whole cable (100). In more specific, the greasy material (105) is melted to serve as a lubricant to reduce friction in between the cable cores (104) and the internal wall surface of the inner sheath (103). Thus, the cable cores (104) can be easily withdrawn out from the cable sheath. Though greater tensile or pulling force can be employed to withdraw the cable cores (104) without melting the greasy material (105) to serve as lubricant, greater tensile force tends to break the cable cores (104) inside the cable sheath especially in the case where the length to be pulled out is long and generating greater friction within. Moreover, presence of the liquefied greasy material (105) also permits the new cables (111) to be smoothly slid into the hollow space left after the cable cores is withdrawn. Without the presence of the liquefied greasy material (105), it is almost infeasible at all to slide in the new cables (111) when considerable length of new cables to be inserted. The cable sheath remained is used to house the new cables (1 1 1). In the preferred embodiment a mechanical clamp (113a) may be used to cor ect the cable cores (104) and the replacement cable (111) together at on end as illustrated in figure 2. To liquefy the greasy material (105). various approaches can be used to attain the similar result. For example, in one embodiment, an electrical potential or current is applied onto the copper wires to generate heat energy through an electrical circuit (1 14) due to electricity resistance in the copper or ferrous wires. In turn, the generate energy melts the surrounding greasy material (105). Preferably, the electric current ranges from 1A to 50A and may be varied subjected to the types and length of the cables.

In accordance with another preferred embodiment, the liquefying step involves introducing a draft of heated air or heated steam through a closed loop venting system (1 15) into the inner cable sheath (103) at one end to melt the greasy material. Preferably, the heated air or steam is introduced into the inner cable sheath (103) under pressure that the air draft or steam is preferably brought to a temperature between 50°C and 100°C or may be varied subject to the type of greasy material, in order to effectively melt the greasy material (105). More preferable, a temperature sensor (118) is located at another end to measure temperature of the released steam or heated air to ensure sufficient heat energy is provided. If the temperature of the heated air drops below a pre-determined level at the discharged end. it indicates that the heat energy supplied may not sufficient to melt the greasy material (105) to the extent which rendering a lubricating effect. Consequently, inputting heated air or steam with higher temperature may be needed or the length of the cables to be treated has to be reduced. Preferably, the heated air or steam is directed into the inner cable sheath (103). Apart from that, the heat air or steam also somehow expands the diameter of the cable sheath that the expansion further facilitate withdrawal of the cable cores (104).

Further, the pulling step is performed by mounting a mechanical clamp (113b) onto one end of the cable cores (104) followed by driving the mechanical clamp (1 13b) to pull the cable cores (104) as shown in the equipment set up illustrated in figure 2. In more particular, partial of the cable cores may have to be exposed by ridding off cable sheaths at one end for mounting of the mechanical clamp (113b) prior to applying a tensile force onto the mechanical clamp (113b) at one end for the pulling. The exposed area preferably in 5cm to 30cm in length. Moreover, a small fraction or bundle is pulled out initially to a length of few meter to loosen the cable cores (104) enough followed by pulling the entire cable cores (104) out from the cable sheaths.

Pursuant to another preferred embodiment, the present invention includes also a method of removing cable cores (104) from an outer cable sheath (101) that the cable cores (104) are soaked within matrix of greasy material (105) enclosed by an inner cable sheath (103) followed by an intermediate cable sheath (102) and the outer cable sheath (101) comprising the steps of dissolving greasy material (105) partially or completely contained within the inner cable sheath (103) by injecting a solvent into the inner cable sheath (103); and pulling at least fraction of the cable cores (104) at one end from the inner cable sheath (103) to remove the cable cores (104), wherein each of the cable cores (104) enclosing a metal wire. In this embodiment, a suitable solvent is used to soften or dissolve the greasy material. It is important to be noted that the solvent is injected specifically into the inner cable sheath to partially or completely dissolve the greasy material into a liquid form thereto providing a lubricating effect. A pumping device (1 19) may be used to continuously inject the solvent into the inner cable sheath (103). Without softening or dissolving the greasy material, the greasy material (105) in solid state render great friction within the cable sheath against to the tensile force applied. As setting forth, the length of the cable to be treated ma}' have to be reduced or the cable cores will be broken off. Preferably, the solvent used is any one or combination of hexane, pentane, chloroform, benzene. x}dene, diethyl ether, ethanol, methyl isobutyl ketone or polar or non polar solvent with proper amount of surfactant.

Similarly, the disclosed method of dissolving the greasy material may comprise additional step of fixing a replacement cable (1 1 1) at another end of the cable cores (104) prior to the pulling step, wherein the replacement cable (11 1) is threaded through the inner cable sheath (103) when the cable cores are being pulled, while the cable cores (104) are exposed partially at one end for attachment of the mechanical clamp (113b) prior to the pulling. Preferably, the pulling step is performed through mounting a mechanical clamp (113b) onto one end of the cable cores followed by driving the mechanical clamp to pull the cable cores.

Preferably, the greasy material can be petroleum jelly, or other filling composition made of Microcrystalline wax, paraffin wax, bees wax, mineral oil, polyethylene or any others chemical elements as stated in their respective formula.

Another preferred embodiment of the present invention is a method of removing cable cores (104) from an outer cable sheath (101) that the cable cores (104) enclosed by an inner cable sheath (103) followed by an intermediate cable sheath (102) and the outer cable sheath (101) comprising the steps of injecting a flowable medium into the inner cable sheath (103) to reduce friction in between the cable cores (104) and the inner cable sheath (103) as well as among the cable cores (104); and pulling at least fraction of the cable cores (104) at one end from the inner cable sheath (103) to remove the cable cores (104), wherein each of the cable cores (104) enclosing a metal wire. Particularly, this embodiment is directed to cables free of greasy material (105) within the inner cable sheath. To reduce the friction in between the cable cores and the internal wall of the inner cable sheath, a flowable medium or lubricant is pumped or injected into the inner cable sheath (103). Preferably, the flowable medium is lubricant made of palm oil or its by-product.

In order to avoid leakage of the flowable medium out of the cable sheaths due to presence of perforated area on the cable sheaths, the present invention may further include a step of detecting availability of perforated area along the inner cable sheath (103), intermediate cable sheath (102) and/or outer cable sheath (101). Owing to the fact that high pressure is used to inject the flowable medium, it is very likely the flowable medium leaks out from the perforated area rather than other end of the treated cable. Insufficient lubrication not only leads to breakage of the cable cores that the operation has to be stopped ,but also one may have to perform the earth work to unearth the whole cable for the replacement as the disclosed method is not feasible anymore considering the broken cable cores are stuck within the cable sheath under the ground. In one of the embodiments, the detecting steps can be performed by applying air pressure into the inner cable sheath (103) at one end and measuring the air pressure at another end to ascertain perforated area. For example, if the detected air pressure at another end falls below a pre-determined value, it is possible there are perforated area available on the cable sheath.

Upon injecting sufficient amount of flowable medium into the inner cable sheath, the pulling step is performed through mounting a mechanical clamp (1 13b) onto one end of the cable cores (104) followed by driving the mechanical clamp (113b) to pull the cable cores (104). As in foregoing description, partial of the cable cores (104) is exposed at one end by ridding off the cable sheaths prior to the pulling for mounting of the mechanical clamp (1 13b).

While in the foregoing specification this invention has been described in relation to certain preferred embodiments thereof and many details have been set forth for purpose of illustration, it will be apparent to those skilled in the art that the invention is susceptible to additional embodiments and that certain of the details described herein can be varied considerably without departing from the basic principles of the invention.

Claims

■AIMS

1. A method of extracting cable cores (104) from an outer cable sheath (101) that the cable cores (104) are soaked w thin matrix of greasy material (105) enclosed by an inner cable sheath (103) followed by an intermediate cable sheath (102) and the outer cable sheath (l Ol)comprising the steps of liquefying greasy material (105) partially or completely contained within the inner cable sheath (103); and

pulling at least fraction of the cable cores (104) at one end from the inner cable sheath (103) to remove the cable cores (104), wherein each of the cable cores (104) enclosing a metal wire.

2. A method according to claim 1 further comprising the steps of fixing a replacement cable (1 11) at another end of the cable cores (104) prior to the pulling step, wherein the replacement cable (1 1 1) is threaded through the inner cable sheath (103) when the cable cores (104) are being pulled.

3. A method according to claim 1 or 2 further comprising the steps of exposing partial of the cable cores (104) at one end prior to the pulling, wherein the pulling step is performed through mounting a mechanical clamp (1 13b) onto one end of the cable cores (104) followed by driving the mechanical clamp (113b) to pull the cable cores (104).

4. A method according to claim 1 or 2, wherein the liquefying step is conducted by applying electric current to the wires to heat the surrounding greasy material (105).

5. A method according to claim 1 or 2, wherein the liquefying step is conducted via passing heated air and steam through the inner cable sheath (103) to melt the greasy material (105).

6. A method according to claim 1. wherein the greasy material (105) is a filling composition made of Microcrystalline wax. paraffin wax. bees wax, mineral oil, polyethylene, petroleum jelly or any combination derives thereof.

7. A method of removing cable cores (104) from an outer cable sheath (101) that the cable cores (104) are soaked within matrix of greasy material (105) enclosed by an inner cable sheath (103) followed by an intermediate cable sheath (102) and the outer cable sheath (101) comprising the steps of dissolving greasy material (105) partially or completely contained within the inner cable sheath (103) by injecting a solvent into the inner cable sheath

(103) ; and pulling at least fraction of the cable cores (104) at one end from the inner cable sheath (103) to remove the cable cores (104), wherein each of the cable cores (104) enclosing a metal wire.

8. A method according to claim 7 further comprising the steps of fixing a replacement cable (11 1) at another end of the cable cores (104) prior to the pulling step, wherein the replacement cable (1 11) is threaded through the inner cable sheath (103) when the cable cores (104) are being pulled.

9. A method according to claim 8 further comprising the steps of exposing partial of the cable cores (104) at one end prior to the pulling.

10. A method according to claim 8 or 9, wherein the pulling step is performed through mounting a mechanical clamp (1 13b) onto one end of the cable cores

(104) followed by driving the mechanical clamp (113b) to pull the cable cores (104).

11. A method according to claim 8 or 9, wherein the solvent is the mixture of chemical solutions made of hexane, pentane, chloroform, benzene, xylene, diethyl ether, ethanol, methyl isobutyl ketone or polar or non polar solvent with proper amount of surfactant. .

12. A method according to claim 8 or 9, wherein the greasy material (105) a filling composition made of Microcrystalline wax. paraffin wax, bees wax, mineral oil, pofyethylene. petroleum jelly or any combination derives thereof.

13. A method of removing cable cores (104) from an outer cable sheath (101) that the cable cores (104) enclosed by an inner cable sheath (103) followed by an intermediate cable sheath (102) and the outer cable sheath (101) comprising the steps of

injecting a flowable medium into the inner cable sheath (103) to reduce friction in between the cable cores (104) and the inner cable sheath (103) as well as among the cable cores (104); and

14. A method according to claim 14 further comprising the steps of detecting . availability of perforated area along the inner cable sheath (103), intermediate cable sheath (102) and/or outer cable sheath (101).

15. A method according to claim 15, wherein the detecting steps is done by applying air pressure into the inner cable sheath (103) at one end and measuring the air pressure at another end to ascertain the perforated area.

16. A method according to claim 14 or 15, wherein the flowable medium is a lubricant made of palm oil & its by-products.

17. A method according to claim 14 or 15 further comprising the steps of exposing partial of the cable cores (104) at one end prior to the pulling.

18. A method according to claim 14 or 15, wherein the pulling step is performed through mounting a mechanical clamp (113b) onto one end of the cable cores (104) followed by ^'driving the mechanical clamp (113b) to pull the cable cores (104).