WO2003083337A2

WO2003083337A2 - Normal cure composite tape seal (nccs) for cable joints

Info

Publication number: WO2003083337A2
Application number: PCT/IN2003/000075
Authority: WO
Inventors: K. Natarajan
Original assignee: Rashtreeya Sikshana Samithi Trust
Priority date: 2002-03-28
Filing date: 2003-03-25
Publication date: 2003-10-09
Also published as: WO2003083337A3; AU2003238665A8; AU2003238665A1

Abstract

a. A cable joint sealing by using normal cure composite tape seal has an insulated wire joint enveloped by insulation tape and the edges are sealed by non curable polysulphide mix. (poly paste-A) b. the said joint is covered with polyester film, the edges of the film are fixed with poly paste-A, followed by winding tightly with insulation tape, then two sides of cable surfaces are cleaned and activated by etching with xylene solvent. End seals are made around cable surface by using curable polysulphide mix. (poly paste-B) and enclosing the entire seal by winding with elastomer tape. Poly gel of curable polysulphide mix. (may or may not) coated on the entire surface and then covered by winding a flexible normal cure composite (NCCS) tape made of glass fibre impregnated with polysulphide mix having polyethylene peel off film. c. The assembly being covered either by winding with elastomer tape followed by insulation tape, and the two terminal ends are tightened by nylon tags or fibre reinforced polyester shells containing the poly paste can be fixed and tightened with nylon tags. d. The above said seal prevents water seepage, termite attacks to the cable joint under ground or under water and resists to mechanical damages.

Description

NORMAL CURE COMPOSITE TAPE SEAL(NCCS) FOR CABLE JOINTS FIELD OF INVENTION

The present invention relates to a normal cure composite tape seal for cable joints enclosure and a process for enabling to seal the cable joints. The main usages of the invention' are to seal the cable joints such as communication cables in order to make the joint, high strength and tightness, resistant to water seepage underground, and moisture resistant, anti termite, anti corrosive, and flexible.

BACKGROUND ART

The following description traces various prior art technologies and method known so far. It addresses the problem associated with prior art. The invention offers a solution to overcome the problem associated with the prior relevant art. A brief summary of relevant patents is as follows.

Reference is made to U.S. patent number 5,301,422, dated 12-4-1994, wherein the device comprises a pair of semi - cylinderical shell pieces which, when assembled together, form a modified cylindrical structure having a central aperture for receiving the ferrules. The drawbacks of this system are the complicated rigid structure which may be damaged on the application of high mechanical loads or impacts. Further it may undergo corrosion underground. It needs skilled labour to fabricate the seal and may not be cost effective method. Reference is made to U.S. patent number 5,952,612, dated Sep.14,1999, wherein a two part range-taking member for providing a seal around a substrate includes a mating pair of resilient components for enclosing the substrate and a co-operating pair of rigid components for urging the resilient components into conformity with the substrate. The member may provide an electrical stress cone for a power cable, for example with two such members being provided in a cable joint. In this method, the filling compound is added to fill the gap in the joint and the outer metal shells. The outer metal shell is of rigid in nature and may undergo failures when it comes in contact with high mechanical loads or impact. The sealing system may not be very tight, which is required to prevent water seepage under ground. Further, it may be more prone to corrosion under ground. It needs skilled labour to fabricate the seal and not cost effective method. Further this patent pertains to electrical cable joints. But in our invention the above drawbacks are rectified.

Reference is made to U.S. patent number 6,064,002, dated May 16, 2000 , where in an electrically insulated cable having a sheath made of a material which is heat-fusible to a polyamide or polyester resin so that a highly waterproof joint portion can be formed between the cable and a housing simultaneously when the housing is injection-molded from a crosslinked resin composition comprising a thermoplastic polyurethane elastomer and a thermoplastic polyester elastomer mixed together in a weight ratio of 80:20 to 20:80. A housing is provided around one end of the sheath of this cable by injection-molding polyamide or polyester engineering plastics to fuse the sheath to the housing, thereby hermetically sealing the interface between the cable and the housing. The sheath may be made from a crosslinked resin composition comprising a thermoplastic polyurethane elastomer and a thermoplastic polyamide elastomer mixed together in a weight of 80:20 to 10:90. It is possible to seal the cable to a housing made of polyamide engineering plastics. The drawbacks of this method are the technique of thermal curing of resin, which may damage the cable wires at high temperatures. This technique needs heating source and skilled labours for fabrication. During the fabrication, materials may be overheated and wasted. Hence the method is not cost effective. Further, re-opening the joints may be very difficult , because the cured materials formed are highly crosslinked and rigid. In our system, all these drawbacks are rectified.

DISCLOSURE OF THE INVENTION

The main objective of the present invention is to provide a Normal Cure Composite Seal (NCCS) which obviates all the drawbacks of the prior art mentioned above. Another objective of the present invention is to provide a Normal Cure Composite Seal (NCCS) which works at normal temperature.(-10°c to 50°c)No heating is required.

Yet another objective of the present invention is to provide a cost effective cable joint sealing techniques and materials..

Further objectives of the invention will be clear from the ensuing description. Accordingly the present invention provides a process for sealing the cable joints. The said process, the insulated wire joint and wire are enclosed by winding with an insulation tape , and the edges are sealed by non curable polysulphide mix (poly paste-A) .

The said joint is enclosed by covering with polyester film. The edges of the film are fixed with the poly paste-A, followed by winding tightly with insulation tape. Then the two sides of the cable surface are physically rubbed with sand paper and cleaned and activated by etching with xylene solvent. Now end seals are made around the cable surface by using curable polysulphide mix (poly pasted The entire seal is enclosed by winding with elastomer tape. Poly gel made by mixing xylene with poly paste-B is coated on the entire surface around the seal (This step may or may not be used). It is then covered by winding with Normal Cure Composite Seal (NCCS) tape comprising of glass fibre impregnated with polysulphide mix . Finally the entire seal can be enclosed by fixing the two halves of fibre reinforced polyester shell containing the poly paste -A and tightening with nylon tags. In an embodiment of present invention the poly paste-A is prepared by reacting polysulphide containing 50 - 70 parts with 5-15 parts of fused silica, 10-15 parts of talc, mixed with 5-10 parts of xylene solvent to get the desired consistency.

In an embodiment of present invention NCCS tape is made out of polysulphide mix. containing 50 - 70 parts of polysulphide paste, 5-15 parts of fused silica , 10-15 parts of talc, mixed with 0.1-0.5% zinc oxide crosslinker and 5-10 parts of xylene solvent to get the desired consistency. This mix. is used to impregnate the glass cloth. Both the sides of the NCCS tape was backed with polyethylene peel off film.

In still another embodiment of the present invention , the two ends of the cable joints are sealed by end seals made of curable polysulphide mix. called poly paste-B, which prevents capillary infiltration of water / moisture / termites entry through the ends. This paste is made from the constituents of polysulphide of about 40-60 parts containing 5-15 parts of fused silica, 10-15 parts of talc, 5-10 parts of lead oxide catalyst containing red oxide or carbon black pigment.

In another embodiment of the present invention, the said cable joint is enclosed externally by only plastic materials without metallic parts. Hence no corrosion occurs under ground.

In further embodiment of the present invention, the said joint is sealed at normal temperature without applying external heating or external pressure. Now the invention will be described in details. The nature of the invention and the manner in which the invention will be performed will be explained in details. The description will be with reference to the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

Figure 1 of the drawing shows in elevation the constructional details of the sealed cable joint known in the art. Figure 2 of the drawing shows in elevation the constructional details of the sealed cable joint according to invention. Figure 3 of the drawing shows in elevation the flexible composite NCCS tape according to invention. Figure 4 shows various steps in sealing the cable joints.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT.

Existing system of sealing the cable joints exhibited in fig-1 describes gell filled thermoshrink closure type joints. This type of sealing is being used currently by most of the Telecommunication departments. In this system the cable joint (1) was filled with petroleum jelly (2) and enclosed by polyethylene sleeves(3). Then the joint was insulated with tapes (4). In the next step the aluminium canister (5) over the splice bundle was fixed. Then degreasing the cables with cleaning tissue for a distance of 200mm from the ends of the splices was carried out and that followed by abrading the cable circumferentially over the degreased length and cleaning with dry cloth. Finally the heat shrink sleeve (6) over the canister was fixed and marked the sleeve ends on the cables. Subsequently the second mark approx.20mm towards the splice was made. Then the cable areas between arrows were heated by means of blow lamps for ten to fifteen seconds. After removing release film the heat shrinkable sleeve (6) was heated until the thermochromic paint changes its colour from green to black. The stainless steel channels and retaining clips were also fixed. The drawbacks in this conventional current system are as follows. i. While heating the thermoshrink sleeve, the temperature produced becomes sufficient enough to damage the interior wire joints . ii. During cooling , the entrapped air containing moisture will be trapped inside the joint, iii. For heating, blow lamps and inflammable solvents and other accessories are to be used, iv. The rigid joint formed may be easily damaged, when high mechanical strength or impact is applied v. The joints cannot be bended or twisted. vi. Re-opening of joint is a tedious procedure and may incur in more damages and waste of materials, vii. The size of the fabricated joint becomes three to four times bigger than the cable size, le., more space accommodation, viii. Gel filling and cleaning steps poses laborious problems and not cost effective, ix. Gel will be eaten away by ants and less resistance to variation of pH of the soil or water. x. Because of the presence of gel, termites and ants can easily enter into the joint and pave a way for water seepage, xi. Use of aluminium metal canister leaves behind empty space between the wire joints and outer surface. This results in the crumbling of joints when it receives high impact, xii. Skilled labour is essential to fabricate the joint. Hence the higher labour cost becomes inevitable, xiii. The working period for fabrication is more, xiv. It is highly impractical to seal the joint during rainy seasons, xv. Wastage of materials, xvi. High cost product xvii. External surface of the seal joint contains stainless steel channel, which undergoes corrosion under ground. The draw backs as afore said was rectified by our newly invented system called Normal cure composite tape seal (NCCS) represented in figure. 2., which, explains the effective system of sealing the cable joint for leak proof, where in part (1) represents cable wire joint covered by insulation. Part (2) constitutes edge seal containing non curable polysulphide mix.(polypaste-A). Part (3) is a polyester film enclosure. Part (4) is an insulation tape winding on poly film. Part (5) end seal containing curable polysulphide mix.(polypaste- B),enclosed by elastomer tape. Part (6) is an elastomer enclosure which envelopes the entire seal. Part (7) is Normal Cure Composite Seal (NCCS) tape which covers the entire seal after the Poly gel coat containing polypaste- A. coating or not. Part (8) is fibre reinforced polyester shells which gives mechanical strength.. Finally both the ends of the enclosure are tightly fitted by means of Nylon grip clip Part (09).

During curing, the sandwich of elasotmer-NCCS tape-elastomer are formed as a flexible skin. This flexible skin, not only arrests the seepage of water and also imparts tightness, high tensile and impact strength to the joint. It protects the joint from deformation while bending or twisting. Finally the two ends of the sealed joints were clamped (09) tightly, which ensures the complete protection of the joint. Fibre reinforced polyester shells (8)are used to produce rigid joints.

SUBSTITUTE SHEET Fig-(3) represents flexible composite NCCS tape in which part (10) represents the polysulphide mix. Part (11) represents glass fibre cloth impregnated with polysulphide mix. and part (12) is the polyester back up film.

Figure (4) Illustrates various steps in the sealing of cable joints according to the present invention. The various steps involved in the process of sealing of cable joints are self evidence and illustrated as such in the flow chart of the process according to invention.

Under ground telephone cable joints are more easily attacked by termites , water seepage and mechanical damages. Currently used sealing kit system fails to meet the above requirements. In order to tackle these problems, the cost effective, improved sealing process technique was invented.

The concept of the invented sealing system is normal cure with no heating, resistance to water seepage, anti termite, flexible, easily processable with inland materials and cost effective.

In the present method of sealing the cable joints, in order to make the joint anti termite, water resistant and leak proof, polysulphide mix. is used. In order to resist crack formation at the joints, while bending or twisting and to make flexible seal the composite tape (NCCS) is made with polysulphide impregnated glass cloth. Edge seals with uncurable (poly paste-A) and end seals with curable polysulphide mix.(poly paste-B) are used to prevent capillary infiltration of water/moisture into the joint.

Normal cure composite seal is simpler, cheaper and superior than the existing thermoshrink sleeve system used currently. By this system, after installation, curing continues and gets completed within 24 hours of time during which more tightness, strength and elasticity are imparted. The other important feature of novelty in the present invention is that the joint after curing works like a tight and flexible joint which prevents cracking that occurs in a rigid joint currently used. Cable jointing system results in flexible and easily reopenable / reworkable properties.

Cable joint is sealed with newly invented composite (NCCS) prepreg tape by winding technique, which imparts not only tightness , strength and shape to the seal at the joint and also works as an effective water/moisture barrier. Without gel filling, the cable joint is ensured for complete protection from water / moisture entry, which helps in reducing the cost, time and labour & easier reopening/reworking at the joints,. The technique of edge sealing ensures the complete leak proof system at the joint. The technique of end sealing at the surface of the cable and sealing with poly paste-B, prevents the capillary infiltration of water or moisture to the joint through the surface of cable. It also increases the grip and tightness at the sealing area. Size of the joint is kept small ( 14 mm more than the actual cable) and flexible. End clipping technique adopted, gives not only additional protection to the joint from water seepage and also makes easy removal or reopening of joints.

Preparation of flexible Normal Cure Composite Seal (NCCS) tape:

With reference to fιg-3, wherein the polysulphide mix. (11) containing 50 - 70 parts of polysulphide paste as obtained from choksy chemicals containing 5-15 parts of fused silica, 10-15 parts of talc mixed with 0.1-0.5 % zinc oxide crosslinker, 5-10 parts of xylene solvent to get the desired consistency. This mix. is used to impregnate the glass cloth. Both the sides of the NCCS tape and was backed with polyethylene peel off film. Figure (4) Illustrate various steps involved in sealing the cable joints.

Now the invention is illustrated by way of examples. These examples are not indented to limit the scope of invention. Tests were conducted as per the standards prescribed by Telecom. Engg.Centre, India.

Example - 1

Tightness test (leak proof test) was conducted for five pair cable straight joints. The cable joint withstands to the internal pressure of 0.7 kgf / cm² for more than one hour, (as per the standard, the value should be around 15 minutes ). Further test was conducted at increased pressures and the joint withstands even at 30.0 kgf/cm for long hours.

ExampJe-2

Vibration test was conducted for five pair cable joints (straight) 100 vibration/min. for two hours followed by tightness test was conducted and no leak was observed. Further 200 vibration /min. for two hours and for three hours and four hours were conducted. No leak was observed.

Example -3

Bending test was conducted for five pair cable joints. A bending cycle consisting of one excursion of bending to 45 ° from the neutral position and maintained for five minutes, back to the neutral and bent in the opposite direction to the limit specified, maintained for five minutes and then returned to the neutral position. After completion of two cycles, the tightness test was conducted. There was no leak. Example -4

Temperature cycling test was conducted by placing the five pair cable joint in a water bath, five cm below the surface of water and subjected to thirty cycles. Each cycle was conducted for 12 hrs. at the temperature range of 85 °C (but in standard it is 65 °C only ). After completion of every ten cycles, the joint was subjected to tightness test. There was no leak.

Example - 5

Thermal shock test was conducted by immersing the cable joint in water bath heated to 85°c (but as per standard, it is only at 65 °C ) five cm. below the water surface. After fifteen minutes the sample was suddenly transferred to ice water (3.0 °C ) for five minutes. At the end of five minutes the sample was again transferred to hot water back. After completing ten cycles, sample was subjected to tightness test. There was no leak.

Example - 6

Corrosion test was conducted as per the standard, by immersing the cable joint in solution of pH value 4.0 and 10.0 for thirty days. After completion of the period, the sample was inspected visually and there was no corrosion and then subjected to tightness test as described earlier. There was no leak. Conclusions of experiments :

The above experiments clearly indicates that the invented normal cure composite tape seal has several advantages over the existing systems, and the method is highly effective in sealing all cable joints (under ground or under water) and in particular for telecommunication cables.;

Further the NCCS tape enclosure, ensures the total prevention of capillary flow of water or moisture through the surface of the cable Into the joint.

Further the elastomer tape (7) winding ensures tightness and leak proof at the joint. This gets tightened further over a period of time. Inorder to impart total protection to the joint, insulation tape (5) was wound finally. The two ends of the seal tightened by means of clips (10). The sealing product was formulated by inland materials.

Advantages of the present invention :

1. Perfect water / moisture sealing render the system / leak proof.

2.Cold cure system. Hence there is no need of blow lamp or torch to cure the materials.

3. High tightness and flexible seal.

4. Less weight / volume. Less space accommodation

5. o moisture entrapment inside the joint after sealing β.After the sealing work the thickness of the cable at the joint .becomes 28 mm for 14 mm diameter 5- pair cable.

7. Low cost ie half the cost of existing jointing kits .

8. Easy processing, less time for sealing / fabrication

9. Easy reopening without damaging the wires.

10. No wastages and no disposable problems.

11. Non toxic or inflammable materials are used. Hence no health hazards and environment friendly.

12. Inland raw materials are used .

13. Withstand at the temperature range of -30 °c to +100 °C .

14. No shrinkage or expansion after complete cure.

15. Processed at any climate and weather conditions.

16. Flexible and bends without any damage at the joints. 17. Elasticity and tightness are imparted during cure . 18.Curing takes place within 24 hrs.

19. Life time to the product will be more than 15 years.

20.Minimum man power and no special skill is required for installation which reduces the labour cost.

21. There is no corrosion at the joints, because no metallic parts are used.

22.Aesthetic look of the cable joints was observed. INDUSTRIAL APPLICABILITY

The present invention finds wide applicability in Cable industries especially in Telecommunication cables, underwater cables, underground cables especially for enclosing the cable joints and also for electrical cables in electrical industries. In water supply and sanitary drainage systems, for sealing the pipes at the joints.

It is to be noted that the description intended was to explain salient features of the invention. With in the stock of invention various modifications are permissible without departing from the scope of invention.

Claims

CLAIMS1j. A process of sealing cable joints by using normal cure composite tape seal(NCCS) which comprises (Normal cure = without heating or cold cure)a. Enclosing the insulated wire joint and wire by winding with an insulationtape , and sealing the edges by non curable polysulphide mix (poly paste -A)b.Covering the said joint with polyester film , the edges of the film are fixedwith poly paste-A, followed by winding tightly with insulation tape then the two sides of the cable surface are cleaned and activated by etching with xylene solvent. End seals are made around the cable surface by using curable polysulphide mix. (poly paste-B), enclosing the entire seal by winding with elastomer tape, poly gel (may or may not be used) made up of curable polysulphide mix is coated on the entire surface which is covered by winding a flexile composite NCCS tape made of glass fibre impregnated with polysulphide mix backed with polyethylene peel off film.C. Covering the said assembly by either winding with elastomer tape followedby insulation tape , and finally the two terminal ends are tightened by nylon grip clips. Or, enclosed by fixing two halves of fibre reinforced polyester shell containing the poly paste -A. 2J A process of sealing cable joints by using normal cure composite tape.sealas claimed in claim 1 were in the poly paste-A is made from the constituents of polysulphide. Tthe poly paste-A is prepared by reacting polysulphide containing 50 - 70 parts with 5-15 parts of fused silica, 10-15 parts of talc, mixed with 5-10 parts of xylene solvent to get the desired consistency.J A process of sealing cable joints by using normal cure composite tape sealas claimed in claims 1-2, in which, wherein Poly paste-B is made from the constituents of polysulphide of about 40-60 parts containing 5-15 parts of fused silica, 10-15 parts of talc, 5-10 parts of lead oxide catalyst containing red oxide pigment or carbon black pigment.|4.| A process of sealing cable joints by using normal cure composite tape sealas claimed in claims 1-3, in which, wherein the polysulphide mix. containing 50 - 70 parts of polysulphide paste as obtained from choksy chemicals containing 5-15 parts of fused silica, 10-15 parts of talc mixed with 0.5-1.0 % zinc oxide crosslinker, 5-10 parts of xylene solvent to get the desired consistency. This mix. is used to impregnate the glass cloth. Both the sides of the NCCS tape was backed with polyethylene peel off film. 5. A process of sealing cable joints by using normal cure composite tapeseal as claimed in claim 1-4 in which, the two ends of cable joints are sealed by end seals made of curable polysulphide mix (poly paste-B). This paste is made from the constituents of polysulphide of about 40-60 parts containing 5- 15 parts of fused silica, 10-15 parts of talc, 5-10 parts of lead oxide catalyst containing red oxide or carbon black pigment. This prevents capillary infiltration of water / moisture / termites entering through the ends.A process of sealing cable joints by using normal cure composite tapeseal as claimed in claims 1-5, the said joint is sealed at normal temperature without applying external heating or external pressure.7. A process of sealing cable joints by using normal cure composite tapeseal as claimed in claim 1-6., in which, the said joint is externally enclosed by anti corrosion material, ie., only plastics and no metallic parts are used or, Fibre reinforced polyester shell8. A process of sealing cable joints by using normal cure composite tape sealas claimed in claim 1-7 wherein a polygel being used, which contains polypaste-B in xylene solvent . This may or may not be used. 9. A process of sealing cable joints by using Normal cure composite tape sealas claimed in claim 1-8 where in normal cure composite tape seal kit (NCCS- kit) contains the following materials i. copper continuity wire ii Insulation tape iii. Polyfilm iv Elastomer tape v. Polysulphide paste A (uncurable) vi Polysulphide paste B (curable) vii. Normal cure composite tape seal (NCCS) tape. viii. Polysulphide gel (may or may not be present) ix. FRP- shells x. Nylon clips. xi. cotton waste xii. cleaning solvent10. A process of sealing cable joints by using normal cure composite tapeseal as claimed in claim 1-09 wherein the abovementioned poly paste A and B, NCCS tape and the sealing technology can be applied for electrical cable jointing enclosure also,A process of sealing cable joints by using normal cure composite tapeseal (NCCS) for cable joints as claimed in claims 1-10, in which, wherein the description and as illustrated by way of flow chart. (Fig-4) FLOW CHART

1. Cable wire joints are covered by winding with insulation tape.

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2. Edge sealing at the joints using Polypaste-A.

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3. Enclosing the joint by winding with Polsyester film

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4. Covering with insulation tape winding

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5. Two sides of the cable surface are cleaned and etched with xylene

6. End seals are fixed on both sides of the cable using Poly paste-B

7. The entire seal is enclosed by tightly winding with elastomer tape

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8. The entire surface may or may not be coated with poly-gel

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9. NCCS tape is wound on the above surface followed by either an elastomer tape or ^

10. Finally FRP-sleeve can be fixed and tightened with clips.