INSULATING ROPE WITH ADSORBENT MATERIAL

Abstract

An insulating rope includes: a non-conductive core; an extruded thermoplastic jacket disposed around the core; and a water adsorbent material disposed between the jacket and the core. A method of making an insulating rope is also described.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Patent application Ser. No. 63/351,992, filed on Jun. 14, 2022.

TECHNICAL FIELD

The invention relates to insulating ropes having a low dielectric constant so as to be electrically insulating, and in particular to insulating ropes containing a water adsorbent material.

BACKGROUND

Insulating ropes (commonly referred to as “dielectric ropes”, “insulative ropes”, “dielectric cables”, “insulating cables”, or “insulative cables”) are used to protect workers on high-voltage transmission lines, power stations, and other energized work environments from electric shocks and other dangers posed by the presence of high voltages. They may be used in multiple applications, including live line working ropes, bare hand work, tag lines, hand lines, pulling and stringing, evacuation and rescue, rope access, helicopter lift (helicopter longlines), safety netting and high strength insulating tool replacements. These insulating ropes must keep workers safe even in the event that they come into contact with high voltage conductors or become energized through induction. In addition to having a low dielectric constant, i.e., a high dielectric strength, the mechanical properties of these ropes must be suited to their application, for example tensile strength and flexibility. This imposes certain practical constraints on their manufacture.

If moisture is present inside the rope, the insulative properties of the rope may be impaired. It is essential that the ropes maintain their insulating properties, to ensure the safety of the workers. To this end, the ropes should be tested regularly, and standards have been established for this testing. A rope that fails a prescribed test may need to be discarded and replaced, due to the difficulty in removing moisture from the interior of the rope. It is also possible that a rope may lose its insulating properties in the time interval between tests, which poses some risk to workers.

One common method of isolating the ropes from moisture is by coating the ropes with an overlay finish, such as a wax. However, this approach has drawbacks, such as making the ropes difficult to clean and maintain, and occasionally trapping moisture, dirt, dust, or other contaminants between the braid interstices of the rope, which can impair the insulating properties of the rope.

Another common method of isolating the ropes from moisture is by coating them with an extruded thermoplastic jacket made from a hydrophobic material such as polyurethane. Such a jacketed cable can have the desired mechanical properties, and maintain its insulating properties even when wet. However, the ropes are often used in harsh conditions and must be cleaned and maintained regularly, and are not always stored or used as recommended. Although these jacketed cables are highly reliable, it is still possible for moisture to occasionally penetrate the jacket, particularly if the rope is left submerged or exposed to high humidity for long periods, or if the jacket is damaged during use. This can result in the failure of the rope to maintain the required insulating properties, which poses a risk to workers and can reduce confidence in the safety of the equipment.

Therefore, there is a desire in the art to further enhance the moisture resistance properties of insulating ropes.

SUMMARY

It is an object of the present invention to provide an insulating rope having improved resistance to water or humidity.

It is an object of the present invention to provide an insulating rope that can maintain its insulating properties, even when exposed to high levels of humidity during use or storage.

It is an object of the present invention to provide an insulating rope having an extruded thermoplastic jacket, that can maintain its insulating properties even when humidity penetrates inside the jacket.

According to a first aspect, an insulating rope includes: a non-conductive core; an extruded thermoplastic jacket disposed around the core; and a water adsorbent material disposed between the jacket and the core.

Optionally, in any of the previous aspects, the water adsorbent material comprises a zeolite or a metal-organic framework (MOF).

Optionally, in any of the previous aspects, the jacket comprises polyurethane.

Optionally, in any of the previous aspects, the non-conductive core comprises a twisted or braided rope.

Optionally, in any of the previous aspects, the braided rope comprises at least one of ultra-high molecular weight polyethylene (UHMWPE), polyester, or aramid.

Optionally, in any of the previous aspects, the insulating rope includes at least one eye near at least one end thereof.

According to a second aspect, a method of making an insulating rope includes: applying a water adsorbent layer to a non-conductive rope; and applying a thermoplastic jacket over the water adsorbent layer.

Optionally, in any of the previous aspects, the water adsorbent layer comprises a zeolite or a metal-organic framework (MOF).

Optionally, in any of the previous aspects, the non-conductive rope is a twisted or braided rope.

Optionally, in any of the previous aspects, the method includes urethane bonding the braided rope.

Optionally, in any of the previous aspects, applying the thermoplastic jacket comprises extruding the thermoplastic jacket over the water adsorbent layer.

Optionally, in any of the previous aspects, the method includes cooling the rope after extruding the thermoplastic jacket.

Optionally, in any of the previous aspects, the method includes sealing the ends of the rope after applying the thermoplastic jacket.

Optionally, in any of the previous aspects, the method includes forming an eye near at least one end of the insulating rope.

BRIEF DESCRIPTION OF THE DRAWINGS

Having thus generally described the nature of the invention, reference will now be made to the accompanying drawings, showing by way of illustration example embodiments thereof and in which:

FIG. 1 is a cut away view of an insulating rope according to an embodiment;

FIG. 2 is a perspective view of an insulating rope according to an embodiment;

FIG. 3 is a flow chart of a method of manufacturing an insulating rope according to an embodiment; and

FIGS. 4A, 4B and 4C show high-voltage leakage current test results on exemplary insulating ropes according to an embodiment.

DETAILED DESCRIPTION

Referring to FIG. 1, an insulating rope 100 according to an embodiment will be described. The insulating rope 100 includes a fiber core 102, which may be composed of any suitable dielectric material having a sufficiently high tensile strength. Typical materials include ultra-high-molecular-weight polyethylene (UHMWPE), polyester, or aramid fibers (sometimes sold under the Kevlar™ brand). It should be understood that any suitable material or materials may be used for the core 102, provided that it has sufficient tensile strength and insulating properties for the intended use of the insulating rope 100. The fibers of the core 102 may be twisted into yarns and then cable-laid (twisted) or braided into a rope, to ensure a high tensile strength suitable for various different types of use.

Outside the core 102 is a water adsorbent layer 104. The water adsorbent layer 104 contains a water adsorbent substance, for example a micro sieve material such as a zeolite or a metal-organic framework (MOF). It should be understood that any suitable material or materials may be used for the water adsorbent layer 104, provided that it has sufficient water adsorbent properties and does not impair the insulating properties of the insulating rope 100. For example, the water adsorbent layer 104 may comprise a desiccant gel, an aluminosilicate, solid desiccants and/or other suitable hygroscopic materials. The water adsorbent layer 104 may comprise a natural zeolite and/or a synthetic zeolite, for example analcime, chabazite, clinoptilolite, erionite, mordenite, phillipsite, ferrierite, Linde-type zeolites, ZSM-5 and SSZ-32 zeolites.

Outside the water adsorbent layer 104 is a thermoplastic jacket 106. The thermoplastic jacket 106 is hydrophobic, and its primary purpose is to prevent water or moisture from permeating the thermoplastic jacket 106 and coming into contact with the core 102. It should be understood that any suitable material or materials may be used for the thermoplastic jacket 106, provided that it is hydrophobic, sufficiently durable and flexible for the intended use of the insulating rope 100, and does not impair the insulating properties of the insulating rope 100.

Referring to FIG. 2, the insulating rope 100 may be spliced or otherwise fastened to form an eye 108 near one or both ends 110, which can be used for fastening the insulating rope 100 to other objects. Each eye 108 may optionally include a thimble 112 to reinforce the eye, maintain its shape, and protect it from damage and wear. The thimble 112 may be made of nylon or steel, or any other suitable material, depending on the intended use of the insulating rope 100. In some embodiments, no eyes are formed at the ends of the rope 100, and the rope may be attached to other ropes or objects by knotting the rope. The ends 110 are preferably sealed to prevent the entry of moisture or humidity into the interior of the insulating rope 100.

Referring to FIG. 3, a method 200 of manufacturing an insulating rope such as the insulating rope 100 will be described.

At step 202, multiple strands of an appropriately selected core fiber are twisted into yarns. The fiber may, for example, be UHMWPE, polyester, aramid, or any other suitable material.

At step 204, the yarns are cable-laid (twisted) or braided to form a rope that may be used as the core 102.

At step 206, the rope is optionally urethane bonded to facilitate handling and increase abrasion resistance.

At step 208, a water adsorbent layer is applied to the rope. This may be done, for example, by applying a silicon-based spray coating or other suitable adhesive to the rope, and then dipping the rope in a zeolite powder or other suitable water adsorbent material. It is contemplated that other suitable methods may alternatively be used.

At step 210, a thermoplastic jacket is applied to the rope in one or more layers. This may be done by extruding the thermoplastic material over the rope. The thermoplastic material may, for example, be a hydrophobic material such as polyurethane. The thickness of the jacket may be selected to provide sufficient durability and impermeability to humidity and moisture, while still permitting sufficient flexibility of the finished rope.

At step 212, the ends of the rope are sealed, to form a hermetically sealed system that prevents the entry of moisture.

At step 214, the completed rope is optionally cooled, to dissipate the heat generated during the extrusion process. The cooling may be done by passing the rope through a tank or trough of water after extrusion.

At step 216, one or both ends of the rope are optionally spliced or otherwise fastened to form an eye. The eye may be formed around a thimble, to reinforce the eye, maintain its shape, and protect it from damage and wear. Alternatively, this step may be omitted, in which case no eyes are formed at the ends.

The insulating rope may optionally be cured.

Referring now to FIGS. 4A and 4B, dry and wet high voltage (HV) tests on exemplary insulating ropes according to the principles described herein are presented. Dry tests comprised exposing insulating ropes comprising a zeolite to 100 kV, 75 mA AC over 12″ with an ASTM disc for a period of 5 minutes. Wet tests comprised placing insulating ropes comprising a zeolite in a climatic chamber at 99% humidity of 100-ohm water for 16 hours prior to testing, followed by exposure to 100 kV, 75 mA AC on 12″ with an ASTM disc for a period of 5 minutes. It will be understood that mV values may be converted to uA for the purpose of this disclosure by multiplying the mV value by a factor of 10.

The insulating ropes according to the present invention exceeded current acceptance standards. In particular, the insulating ropes meet and exceed current acceptance standards when exposed to 100 kV AC on 12 inches. For example, a leakage current test comprising exposure to 100 kV on 12 inches is approximately twice as severe as a currently accepted ASTM insulation test.

As shown in FIG. 4A, a dry leakage current test as described above on an about ½″ insulating rope resulted in a maximum logged leakage current of 1.92 uA, compared with a present ASTM acceptance threshold of 100 uA. As shown in FIG. 4B, a wet leakage current test as described above on an about ½″ insulating rope resulted in a maximum logged leakage current of 2.47 uA, compared with a present ASTM acceptance threshold of 250 uA.

Referring now to FIG. 4C, a wet conditioning leakage current test on an insulating rope comprising a zeolite according to the present invention is presented. The wet high-voltage test comprised soaking insulating ropes according to the present invention in a basin of 100-ohm conductive water, immediately followed by leakage current testing at 100 kV over 15 inches with an ASTM disc for a period of 5 minutes. Such a test may simulate a hypothetical worst case scenario where an insulating rope is exposed to extremely wet conditions, for example extremely intense rainfall. For example, the rope may be exposed to a flood or to intense rainfall while in unprotected storage, or be exposed to intense rainfall while in use by maintenance personnel, for example during an intense storm. The exemplary test shown in FIG. 4C comprised soaking an insulating rope for 1 h as described above. As shown in FIG. 4C, the maximum logged leakage current was 2 uA, compared to a current wet ASTM acceptance threshold of 200 uA.

It will be understood that the broad principles and acceptance thresholds of ASTM standards may be applicable and/or substantially similar to principles and acceptance thresholds of other standards, e.g. IEC standards, and that the insulating ropes according to the present invention exceed IEC and other recognized acceptance criteria as well.

Insulating ropes according to the present invention therefore provide substantial security to personnel and equipment exposed to electrical currents, or working in conditions wherein support equipment, such as ropes, may be in contact with an energized source while making contact with the ground. For example, maintaining energy in a portion of an electrical grid or in an electrical line during maintenance or repair work may improve response, maintenance and repair times without compromising user and/or worker safety.

An insulating rope as described herein has a low dielectric constant and therefore a high dielectric strength, and is suitable for use in electrified environments.

An insulating rope as described herein may have one or more advantages such as improved resistance to the penetration of humidity and moisture, improved reliability of the insulative properties of the rope, and increased service life of the rope.

An insulating rope as described herein may provide improved usability and performance. For example, a user's ability to twist, knot, flex and otherwise deform the insulating rope during use may be improved without sacrificing user safety.

The insulating ropes according to the present invention met and exceeded ASTM insulation standards rapidly following production according to the methods disclosed herein. The production time of insulating ropes may comprise several phases, including some or all of production planning, raw materials reception, material incorporation, extrusion, curing, batch testing, finishing and shipping.

Although some steps may be rate-limiting or difficult to shorten, the present invention provides a high-performance product that meets current and future applicable standards and reduces the duration of the manufacturing process. Accordingly, manufacturers may respond rapidly to customer demand while reducing resource use

The embodiments described above are intended to be examples only. The scope of the invention is therefore intended to be limited solely by the appended claims.

Claims

1. An insulating rope, comprising:

a non-conductive core;

an extruded thermoplastic jacket disposed around the core; and

a water adsorbent material disposed between the jacket and the core.

2. The insulating rope of claim 1, wherein the water adsorbent material comprises a zeolite or a metal-organic framework (MOF).

3. The insulating rope of claim 1, wherein the jacket comprises polyurethane.

4. The insulating rope of claim 1, wherein the non-conductive core comprises a twisted or braided rope.

5. The insulating rope of claim 4, wherein the braided rope comprises at least one of ultra-high molecular weight polyethylene (UHMWPE), polyester, or aramid.

6. The insulating rope of claim 1, further comprising at least one eye near at least one end thereof.

7. The insulating rope of claim 1, wherein the insulating rope passes ASTM high voltage leakage current tests at 100 kV across 12 inches.

8. A method of making an insulating rope, comprising:

applying a water adsorbent layer to a non-conductive rope; and

applying a thermoplastic jacket over the water adsorbent layer.

9. The method of claim 8, wherein the water adsorbent layer comprises a zeolite or a metal-organic framework (MOF).

10. The method of claim 8, wherein the non-conductive rope is a twisted or braided rope.

11. The method of claim 10, further comprising urethane bonding the braided rope.

12. The method of claim 8, wherein applying the thermoplastic jacket comprises extruding the thermoplastic jacket over the water adsorbent layer.

13. The method of claim 12, further comprising cooling the rope after extruding the thermoplastic jacket.

14. The method of claim 8, further comprising sealing the ends of the rope after applying the thermoplastic jacket.

15. The method of claim 8, further comprising forming an eye near at least one end of the insulating rope.

16. The method of claim 8, further comprising curing the insulating rope.