CA2066982A1 - Suppression blanket - Google Patents

Abstract

Abstract of the Disclosure A suppression blanket for protecting lineworkers from the effects of electrical arcs at wire splices or the like is provided. The suppression blanket comprises a blanket portion and a mounting arrangement.
The blanket portion has an inner body portion and an outer face sheet arrangement. The inner body portion is preferably formed from an aramid fiber material sufficient to withstand blasting contain arc. The mounting arrangement preferably comprises a plurality of straps with a hook and loop mounting arrangement thereon.

Description

2 ~ 8 ~
~UPPRE~8ION BLANKET

Field of the Invention The present invention relates to devices for protecting lineworkers from the effects of electrical arcs in wire splices at or near work areas. The invention more specifically concerns a type of suppression blanket or protective jacket positionable between the splice and the worker, for protection of the worker from explosion or arc.

ackground of the I~vention In many metropolitan areas electrical cables or the like are carried through underground passageways or pipelines. At points where cable junctions and control boxes are positioned, there will be large and sometimes very complicated electrical splices accessible in small work spaces, for example beneath a manhole cover or the like.
For various reasons, lineworkers will occasionally need to obtain access to some part of an electrical splice or junction, in these underground sites. Safety for the worker(s) in the underground site or hole is of a critical concern. More specifically, a live electrical splice can "arc" or short. Especially in the enclosed area of an underground hole or site, this can create a rather large explosion posing a substantial danger to the worker. In addition, sparks or fires set off by the arc can create further hazard.
For safety, the lineworker will preferably degenerize the electrical splicer in and around the work area. However, in many instances complete degenerization of all splices contained within a hole or worksite may not be practical or feasible. Thus, avoidance of any risk of arc or explosion may not always be possible.
In general, the likelihood of arc or blast increases, with the age of the splice. Reasons for this -2- 2~ 3~` ~

generally concern the natural degeneration of the insulation.
Workers in underground sites or holes take precautions for protection from arcing or sparking, in the nature of protective clothing, insulated gloves, insulated shoes, etc. However, such equipment is generally not designed for, or appropriate for, protection from a major arc or blast. In particular, it can do little to alleviate the problems from the concussive forces or projectiles.
Several approaches to the problem have been developed. In some instances sheets of plywood or the like are positioned between the worker and the "live"
splice. The sheet of plywood will tend to absorb the explosion, and protect the worker against the blast and the electrical spark. Problems with such arrangements include: the difficulty of positioning the large sheet of plywood; the fact that it cannot always be efficiently or effectively po~-itioned for maximum protection; that it may not be convenient to transport to the worksite; and, that it is not a particularly strong means for protection. In addition, large sheets of plywood are bulky and are hard for a single worker to readily control.
In some fields concerning electrical work insulation is provided by means of rubber blankets or the like. Such blankets have provided some protection:
however, they have not been fully satisfactory for a number of reasons. First, they generally do not provide very good explosion protection, as they may not be particularly strong. Secondly, a minor flaw in such systems may go unnoticed for years and, when the explosion or dangerous arc finally occurs, the system may fail. In addition, satisfactory means for mounting such arrangements in an underground hole or the like have not generally been provided.

_~_ 2 ~`$ ~f~u What has been needed has been a system or arrangement which is convenient to transport, relatively easy to install, and which will be effective in providing protection against arc or blast in and around a site of electrical work, including in an underground splice area.
What has been particularly needed has been an arrangement which can be readily manipulated by a lineworker wearing typical safety equipment including heavy gloves. What is preferred is such an arrange~ent which is relatively easy to manufacture and assemble. What has also been needed is an arrangement which can be stored for long periods of time without unacceptable deterioration, and which can be set up and taken down repeatedly without unacceptable wear.
Summary_of the Invention ~ ccording to the present invention there is provided a suppression blanket and arrangement comprising a blanket portion and mounting means. The mountiny means is adapted for mounting the blanket portion to a bar, cable or the like, in use. The mounting means preferably comprises a plurality of straps mounted onto the blanket portion. In preferred embodiments, the plurality of straps include thereon hook and loop mounting arrangements such as Velcrc , to facilitate attachment and dismounting.
The blanket portion preferably comprises a body portion enclosed within a cover or face sheet arrangement or envelope. The enclosed body portion is generally that portion constructed and arranged to withstand explosive forces during arcing, and preferably is provided from a material sufficient to provide arc fault containment of at least 42,000 amps at 12 and 1/~ plus cycles, without blowing through. The face sheet arrangement is preferably provided in protective arrangement to the body portion, for example surrounding same. Preferably the ~4~ ~ 3 face sheet arranyement is stitched to the body portion, for overall strength and integrity. In preferred arrangements a plurality of rows and columns of stitching is provided, to provide a plurality of rows and columns of segm~nts or quilts in the overall pattern. This leads to strength, as indicated herein below.
In preferred applications, the body portion comprises two sheets of filament weave fabric, positioned in face-to-face relation to one another. Preferably the filament weave fabric comprises aramid fiber material having a 24 X 24 count/ and a tensile strength of at least about 1100 lbs warp and about 1200 lbs fill.
Preferably the material from which the face sheet arrangement is ~ormed comprises rip stop weave, fire retardant, aramid fiber material. Most preferably it is formed from an aramid material which will provide ultra-violet protection for the body portion.

Brief Description of the Drawings The drawings constitute a part of the specification including exemplary embodiments of the invention, which may be embodied in various forms. In the drawings relative material thicknesses and component sizes may be shown exaggerated, for clarification.
Fig. 1 is a front view of a suppression blanket according to the present invention.
Fig. 2 is an elevational view of the arrangement depicted in Fig. 1 shown suspended in a typical use orientation.
Fig. 3 is an enlarged fragmentary cross-sectional view taken generally along line 3-3, Fig. 2.

Detailed Description of the Invention Herein are presented detailed descriptions of preferred embodiments of the present invention. It is to 2 ~ r,j ~ ~
be understood that the embodiments are exemplary only, and the invention may be applied in any o~ a variety of forms and arrangements.
Reference 1, Fig. 1, designates a suppression blanket arrangement 1 according to the present invention.
Blanket arrangement 1 generally comprises a blanket or blanket portion 4 and mounting means or arrangement 5.
The mounting arrangement 5 is used to operably position the blanket portion 4 in place, with respect to an electrical splice.
Referring to Fig. 2, suppression blanket arrangement 1 is shown suspended from line or pipe 10.
In general, blanket arrangement 1 will be positioned adjacent a splice, and between that splice and a worker, for protection.
Advantages are obtained both from the specific construction of, and materials utilized for, the blanket portion 4; and, also from the preferred arrangement utilized for mounting arrangement 5. These will be apparent from the following descriptions.
Referring again to Fig. 1, preferably blanket portion 4 comprises an internal body e~closed within a face sheet arrangement or cloth. With respect to this, attention is directed to Fig. 3, a fragmentary cross-sectional view. In Fig. 3 the internal body is generallydesignated at 15, and the opposite surfaces of the face sheet arrangement at 16.
For preferred constructions according to the present invention, the strength and durability to the blanket portion 4 is generally provided by means of the body 15. The primary purpose of the face sheet arrangement 16 is not so much to absorb impact or blast, but rather to protect the body 15 from deterioration or damage, for example during storage and handling.
Preferably the face sheet arrangement 16 is formed from a material which will, among other things, protect the body -6- 2 ~

15 from deterioration due to ultra-violet radiation.
Thus, preferably face sheet arrangement 16 is formed from a material not readily penetrat~d by ultra-violet light.
Also, preferably face sheet arrangement 16 is made from a strong durable material which is fire retardant.
As indicated generally above, it is foreseen that suppression blankets according to the present invention may be stored for long periods of time between use, and will be subject to some substantial abuse during use, for example due to handling in the back of trucks, and passage into and out of manholes or the like. They also may be utilized over a period of years, before the conditions of an explosion or major arc, if ever, are encountered. In general it will be preferred that the face sheet arrangement or cover 16 be such that should a minor rip or tear occur in its surface, major damage to the overall integrity of the suppression blanket 1 will not result. Thus, preferably face sheet arrangement 16 is provided from a woven material having a rip-stop weave. As a result, a minor puncture or tear in face sheet arrangement 16 will not result in exposure of substantial portions of the body 15 to possible damage or deterioration.
As will be apparent from further description herein below, the body 15 is that portion of the suppression blanket 1 which provides the strength and durability to withstand the explosive forces associated with an arc or short. Body 15 will therefore preferably be a relatively heavy material. If the heavy body 15 were merely enclosed within an envelope or face sheet arrangement 16 undesirable results might occur. First, the weight of the body 15 would tend to apply substantial stress to the edge seams 19 of the envelope of face cloth 16. Also, should the body 15 tend to settle within the envelope, it may leave a gap or unprotected area within the envelope or blanket portion.

2 0 ~ 8 2 To help protect against the problems described in the previous paragraph, and provide overall strength and integrity to the blanket portion 4, the face sheet arrangement 16 and body 15 are joined to one another along a stitched or "quiltN pattarn. A variety of patterns may be utilized to advantage. A preferred such pattern is illustrated at Fig. 1, wherein rows and columns of stitching 20 are used to divide blanket portion 4 into a plurality of rows and columns of segments 22. Stitching 20, it will be understood, extends completely through blanket portion 4, thus stitching face sheet arrangement 16, on opposite sides, to body 15. Small segments will tend to add strength and integrity to the system, inhibit settling of the body 15 and providing an overall strength and integrity which lessens strain on edge seams 23.
Again, a variety of stitching patterns may be utilized. In general, patterns of rectangles about 8-12"
by about 10-14n will be convenient to prepare, and be effective in providing the amount of support desired.
A variety of materials may be utilized as the "threadn for the stitching 20. In preferred constructions according to the present invention, aramid thread will be used, due to its strength and durability.
Attention is now directed to Fig. 3. As previously indicated, Fig. 3 is a cross-section of Fig.
2, illustrating body 15 positioned between layers of face sheet arrangement 16. For the arrangement shown in Fig.

3, body 15 comprises multiple layers 30 of material. For the particular preferred embodiment illustrated, body portion 30 comprises first and second layers 31 and 32.
The two layers 31 and 32 are oriented juxtaposed, or in face-to-face relation, to one another.
Advantages with respect to safety and integrity result when the body portion 15 is formed from multiple layers 30 of material. In particular, should a sheet of material from which body portion 15 is formed have, or develop, a minor flaw therein, the region where that flaw exists will be reinforced by the second layer. Referring again to Fig. 1, stitching 20 will, in general, maintain positioning of the multiple layers 30 such that they do not move or slide relative to one another, in the blanket portion 4.
It is foreseen that suppression blankets 1 according to the present invention may be utilized in a variety of applications. For a construction useable over a particularly wide range of applications, including with sufficient integrity to withstand arcing in a typical underground ~hole" where linepersons may work, and provide adequate protection, it will be desirable that the construction be such as will provide arc fault containment of at least 42,000 amps at 12 1/2 plus cycles, without blowing through. As indicated above, in general the strength of the system, with respect to this, will be provided by body 15. Thus, layers 30 should be chosen such that the composite resulting in body portion 15 is of a material that will provide the arc fault containment at least as great as that described.
Hereinbelow specific comments and descriptions are given with respect to the materials from which preferred layers 30, and preferred constructions according to the present invention, may be made. In general a material which is not flammable should be usedO
Preferably the material will comprise continuous filament strand, woven, material, rather than collected spun fibers. A filament weave ballistics fabric, such as a material used in bullet proof vests or bomb blankets, may be used. Preferred such materials would be those having a tensile strength of about 1000-1200 lbs. warp and about 1100 to 1300 lbs fill, preferably at least 1100 lbs. warp and 1200 lbs. fill. It has been found that certain 2 ~
aramid (aromatic polyamide) materials are acceptable and preferred.
Referring to Fig. 2, in general suppression blanket 1, in use, will be suspended from a pipe 10 or the like, iJl a "hole~ or work area. A variety of mounting means or arrangements 5 may be utilized to accomplish this. For the arrangement shown in Fig. 2, the mounting arrangement 5 comprises a plurality of straps 35 attached to blanket portion 4 and strung over pipe 10.
In general, it will be preferred that the mounting arrangement 5 be such that it can be readily manipulated for mounting and dismounting by a worker wearing heavy rubber gloves or the like. In addition, flexibility to allow ease of mounting in a variety of systems will be desired. Further, should a blast occur, following that blast in general there will have been a complete shorting or arcing of the splice. That is, the splice of concern will be degenerized. However, sparks and small fires may have been started by the process.
Suppression blanket 1 may be utilized to contain or smother such arcs or fires, if it can be readily dismounted from pipe lO. Thus, preferably mounting arrangement 5 is such that a worker, even under the most adverse and extreme emergency conditions, can accomplish dismounting 10 with relatively little difficulty, to manipulate or move suppression blanket 1 as may be desired.
The arrangement 1, Fig. 1, is depicted with a particular mounting arrangement 5 to achieve the above desired results. Referring to Fig. 1, mounting arrangement 5 again comprises a plurality of straps 35.
Each of straps 35 is stitched to edge 40 of blanket portion 4, as indicated at regions 41. In general, this is accomplished through stitching 42. The thread utilized for stitching 42 may, in general, be the same -10- ~ l3 ~ Cjl '?

type of thread as preferably utilized for stitching 20, described above.
For ease of mounting and dismounting, even under adverse conditions and by a worker wearing heavy gloves or the like, preferably straps 35 are hea~y duty straps constructed and arranged to attach around the bar 10 by means of a hook and loop mounting system, such as Velcro . For the arrangement shown in Fig. 1, each strap 35 includes a hook portion 45 and a loop portion 46.
Thus, each strap 35 can be readily mounted over pipe 10 by folding the strap 35 thereover, engaging each hook portion with its associated loop portion, (or vice versa) Fig. 2. The blanket can be readily dismounted, by merely stripping the two portions of material (hook and loop) away from one another.
Preferably a fire retardant material is utilized as straps 35. This will facilitate safe operation.
Suppression blankets 1, according to the present invention, may be prepared in a variety of sizes and dimensions. It is foreseen that 4 ft. by 5 ft.
arrangements and 4 ft. by 8 ft. arrangements will be preferred, for any applications. In general, such arrangements will be approximately 1/4 to 1/2n thick, depending upon the particular materials chosen. An arrangement of such thickness will in general be relatively easy to handle and suspend.
The mounting straps should in general be spaced about 1 to 1 1/2 ft. apart. Thus, a 5 ft. "wide" blanket will generally require about 4 straps, and an 8 ft. wide blanket will generally require about 6 straps.
Preferably each strap is about 2" wide by 24n in length, to facilitate ease of mounting to a variety of pipe to cables.

2~ -~',3~2 The hlanket may be provided with a tie system or strap, not shown, to retain the arrangement "rolled up", between uses.

Materials While a variety of materials may be utilized to generate constructions according to the present invention, through testing an analysis it is to be found that certain materials are preferred for providing strength and adequate containment, flexibility, ease of storage, handling, mounting and dismounting; storage for long periods without substantial deterioration, etc.
These preferred materials, and suppliers of them, are described herein below.
~hs Body Portion ~5 As explained above, preferably the body portion is formed from sheets or panels of a continuous filament strand woven material, such as a filament weave ballistics fabric, arranged in face-to-face relation.
One usable such material as an aramid 24 by 24 count (24 ends per inch in one direction and 24 picks per inch in the other) material having a weight of 9.4 ounces per square yard, and tensile strength of at least about 1100 lbs. warp and about 1200 lbs. fill. If the body portion is formed from two sheets of such material, it will generally be quite adequate for applications of the present invention. One such material is Kevlar 29 aramid S/710-1500 denier available from E.I. Du Pont De Nemoures & Co., Fibers Department, Wilmington, Deleware 19880.

The Face Cloth The face cloth should, in general, be a rip stop weave sufficiently strong to contain the body portion, and such as to provide ultra-violet protection -12- 2~

to the aramid fibers of the body portion. It is preferably formed from a fire retardant or fire resistant material. One such material is an aramid pajama check having a weight of 3.8 ounce per square yard, rip stop weave, trapezoid tear strength of at least about 25 lbs.
warp and 8 lbs. fill. Such a material is available under the designation Nomex from Southern Mills, Inc., Union City, Georgia 30291.

The Hook and Loop Mounting 8traps A particularly desirable material for the hook and loop mounting straps is heavy duty 2" X 24" FR (fire retardant) Velcro strap, available from Aplix Inc., Moorpark, California 93021.
The Stitchinq A particularly useful filament thread for stitching arrangements according to the present invention is aramid thread available under the designation Nomex from Southern Mills, Inc., Union City, Georgia 30291.

Test Conditions Suitability of body material was tested according to the following procedure. A length of 500 NCM copper cable was connected to the bus of high current transformers with a short piece of 2/0 copper cable in the middle to simulate a fusible element. The blanket was placed over the fusible element to be subjected to the full effects of cable fusing and burned into two pieces. The tests were initiated by a timed closing switch. Power for the tests was supplied by a high-current generator and high-current transformers.

Claims (6)

1. A suppression blanket arrangement comprising:
(a) a blanket portion comprising a body portion enclosed within a face sheet arrangement;
(i) said body portion being formed from a material sufficient to provide arc fault containment of at least 42,000 amps at 12 1/2 plus cycles, without blowing through; and, (ii) said face sheet arrangement being stitched to said body portion; and, (b) mounting means for mounting said blanket portion to a bar or the like; said mounting means comprising a plurality of straps mounted on said blanket portion.

2. An arrangement according to claim 1 wherein said body portion comprises two sheets of filament weave fabric, positioned in face-to-face relation to one another.

3. An arrangement according to claim 2 wherein said face sheet arrangement is stitched to said body portion in a pattern comprising a plurality of rows and a plurality of columns of segments.

4. An arrangement according to claim 2 wherein said face sheet arrangement comprises rip-stop weave, fire retardant, aramid fiber material.

5. An arrangement according to claim 2 wherein said body portion comprises two sheets of aramid fiber material having a 24 X 24 count and a tensile strength of at least about 1100 lbs. warp and about 1200 lbs. fill.

6. An arrangement according to claim 1 wherein each one of said plurality of straps includes a hook and loop mounting arrangement thereon constructed and arranged for mounting each strap over a bar or the like.