Patent Application
20210108436
The present invention relates generally to support poles for elevated objects such as utility lines, and particularly to protecting wood utility poles from fire damage.
Utilities commonly install wood poles for suspending utility lines such as electric conductors and cables. A long-standing problem is that wood poles exposed to fire will ignite and burn near the ground level. Severely burnt poles can fail and come down, causing safety and reliability issues, as well as blocking access. This is particularly problem-some in areas that are remote and/or that have high incidences of wildfires, for example much of the western United States.
One conventional practice is to apply a fire retardant to the exposed base of each pole in an effort to reduce the likelihood of the pole igniting. Another conventional practice is to apply herbicides on the ground around the base of each pole in an effort to minimize the growth of vegetation that can ignite and in turn cause the pole to ignite. These solutions require regular vegetation-maintenance visits for reapplications and growth removal, and as such have not proven satisfactory in practice.
Accordingly, it can be seen that needs exist for improvements in protecting wood support poles from fire damage. It is to the provision of solutions meeting this and other needs that the present invention is primarily directed.
Generally described, the present invention relates to pole-protection systems and methods that include a peripheral apron positioned around the pole and sized to form a desired vegetation-free zone, and a cover that covers and protects the apron. In example embodiments, the apron is made of a woven geotextile fabric with an annular shape, with a central opening for receiving the pole, with a radial slit forming free ends for displacing to install the apron around the pole and for returning and fastening in place to form a continuously extending peripheral sheet. And the cover is made of crushed and washed rock forming a rock bed that covers the apron to protect and insulate it from UV radiation and fire damage. Accordingly, the pole-protection systems and methods protect the poles from fire damage by forming a vegetation-free buffer zone around them that needs little or no routine maintenance to retain its effectiveness.
The specific techniques and structures employed by the invention to improve over the drawbacks of the prior art and accomplish the advantages described herein will become apparent from the following detailed description of example embodiments of the invention and the appended drawings and claims.
Referring now to the drawing figures,
The pole protector 10 is shown and described herein for use in protecting poles 8, which are intended to be broadly construed to include not just conventional cylindrical wooden utility poles but also other wood structures (e.g., frames, masts, uprights, posts, trees, large irrigation risers, etc.) for supporting other elevated objects and also poles made of other materials (e.g., metal poles that are not flammable but that can structurally weaken upon exposure to extreme heat). Also, the pole protector 10 is described herein for use in protecting poles 8 supporting elevated electric utility lines (e.g., conductors and cables) 4, but it can alternatively be used to protect poles supporting other elevated objects (e.g., CATV lines, outdoor lamps, cellular-network communications equipment, etc.) as well as to protect other objects such as pad-mounted utility and telecommunications equipment.
Referring to
The apron 12 is made of a material selected for high strength and balanced permeability. In particular, the material of the apron 12 has a permeability (including water flow rate) that is sufficiently high to enable rainwater from normal rainfalls to drain/flow through it and into the ground 6 so that the water does not pool on the apron 12 and sit in or on the cover 14 enabling vegetation to grow upward from on top of the apron 12. At the same time, the material of the apron 12 has a permeability (including apparent opening/pore size) that is sufficiently low (with a sufficiently small opening/pore size) to prevent or at least minimize vegetation growth upward through it. For example, the apron material can have a permeability of about 0.0048 cm/sec to about 0.0032 cm/sec (or about 0.0044 cm/sec to about 0.0036 cm/sec more typically, or about 0.004 cm/sec in an example commercial embodiment) and a water flow rate of about 7.2 g/min/sf to about 4.8 g/min/sf (or about 6.6 g/min/sf to about 5.4 g/min/sf more typically, or about 6 g/min/sf in an example commercial embodiment).
Also, the material of the apron 12 has as a strength (e.g., tensile strength and puncture strength) that is sufficiently high to resist penetration by vegetation growth (e.g., it does not deform or fail under forces from vegetation growth) and to provide good durability (i.e., it's not easily punctured or torn by forces created by uneven ground 6, by the cover 14, and/or by persons walking on the cover 14). For example, the apron material can have a tensile strength of about 240 lbs to about 160 lbs (or about 220 lbs to about 180 lbs more typically, or about 200 lbs in an example commercial embodiment) and a puncture strength of about 120 lbs to about 80 lbs (or about 110 lbs to about 90 lbs more typically, or about 100 lbs in an example commercial embodiment).
This balanced permeability, combined with this high strength, prevent the majority of vegetation from being able to grow in the area where the apron 12 is installed around the pole 8. The balanced permeability of the apron 12 enables rainwater to flow down through it, past and away from the cover 14, to help keep the cover 14 clean so that windblown seeds to not lodge in the cover 14 and sprout vegetation growth, and at the same time is not easy for vegetation to grow through from below. Small amounts of short grasses may sprout seasonally, but any such growth would be insignificant because it would have almost no ability to root (the roots cannot typically grow downward through the apron 12 due to its permeability as described above). As such, the term “vegetation-free” is intended to mean substantially free of vegetation (not necessarily absolutely free of all vegetation) and further to refer to vegetation that is rooted in the ground and can act as fuel for fire, such that scattered tufts of unrooted short grass may still sprout/occur. In this way, use of the pole protector 10 eliminates, or at least substantially limits/controls, growth in the vegetation-free zone of any vegetation that can act as fuel for a fire.
In addition, the apron 12 material is typically selected with a sufficient flexibility so that it can be laid down on uneven ground and will generally conform to the ground (e.g., under the force of its own weight and the weight of the cover 14) for stability and to prevent undergrowth of vegetation. Also, the apron 12 material is typically selected with sufficient roughness/gripping properties that the cover 14 is frictionally encouraged to stay in place over it without additional securement.
In example embodiments, the apron 12 is made of a sheet of geotextile fabric selected with the prescribed high strength and balanced permeability. Typically, the geotextile fabric is a woven material, for example a cross-woven geotextile fabric in the medium strength category (e.g., about 150 oz to about 315 oz). In an example commercial embodiment, the medium-strength woven geotextile fabric is a 200 oz. woven geotextile fabric, for example about 22 mils thick, and for example made of high UV, non-biodegradable polypropylene tapes. One such geotextile sheet material is commercially available under the name AEF 200W woven geotechnical fabric (manufactured by American Engineered Fabrics) and available for purchase from US Fabrics, Inc. (Cincinnati, Ohio). Example properties of the AEF 200W geotextile sheet material are provided in Table A.
In other embodiments, the apron is made of another geotextile or other sheet material having the prescribed high strength and balanced permeability. Such other materials can include plastics, metals, composites, etc.
In addition, the apron 12 is sized to provide the desired vegetation-free zone around the pole 8. In typical embodiments, the apron 12 has an outer dimension 16 at its outer edge that defines the laterally outward extent of the vegetation-free zone and an inner dimension 18 at its inner edge that defines an internal opening 20 for receiving the pole 8. In typical embodiments, the pole 8 is cylindrical and the apron 12 has an annular shape with an inner diameter 18 forming a central opening 20 and with an outer diameter 16 forming a circular vegetation-free zone. In other embodiments, the apron can have another shape (including rectangular, polygonal, or another regular or irregular shape) as may be desired for a particular application.
Typically, the annular apron 12 has an outer diameter/edge 16 selected based on the particular application, specifically, to provide a vegetation-free buffer zone of a large-enough size for the type of vegetation/fuel present in that area (taller vegetation needs to be kept farther away from the pole 8 so that it does not grow laterally against and/or get blown against the pole 8). For example, in one embodiment the annular apron 12 has an outer diameter 16 of about 4 feet for use in areas with relatively short grasses (e.g., under about 10 inches in height), in another embodiment the annular apron 12 has an outer diameter 16 of about 8 feet for use in areas with relatively tall grasses (e.g., about 12 inches to about 48 inches in height) and/or relatively low bushes (e.g., about 12 inches to about 96 inches in height), and in yet another embodiment the annular apron 12 has an outer diameter 16 of about 10 feet for use in areas with relatively tall bushes (e.g., about 60 inches or more in height, such as manzanita, bottle brush, and/or scotch broom). In another embodiment, the annular apron 12 has an outer diameter 16 of about 20 feet for use at non-exempt locations (e.g., for poles supporting lightening arrestors, fuses, solid-blade disconnect switches, and/or other pole-mounted electrical equipment) not just insulators, where some jurisdictions require a minimum 15-foot radius area treated with herbicide or cleared down to dirt at all times. As such, the apron 12 typically has an outer diameter/edge 16 of anywhere in the range of about 4 feet to about 20 feet, though in other embodiments it can be larger or smaller.
In addition, the annular apron 12 has an inner edge/diameter 18 selected based on the lateral size/dimension (e.g., diameter) of the pole 8 to be protected. In particular, the inner edge diameter 18 is selected so that the central opening 20 provides a snug fit against the pole 8 so that there's insufficient space between the apron 12 and the pole 8 for vegetation to grow through. As such, the inner diameter 18 of the apron 12 generally conforms to the outer diameter 7 of the butt of the pole 8, with the apron inner diameter thus typically being about the same as, or nominally smaller than, the outer diameter 7 of the pole 8. For example, in one embodiment the annular apron 12 has an inner diameter 18 of about 12 inches for use with a pole 8 having an outer diameter of about 12 inches, in another embodiment the annular apron 12 has an inner diameter 18 of about 16 inches for use with a pole 8 having an outer diameter of about 16 inches, and in yet another embodiment the annular apron 12 has an inner diameter 18 of about 20 inches for use with a pole 8 having an outer diameter of about 20 inches.
The apron 12 can be preformed and provided in several different sizes for the various applications, for example including the diameters indicated above. In some embodiments, the apron 12 is provided with an outer diameter 16 for forming one of the larger vegetation-free zones and with an inner diameter 18 for use with one of the smaller sizes of poles 8, and then during installation the apron 12 can be field cut to enlarge the inner diameter 18 for use with a pole 8 having a larger outer diameter 7. For such embodiments, the apron 12 material is selected with a thickness, weight, and/or strength that is not so great that the apron 12 cannot be field-fitted using conventional hand-held cutting tools.
Furthermore, in typical embodiments the apron 12 includes a slit 22 extending radially all the way through the apron from the outer diameter 18 to the inner diameter 16. The radial slit 22 enables the free ends 24 (formed by the slit) to be displaced relative to each other so that the opening 20 can be “opened” to place the apron 12 around the pole 8 and then “closed” to form the continuously extending peripheral configuration for use. Fasteners 26 can be provided for securing the free ends 24 in place (e.g., to the ground and/or to each other) after the apron 12 has been configured for use (i.e., positioned around the pole 8 with the opening 20 closed). In example embodiments, the fasteners 26 are provided by U-shaped staples made of steel or another metal and for securing into the ground 6. In other embodiments, other fasteners are used (e.g., anchors or stakes). And in some other embodiments, the apron is provided without the slit and is for use in new pole installation only (the apron is set down in position around a pole hole before the pole is erected) and/or a radial slit is field-cut if used for retrofit installation on an existing pole (including poles installed recently and those installed long ago).
Turning now to the cover 14, it protects the apron 14 from UV degradation and fire damage. As such, the cover 14 is selected so that it completely covers the apron 12 such that the apron 12 is substantially (if not completely) shielded from exposure to sunlight (and thus substantially concealed from view) so that it does not degrade and thereafter allow vegetation to grow through it. Also, the cover 14 is selected so that it insulates the underlying apron 12 from heat during a fire sufficiently that the apron 12 does not degrade and thereafter allow vegetation to grow through it. Because the cover 14 completely covers the apron 12, it extends peripherally and continuously all the way around the pole 8, and as such it has an internal (e.g., central) opening as well.
In some embodiments, the cover 14 can be further selected as a ballast to assist in holding the apron 14 in place (e.g., so that the apron's outer/free edges do not get upturned and allow vegetation undergrowth), while in other embodiments the apron is secured in place (e.g., to the ground) by conventional fasteners (e.g., staples, anchors, stakes, or clips) and the cover need not function to help secure the apron in place but merely to protect it. And in some embodiments, the cover 14 can be further selected to form a stable platform upon which workers can walk and stand.
As noted above, in the depicted embodiment, the cover 14 is a layer of rock material forming a rock bed. The rock-bed cover 14 can be provided by for example about ½-inch to about 2-inch rock, typically about ¾-inch to about 1%-inch rock, and preferably about ¾-inch to about 1-inch rock (this size tends to compact and lock together well). And the rock is stacked about 2 inches to about 8 inches in height (the rock-bed thickness), typically about 2 inches to about 3 inches (this thickness sufficiently covers the apron 12 and avoids unnecessary digging out of rock for sub-surface pole inspections). The resulting rock bed cover 14 provides a thickness for sufficient heat-insulation to minimize heat damage to the apron 12 from surrounding fires, provides a shield from UV sunlight damaging the apron 12, and provides a sufficiently heavy ballast to hold the apron 12 in place. Typically, the rock is crushed and then washed so that it contains no fines and is free of seeds, and is from a quarry that is free of native material such as seeds. Such rock is commercially available in for example 9 cu ft bags.
In other embodiments, smaller or larger rock is used to form a rock bed of larger or smaller height/thickness, for example pea rock, D-Ballast, gravel, flat stones, crushed concrete, or composites can be used. In other embodiments, the rock bed can be made of other types of rock material such a bricks, concrete blocks, or cinder blocks. And in still other embodiments, other types of cover can be used such as asphalt paving or poured-in-place concrete. Generally, the cover can be provided by any material meeting the UV and fire protecting functions and typically also assisting in the securing function, but that does not support vegetation growth. As such, dirt and other vegetation-supporting materials are typically not used as or mixed into the cover material.
Referring now to
Finally,
In applications in areas where permitted, a herbicide can be applied, for example on top of the cleared ground 6, on top of the apron 12, and/or on top of the cover 14. For example, a slow-release granular pre-emergent herbicide can be used.
The pole protector 10 thereby provides a strong barrier against vegetation growth that eliminates (or at least substantially limits/controls) vegetation growth around wood poles 8, effectively providing a defensible vegetation-free buffer zone for the pole. Eliminating the “fuel” near the pole 8 drastically reduces the likelihood of the pole 8 catching fire. And the pole protector 10 is effective over long periods of time, so it keeps vegetation away from the poles 8 with minimal or no routine maintenance. The result is a significant decrease in pole-line losses from wildfire and in pole-line vegetation-removal maintenance. In addition, because the pole protector 10 keeps the area around the poles 8 clean, it also results in improved access for maintenance and inspection. Accordingly, the pole protector 10 can be advantageously used in applications including newly built hardened utility lines in rural tier ⅔ areas, wood pole lines along critical evacuation routes, or just an everyday pole line running through a grassy field that burns often.
It is to be understood that the invention is not limited to the specific devices, methods, conditions, or parameters described and/or shown herein, and that the terminology used herein is for the purpose of describing particular embodiments by way of example only. Thus, the terminology is intended to be broadly construed and is not intended to be unnecessarily limiting of the claimed invention. For example, as used in the specification including the appended claims, the singular forms “a,” “an,” and “one” include the plural, the term “or” means “and/or,” and reference to a particular numerical value includes at least that particular value, unless the context clearly dictates otherwise. In addition, any methods described herein are not intended to be limited to the sequence of steps described but can be carried out in other sequences, unless expressly stated otherwise herein.
While the invention has been shown and described in example forms, it will be apparent to those skilled in the art that many modifications, additions, and deletions can be made therein without departing from the spirit and scope of the invention as defined by the following claims.
