The present disclosure relates generally to lifting equipment, and more specifically to lifting equipment used in the electric utility industry.
The electric utility industry is seeking to correct existing ground or aerial transmission line clearance problems or increase the capacity of existing electric power transmission lines while maintaining the required ground clearance through upgrades to the current transmission infrastructure. Utilities have increased the loads carried by power lines to meet ever-increasing demand during peak loading conditions, such as, for example, those that occur with seasonal heating and air-conditioning loads. This increased line loading creates additional transmission line sag resulting in wire to ground and or object clearance violations. Also, utilities are faced with increasing wire/hardware ground and aerial clearance requirements brought on by erection of nearby structures and/or new codes and/or regulations, which impose new clearance requirements on existing tower line infrastructure.
To mitigate changing (increasing) line height requirements, some utilities in the industry have addressed the need to increase tower heights by adding a tower extension (insert) to the body of the tower generally located at the waist or mid-portion of the tower. The tower extension increases the tower height and eliminates the need to replace or change out the existing lattice structure or string new cables. The current method involves splitting the tower at its connection location and using a crane to lift the top section of the tower to the desired height so the extension can be placed within the open section of the tower. The extension is then attached to both the top and bottom section of the existing tower. When tower extensions are performed in this manner the power lines, communication lines, and other equipment carried must be de-energized and disconnected and reconnected to the structure once the extension is put in place. This results in considerable downtime of the entire power transmission and communication system. Moreover, this procedure can only be conducted on structures which have near perfectly balanced weight loads so the top suspended section of the tower can be hoisted without rotation. If the weight loads are unbalanced the tower height cannot be increased in this manner.
The present disclosure may comprise one or more of the following features and combinations thereof.
In illustrative embodiments, the present disclosure is directed to an electrical transmission tower lifting device for elevating an upper portion of the electrical transmission tower with respect to a lower portion of the tower from a first elevation to a second elevation. The tower lifting device includes a lower lifting structure, having a plurality of mounts to allow the lower lifting structure to be releasably secured to the lower portion of the tower a distance from the foundation of the tower and a series of lower support members that are interconnected to form the lower lifting structure.
In illustrative embodiments, the tower lifting device also includes an upper lifting structure, that is positioned above and connected to the lower lifting structure, the upper lifting structure includes a plurality of mounts to allow the upper lifting structure to be releasably secured to the upper portion of the tower. The upper lifting structure including a series of upper support members that are interconnected to form the upper lifting structure. Hydraulic lifting cylinders are adapted to be coupled to one of the lower or upper lifting structures to lift the upper lifting structure away from the lower lifting structure to raise the upper portion of the tower to the second elevation. The lifting tower device also includes a controller that is configured to control the movement of the hydraulic lifting cylinder to raise the upper portion of the tower.
These and other features of the present disclosure will become more apparent from the following description of the illustrative embodiments.
For the purposes of promoting an understanding of the principles of the disclosure, reference will now be made to a number of illustrative embodiments illustrated in the drawings and specific language will be used to describe the same.
A tower lift device 10 is shown in
Tower lifting device 10 includes a lower lifting structure 14 and an upper lifting structure 16 that can be raised and lowered with respect to the lower lifting structure 14, as shown in
Lower lifting structure 14 includes the four lifting cylinders 18 that are controlled by a hydraulic controller 24, as shown, for example in
Lower lifting structure 14 also includes a series of brace members 40 that are coupled at a first end 42 to the brackets 26, 30 and to a central hub 44 at a second end 46 to form the lower lifting structure 14. The brace members 40 include removable pins 48 at their ends to permit removal and assembly. Brace members 40 are adjustable so that they can be lengthened or shortened as needed to properly square lower lifting structure 14. Some brace members 40 extend diagonally between lift cylinders 18 and some extend horizontally to for a rigid lower lifting structure 14. Upper ends 28 of lift cylinders 18 include a boot 50. Boot 50 is an independent piece, which threads onto second end 56 of vertical supports 52 to allow for fine adjustment between the connection of the upper and lower lifting structures.
The upper lifting structure 16 including four vertical supports 52 that are coupled to the shafts 54 of the hydraulic lifting cylinders 18, as shown in
Upper lifting structure 16 also includes brace members 40 that are coupled at a first end 42 to the brackets 60 and to a central hub 44 at a second end 46 to form the upper lifting structure 16. The brace members 40 include removable pins 48 at their ends to permit removal and assembly. Brace members 40 are adjustable so that they can be lengthened or shortened as needed to properly square upper lifting structure 16. Some brace members 40 extend diagonally between vertical supports 52 and some extend horizontally to for a rigid upper lifting structure 16.
Overall height of transmission tower 12 is increased by use of tower lift device 10, as shown in
While a four legged tower is shown, it is to be understood that the tower lifting device 10 can be applied to any lattice tower configuration including multiple column framed structures and three and four legged structures. An example would be an H-frame lattice structure, which includes four legs in each of its columns. The tower lifting device 10 can also be used with any voltage source including AC or DC and for any voltage level, for low voltage distribution to high voltage transmission and from single circuit to multiple circuit tower configurations. The tower lifting device 10 can also be utilized to raise tangent and angle and dead-end towers including unequal span tensions across the cable attachment points.
As
The upper tower section 20 is similarly formed of lattice frame members 66, as shown in
When the transmission tower 12 includes an inclined foundation portion 78 in which a horizontal width of the tower becomes narrower with increasing distance from the foundation, the upper and lower tower sections 20, 22 are selected such that the foundation portion 78 is fully defined within the lower tower section and such that the upper tower section is fully spaced above the foundation portion. Accordingly, the lattice frame members 66 between upper and lower tower sections 20, 22 comprises vertically oriented frame members.
In the next step in the process, mounting locations for the hydraulic lifting cylinders 18 and vertical supports 52 are identified as illustrated at in
In the next step in the process, tower lifting device 10 is installed in lattice tower 12 and splice plates 76 are removed from the tower 12, as shown, for example in
In the next step of the process and after the upper tower section 20 of the lattice tower 12 is elevated to the desired height, tower extensions 82 are installed, reconnecting the upper and lower tower sections 20, 22, as shown in
The hydraulic lifting cylinders 18 and the vertical supports 52 collectively define a lifting assembly. The vertical supports 52 of the upper lifting structure 16 include mounts 56, 58 for coupling to the lattice frame members 66 of the upper tower section 20. The hydraulic lifting cylinders 18 also include a plurality of lower mounts 34 for coupling to the lattice frame members 66 of the lower tower section 22.
The size and number of hydraulic lifting cylinders 18 are pre-determined based on the weight of the upper tower section 20 to be lifted and load carrying capacities of the hydraulic lifting cylinders 18. While the system illustrated herein includes four hydraulic lifting cylinders 18, depending on tower size and lift 10 requirements a single hydraulic lifting cylinder 18 may be sufficient or a grouping of four (or more) may be required.
Additional temporary bracing in the form of the upper and lower brace members 40 are secured to the hydraulic lifting cylinders 18 through pin/bolted connections at mounting locations in order to transmit static/dynamic loading from the hydraulic lifting cylinders 18 back to the original tower lattice structure 12. The tower lifting device components are arranged to be assembled so that they are fully contained within a perimeter boundary defined by the lattice frame members 66 of the upper and lower tower sections 20, 22. The reinforcement structure also provides structural support for temporary working platforms 83 from which personnel can carry out required activities, as shown in
The worker platform 83 which is arranged to support workers thereon is preferably supported on either one of the lower or upper lifting structures 14, 16 of the tower lifting device 10 so as to be also fully contained within the perimeter boundary defined by the lattice frame members 66 of the upper and lower tower sections 20, 22. The material, component thicknesses, and geometric orientation of the temporary supporting truss structure are pre-determined so as to provide the required additional structural support as required to ensure the original lattice frame members 66 are not overloaded.
Once lifting and temporary bracing components have been secured the hydraulic lifting cylinders 18 are pre-loaded so as to remove tension/compression from the lattice tower frame members 66 by applying pressure from the jacking system in the appropriate direction(s). Pre-loading of the lifting system permits the loosening of tower bolts on the splice plates 76 joining the upper tower section 20 and the lower tower section 22.
Once the splice section bolts are loosened the lifting jack pressure(s) are adjusted until the hydraulic lifting cylinders 18 and temporary vertical supports 52 are taking up the entire upper section static load and then the splice bolts are removed allowing separation of the upper tower section 20 from the lower tower section 22.
Once the upper tower section 20 is free from the lower section 22 the hydraulic lifting cylinders 18 can be used to raise the upper section 20 to a desired raised height as shown in
Once the load of the upper tower section 20 and cables is carried by the tower lifting device 10, the hydraulic lifting cylinders 18 of the are uniformly actuated to raise the vertical supports 52 and the upper tower section 20 coupled thereto relative to the lower tower section 22 coupled thereto from a first elevation to a second elevation. The hydraulic lifting cylinders 18 include respective individual fluid volume controls such that each actuator individually and independently lockable for statically supporting the upper tower section 20 relative to the lower tower section 22 at either one of the first or second elevations or any desired elevation in between.
The fluid volume controls associated with the hydraulic lifting cylinders 18 permit the hydraulic lifting cylinders 18 to be uniformly extended by delivering a controlled volume of hydraulic fluid to each hydraulic lifting cylinder 18 to evenly and uniformly raise the upper tower section relative to the lower tower section even if some of the hydraulic lifting cylinders 18 are under tension and other hydraulic lifting cylinders 18 are under compression. The hydraulic lifting cylinders 18 are also provided with a pressure relief arranged to release the actuation thereof in response to a hydraulic fluid pressure which exceeds a prescribed upper limit indicative of deformation of the lattice frame members 66 of the upper or lower tower sections 20, 22.
With the upper tower section 20 raised, tower extensions 85 are installed in any safe construction fashion, including aerial framing piece by piece in a safe and efficient manner. The tower extensions 85 comprises a plurality of auxiliary frame members which are fixed between the lattice frame members 66 of the upper tower section 20 and the lattice frame members 66 of the lower tower section 22 with suitable bolted or pinned connections for permanently supporting the upper tower section 20 on the lower tower section 22 at the second elevation.
Depending on tower configuration the tower extensions 85 can be secured to either the upper or lower sections 20, 22 first and then to the opposing section next. In this step, it is preferred if the bolts are left loose to allow for easier attachment of the opposing end of the tower extensions 85. After the tower extensions 85 have been loosely secured, the tower can be checked for level and plumb and adjusted accordingly using the hydraulic lifting cylinders 18.
After ensuring the inserted tower extension 85 is level and plumb all the bolts attaching the new tower extension 85 can be torqued to the appropriate specification. Once all the tower bolts are tightened, the hydraulic lifting cylinders 18 can operated to transfer the load to the auxiliary frame members of the inserted tower extensions 85 which then supports the upper tower section 20 on the lower tower section 22 at the second elevation. The tower lifting device 10 can then be removed with any temporary modifications to the original tower and or bracing including the addition or removal of additional bracing restored to pre-lift conditions. Any field drilled holes are to be treated as per the utility specifications to prevent corrosion.
While the disclosure has been illustrated and described in detail in the foregoing drawings and description, the same is to be considered as exemplary and not restrictive in character, it being understood that only illustrative embodiments thereof have been shown and described and that all changes and modifications that come within the spirit of the disclosure are desired to be protected.
This application claims priority under 35 U.S.C. § 119(e) to U.S. Provisional Application Ser. No. 61/638,165, filed Apr. 25, 2012 and Application Ser. No. 61/749,541, filed Jan. 7, 2013, which are both expressly incorporated by reference herein.
Number | Date | Country | |
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61638165 | Apr 2012 | US | |
61749541 | Jan 2013 | US |