Abstract:
A mobile jack for raising and lowering a floating storage tank roof. The mobile jack includes a fluid-actuated cylinder and ram housed in a jack structure having multiple telescoping sections. The jack is designed to slide onto the forks of equipment to transport the jack to a desired location beneath the roof in preparation for lifting the roof and can be clamped to retain the jack in place during transport. The cylinder and ram are utilized to extend and retract a portion of the jack structure to raise and lower the roof of the floating roof storage tank.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates generally to storage tanks and, more particularly, to storage tanks having floating roofs, that is, roofs that float on material contained in the storage tank and move upwardly and downwardly depending upon the volume of material contained in the tank. More particularly, various embodiments of the present invention provide a system and method for servicing (e.g., maintaining and repairing) floating roof storage tanks. In one example, a mobile jack is provided to raise and lower the roof of a floating roof storage tank in a safe and effective manner to service the tank, for example, to enable replacement of one or more deteriorated sections of the floor of the tank. 
         [0003]    2. Description of the Prior Art 
         [0004]    By way of background, storage tanks that comprise floating roofs are commonly employed to store fluid materials such as petroleum products. For example, a storage tank having a floating roof is disclosed in U.S. Pat. No. 3,521,416. The disclosure in that patent is hereby incorporated in its entirety by this reference and discloses an example of a floating roof storage tank structure. The storage tank comprises a cylindrical side wall indicated by the numeral  16 , a flat floor  17 , a center column  18 , and a floating roof  36 . 
         [0005]    The roofs inside such storage tanks float on the products contained in the tanks while the tank is in service. When the tank is empty, multiple legs that extend downwardly move into contact with the floor of the tank to support the roof. 
         [0006]    The floors of storage tanks with floating roofs are typically constructed from metal plates that are joined together, for example, by welding. These floor plates are known to deteriorate over time due to corrosion caused by contact with the stored products and electrolysis, as well as mechanical forces including the weight of the stored products, settling due to gravity, and fatigue due to climate changes such as temperature variations. Consequently, the mechanical integrity of the floor plates can be compromised and, also, leaks may result creating a risk of damage to the environment. Therefore, the condition of the floor must be periodically inspected, and the floor plates must be repaired or replaced if damage to the floor is detected. 
         [0007]    While repairing or replacing a floor in the storage tank, each of the legs must be lifted to slide a new floor plate(s) under the legs. Furthermore, if a leg is deteriorated, the load on the leg primarily due to the weight of the floating roof must be relieved by lifting the roof so that the deteriorated leg may be removed and replaced. Also, there is typically a leg pad that protects the floor during contact with the leg, which also requires lifting the floating roof to slide the leg pad under the associated leg. 
         [0008]    Servicing of floating roof storage tanks is hazardous. Prior to servicing, any remaining stored material is drained from the tank, and consequently the legs support the roof. The roof is typically jacked off the floor to lift the roof and enable the floor plates to be repaired of replaced. However, floating roofs can become unstable and can collapse when jacking the roof to perform the service. The amount of time spent jacking the roof and working under a floating roof while servicing the tank determines the time that a worker is exposed to various risks. Jacking is also an inherently safety-sensitive operation which can jeopardize safety when known jacking equipment is employed to lift the roof. 
         [0009]    Thus, there are shortcomings to known jacking equipment for floating storage tank roofs that render the jacking equipment ineffective and/or expose workers to hazards during use. In view of the shortcomings of known jacking equipment, the jacking device in accordance with the embodiments of the present invention will greatly reduce the amount of time required to jack each leg of a floating roof. The jacking device in accordance with the embodiments of the present invention will also provide a very dependable and repeatable jacking method compared to various other techniques commonly used. 
         [0010]    The present invention solves the long-extant problem of safely lifting a floating storage tank roof, so that the roof is raised with reduced risk of injury to workers servicing the tank. One preferred embodiment in accordance with the present invention provides a mobile hydraulic floating roof jack and method for lifting the roof of a floating roof storage tank. Furthermore, various embodiments of the present invention provide an improved jacking device of the character described that may be manufactured at low cost. 
       SUMMARY OF THE INVENTION 
       [0011]    It is a general object of the present invention to provide an apparatus to efficiently and safely lift a roof of a substantially empty floating roof storage tank for the purpose of servicing the tank. Generally, the embodiments in accordance with the present invention provide a mobile jacking device specifically designed for use under floating roofs of storage tanks. For example, one embodiment provides a mobile jacking device adapted to lift a leg attached to the roof, as well as any protective pad between the leg and a floor of the tank, sufficiently above the floor so that the floor, which may comprise a pattern of metal plates that are joined together, can be repaired or a particular plate or plates can be replaced. 
         [0012]    Various embodiments are provided in accordance with the present invention. In accordance with one example embodiment, the mobile jacking device comprises a fluid-actuated, for example, a hydraulic, jack for raising the roof of a floating roof storage tank. The jacking device comprises a hydraulic ram cylinder integrated into a structural support system. The support system is designed to slide onto the forks of transport equipment such as a typical skid-steer loader. The forks of the skid-steer loader insert into channels on the base to which the jacking device is mounted and can be clamped to retain the jacking device in place. The mobile jacking device can then be transported to a desired location beneath the roof in preparation for lifting the roof. The hydraulic ram cylinder is preferably constructed to be hydraulically actuated by the hydraulic supply system that is already present on the transport equipment. 
         [0013]    In operation, the skid-steer loader operator drives the jacking device from jack point to jack point to position the jack on the floor of the storage tank and then using the onboard hydraulics to actuate the hydraulic ram cylinder to lift the floating roof. The structural support system is designed to have a failure capacity above the hydraulic cylinder capacity, rendering the jacking device inherently safe, as the hydraulic system is incapable of overloading the structure. Also, the jacking device provided by the invention is preferably used by a worker located inside the safety cage of the skid-steer loader, so that additional inherent safety is provided to the worker operating the jacking device. 
         [0014]    Accordingly, the jacking device in accordance with the various embodiments of the present invention will greatly reduce the amount of time required to jack each leg of a floating roof. It will also provide a very dependable and repeatable jacking method compared to known commonly used techniques. 
         [0015]    The foregoing and other objects, features, and advantages of the present invention will become more readily apparent from the following detailed description of various embodiments, which proceeds with reference to the accompanying drawing. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0016]    The various embodiments of the present invention will be described in conjunction with the accompanying figures of the drawing to facilitate an understanding of the present invention. In the figures, like reference numerals refer to like elements. In the drawing: 
           [0017]      FIG. 1  is an isometric view illustrating an embodiment of the jacking device in accordance with the present invention, in which a fluid-actuated ram cylinder or piston is disposed to raise the roof of a floating roof storage tank. 
           [0018]      FIG. 2  is an isometric view illustrating the base, the lower section of the housing for the fluid-actuated ram cylinder, and telescoping structure forming the jack, as well as the fluid supply fittings for the actuator of the jacking device, in accordance with the embodiment of the present invention shown in  FIG. 1 . 
           [0019]      FIG. 3  is an isometric view illustrating the upper section of the housing for the fluid-actuated ram cylinder and the middle and upper portions of the telescoping jack structure of the jacking device in accordance with the embodiment of the present invention shown in  FIG. 1 . 
           [0020]      FIG. 4  illustrates a schematic diagram of an example of a mechanism for extending and retracting a telescoping jack structure comprising the embodiment shown in  FIG. 1 . 
           [0021]      FIG. 5  illustrates the embodiment of the mobile jacking device shown in  FIG. 1  mounted on the forks of a skid-steer loader to transport the mobile jacking device to a desired location. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0022]    Various example embodiments are contemplated in accordance with the present invention. Referring now to the drawing,  FIG. 1  is an isometric view illustrating an embodiment of the jacking device in accordance with the present invention, generally indicated by the numeral  10 . The jacking device  10  comprises a roof jack base  12 . Preferably, a first channel  14 A and a second channel  14 B are provided on the base  12 . For example, the channels  14 A and  14 B may be constructed from steel and welded to the base  12 . The dimensions of the channels  14 A and  14 B may be approximately 7.0 inches wide and 2.625 inches high so that they are sized to receive forks of transporting equipment, as will be described in more detail later. The channels  14 A and  14 B preferably comprise one or more threaded holes  14 A 1  and  14 B 1  into which respective bolts  16 A and  16 B are threaded and which may be tightened to firmly secure the base  12  to the forks of the transporting equipment. 
         [0023]    As shown in  FIGS. 1 and 4 , the jacking device  10  also comprises a jack structure  18  which houses a fluid-actuated actuator  20  to raise the roof of a floating roof storage tank when the fluid-actuated actuator is actuated. As shown in  FIGS. 1 and 4 , in a first embodiment, the jacking device  10  comprises a hydraulic jack  22  having a ram  24  disposed in a first, or lower, section  26  of the jack structure  18 . 
         [0024]    Referring to  FIGS. 1 ,  2 , and  4 , the lower section  26  of the jack structure  18  comprises a tubular structure, for example, an approximately 8-inch square steel tube. In one example embodiment, the lower section  26  of the jack structure  18  is removably attached to the base  12 . In the example embodiment, as best shown in  FIGS. 1 and 2 , four steel flanges  28 A,  28 B,  28 C, and  28 D are attached to the base  12 . For example, the flanges  28 A-D may be welded to the base  12 . Additionally, four steel flanges  30 A,  30 B,  30 C, and  30 D are attached to the lower section  26  of the jack structure  18 . For example, the flanges  30 A-D may be welded to the lower section  26  of the jack structure  18 . The flanges  28 A-D and  30 A-D are provided with holes, for example, two vertically spaced holes. The holes in the respective flanges  28 A and  30 A,  28 B and  30 B,  28 C and  30 C, and  28 D and  30 D align when the bottom portion of lower section  26  of the jack structure  18  is mated to the base  12 . As shown in  FIGS. 1 and 4 , the lower section  26  of the jack structure  18  may also comprise lifting lugs  31 A and  31 B to which a hoist (not shown) may be connected to facilitate positioning of the lower section  26  of the jack structure  18  with respect to the base  12  during assembly. After the holes in the flanges  28 A-D and  30 A-D are aligned, securing means  32 , for example, bolts that extend through the aligned holes and onto which a washer and lock washer are placed and then a nut is threaded, is employed to securely attach the lower section  26  of the jack structure  18  to the base  12 . The base  12  of the jacking device  10  preferably includes these bolted connections so that the jacking device can be disassembled to remove and replace the hydraulic cylinder  22  and ram  24  if necessary. 
         [0025]    In the example embodiment shown in  FIG. 4 , the hydraulic jack  22  having the ram  24  is disposed in the lower section  26  of the jack structure  18 . In order to actuate the hydraulic jack  22  to extend or retract the ram  24 , access holes  34 A and  34 B are provided in the lower section  26  of the jack structure  18 . As shown in  FIG. 2 , cylinder nipples  36 A and  36 B extend through respective holes  34 A and  34 B. Cylinder couplings  38 A and  38 B are attached to cylinder nipples  36 A and  36 B, respectively. Preferably, cylinder couplings  38 A and  38 B are hydraulic quick coupler type couplings. Hydraulic supply lines, or hoses,  40 A and  40 B may then be attached employing the cylinder couplings  38 A and  38 B, respectively, as shown in  FIGS. 1 ,  2 , and  4 . 
         [0026]    As shown in  FIGS. 1 ,  3 , and  4 , the example embodiment of the jack structure  18  also preferably comprises a second, or middle, section  42  comprising a tubular structure, for example, an approximately 7-inch square steel tube. As shown in  FIG. 4 , the middle section  42  of the jack structure  18  is slidably mounted within the lower section  26  of the jack structure, and the bottom of the middle section is engaged by the top of the ram  24 . Accordingly, when the hydraulic cylinder  22  is actuated to extend or retract the ram  24 , the middle section  42  of the jack structure  18  telescopes upwardly or downwardly within the lower section  26  of the jack structure. 
         [0027]    In accordance with the example embodiment shown in  FIGS. 1 ,  3 , and  4 , the jack structure  18  also preferably comprises a third, or upper, section  44  comprising a tubular structure, for example, an approximately 6-inch square steel tube, to which a roof-engaging circular plate, or pedestal,  46  is attached. For example, the pedestal  46  may be a 1.0-foot circular steel plate welded to the top of the upper section  44  of the jack structure  18 . As shown in  FIG. 4 , the upper section  44  of the jack structure  18  is slidably mounted within the middle section  42  of the jack structure, such that the upper section of the jack can telescope within the middle section. However, a reinforced hole  48  is preferably provided in the top portion of the middle section  42  of the jack structure  18  to accommodate a hitch pin  50 . Also, a plurality of holes  52  is provided along the length of the upper section  44  of the jacking structure  18 . For example, the holes  52  may be spaced approximately 4.0 inches apart center-to-center. Consequently, the upper section  44  of the jacking structure  18  can be locked in position with respect to the middle section  42  by aligning one of the holes  52  in the upper section with the hole  48  in the middle section and inserting the hitch pin  50  through the aligned holes. Therefore, when the hydraulic cylinder  22  is actuated to extend or retract, the middle section  42  and upper section of the jack structure  18  telescope together with respect to the lower section  26  of the jack structure. As a result, the top of the jacking device  10  preferably has an extension section that can be pinned in position at various lengths. This allows the jacking device  10  to be employed for various heights of floating roofs, but still utilize a commercially available hydraulic cylinder  22  typically having a standard 18-inch stroke. 
         [0028]    The jack structure  18  and hydraulic cylinder  22  in accordance with an example embodiment are preferably constructed to have a tight fit and have a stable base  12  so that the jacking device  10  does not allow excessive lateral movement of the floating roof when the roof is lifted. To this end, spacers (not shown) may be welded to the interior corners or interior or exterior surfaces of the square tubes utilized to construct the lower section  26 , middle section  42 , and/or upper section  44  if needed to provide a tight fit of the hydraulic cylinder  22  within the lower section  26  and/or to reduce the gap between the various sections of the jack structure  18  to enable the sections to telescope without allowing unacceptable wobble of the sections. 
         [0029]    The jack structure  18  is preferably designed to have a failure capacity above the rated capacity of the hydraulic cylinder  22 . Consequently, the jacking device  10  is inherently safe as the hydraulic supply system is incapable of overloading the structure. 
         [0030]    In operation, referring to  FIGS. 4 and 5 , an operator of transporting equipment, for example, a skid-steer loader  60  having a protective cage  62 , drives the jacking device  10  from jack point to jack point. At each jack point, the operator locates the jacking device  10  on the floor of the storage tank and positions the pedestal  46  directly beneath the desired contact area of the floating roof. Then, using the onboard hydraulics of the skid-steer loader  60 , the operator hydraulically actuates the hydraulic cylinder  22  to extend the ram  24  and impart upward movement to the middle and upper sections  42  and  44  of the jack structure  18  to raise the floating roof. 
         [0031]    In summary, the jacking device  10  in accordance with the various example embodiments shown in  FIGS. 1-5  and described above comprises a hydraulic cylinder  22  and ram  24  integrated into a structural support system comprising the base  12  and first section  26  of the jack structure  18 . The support system is designed to slide onto and be transported using the forks of a typical transporting equipment, such as a skid-steer loader, fork lift, or the like. The forks of the transporting equipment insert into channels  14 A and  14 B on the base  12  to which the jacking device  10  is mounted and can be clamped to retain the jacking device in place. After the jacking device  10  is selectively positioned at a desired location beneath the floating roof, the hydraulic cylinder  22  is adapted to be hydraulically actuated by the hydraulic supply system that is already present on the transporting equipment to extend and retract the second section  42  of the jack structure to lift the floating roof. During operation, the operator of the transporting equipment is preferably protected within a protective cage. 
         [0032]    While the foregoing description has been with reference to particular examples of embodiments of the present invention, it will be appreciated by those skilled in the art that changes in these embodiments may be made without departing from the principles and spirit of the invention. For example, other structures known to those persons skilled in the art may alternatively be employed for extending and retracting a ram such as the ram  24  shown in  FIG. 4 , for example, a pneumatic cylinder. Alternatively, a mechanically actuated ram may be substituted, for example, a rotated screw-driven device. Furthermore, the materials of construction may be varied to suit the requirements for any specific load capacity. Accordingly, the scope of the present invention can only be ascertained with reference to the appended claims.