Patent Publication Number: US-7905529-B2

Title: Riser lifting tool

Description:
FIELD OF THE INVENTION 
     The present invention relates to tools for supporting an oilfield riser during relocation on a rig. More particularly, this invention relates to an improved tool which reliably engages and manipulates an oilfield riser while reducing the risk of personal injury or damage to the riser. 
     BACKGROUND OF THE INVENTION 
     Oilfield risers are conventionally used in offshore oil drilling operations, and comprise pipe sections intended to surround and isolate casing from the sea water. During makeup and breakout of the riser string, the individual riser sections are generally stacked on the rig floor and are repositioned between a riser storage area and a staging area. Risers typically have one or more fluid conduits or cables exterior of the riser, which complicates the riser handling operation. 
     U.S. Pat. No. 4,202,653 discloses a pipe handling system including a bridge crane. U.S. Pat. No. 4,808,034 discloses a riser with a ring guide for positioning the riser. U.S. Pat. No. 6,877,281 discloses a stackable riser with a riser cover. None of the above prior art provides an effective system for safely and reliably positioning a riser on a rig between a storage area and a staging area. 
     Individual riser sections are commonly moved from a staging area to a storage area by a crane. More particularly, a scissors-type tool is conventionally suspended from the crane and is used to grab the riser for manipulation by the crane. In many applications, however, the scissors tool cannot reliably grasp a stacked riser section, and accordingly another initial manipulation mechanism is provided for initially positioning the riser from the stack so it may be subsequently grabbed by the scissors tool. In some cases, this initial manipulation is accomplished by a smaller crane and a series of straps which may be passed under the riser and connected to the smaller crane. Considerable time and expense are involved in using two such cranes to manipulate the riser, and the reliability of the system is a function of the number and correct positioning of the straps, and also the reliability of a scissors-type tool which is merely grasping opposing sides of the riser section. 
     The disadvantages of the prior art are overcome by the present invention, and an improved lifting tool for supporting an offshore riser during manipulation on a rig is hereinafter disclosed. 
     SUMMARY OF THE INVENTION 
     A lifting tool is provided for supporting an oilfield riser during the relocation by a crane having a support line. In one embodiment, a tool body is suspended from the support line and has an inverted U-shaped configuration, a central opening for receiving the riser, and a downwardly facing throat. An arcuate member is supported on the tool body and is rotated about a central axis between an open position wherein a spacing arcuate member is circumferentially aligned with the open throat, and a closed position wherein the arcuate member at least substantially closes the open throat. A powered drive is provided for rotating the arcuate member between the open position and the closed position. 
     One embodiment of the method of supporting an oilfield riser during relocation on a rig comprises suspending a tool body from the support line and with the tool body having an inverted U-shaped configuration, a central opening for receiving the riser, and downwardly facing throat. An arcuate member is supported on the tool body and is rotated about a central axis between an open position and a closed position. In the closed position, the arcuate member substantially closes the open throat such that the arcuate member supports the riser when positioned within the central opening of the tool body when the tool is raised. 
     These and further features and advantages of the present invention will become apparent from the following detailed description, wherein reference is made to the figures in the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side view of a lifting tool supported from a crane support line. 
         FIG. 2  is a side view of a lifting tool shown in  FIG. 1 . 
         FIG. 3  is a side view of a portion of the lifting device wherein some of the tool components are removed for clarity of the remaining components. 
         FIG. 4  is a side view of the device shown in  FIG. 3 . 
         FIG. 5  is a pictorial view of a portion of the lifting device, including its functional components. 
         FIG. 6  is an expanded view of a portion of the device shown in  FIG. 5 . 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       FIG. 1  discloses a lifting tool  10  according to one embodiment of the invention. The tool  10  includes a tool body  12  for suspending from the support line  14  of a crane  16 . As shown in  FIG. 1 , the tool body has an inverted U-shaped configuration, with a central opening  18  for receiving the riser therein, and a downwardly facing open throat  20 , which allows the tool to be lowered over a riser section. The tool body also includes an arcuate member  22  which is supported on the tool body and is rotatable about a central axis  24 . The arcuate member  22  is shown in  FIG. 1  in the closed position, such that the arcuate member at least substantially closes the open throat and the arcuate member supports the riser when positioned within the central opening  18  of the tool body when the tool and riser section are raised by the support line  14 . In a preferred embodiment, the closed arcuate member fully closes off the open throat in the tool body. Also, the circumferential width of the spacing in the arcuate member is substantially equal to the circumferential spacing of the open throat, thereby maximizing the holding ability of the closed arcuate member to support the riser. 
     Referring briefly to  FIG. 3 , a Y-shaped hangar  26  is shown connected to the tool body  12 . The upper interior surface  28  of the tool body and the side surfaces  30 ,  32  are configured for accepting a particular type of riser with a known quantity and configuration of external flow lines. The tool body  12  may thus be modified for different size risers and risers with different flow line configurations.  FIGS. 3 and 4  illustrate a drive motor  36  powering a drive sprocket  38 , wherein more chains or belts and an optional intermediate sprocket are used between the drive motor  36  and the sprocket  38 . Returning briefly to  FIG. 4 , a chain  40  is mounted to the radially exterior surface of the arcuate member  22 , and is driven by the rotating sprocket  38  to rotate the arcuate member between the open position as shown in  FIG. 3  and the closed position as shown in  FIG. 5 . Alternatively, teeth may be formed directly on the arcuate member, or another type of powered drive may be used to rotate the arcuate member. 
     While a preferred embodiment of the tool utilizes the tool body itself to slidably engage the arcuate member and thereby control rotation of the arcuate member, one or more bearings may be provided along the travel path of the arcuate member for engaging and guiding the arcuate member during rotation, thereby minimizing friction. 
       FIG. 5  discloses in further detail the drive  36  which conveniently may be a hydraulically powered drive motor which rotates drive belt  42  and thereby rotates sprocket  44 , which in turn rotates about the drive belt  46  which rotates sprocket  38 , which engages the chain  40  and thereby drives the arcuate member  22 . 
     Referring now to  FIG. 2 , the tool body may be manufactured in two halves, with a body centerline through the central plane  48 . Body segments  12 A,  12 B of the tool body thus guide the arcuate member  22  during rotation, with the arcuate member being positioned in an arcuate groove on each half  12 A,  12 B.  FIG. 3  illustrates an arcuate slot  52  in one half of the tool body, while  FIG. 5  illustrates half of the arcuate member  32  positioned within arcuate slot  52  on half the tool body. 
     Although specific embodiments of the invention have been described herein in some detail, this has been done solely for the purposes of explaining the various aspects of the invention, and is not intended to limit the scope of the invention as defined in the claims which follow. Those skilled in the art will understand that the embodiment shown and described is exemplary, and various other substitutions, alterations and modifications, including but not limited to those design alternatives specifically discussed herein, may be made in the practice of the invention without departing from its scope.