Abstract:
A method and apparatus for verifying the complete cut through of a tubular member by a fluid cut through device. A follower runs in the kerf created in the tubular member by the fluid cut through device until the follower encounters an incomplete cut, or hanger. The follower rotates away from the fluid cut through device when the follower encounters a hanger, thereby disengaging a switch to interrupt the fluid cut through device.

Description:
[0001]    This application claims priority and the benefit under 35 U.S.C. §119(e) from U.S. provisional patent application 61/237,607 for “Method and Apparatus for Through-Cut Verification” filed Aug. 27, 2009, which is hereby incorporated by reference. 
     
    
     BACKGROUND 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates generally to apparatus and methods for confirming thorough cut-through of a down hole abrasive fluid jet cutting device. 
         [0004]    2. Description of Related Art 
         [0005]    Down hole operations sometimes require a tubular string to be cut with an abrasive fluid jet cutting tool lowered within the tubular string. Where the cutting tool does not cut a full kerf “hangers” are formed which may impede the down hole operation. 
         [0006]    All references cited herein are incorporated by reference to the maximum extent allowable by law. To the extent a reference may not be fully incorporated herein, it is incorporated by reference for background purposes and indicative of the knowledge of one of ordinary skill in the art. 
       BRIEF SUMMARY OF THE INVENTION 
       [0007]    A method and apparatus for verifying the complete cut through of a tubular member by a fluid cut through device. A follower runs in the kerf created in the tubular member by the fluid cut through device until the follower encounters an incomplete cut, or hanger. The follower rotates away from the fluid cut through device when the follower encounters a hanger, thereby disengaging a switch to interrupt the fluid cut through device. 
         [0008]    Other objects, features, and advantages of the present invention will become apparent with reference to the drawings and detailed description that follow. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is a partial cutaway view of an abrasive fluid jet cutting device in use; 
           [0010]      FIG. 2A  is a close-up view of an abrasive fluid jet cutting device showing a clean cut; 
           [0011]      FIG. 2B  is a close-up view of an abrasive fluid jet cutting device showing a hanger; 
           [0012]      FIG. 2C  is a close-up view of an abrasive fluid jet cutting device showing a follower engaging the hanger; 
           [0013]      FIG. 2D  is a close-up view of a follower as shown in  FIGS. 2A-2C ; 
           [0014]      FIG. 2E  is a close-up view of the removal of the blade of the follower shown in  FIG. 2D ; 
           [0015]      FIG. 2F  is a close-up view of the blade removed; 
           [0016]      FIG. 3  is a close up view of an alternatively mounted blade follower; 
           [0017]      FIG. 4A  is a close-up view of an abrasive fluid jet cutting device showing a clean cut and a loop-type second alternative follower; 
           [0018]      FIG. 4B  is a close-up view of an abrasive fluid jet cutting device showing a hanger; 
           [0019]      FIG. 4C  is a close-up view of an abrasive fluid jet cutting device showing the alternative follower engaging the hanger; 
           [0020]      FIG. 4D  is a close-up view of a follower as shown in  FIGS. 4A-4C ; 
           [0021]      FIG. 4E  is a close-up view of the removal of the loop of the follower shown in  FIG. 4D ; 
           [0022]      FIG. 4F  is a close-up view of the loop removed; 
           [0023]      FIG. 5  is a cutaway view of an abrasive jet cutting head in use; and 
           [0024]      FIG. 6  is a side view of a complete abrasive jet cutting apparatus in use. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0025]    All references cited herein are incorporated by reference to the maximum extent allowable by law. To the extent a reference may not be fully incorporated herein, it is incorporated by reference for background purposes and indicative of the knowledge of one of ordinary skill in the art. 
         [0026]    In the following detailed description of the preferred embodiments, reference is made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration specific preferred embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is understood that other embodiments may be utilized and that logical mechanical and electrical changes may be made without departing from the spirit or scope of the invention. To avoid detail not necessary to enable those skilled in the art to practice the invention, the description may omit certain information known to those skilled in the art. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined only by the appended claims. 
         [0027]    Referring to  FIG. 1 , an abrasive fluid jet cutting device  10  forms a through-cut  12  in a tubular  14 . The direction of the movement of the abrasive fluid jet cutting device  10  is indicated by the arrow  16 . 
         [0028]    The abrasive fluid jet cutting device  10  is provided with a follower  20 . The purpose of the follower  20  is to detect portions of the through-cut  12  which were not properly completed. When the follower  20  detects a “hanger,” the term used by those in the industry to denote a section of the through-cut  12  that was not properly completed, the follower  20  pivots away from the abrasive fluid jet cutting device  10  thereby signaling the need for remedial action. 
         [0029]      FIG. 2A  illustrates the abrasive fluid jet cutting device  10  and the follower  20  in greater detail. The follower  20  is pivotally supported at  22  and a switch  24  is actuated whenever the follower  20  is pivoted away from its nominal orientation. 
         [0030]    Referring to  FIGS. 2B and 2C , the abrasive fluid jet cutting device  10  is forming the through-cut kerf  12  in the tubular  14 . The abrasive fluid jet cutting device  10  has previously failed to function properly thereby resulting in a “hanger”  26 . 
         [0031]    When the follower  20  engages the hanger  26  the switch  24  is activated thereby discontinuing the operation of the abrasive fluid jet cutting device  10 . The abrasive fluid jet cutting device  10  is then moved in a direction of that opposite to that of the arrow  16  to a location beyond the hanger. The abrasive fluid jet cutting device  20  is operated either during reverse movement thereof, or during subsequent forward movement thereof, or both, in order to remove the hanger and resume normal cutting operations. 
         [0032]      FIGS. 2D ,  2 E and  2 F illustrate the “break-away” construction feature of the follower  20 . This feature has been designed to ensure that the abrasive fluid jet cutting device is not trapped in tubular if the kerf closes and traps the follower due to axial compressive loads in the tubular. In the specific case of offshore platform decommissioning, the axial compressive force is often a result of structure dead weight.  FIG. 2D  shows the follower  20  mounted in the support structure  30 . In the case where the blade  28  is trapped in the kerf  12 , cutting operations will be discontinued when the follower  20  is pivoted away from its nominal orientation. Reversing the cutting head direction would not result in de-energizing switch  24  as would be the case if a hanger had been encountered. In such a situation, the operator would retract the fluid jet cutting apparatus  10  and the verification arm  20  on parallel arms  50  initiating the break-away of the follower  20  from the support structure  30 . 
         [0033]    This is illustrated in  FIG. 2E  where the cutting head retraction is prying the follower grip “fingers” away from the support structure.  FIG. 2F  shows the follower configuration after break-way. 
         [0034]      FIG. 3  illustrates an alternative follower support structure. Those skilled in the art will appreciate the fact that follower  20  may comprise a variety of types and kinds of blades which are removable from the associated support structure utilizing various well-known techniques. 
         [0035]      FIGS. 4A through 4F , inclusive, illustrate an alternative embodiment of the invention. In accordance with the alternate embodiment the follower  20  of  FIGS. 1  through  3  is replaced by a wire loop  40 . Otherwise, the embodiment of the invention shown in  FIGS. 4A through 4F  functions identically to the embodiment shown in  FIGS. 1 through 3  and described hereinabove in conjunction therewith.  FIG. 4D  illustrates the engagement of the loop  40  with its support structure  42 .  FIGS. 4E and 4F  illustrate the disengagement of the loop  40  from the support structure  42  if the loop  40  were to be trapped in the kerf. 
         [0036]      FIGS. 5 and 6  illustrate the supporting and positioning mechanism for the through-cut verification system of the present invention. Referring particularly to  FIG. 5 , the abrasive fluid jet cutting apparatus  10  and the verification arm  20  are supported by spaced apart pairs of parallel arms  50 . The arms  50  function to move the abrasive fluid jet cutting apparatus  10  and the verification arm  20  perpendicular to the axis of the tubular  14 . Referring to  FIG. 6 , the parallel arms  50  and its support structure are, in turn, supported on a structure  52  which assures that the axis of rotation of the abrasive fluid jet cutting device  10  and the follower  20  is exactly aligned with the centerline of the tubular  14  that is being through-cut.