Abstract:
Makeup plates on the abutting surfaces of a tool joint pin and a tool joint box are provided. The makeup plates are recessed in a short distance from the outer diameter of the tool joint elements, such that when the joint is made up, the makeup plate develops an easily visible gap between the tool elements. In this way, a quick determination may be made, without measurement, as to whether the joint can be refaced, or require re-machining.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    This present invention relates general to tool joints and more particularly to an externally visible indicator for facing the tool joints of drill pipe and other tubulars.  
           [0002]    As described in U.S. Pat. No. 4,438,953 to Timme, Jr., a string of oil and gas well drill pipe is made up of sections of pipe, each about 30 feet long. Each section has an externally threaded pin on one end and an internally threaded box on the other end. When coupled together, the pin and the box form a tool joint. Each set of threads is tapered and has a point where the pitch diameter is a specific amount, this point being known as the gage point. A make-up shoulder is spaced a selected distance from the gage point of the threads on the pin. Another make-up shoulder is located at the outer end of the box. When fully made-up, these make-up shoulders contact each other under a selected amount of compression to provide a fluid-tight seal. To achieve the proper amount of compression, the distance from the pin make-up shoulder to the gage point of the pin threads, and the distance from the box make-up shoulder to the gage point of the box threads, must be carefully controlled.  
           [0003]    During use, the make-up shoulders may gall and score. To achieve a smooth surface again, the shoulders are redressed. It is important that the total material removed from the two mating shoulders be no more than {fraction (1/16)} inch from original, or no more than {fraction (1/32)} inch from any shoulder. If the material removal totals more than {fraction (1/16)} inch from mating shoulders, inadequate compression may occur during make-up, thus requiring the mating faces to be remachined. Without such corrective measures, fatigue failures and washouts may result.  
           [0004]    The American Petroleum Institute recommends to manufacturers the use of an indented circle and tangent bar or line stamped into the tool joint pin and the box counterbore. The bar would be impressed into the metal exactly ⅛ inch from, and parallel to, the make-up shoulder. This method has two shortcomings. First, it must be hand-applied. Therefore, it is time consuming and potentially unreliable. Also, this method marks only one point of the pin or box.  
           [0005]    In the &#39;953 patent, Timme, Jr. taught a bench mark consisting of a bench mark shoulder formed around the pin outer diameter ⅛ inch from the make-up shoulder. The box counterbore had a step formed around it ⅛ inch from the make-up shoulder. The bench mark shoulder provided a reference line to determine the distance from the makeup shoulder to the reference line, after the make-up shoulder had been redressed. Because the bench mark was a continuous step around the circumference of the pin outer diameter, and a continuous counterbore around the circumference of the box inner diameter, it also served as an indicator of uneven machining of the tool joint shoulder. The mark was placed on the tool joint during the operation in which threads were machined onto the tool joint.  
           [0006]    The benchmark shown and described in the &#39;953 has proven to be successful, but suffers from a drawback in that, when the joint has been made up, the benchmark can neither be seen nor measured. In order to determine if the maximum amount of facing has been performed on the mating shoulder surfaces, the joint must be uncoupled, and a measurement made to make this determination. Also, certain prior art benchmarks require the removal of a thread protector, and a certain amount of cleaning of the connection itself prior to making a determination as to whether or not the faces must be machined.  
           [0007]    Thus, there remains a need for a externally visible and measurable refacing indicator for a tool joint. Such an indicator should be easily manufactured, and not increase the cost of the pin or the box elements which make up the tool joint. The present invention is directed to this need in the art.  
         SUMMARY OF THE INVENTION  
         [0008]    The present invention addresses this and other needs in the art by providing a makeup plate on the abutting surface of a tool joint pin and a tool joint box. The makeup plate is recessed in a short distance from the outer diameter of the tool joint element, such that when the joint is made up, the makeup plate develops an easily visible gap between the tool elements. In this way, a quick determination may be made, without measurement, as to whether the joint can be refaced, or require re-machining.  
           [0009]    These and other features and advantages of the invention will be apparent to those skilled in the art from a review of the following detailed description, along with the accompanying drawing figures. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    [0010]FIG. 1 is a side view of a tool joint pin having a prior art bench mark.  
         [0011]    [0011]FIG. 2 is a side section view of a tool joint box adapted to receive the prior art bench mark of FIG. 1.  
         [0012]    [0012]FIG. 3 is a side view of a tool joint pin having a bench mark in accordance with this invention.  
         [0013]    [0013]FIG. 4 is a side section view of a tool joint box adapted to receive the tool joint pin of FIG. 3.  
         [0014]    [0014]FIG. 5 a  is a detail view of the facing indicator of the invention. FIG. 5 b  is a detail view of an alternative embodiment of the invention, showing an edge of the facing indicator as vertical, rather than beveled as in FIG. 5 a.    
         [0015]    [0015]FIG. 6 is a detail view of abutting surfaces of a made up tool joint employing the present invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0016]    [0016]FIGS. 1 and 2 are provided to show a prior art tool joint bench mark, in order to gain a clearer understanding of the indicator of the present invention. A tool joint pin  11  for a drill pipe member has a cylindrical surface  13  containing an inner bore (not shown). External threads  15  are formed on the end of the cylindrical surface  13 . The threads  15  have a first end  15   a  located at the extreme end of the tool joint pin  11 . The threads  15  extend along the tool joint  11  for a selected distance, terminating at a second end  15   b . The threads  15  are tapered, resulting in a smaller outer diameter at the first end  15   a  than at the second end  15   b.    
         [0017]    A make-up shoulder  17  is formed in the tool joint  11  a selected distance from the gage point of the threads  15  and inward from the end  15   b . The make-up shoulder  17  is an annular surface located in a plane perpendicular to the axis of the tool joint pin  11 . The make-up shoulder  17  faces outwardly and has a bevel  19  formed at its intersection with the cylindrical surface  13 .  
         [0018]    A cylindrical section  15   c  is also defined between the end  15   b  and a bench mark  27 . The bench mark  27  is formed between the make-up shoulder  17  and the cylindrical section  15   c . The bench mark  27  faces outwardly and defines an edge contained in a plane that is parallel with the make-up shoulder  17 . As indicated by the arrows  33  in FIG. 1, the bench mark  27  is used to measure the distance from the make-up shoulder  17  to the bench mark, which originally is preferably ⅛ inch. Should the make-up shoulder  17  be redressed, this reference distance will increase, and will serve as an indication of whether or not a sufficient amount of compression will be able to be achieved. If the increase in the reference distance exceeds a selected standard amount, such as {fraction (1/32)} inch, then the tool joint pin  11  will not be suitable for further use.  
         [0019]    [0019]FIG. 2 depicts a corresponding tool joint box  35 . Tool joint box  35  has a cylindrical outer surface  37 . On its extreme outer end, a make-up shoulder  39  is formed. The make-up shoulder  39  is an annular surface located in a plane that is perpendicular to the axis of tool joint box  35 . The tool joint box  35  has an inner bore  41 . A set of internal threads  43  are machined into the bore  41 . The threads  43  have an outer end  43   a  that is located a selected distance from make-up shoulder  39 , and an inner end  43   b  that is located a selected distance further inward. The threads  43  are tapered, or formed in a frusto-conical surface, with the inner end  43   b  being of a lesser diameter than the outer end  43   a . A bevel  45  is formed at the intersection of the make-up shoulder  39  with the cylindrical surface  37 . As indicated by the arrows  57  in FIG. 3, bench mark  51  will indicate the distance from make-up shoulder  39  to bench mark  51 . If this distance becomes too small, due to redressing of the make-up shoulder  39 , then this will indicate that the tool joint  35  must be discarded.  
         [0020]    When the pin  11  and the box  35  are made up, the cylindrical section  15   c  mates up with a complementary inside cylindrical section  51   a  and a bench mark  51  mates up with the bench mark  27 . Thus, when the make-up shoulder  17  is in abutting contact with the make-up shoulder  39  the bench marks  51  and  27  will be obscured. The present invention addresses this drawback, as shown in FIGS. 3 and 4.  
         [0021]    As shown in FIG. 3, a tool joint pin  60  defines a cylindrical surface  62  which has an internal bore (not shown). Frusto-conical or tapered threads  64  extend from the surface  62  of the pin  60 , terminating in an outer end  66 . To this point, the pin  60  is similar to the pin  11  previously described in respect of FIG. 1. However, the pin  60  does not include the bench mark  27 ; rather, the pin  60  defines a bevel shoulder  68  which extends annularly around a surface  70  at the end of the surface  62 . Further, an annular surface  72  defines a makeup plate  74 , when the pin  60  is made up with the box shown and described below in respect of FIG. 4. It is to be understood that the term “makeup plate” is used to define the structure, while the makeup plate is preferably formed as a unitary body with the pin, and not as a separable manufacture, although such a separable manufacture would fall within the scope and spirit of the invention.  
         [0022]    When the pin  60  is refaced, the annular surface  72  is reduced, up to a maximum of {fraction (1/16)}″, and thus a thickness T of the makeup plate  74  is initially {fraction (1/16)}″, and is reduced as the pin is refaced.  
         [0023]    [0023]FIG. 4 depicts a tool joint box  80  of the invention. The tool joint box  80  has a cylindrical outer surface  82 . At the extreme outer end of the surface  82 , a makeup plate  84  of thickness T′ is provided. The makeup plate  84  abuts the makeup plate  74  when the tool joint is made up, as shown and described below regarding FIG. 6. The the box  80  is refaced, the thickness T′ of the makeup plate  84  is reduced. The tool joint box  80  has the inner bore  41 . A set of internal threads  43  are machined into the bore  41 . The threads  43  have an outer end  43   a  that is located a selected distance from a mating surface  86  of the makeup plate  84  and an inner end  43   b  that is located a selected distance further inward. The threads  43  are tapered, or formed in a frusto-conical surface, with the inner end  43   b  being of a smaller diameter than the outer end  43   a.    
         [0024]    As shown in FIGS. 5 a ,  5   b , and  6 , the makeup plate  84  preferably defines a bevel  90  at the bevel shoulder  68 . Alternatively, as shown in FIG. 5 b , the makeup plate may have a vertical surface into the box  80 . The pin may be formed in a similar fashion, with the makeup plate  74  defining a vertical edge. When the pin  60  and the box  80  are made up together, the makeup plates  74  and  84 , respectively, define a measurable gap  94 , shown in FIG. 6. To determine if the surfaces of the tool elements can be refaced, however, one need not make a measurement of the gap. If the gap  94  measures zero, then the elements must be re-machined. It is further to be understood that while the ability to measure the gap while the box and pin are made up is a feature of the invention, the invention is further defined by the makeup plate extending axially toward the threaded connection.  
         [0025]    The invention has a number advantages. The makeup plates provide a visible gap when the pin and box are made up, and thus provide an immediately apparent indicator for refacing the elements. This feature of the invention allows a user to determine visually, without measurement, whether or not a connection may be further refaced. The visual indicator may take several forms, two of which have been shown and described. The invention provides the further advantage in that it is adaptable to other products such as for example drill collars and heavyweights which have stress relief grooved pins making the present invention particularly attractive to such applications.  
         [0026]    While the invention has been shown in only two of its forms, it should be apparent to those skilled in the art that it is not so limited but is susceptible to various changes and modifications without departing from the spirit of the invention.