Patent Publication Number: US-10307852-B2

Title: Mobile hardbanding unit

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to hardbanding drill string sections, such as drill collars and drill pipes. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated into and form a part of the specification, illustrate one or more embodiments of the present invention and, together with this description, serve to explain the principles of the invention. The drawings merely illustrate a preferred embodiment of the invention and are not to be construed as limiting the scope of the invention. 
         FIG. 1  is a left side perspective view of a mobile hardbanding unit made in accordance with a preferred embodiment of the invention. The unit comprises an enclosed trailer with gooseneck hitch being pulled by a pickup truck. 
         FIG. 2  is a right rear perspective view of the unit with the doors closed. 
         FIG. 3  is a right front perspective view of the unit with both side doors opened. 
         FIG. 4  is a left side view of the unit with both side doors opened. 
         FIG. 5  is a right rear view of the unit with the rear door opened showing the welding compartment. 
         FIG. 6  is an enlarged view of the welding compartment in the rear of the unit. 
         FIG. 7  is a schematic illustrating the hydraulically controlled pipe management assembly of the unit. 
         FIG. 8  is an enlarged view from the right side of the unit of the adjustable bracket for supporting the welding torches. A PTA torch is supported on the bracket. 
         FIG. 9  is an enlarged view from the rear of the unit showing the adjustable bracket supporting the PTA torch. 
         FIG. 10  is an enlarged view from the rear of the unit showing the adjustable bracket supporting a MIG torch. 
         FIG. 11  is a view from the rear of the unit showing the PTA torch working and the MIG torch parked on the side of the weld box. 
         FIG. 12  is a view from the left side of the unit showing the MIG torch in the parked position. 
         FIG. 13  is an enlarged view from above the weld box showing the MIG torch parked. 
         FIG. 14  is a view from the rear of the unit showing the MIG torch working and the PTA torch parked on the front of the storage cabinet beside the weld box. 
         FIG. 15  is an enlarged view of the parked PTA torch. The parking stub and the nozzle holster for the MIG torch are also shown. 
         FIG. 16  is an enlarged view of the parked PTA torch viewed from the back of the trailer. 
         FIG. 17  is an enlarged view of the parked PTA torch viewed from the left side of the trailer. 
         FIG. 18  is an operational schematic of the welding system. 
         FIG. 19  is a schematic illustrating the electrically controlled components of the unit. 
         FIG. 20  is a view from the right side of the unit into the weld compartment showing the swivel arm that supports the powder hopper for the PTA torch assembly. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S) 
     In oil and gas well drilling, rotational drill strings are commonly used to drill a wellbore that may reach as far as several miles in length. The drill string is composed of multiple interconnecting tubular steel sections with a drill bit and often other tools on the end. The interconnecting sections, referred to herein generally as “drill string sections,” include drill pipe and drill collars. Drill pipes, both standard and heavy weight, make up most of the drill string and typically are 18 to 45 feet long and may weigh as much as 14,000 pounds. Welded to each end of the drill pipe sections are threaded tool joints, the means by which the drill pipe sections are connected together to form the drill string. 
     Drill collars are shorter but much heavier tubular members usually placed near the end of the drill string to add weight above the bit. Drill collars also have threaded ends, but they are machined directly into the elongated tubular pipe. 
     The process of advancing the drill string through the well bore subjects the tubular sections, and particularly the drill pipe sections, to substantial stress and frictional forces. As a general rule, the threaded tool joints are the part of the drill string that is most susceptible to failure, and the useful lifetime of pipe and collar sections is, therefore, directly dependent on the durability and structural integrity of the tool joints. 
     In an effort to extend the useful life of these drill string sections, it is common to apply a band of hardened metal to the outer surface of the pipe in close proximity to the tool joints. Such hard metal bands are applied to the sections by conventional welding processes. The use of hardbands has proven to be extremely effective both in retarding the rate of frictional wear at the tool joints and in significantly improving the tool joint&#39;s structural strength. 
     In the so-called “raised face” hardbanding technique, the hardbands are welded directly onto the surface of the sections creating a larger overall diameter than the outer diameter of the drill section itself. Frictional forces are thus focused at the thicker hardbanded regions during drilling operations so that the hardbands absorb most of the wear. Thus, hardbanding makes it possible to extend the lifetime of drill pipes or collars almost indefinitely by periodically replacing the hardbands. 
     Initially, hardbanding was applied to drill string sections at permanent welding facilities. The cost to transport the pipe sections to and from the facility was high. In addition, the well operator was required to maintain a large inventory of hardbanded pipe sections so that the periodic maintenance or replacement of worn sections would not necessitate a lengthy and expensive shutdown. 
     Mobile hardbanding units have taken the hardbanding process to the well site. These mobile units have eliminated the costs and delays associated with transporting the pipe sections to a permanent facility and have greatly reduced the strain on the operator&#39;s pipe inventory caused by the down time of the sections being treated. 
     A variety of welding methods have been used to apply hardbanding to drill string sections. These welding techniques include TIG (tungsten-inert-gas), MIG (metal-inert-gas), GMAW (gas metal arc welding), GTAW (gas tungsten arc welding), PTA (plasma transferred arc), and FCAW (flux cored arc welding). In many applications, the PTA technique is preferred; it is easily automated, provides a precise application of the deposited material, and creates a band that is metallurgically fused to the pipe. Still further, a band created by PTA welding is harder and more abrasion resistant and yet provides a smoother, more “casing-friendly” surface. 
     To date, mobile hardbanding units have been limited to certain types of welding, such as MIG and TIG welding. One such unit is shown and described in U.S. Pat. No. 4,431,902, issued on Feb. 14, 1984, and entitled “Portable Hardbander,” the contents of which are incorporated herein by reference. 
     The present invention provides a mobile hardbanding system that uses PTA welding. Moreover, in a preferred embodiment, the inventive system allows alternate use of PTA and MIG welding. Both a PTA torch and a MIG torch are provided, and switching between one and the other is simplified by including separate electrical, gas, and cooling conduits for each torch. In this way, connection and reconnection of the various conduits is unnecessary to convert from one process to the other. 
     Turning now to the drawings in general and to  FIG. 1  in particular, there is shown a mobile hardbanding unit constructed in accordance with a preferred embodiment of the present invention and designated generally by the reference number  10 . The unit  10  comprises a mobile platform, such as a trailer. Most preferably, to enable use of the unit  10  in inclement weather, the platform is a partially or fully enclosed trailer  12 . The trailer  12  may be hitched to a truck or other towing vehicle  14  using a hitch, such as the gooseneck  16 . Although an enclosed trailer as shown is preferred in most instances, the platform alternately may be supported on a skid. 
     The trailer  12  in generally divided into a front section  20  and a back section  22 . As will become apparent, the front section  20  is configured to house or carry some of the consumables and larger equipment. The rear section  22  comprises a welding compartment, where the welding operations are performed. As seen in  FIGS. 1 and 2 , the left side of the trailer  12  has two large doors  26  and  28 , and similarly the right side of the trailer, seen in FIGS.  3  and  4 , has two large doors  30  and  32 . As used herein, “right” and “left” refers to the driver&#39;s perspective, that is, “left” refers to the driver&#39;s side of the trailer or unit, and “right” refers to the passenger side of the trailer or unit. The rear side doors  28  and  32  ( FIGS. 1 &amp; 2 ), which enclose the welding compartment, may be provided with windows, as this is the area where the operator spends most of the time monitoring the welding operations. 
     As seen in  FIGS. 1 and 2 , the back of the trailer  12  has a large full-wall door  36 . A smaller access door  38  is provided for the operator to enter and exit the welding compartment without having to lift up the full-wall door  36 . A small pipe door  40  is included for the drill string section that is being hardbanded. This allows the larger door  36  to remain closed, when necessary for the operator&#39;s comfort. 
       FIGS. 3-5  illustrate the unit  10  with the doors open. As best seen in  FIG. 3 , a partition  42  preferably is provided to separate the front and rear sections  20  and  22  of the trailer  12 . The right front door  30  covers a right front compartment  44  that contains the main welder generator  48 . The adjacent partition  42  is a convenient location for a PTA/MIG polarity switch  50 , which will be explained in more detail below. The right rear door  32  encloses the side of the welding compartment  54 . 
     Turning to  FIG. 4 , on the left side of the trailer  12 , the left front door  26  encloses a large gas storage compartment  60  configured for carrying gas containers. In the unit shown, the compartment  60  carries six (6) tanks of welding gases (helium, argon, etc.), designated generally at  62 . Additionally, there is room for a propane tank (not shown) behind the welding gas tanks  62 , which is needed for warming the drill string sections prior to the hardbanding operation. As will be explained hereafter, the PTA welding torch requires a cooling system, and thus a chiller  66  is provided; it may be mounted adjacent the partition  42 . On the opposite side of the partition  42 , in the welding compartment  54 , an enclosed storage cabinet  68  is mounted so that it opens to the side of the trailer  12  for easy access. 
     With reference now also to  FIG. 6 , the layout of the welding compartment  54  is illustrated. Positioned centrally in the compartment  54  is a weld box  70 . A seat  72  ( FIG. 5 ) for the operator may be mounted to one side of the weld box  70 , where the several control panels are located. The main electrical control panel  76  and the hydraulic panel  78  ( FIG. 6 ) thus are located to the operator&#39;s right as he faces the weld box  70 . The remote box  80  is mounted directly to the side of the weld box  70  adjacent the operator&#39;s view window (not shown) for constant monitoring and control of the welding process. Of course, an opening  84  is provided in the front of the weld box for inserting the drill string section. This rear pipe entry configuration is particularly preferred, but the compartment may be configured for side loading as well. 
     As previously indicated, the unit  10  is designed to be parked temporarily at the well site near a pipe rack containing the drill string sections to be hardbanded. The components to lift, move and rotate the drill pipe sections, referred to herein generally as a pipe management assembly  90  are conventional and, thus, are illustrated only schematically in  FIG. 7 , to which attention now is directed. The unit  10  preferably is equipped with a pair of hydraulic pipe jacks  92  which can be stationed adjacent the pipe rack. The height of the pipe jacks may be hydraulically adjustable to match the height of the adjacent pipe rack. The pipe cradles on the jacks include ball transfer rollers for facilitating the movement of the pipe section into and out of the weld box  70 . There may be a third pipe jack  94  behind the chuck for supporting the end of heavy weight drill pipe. One or more additional jacks with motorized rollers (not shown) may be included to assist the operator with loading and unloading heavier sections, such as drill collars. A hydraulic chuck assembly  96  is mounted in the welding compartment  54  for gripping and rotating the section. A hydraulic chuck stand  96   a  and  96   b  may be used to position the weld box  70  vertically and axially (extend and retract) relative to the pipe section. 
     The unit  10  may be provided with a propane-fueled pre heater (not shown) for heating the pipe joint in advance of the hardbanding procedure. Additionally, several cooling cans (not shown) may be supplied on the unit  10  to modulate the cooling of the pipe joints after completion of the hardbanding process. The unit  10  may house a diesel fuel tank, a hydraulic tank, heaters for the hydraulic tank, and other equipment typically utilized during a conventional hardbanding operation. As these components are well known to those familiar with the hardbanding process, they are not shown or described in detail. 
     Referring again to  FIG. 6 , a torch management assembly  100  is supported above the weld box  70 . This assembly  100  allows the welding torch to be positioned precisely, and it also provides for automated oscillation for creating a specific band width on the tool joint. As this technology is conventional, it will not be described or shown in detail. 
     With reference now to  FIGS. 8-17 , in accordance with the present invention, the torch mounting management assembly  100  comprises a torch mounting plate  102  supported over the weld box  70 . A torch mounting stub  104  extends from the plate  102 . The PTA torch  108  comprises a torch holder  110  that includes a stub sleeve  112  ( FIG. 17 ) that slidably receives the mounting stub  104  ( FIG. 8 ). In this way, the PTA torch  108  is removably secured to the torch management assembly  100 . 
     In addition to the PTA torch  108 , the unit also may include a non-PTA torch, such as a MIG torch  120  ( FIGS. 10 &amp; 11 ). The MIG torch  120  may also be provided with a torch holder  122  that includes a stub sleeve  124  similar to the stub sleeve  112  on the PTA torch holder  110 . Thus, the PTA torch  108  and the MIG torch  120  are supportable alternately in the weld box  70 . 
     The hardbanding unit  10  may be equipped with a torch mount for each of the PTA torch  108  and the MIG torch  120  when they are not in use. As shown in  FIGS. 12-17 , these torch mounts, designated respectively at  126  and  128 , are conveniently located in the welding compartment  54  on the side of the welding box  70  opposite of the operator station. The PTA torch mount  126  may be mounted to the side of the storage cabinet  68  ( FIGS. 16 &amp; 17 ), and the MIG torch mount  128  ( FIGS. 11-13 ) may be fixed to the side of the weld housing or weld box  70 . 
     Each of the torch mounts  126  and  128  has a torch parking stub  132  and  134 , respectively. The torch parking stubs  132  and  134  may be similar to the torch mounting stub  104  on the torch mounting plate  102 . In this way, the stud sleeves  112  and  124  on the torch holders  110  and  122  will also fit the torch parking stubs  132  and  134 . As best seen in  FIGS. 12 and 15 , the MIG torch mount  128  may include a socket or holster  138  for securing the disconnected free end of the cable from the parked MIG torch  120 . The PTA torch mount  126  may also include a locking pin assembly  140  ( FIGS. 11, 16 , &amp;  17 ) to ensure that the parked PTA torch remains secure during travel and storage of the unit  10 . 
     Having described the various components of the unit  10 , the operation of the unit will be summarized with reference to the schematic in  FIG. 18 . The PTA assembly is shown on the left side of the drawing and the MIG assembly is on the right. Power to the electrode  150  of the PTA torch  108  for the main plasma arc is supplied by the primary welder generator  48  by the electrical conduit  152   a  and  152   b . A power source with a strong engine is necessary as relatively small variations in amperage can break the transferred arc. The power source must be able to maintain constant current and voltage without deviation in order to maintain a table transferred arc during the welding process. A preferred welding machine for this purpose is a 500 amp engine-driven welder with a turbo-charged Perkins brand engine, such as the Vantage 500 brand machine from Lincoln Electric (Cleveland, Ohio), which is powered by the diesel motor  154 . 
     For the pilot arc, a secondary, smaller welder  156  is used with a high frequency transformer  158 . These may be located in a smaller storage cabinet  160  ( FIG. 5 ) in the welding compartment  54 . A preferred unit for the secondary power source is the Invertec V160-T TIG brand welder also by Lincoln Electric. Electrical conduits  162   a  and  162   b  connect the secondary welder  156  to the PTA torch  108 . 
     The PTA powder is contained in a hopper  166  (see also  FIGS. 6 and 20 ) and is metered by a powder feeder  168  driven by the motor  170 . The carrier or powder gas preferably is one hundred percent (100%) helium supplied by a tank  62  ( FIG. 4 ). The gas-entrained PTA powder is supplied to the PTA torch  108  by the conduits  174  and  176 . A valve  172  controls the powder gas flow. The center or plasma gas, which is preferably one hundred percent (100%) argon gas, is supplied to the PTA torch  108  by the conduit  180 . A valve  178  controls the center gas flow. The shield gas, which also is preferably one hundred percent (100%) argon gas, is supplied to the PTA torch  108  by the conduit  182 . A valve  184  controls the shield gas flow. The center gas and shield gas are all supplied from tanks  62 . 
     The chiller  66  ( FIG. 4 ) circulates chilled water to the PTA torch  108  and power cables through the conduits  186  and  188 . A safety flow switch  190  should be included to immediately shut down the operation in the event the flow of the water drops below a predetermined level. As indicated in the schematic of  FIG. 18 , the chiller  66  may be used to cool the welding conduits as well as the PTA torch head. Additionally, it should be noted that the chiller is a refrigerant-to-water heat exchanger rather than an air cooled system. 
     The primary welder  48  also supplies power to the MIG torch  120  by the electrical conduits  196   a  and  196   b . The polarity switch  50  is interposed in the electrical conduits  152   a  and  152   b  of the PTA torch assembly and the conduits  196   a  and  196   b  of the MIG torch assembly. 
     The consumable wire electrode  200  in the MIG torch  120  may be a wire fed from a spool  202  by wire feeder  204  driven by an electric motor  206 . A wire straightener  208  may be included. 
     The shield gas for the MIG torch  120 , which also is preferably ninety-eight percent (98%) argon and two percent (2%) oxygen, is supplied to the MIG torch  120  by the conduit  212 . A valve  214  controls the shield gas flow. The shield gas is also supplied from tanks  62 . 
     Occasionally, particulate or pulverized hard metal, such as tungsten carbide powder, will be introduced to the weld pool when using the MIG welding process. To that end, the unit  10  includes a hopper  220  with a feeder  222  driven by the motor  224 . The particulate is supplied to the tip of the MIG torch  120  by the conduit  226 . The trickle wheel meters and agitates the tungsten carbide particulate. 
     The unit  10  also includes an electrical control system  230  which is located in the operator&#39;s station in the welding compartment  54 . As previously described and as illustrated in the schematic in  FIG. 19 , the electrical control system  230  is operatively connected to the gas valves  172 ,  178 ,  184 , and  214  and to the motors  170 ,  206  and  224 . The system  230  also controls secondary pilot arc welder  156  and the transformer  158 , as well as the chiller  66 . The torch oscillator, which is part of the torch management assembly  100 , is also controlled by the system  230 . Finally, the control system  230  operates the primary welder  48  and the hydraulic pump for the hydraulic system  90  ( FIG. 7 ). 
     Now it will be appreciated that the mobile hardbanding unit  10  of the present invention brings the advantages of the PTA welding process to the well site. Moreover, the unit  10  offers the versatility of being used for MIG welding in addition to PTA welding. Converting from one system to the other is simplified because each torch is provided with its own dedicated set of conduits (powder, gas, electrical). The torch not in use is simply dismounted from the torch management assembly and parked a few feet away in a designated location. As indicated previously, reversal of current through the welding assembly when switching between MIG and PTA welding is easily accomplished by a conveniently located polarity switch  50 . 
     Several other adaptations may make the switch between welding systems even smoother. For example, the PTA powder hopper  166  may be mounted on a swivel arm  240 , as seen in  FIG. 20 , for supporting it between a PTA position and a MIG position, wherein in the PTA position the hopper is supported near the weld box  70 , and wherein the MIG position the hopper is parked a distance away from the weld box. 
     In accordance with the method of the present invention, a mobile hardbanding unit is provided at a first well site. The unit comprises a PTA welding assembly. Sections of the drill string are sequentially treated in the unit to add, replace, or refurbish hardbands at the tool joints. The drill string sections may be regular drill pipe, heavy-weight drill pipe, drill collars or other tubular members in the drill string. In a preferred embodiment, the method comprises converting the welding assembly in the unit to a non-PTA welding system and providing the unit to a second well site. Sections of drill string are sequentially treated at the second well site to add, replace, or refurbish hardbands at the tool joints using the non-PTA welding assembly. 
     The embodiments shown and described above are exemplary. Many details are often found in the art and, therefore, many such details are neither shown nor described herein. It is not claimed that all of the details, parts, elements, or steps described and shown were invented herein. Even though numerous characteristics and advantages of the present inventions have been described in the drawings and accompanying text, the description is illustrative only. Changes may be made in the details, especially in matters of shape, size, and arrangement of the parts within the principles of the invention to the full extent indicated by the broad meaning of the terms of the attached claims. The description and drawings of the specific embodiments herein do not point out what an infringement of this patent would be, but rather provide an example of how to use and make the invention. Likewise, the abstract is neither intended to define the invention, which is measured by the claims, nor is it intended to be limiting as to the scope of the invention in any way. Rather, the limits of the invention and the bounds of the patent protection are measured by and defined in the following claims.