Patent Application
20100050407
The invention relates to wrenches or tongs use for making-up and breaking-out threaded connections on drill pipe and other tubular members employed in the oil and gas industry. More specifically, the invention relates to repairing the jaw component of such tongs.
Many different tong devices are used in the oil and gas industry to makeup (connect together) and breakout (disconnect) the threaded joints of tubular members (e.g. casing, tubing, pipe, or drill pipe) employed in the oil and gas exploration and production industry. One such device is produced by National Oilwell VARCO under the designations ST-80 or ST-80C (see also U.S. Pat. No. 7,188,547) and combines a torque wrench and a spinning wrench to connect and disconnect tubular members.
The torque wrench includes a jaw member which closes on and grips the tubular member. Typically, the jaw member will have a removable die insert which provides the surface actually contacting the tubular. The die inserts will have some type of gripping surface (e.g., a series of grooves, a knurled tooth pattern, etc.) on the side designed to engage the tubular and a feature for connecting to the jaw member on the opposite side (e.g., grooves, a dovetail shape, a key and keyway arrangement, or a combination thereof).
Often the jaw member and the die inserts are of dissimilar metals, for example the body of the jaw member could be constructed of a AISI 4XXX series alloy steel while the die has been made from other alloys which are carburized or heat treated to have different characteristics. When sea water, drilling mud, or other corrosive fluids become trapped between the jaw member and the die insert, combined with repeated working of this contact area (or interface) when the tong is in use, significant corrosion can occur at this interface. If the corrosion becomes sufficiently advanced, the die insert does not properly maintain its precise position on the jaw member and the tong must be taken out of service for repaired. Certain tools use relatively fine grooves to transfer the tangential load between the jaw and die, making these tools more sensitive to corrosion failure than alternate coarser, more robust connection systems. Currently, the typical repair method is to replace the entire jaw member, a large and expensive component. It would be a significant advantage in the art if the jaw member could be repaired without being completely replaced.
One embodiment of the present invention includes a method for repairing a damaged or corroded tong jaw having a jaw root and an original seating component. This embodiment includes the steps of: (a) machining away corroded or damaged portions of the original seating component; (b) machining into a non-damaged portion of the original seating component and/or jaw root, thereby forming a machined base configured to receive a new seating component. In this embodiment, the new seating component includes a feature adapted for engaging the machined base. Then the new seating component is connected onto the machined base.
One embodiment of the invention may be used to repair the jaws of tongs such as the model ST-80 sold by National Oilfield Varco. However, the method may be applicable to other tong jaws and gripping apparatuses and should not be considered as limited to only the ST-80 product line.
In one embodiment of the repair process, the damaged or corroded portions of the original seating surface 3 is first removed by machining away the damaged portion or removing it by any other suitable process. As used herein, “machining” means any conventional or future developed method of forming features on metal, including as nonlimiting examples, a vertical mill, a horizontal machining operation, or electrical discharge machining (EDM). In certain embodiments, the initial removal of the damaged portion could be accomplished with low precision grinding. Next, the underlying portions of the non-damaged original seating surface 3 and/or jaw root 2 are machined to create a shaped machined base 17.
Naturally, the invention is not limited to the dovetail configuration shown in the figures and many other configurations could be used in the alternative. Non-limiting examples of these alternatives include splines such as in U.S. Pat. No. 4,576,067 (incorporated by reference herein), a machined key-way and matching key, or a series of pins located in holes bored into the jaw. The dovetail configuration may be advantageous in certain instances as it retains the component in the radial and tangential directions. The alternate configurations mentioned above will resist the tangential loads but require an alternate method such as fasteners to provide radial retention. Additionally, the dovetail configuration can withstand very high loads when compared to many alternative methods.
An alternate repair method could employ low precision grinding, followed by welding a replacement slab of material in place or building up the area using multiple passes of weld filler materials. Ultimately, the imperfectly repaired area would be machined to the geometry necessary to accept the gripping die. The use of welding with alloy steels has many potential disadvantages including cracking in the weld heat affected zone and is likely to require the entire part be subject to a heat treating process to return the heat affected zone to an acceptable hardness level.
Nonlimiting examples of corrosion resistant materials include heat treated stainless steels, nitride carbon steels, or metals such as titanium. While non-metal materials typically will be less suited for constructing the new seating component, some non-metal materials may be suitable for handling loads encountered in this class of gripping tools. Non-limiting examples could include reinforced materials employing carbon fiber, nano-materials, and other super strength class composites. Any other method of creating a corrosion resistant surface on the new seating component is within the scope of the present invention. For example, forming a new seating component of a less corrosion resistant material and then plating it with a more corrosion resistant material. The corrosion resistant material could be limited to just the surface in contact with die 4, but more preferably covers most or all of new seating component 13.
After securing the new seating component 13 to the machined base 17, the next step is to fasten a key 9 (
Although the figures illustrate one particular embodiment, it will be understood that the invention includes all obvious variation and modifications. For example, while machined base 17 is shown as having a dovetail shape, machined base 17 could be configured to receive a new seating component 13 by being formed into any shape that provides a “tongue and groove” type engagement. In a similar manner, the bottom of new seating component 13 could include any mating feature. Nor does machined base 17 need to form the “tongue,” but could form the “groove” by having a cavity machined therein. In this embodiment, the feature on new seating component 13 would be tongue portion which engages the groove or cavity on machined based 17. Further, the invention is not even limited to a tongue and groove configuration, but could be any manner of securely attaching a new seating component to a jaw that has any type of machined base. And while certain embodiments utilize a machined seating component 13, other embodiments could utilize a cast seating component 13 or a reinforced composite material seating component. All such variations and modifications are intended to come within the scope of the following claims.
