# US 2018/0324902 A1 · System And Method For Heat Treating A Tubular > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2018/0324902 A1 - Document ID: US20180324902A1 - Status: Published application - Kind: A1 - Application number: 16/025,216 - Filed: 2018-07-02 - Published: 2018-11-08 - Earliest claimed: 2013-03-15 - Assignees: National Oilwell Varco, L.P. - Applicants: National Oilwell Varco, L.P. - Inventors: Kevin Joseph Wyble; Daniel Lyle Hannahs; Daryl Stevenson; Shawn Lee Cunningham - Web page: https://patentgrep.com/patent/US20180324902A1 ## CPC - H05B 6/06: Control, e.g. of temperature, of power - H05B 6/101: {for local heating of metal pieces} - H05B 6/38: specially adapted for fitting into hollow spaces of workpieces - H05B: ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL ## Abstract A system and method for heat treating a tubular. In one embodiment, a system for heat treating a tubular includes a first coil and a second coil. The first coil is configured to circumferentially surround the tubular and induce, from without the tubular, current flow in a cylindrical portion of the tubular adjacent the first coil. The second coil is configured to be inserted into a bore of the tubular and induce, from within the tubular, in conjunction with the first coil, current flow in the cylindrical portion of the tubular. ## Claims ### Claim 1 A method for heat treating a tubular, comprising: positioning a first coil to encircle a portion of a tubular to be heat treated; positioning a second coil within a bore of the tubular at a location aligned with the portion of the tubular to be heat treated; providing alternating current to the first coil at a first frequency; and providing alternating current to the second coil at a second frequency while providing alternating current to the first coil at the first frequency, wherein the first frequency is different from the second frequency; and heat treating the portion of the tubular by inducing current flow about an exterior cylindrical wall and an interior cylindrical wall of the portion of the tubular via the first coil and the second coil. ### Claim 2 (depends on 1) The method of claim 1, further comprising: providing the alternating current to the second coil at a frequency that is higher than the frequency at which the alternating current is provided to the first coil. ### Claim 3 (depends on 1) The method of claim 1, wherein the first frequency is approximately 180 hertz. ### Claim 4 (depends on 1) The method of claim 1, wherein the second frequency is a frequency in a range of approximately 3 kilohertz to approximately 10 kilohertz. ### Claim 5 (depends on 1) The method of claim 1, wherein providing the alternating current to the first coil comprises: providing at least approximately 150 kilowatts of power to the first coil. ### Claim 6 (depends on 1) The method of claim 1, wherein providing the alternating current to the second coil comprises: providing at least approximately 125 kilowatts of power to the second coil. ### Claim 7 (depends on 1) The method of claim 1, further comprising: measuring temperature of the tubular during the heat treating; determining a level of the alternating current to provide to at least one of the first coil and the second coil based on the measured temperature; and providing the determined level of the alternating current to the at least one of the first coil or the second coil. ### Claim 8 (depends on 1) The method of claim 1, wherein the heat treating comprising: increasing a temperature of the portion of the tubular to at least a predetermined temperature value associated with the tubular; and maintaining the predetermined temperature value for a predetermined time period associated with the tubular. ### Claim 9 (depends on 1) The method of claim 1, further comprising: forming a heat affected zone having a parabolic outline that faces away from a weld line based on heat treating the portion of the tubular. ### Claim 10 (depends on 1) The method of claim 1, wherein the tubular comprises a drill pipe, a drill collar, or a downhole tool housing. ### Claim 11 A method for heat treating a tubular, comprising: positioning an exterior induction coil to encircle a portion of a tubular to be heat treated; positioning an interior induction coil within a bore of the tubular to be heat treated; simultaneously energizing the exterior induction coil and the interior induction coil, wherein simultaneously energizing the exterior induction coil and the interior induction coil comprises providing alternating current to energize the exterior induction coil and the interior induction coil; wherein a frequency of the alternating current provided to the exterior induction coil is different than a frequency of alternating current provided to energize the interior induction coil; and concurrently heat treating a selected cylindrical portion of the tubular from an exterior and an interior of the tubular based on the simultaneous energizing. ### Claim 12 (depends on 11) The method of claim 11, wherein the frequency of the alternating current provided to the exterior induction coil is higher than the frequency at which current is provided to the interior induction coil. ### Claim 13 (depends on 11) The method of claim 11, wherein the frequency at which the alternating current is provided to the exterior induction coil is approximately 180 hertz. ### Claim 14 (depends on 11) The method of claim 11, wherein the frequency at which the alternating current is provided to the interior induction coil is in a range of approximately 3 kilohertz to approximately 10 kilohertz. ### Claim 15 (depends on 11) The method of claim 11, wherein energizing the exterior induction coil comprises: providing at least approximately 150 kilowatts of power to the exterior induction coil. ### Claim 16 (depends on 11) The method of claim 11, wherein energizing the interior induction coil comprises: providing at least approximately 125 kilowatts of power to the interior induction coil. ### Claim 17 (depends on 11) The method of claim 11, further comprising: measuring a temperature of the tubular during the heat treating; determining a level of the alternating current to provide to at least one of the exterior induction coil and the interior induction coil based on the measured temperature; and providing the determined level of current to the at least one of the exterior induction coil or the interior induction coil. ### Claim 18 (depends on 11) The method of claim 11, wherein the heat treating comprising: increasing a temperature of the portion of the tubular to at least a predetermined temperature value associated with the tubular; and maintaining the predetermined temperature value for a predetermined time period associated with the tubular. ### Claim 19 (depends on 11) The method of claim 11, further comprising: forming a heat affected zone having a parabolic outline that faces away from a weld line based on heat treating the portion of the tubular. ### Claim 20 (depends on 11) The method of claim 11, wherein the tubular comprises a drill pipe, a drill collar, or a downhole tool housing.