METHOD FOR COUNTING TURNS WHEN
MAKING THREADED JOINTS
CROSS REFERENCE TO RELATED
This Application is a Divisional Application of Copending Ser. No. 941,894, filed Sept. 12, 1978, entitled "Method And Apparatus For Counting Turns When Making Threaded Joints".
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates in general to an apparatus for monitoring the operation of making threaded tubular joints and in particular to an apparatus for controlling the applied torque and number of turns in such an operation.
2. Description of the Prior Art
After a bore hole has been drilled to an oil or gas deposit, pipe strings are run into the bore hole for removing the oil or gas. The pipe strings are assembled at the well site from pipe sections each having external threads at one end and an internally threaded box member at the other end or external threads at both ends for use with an internally threaded coupling collar. As the pipe sections are connected together, they are run into the bore hole. Each pipe section is assembled to the top of the pipe string utilizing a power tongs unit which has a rotary jaw member for gripping the pipe and a motor for rotating the jaw member until the pipe section has been tightened to the desired degree. The joint must be tight enough to prevent leakage and to develop high joint strength but not so tight so as to damage the threads which can leak.
Early prior art techniques involved the determination of the applied torque to achieve the desired degree of tightness in the joints. For example, one technique involved the adjusting of the air supply maximum output pressure to a pneumatically driven tong motor to provide the required maximum torque as dictated by joint properties and tong power characteristics. Thus, the proper torque was developed when the tong motor stalled. Another technique involved the counting of the number of turns after the threads had been engaged at a "hand tight" point. These early techniques were unsatisfactory since the desired torque could be developed early as a result of damaged or dirty threads.
One prior art device which attempted to solve the problem included means for producing a signal indicating of the number of turns of the pipe section after measurement of a given torque by the torque measuring means. The device produced a warning of a bad joint upon the measurement of a predetermined torque before a measurement of a minimum number of turns had occurred or the measurement of the maximum number of turns before the measurement of the predetermined torque had occurred. The device indicated a good joint upon the measurement of the predetermined torque value between the measurement of the minimum and maximum number of turns. Such a device is shown in U.S. Pat. No. 3,368,396 issued Feb. 13, 1968. Improvements to that device are disclosed in U.S. Pat. No. 3,606,664 issued Sept. 21, 1971, U.S. Pat. No. 3,745,820 issued July 17, 1973, and U.S. Pat. No. 4,091,451 issued May 23, 1978.
SUMMARY OF THE INVENTION
The present invention concerns a control means for an apparatus for assembling threaded members, such as
5 pipe sections, to form a pressure sealed joint. The assembly apparatus includes power tong means connected to one of a pair of pipe sections for rotating that pipe section with respect to the other pipe section, transducer means responsive to the torque applied to the one
10 pipe section by the pipe rotating means for generating a signal representing the applied actual torque value, and means responsive to the rotation of the one pipe section for generating a signal representing the turns of the one pipe section.
15 The control means includes means for generating a signal representing a reference torque value; means responsive to the reference torque signal and the actual torque signal for generating an up count signal and a down count signal when the value of the actual torque
20 signal is greater than and less than the value of the reference torque signal respectively, the up and down count signals being generated only after the first time the value of the actual torque signal exceeds the value of the reference torque signal; means responsive to the
25 actual turns signal for counting the turns, the counting means being responsive to the up count signal for incrementing a count total of the turns in response to the actual turns signal and being responsive to the down count signal for decrementing the count total in re
30 sponse to the actual turns signal; means for generating an average actual turns signal representing the count total of the counting means; and means responsive to the actual torque signal and the average actual turns signal for controlling the rotating means.
35 The present invention also concerns a method for making threaded joints from a pair of cooperatively threaded members within a range of predetermined applied torque and turns values. The method includes the steps of engaging the cooperating threads and rotat
40 ing one of the members with respect to the other of the members; monitoring the actual torque applied to the one member; accumulating a count total of the turns made by the one member after a predetermined reference torque value has been reached, adding turns to the
45 count total when the actual torque is greater than the reference torque and subtracting turns when the actual torque is less than the reference torque; and indicating when the count total and the actual torque values are within the range of predetermined applied torque and
50 turns values.
It is an object of the present invention to reduce the potential for damage to threaded members when making threaded joints. It is another object of the present invention to accu
55 rately count the number of turns made when joining threaded members.
It is a further object of the present invention to increase the quality of threaded joints such as joints between pipe sections.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram of an apparatus for threading pipe and a control system therefor according to the present invention. 65 FIG. 2a is a plot of torque versus turns illustrating joint make-up values for typical joints.
FIG, 2 b is a plot of torque versus turns illustrating the turns averaging feature of the present invention.