Ultrasonic Testing of OCTG Threaded Joints
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Solution Overview
Problem
Conventional methods for evaluating the fastening state of threaded joints in Oil Country Tubular Goods (OCTG) are inaccurate due to the inability to independently assess the adherence or non-adherence of thread, metal seal, and shoulder parts, and fail to detect defects or non-adhering portions at the contact region, leading to difficulties in quality control and air leakage efficiency.
Innovation Solution
An ultrasonic testing method that transmits and receives ultrasonic waves along the axial direction of threaded joints to detect echo intensities and reception times, allowing for the identification of abnormal portions such as defects, non-adhering portions, and seized portions by analyzing the axial directional distribution of these parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If torque monitoring is used to evaluate fastening state, then the evaluation process is simple, but the measurement precision is insufficient to independently assess adherence of thread, metal seal, and shoulder parts
Solution Approach 1:
The invention segments the threaded joint into three distinct evaluation zones: thread part (first axial position), metal seal part (second axial position), and shoulder part (third axial position). By transmitting ultrasonic waves to each zone independently and evaluating echo intensities separately, the system can independently assess the adherence state of each component, resolving the inability of conventional torque monitoring to provide differentiated adherence information.
2Ease of operation
If torque monitoring is used to detect fastening completion, then the detection method is straightforward, but the reliability is insufficient to distinguish between proper fastening and seizing
Solution Approach 1:
The invention applies local quality evaluation by analyzing echo intensity characteristics specific to each axial position within the threaded joint. The thread part, metal seal part, and shoulder part each have distinct expected echo intensity ranges. By comparing measured echo intensities against these position-specific reference values, the system can reliably distinguish between normal fastening (where each zone shows expected characteristics) and abnormal conditions like seizing (where echo intensities deviate from expected patterns), thereby improving detection reliability.
3Reliability
If conventional ultrasonic testing is used to detect defects, then defect detection capability is provided, but the device complexity increases due to additional testing equipment
Solution Approach 1:
The invention makes the ultrasonic testing device multi-functional by integrating three evaluation capabilities into a single system: (1) adherence evaluation of the thread part, (2) adherence evaluation of the metal seal part, and (3) defect detection. By using a single ultrasonic wave transmission system that evaluates echo intensities at multiple axial positions with different reference criteria, the device performs multiple functions without requiring separate testing equipment for each function, thus avoiding increased device complexity while maintaining comprehensive reliability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables accurate detection of abnormal portions with high precision, distinguishing between adhering and non-adhering states, and identifying defects or seized portions, thereby improving quality control and maintaining air leakage efficiency.
Implementation Method 1
transmitting and receiving ultrasonic waves to and from a plurality of locations of the threaded joint in at least one of the internal thread part, the metal seal part, and the shoulder part of the box; and detecting echo intensities of echoes for the plurality of locations
Data Source
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Figure 3A~3E
AI summary
There is provided a method for detecting an abnormal portion (defect, non-adhering portion, and seized portion) lying at a contact region between each part of a pin and each part of a box forming a threaded joint to be used as a joint of pipe or tubes such as OCTG. This invention provides an ultrasonic testing method of a threaded joint of pipes or tubes including a pin having an external thread part, a metal seal part, and a shoulder part on an outer peripheral surface, and a box having an internal thread part, a metal seal part, and a shoulder part corresponding to each part of the pin on an inner peripheral surface and being fastened with the pin by way of a lubricant. The method according to the present invention comprising the steps of: transmitting and receiving ultrasonic waves to and from a plurality of locations along an axial direction of the threaded joint in at least one of the internal thread part, the metal seal part, and the shoulder part of the box; detecting echo intensities and reception times of echoes for the plurality of locations; and detecting an abnormal portion in the threaded joint based on axial directional distribution of the echo intensities and axial directional distribution of reception times of the echoes.