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PRCI PR-220-9437
- Evaluation of Ultrasonic Technology for Volumetric Weld Inspection of Pipeline Girth Welds
- Report / Survey by Pipeline Research Council International, 12/01/1997
- Publisher: PRCI
$448.00$895.00
L51776e
RTD Quality Services (Rontgen Technische Dienst bv)
Need: A system for mechanized ultrasonic inspection of girth welds during pipeline construction, the RTD Rotoscan, has already been available for twenty years. Its development started back in 1977. First commercial use started around 1981. Today, RTD Rotoscans are being used all over the world whereby, for a number of pipeline projects, it replaces radiography as a sole girth weld inspection technique. Although the early version of the Rotoscan system, as already stated, was already commercially in use and improvements were considered, it was thought that a thorough and structured evaluation of the potentials of mechanized UT systems for pipeline girth welds was highly desirable. A major obstacle in the introduction of this kind of systems was found to be the fact that in industry only a limited generic insight was present on the performance of mechanized UT systems in terms of Probability Of Detection (POD) and sizing capabilities on one hand, and the likelihood of "false calls", causing unnecessary and costly repairs on the other hand. It had been experienced that, rather than generic acceptance, potential customers therefore wish to evaluate the system for their own specific applications and on their own representative test welds for the purpose of system qualification.
Benefit: The work performed in this project can be regarded as a continuation of an earlier PRCI project: "Evaluation of Ultrasonic Inspection Techniques for the Root Region of Girth Welds" (project PR-220-9123), which was completed by the end of 1995. In that project, the performance of modern systems for mechanized ultrasonic inspection of girth welds in pipelines was evaluated with the emphasis on the weld root, which can be considered historically as the most difficult part of the weld when it comes to conventional ultrasonic inspection. In the current project, this was extended to the entire weld. Already in report PR-220-9123, it was stated that a structured evaluation would also help to arrive at a generic approval of mechanized UT systems for use in pipeline industry, to reduce or replace job-specific qualification tests. This point is still valid. The results of the first project, and hopefully also of this one, will be an important basis for international efforts currently being undertaken to develop such approvals, as well as to arrive at adapted acceptance criteria for weld defects. The current project was, similarly to the previous one, built around a number and a variety of representative test welds, using different welding techniques. These were inspected with Rotoscan, also using improvements (such as simultaneous TOFD), partly initiated on the basis of the work done in the previous project, and with radiography. They were then destructively tested for correlation with the NDE results.
Result: The results of this project confirm that mechanized ultrasonic inspection can be considered as a mature alternative for radiography. In terms of inspection quality, mechanized ultrasonic inspection can even be superior over radiography, if applied with optimum inspection parameters. Moreover, ultrasonic methods can, contrary to radiography, be applied with Engineering Critical Assessment (ECA) acceptance criteria.
RTD Quality Services (Rontgen Technische Dienst bv)
Need: A system for mechanized ultrasonic inspection of girth welds during pipeline construction, the RTD Rotoscan, has already been available for twenty years. Its development started back in 1977. First commercial use started around 1981. Today, RTD Rotoscans are being used all over the world whereby, for a number of pipeline projects, it replaces radiography as a sole girth weld inspection technique. Although the early version of the Rotoscan system, as already stated, was already commercially in use and improvements were considered, it was thought that a thorough and structured evaluation of the potentials of mechanized UT systems for pipeline girth welds was highly desirable. A major obstacle in the introduction of this kind of systems was found to be the fact that in industry only a limited generic insight was present on the performance of mechanized UT systems in terms of Probability Of Detection (POD) and sizing capabilities on one hand, and the likelihood of "false calls", causing unnecessary and costly repairs on the other hand. It had been experienced that, rather than generic acceptance, potential customers therefore wish to evaluate the system for their own specific applications and on their own representative test welds for the purpose of system qualification.
Benefit: The work performed in this project can be regarded as a continuation of an earlier PRCI project: "Evaluation of Ultrasonic Inspection Techniques for the Root Region of Girth Welds" (project PR-220-9123), which was completed by the end of 1995. In that project, the performance of modern systems for mechanized ultrasonic inspection of girth welds in pipelines was evaluated with the emphasis on the weld root, which can be considered historically as the most difficult part of the weld when it comes to conventional ultrasonic inspection. In the current project, this was extended to the entire weld. Already in report PR-220-9123, it was stated that a structured evaluation would also help to arrive at a generic approval of mechanized UT systems for use in pipeline industry, to reduce or replace job-specific qualification tests. This point is still valid. The results of the first project, and hopefully also of this one, will be an important basis for international efforts currently being undertaken to develop such approvals, as well as to arrive at adapted acceptance criteria for weld defects. The current project was, similarly to the previous one, built around a number and a variety of representative test welds, using different welding techniques. These were inspected with Rotoscan, also using improvements (such as simultaneous TOFD), partly initiated on the basis of the work done in the previous project, and with radiography. They were then destructively tested for correlation with the NDE results.
Result: The results of this project confirm that mechanized ultrasonic inspection can be considered as a mature alternative for radiography. In terms of inspection quality, mechanized ultrasonic inspection can even be superior over radiography, if applied with optimum inspection parameters. Moreover, ultrasonic methods can, contrary to radiography, be applied with Engineering Critical Assessment (ECA) acceptance criteria.
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