API REPORT 1114-5-ed.1996

Anotace textu normy API REPORT 1114-5-ed.1996 :

API REPORT 1114-5, 1996 Edition, 1996 - Ultrasonic Testing Requirements for Single-Sided Butt Welds in Offshore Fabrications

EXECUTIVE SUMMARY

Background

This project was concerned with investigating alternative ultrasonic test techniques and alternative acceptance criteria for the examination of single-sided butt welds. The approach involved collecting a large volume of ultrasonic test data, covering both best and worst cases, from which the recommendations are drawn.

Objectives

• To evaluate the creeping wave, tandem and time-of-flight diffraction (TOFD) techniques for the inspection of single-sided butt welds.

• To formulate prototype ultrasonic test acceptance criteria which fit into the RP2X framework but apply specifically to single-sided butt welds.

• To demonstrate, as far as possible, that those acceptance criteria are effective for the inspection of single-sided butt welds.

Work Undertaken

• Four welded testpieces containing surface breaking and embedded EDM slots were manufactured.

• A series of ultrasonic detection and classification trials took place using TWIs P-scan system.

• These data were analysed so that the relative merits of each technique could be compared and absolute amplitude threshold information could be extracted.

• A number of recommendations have been made.

Principal Recommendations

• The use of creeping wave and tandem techniques are recommended only for certain situations such as where there is limited access.

• The use of the TOFD technique is recommended only where speed of inspection justifies the reduced effectiveness to detect certain types of flaw.

• A set of alternative acceptance criteria which are recommended for the examination of single-sided butt welds is given in the report.

Conclusions

1. The use of the creeping wave technique does not improve the examination of single-sided butt welds for planar surface-breaking flaws.

2. The use of the tandem technique does improve the examination of single sided butt welds for embedded planar flaws.

3. The use of the TOFD technique is unlikely to result in as good an examination of singe-sided butt welds as pulse-echo techniques.

4. The use of automated (pulse-echo) ultrasonic test techniques, where an image of the weld can be produced, is likely to improve the examination of the root region of single-sided butt welds.

5. In a 40mm thick, single-sided butt weld, the size of planar flaw which results in a 50% detection rate is about 9mm long by between 1 and 2mm high.