Apr 2016
Gas Transmission
Ultrasonic testing of thin wall pipeline girth welds using high frequency probes
Apr 2016
Aug 2016
National Grid Gas Transmission
Alan Kirkham, box.GT.innovation@nationalgrid.com
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Network Innovation Allowance
Gas Transmission Networks
Thin walled pipes are increasingly required to be tested non-destructively to the requirements of National Grid Standard T/SP/NDT/2 which then refers to BS EN ISO 17640.

Conventional ultrasonic testing (according to BS EN ISO 17640) limits thicknesses that can be examined to less than 8mm. Similarly, the draft phased array standard BS EN 13588 goes down to 6mm. Smaller thicknesses are frequently inspected by radiography,

The main purpose of this work is therefore to examine whether the normal manual ultrasonic procedures used in the standard can be applied with minimum modification to inspect arc welds in thin sections can improve on this. The reason that the 8mm limit applies in most cases is that it is not possible with thinner sections to apply standard UT probes because they cannot approach the weld close enough nor can the beam be easily defined. The modification to the standard procedure adopted is to allow the use of high frequency 10MHz angled beam probes.

To determine if by using higher frequency probes acceptable results can be achieved to allow there use on thin wall pipe weld inspection.

Tests will be carried out on a range of thin wall pipe samples using High frequency probes, the results will be compared to conventional test probes, and a report produced to compare the results.

Subject to successful demonstration the technique this will feed into the update of T/SP/NDT/2 for National Grid and allow the extension of ultrasonic and reduce the need for radiography.