ASME Sec. 5 - line pair test pattern

[FullSail]

I am trying to find out acceptance standards for real time radioscopic exam using a line pair test pattern. The calibration requirements are stated in Article 2, App. 2, II-236 but it doesn't seem to reference acceptance standards criteria. Does anyone know where to find it?

 

[jackvarner]

The line pair test pattern is one of three required tests to prove system performance.

To measure resolution, you use the Line Pair (lp) test pattern; to measure contrast you use the step wedge(s); and a sample with known flaw(s) is used to prove flaw detection both in the static and dynamic modes.

In regards to the line pair test pattern, it is placed in the same proximity as the items that you normally real-time. You will have to manipilate the LP pattern to get a clear view and adjust the kV for optimum
resolution.

Then you visually determine how many line pairs/mm that you can discern.

A good resolution for ASME is 2.5 lp/mm or better.

To determine the smallest flaw that you can detect with a system resolution of 2.5 lp/mm, you do the following:

1) 2.5 lp/mm = 5 lines/mm

2) divide 1 by the number of lines (5)
to get the size (.2 mm) of the smallest detectable indication.

3) compare this number with the IQI requirements of ASME V Article 2 for
for a 2-2t sensitivity on the appropriate IQI for your application from table T-233.1

4)For example, the 2t hole in the thinnest hole IQI is .51 mm. At 2.5 lp/mm resolution, you can detect a flaw .2 mm in size which is well below what the code says is the minimum.

Jack Varner, NDE Level III

You can contact jackvarner at jackvarner@comcast.net.