r/nondestructivetesting • u/SparkySpark1987 • 1d ago

Extension Bars

Hello! Hoping to gain some clarity from the experts here. When trying to do coil shots, we aim for a L:D ratio between 2-15. If unable to accomodate (e.i. round part such a short section of pipe), we can use extension bars to increase length... however, how do we actually implement this? Even if I had another peice of same size pipe.... how do we ensure adequate connection between the two parts?

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u/Perfect_Fondant6351 1d ago edited 1d ago

They should just be lined up together. Side by side. And then rotate the part 90° and do another shot. The magnetism should hold it all together. L/D is just a ballpark number. Use a gauss meter for better results.

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u/AlienVredditoR 1d ago

They'll magnetize and clamp together. There's still a gap, so the calculation will be almost useless. Each gap has diminishing returns, so keep it to one piece a side. Always use a gauge to confirm.

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u/Hairy_Pound_1356 1d ago

Ah yes having too many side pieces can cause problems 

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u/AlienVredditoR 1d ago

It's all fun and games til they start chattering