How Pipe Ends and Wall Thickness Are Inspected After Rolling

Why Pipe Ends Are Cropped

Defects such as uneven wall thickness can exist at both ends of a pipe once rolling is complete, so each pipe has part of both ends removed. The quality of the pipe end is data that has to be tested, and an unqualified pipe end has to be cut off before the pipe is released.

What Can Go Wrong at the End

After the pipe passes through the sizing machine, part of the pipe end can show wall wrinkling and inward collapse. That collapse prevents the laser probe of a wall thickness measuring device from reaching into the bore, so the end has to be assessed before thickness can be measured at all.

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Detecting the Collapse

Industrial camera photography with image processing is used to detect pipe end defects. Image processing identifies whether a collapsed pipe wall cross section is present in the bore under a statistical model, and how large the collapse is, which then determines whether the pipe end needs to be sawn off.

Measuring the Wall

Once the end is confirmed clear, the measuring end of the laser thickness gauge can pass through the port of the pipe under test, which makes wall thickness defect detection possible along the length.

How Pipe Is Classified

Steel pipe has a hollow cross section whose length is far greater than its diameter. It is classified by material into carbon structural, low alloy structural, alloy and composite steel pipe, by use into pipeline, engineering structure, thermal equipment, petrochemical, machinery manufacturing, geological drilling and high pressure equipment pipe, and by production process into seamless and welded, with seamless split into hot rolled and cold drawn and welded split into straight seam and spiral.

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