API 570 Piping Inspector Practice Test

In facilities with very harsh service conditions, which pipe material is commonly specified for primary lines?

Seamless pipe Welded pipe ERW pipe Cast iron pipe

Correct Answer:

Seamless pipe

Explanation:

In harsh service conditions, primary lines are built for maximum reliability, so seamless pipe is preferred. It is produced without a welded seam, eliminating the weld bead and heat-affected zone that can become initiation points for cracks or corrosion under high pressure, temperature, or aggressive fluids. This gives more uniform strength, better toughness, and higher resistance to failure, which is crucial for critical piping. Welded pipes, including ERW, have seams that can be vulnerable in demanding service, and cast iron is brittle and generally not suitable for high‑pressure primary lines. For these reasons, seamless pipe is commonly specified for primary SAMPLElines.

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