Precise temperature monitoring (usually 1150–1300°C for steel billets, lower for copper) using infrared pyrometers and thermocouples to avoid overheating (which causes grain coarsening, scaling, or decarburization) or underheating (leading to cracking during piercing).
Uniform heating checks across the billet cross-section to prevent eccentric wall thickness in final pipes.
Surface oxidation and scale inspection before discharge—excessive scale can embed into the pipe wall, causing surface defects.
Billet surface visual and ultrasonic pre-checks to detect cracks or inclusions that could propagate in later stages.

Real-time monitoring of piercing parameters: feed angle, roll speed, plug position, and billet centering to minimize eccentricity and wall thickness variation.Immediate post-piercing inspection of the capillary tube: ultrasonic testing (UT) for internal laminations, cracks, or voids; visual and dimensional checks for inner/outer surface quality.
Temperature control during piercing to avoid overheating the plug or causing helical tears ("spiral inside surface defects").Eccentricity and wall thickness measurement using laser or ultrasonic gauges—critical for preventing uneven deformation in subsequent rolling.Defect rejection criteria: any capillary showing >5–8% eccentricity or visible forging laps is typically rejected or reworked.

Online wall thickness and diameter monitoring using laser micrometers or ultrasonic sensors during rolling/extruding to maintain tolerances within ±5–10%.Surface quality checks for rolling/extrusion marks, scratches, or laps—eddy current or magnetic particle testing detects surface-breaking flaws.Temperature control between passes to ensure uniform microstructure and avoid hot shortness or excessive grain growth.For extrusion (especially copper tubes): monitoring ram pressure, die condition, and lubrication to prevent surface tearing or internal voids.Real-time eccentricity correction via adjustable guide shoes or rolls, with post-rolling UT or eddy current scanning for internal defects.

Immediate inspection after ejection for internal surface quality—removing mandrel marks, scratches, or lubricant residue that could affect later sizing or finishing.Ultrasonic or eddy current testing to detect any newly formed internal defects caused by mandrel drag or uneven cooling.Visual and dimensional verification of the hollow shell before entering sizing/reducing mills.Cooling rate control (air cooling or controlled quenching) to prevent distortion, residual stress, or microstructural issues.For copper tubes: special attention to oxidation prevention during ejection and transfer to avoid surface discoloration or pitting.