In the oil and gas transportation system, the ellipticity of the pipeline's cross-section is a frequently discussed technical indicator. Excessive ellipticity deviation can lead to stress concentration on the inner wall of the pipeline, and buried pipelines are more prone to fatigue failure when under pressure.
The traditional cold bending forming process, if the roller design is unreasonable or the reduction amount is not properly controlled, it is very likely to form "elliptical pipes" before welding. Although this can be corrected by a diameter expansion machine later, it not only increases costs but may also introduce new residual stresses.
Some customers have reported on-site that for the same 12-meter pipe, the roundness is qualified in the front half but gradually deviates in the rear half. This is often related to the feeding accuracy of the equipment and the wear of the forming roller.
This is why high-grade oil and gas pipeline equipment has increasingly higher requirements for the feeding system and closed-loop control. Instead of making up for it at the downstream stage, it is better to control the ellipticity at the source. This is precisely the detail that many customers are most concerned about.