... 3.API - 5L,GB9711.1,GB9711.2 Standards ERW Tube Mill(219mm-630mm)High-grade, large caliber and high frequency ... .In recent years,with learning & developing large caliber ERW production lines (Φ219mm –Φ2540mm )with our own intellectual ... We have finished designing large caliber ERW production lines specifications:16” ERW, 20” ERW, 24” ERW. ERW tube mill Horizontal LoopPost welding seam heat treatment ...