In the cross-section of the lsaw steel pipe
, there is a phenomenon that the outer diameter is not equal, that is, there is a maximum outer diameter and a minimum outer diameter which are not necessarily mutually perpendicular, and the difference between the maximum outer diameter and the minimum outer diameter is ellipticity (or not Roundness). In order to control the ellipticity, some lsaw steel pipe standards specify the allowable index of ellipticity, which is generally specified as not to exceed 80% of the outer diameter tolerance (executed after consultation by the supply and demand sides).
LSAW steel pipe is curved in the length direction, and its curve degree is called curvature. The bending degree specified in the standard is generally divided into the following two types: Partial bending: Using a one-meter-long straight ruler at the maximum bending of the steel pipe, measure the chord height (mm), which is the value of the local bending degree. Its unit is Mm/m indicates the method is 2.5mm/m. This method also applies to tube end curvature. Full-length total bending: Using a string, pull from both ends of the tube, measure the maximum chord height (mm) at the bend of the steel tube, and convert it into the length (in meters) as the percentage of the length of the tube.