Patent ID: 7231314
Filing Date: 2007-06-12
Classification: G01B

Abstract:
1. A method for determining the maximum and minimum diameter, wall thickness and ovality of a tubular item at a selected position along the length of the tubular item comprising: determining the circumference of the tubular item at the selected position; calculating the diameter of a circle having a circumference equal to the determined circumference; contacting the external surface of the tubular item at two points in a plane substantially perpendicular to the major axis of the tubular item; rotating the tubular item while measuring the distance from the surface of the tubular item at a point halfway between the two points of contact to a measuring device located at a known distance from a line connecting the two points of contact; measuring the wall thickness of the tubular item while the tubular item is being rotated; calculating a set of observed radii from the measured distances from the surface of the tubular item at a point halfway between the two points of contact to the measuring device and the length of the line connecting the two points of contact; selecting the minimum and maximum values from the set of observed radii; calculating the ovality of the tubular item using the difference between the maximum and minimum diameters determined per revolution; correlating calculated ovality and measured wall thickness values; and reporting correlated ovality and wall thickness values.