Abstract
In risk-based design of well casing and tubing, part of the calculations for burst and collapse reliability depend on the statistical distribution of the pipe wall thickness and ovality properties. It is not sufficient to have random or local (point-wise) readings of these parameters. Instead, the calculations must account for the actual minimum and average values as they occur statistically along each entire joint of pipe. This paper explains the methodology and results from the development of a data acquisition system designed to acquire and report comprehensive pipe wall and diameter measurements as part of the standard pipe inspection process.
An online data acquisition system with six analog input channels was developed to acquire and store wall and diameter data for tubulars with diameters between 4.5 in. and 20.0 in. This system was designed so that it would neither interfere with nor add any cost to the existing inspection process at ICO. The wall thickness measurement is incorporated into already existing ultrasonic inspection equipment. The system yields 600 wall readings per pipe revolution. With a typical advancement speed of 1.375 revolutions per inch of travel, this translates into over 160,000 wall readings per typical joint of pipe. Software, covered in this paper, processes and reduces this data to minimum and average wall values on a per-joint basis.
The diameter measurements are obtained from collimated light sources, which cast shadows onto optical sensing arrays. The pipe diameter is determined by the fraction of array elements not receiving light. This system also yields 160,000 readings per typical joint of pipe. Noise and inconsequential ovalities (ovalities over lengths less than 6 diameters) are removed, yielding a maximum and minimum ovality for each joint.
