Inspect Your Primary Process Small Bore Piping the Right Way, Using Profile Radiography

Introduction

Small Bore Piping (SBP), defined as pipe or piping components that are less than or equal to nominal pipe size (NPS) of 2”, is a major element of every mechanical integrity (MI) program. This category of equipment includes a majority of plant process piping and ancillary systems, including many critical piping systems that are fabricated with SBP, such as, level bridles, flow control loops, pressure and temperature indicating systems, and bypass and pressure relief systems. Despite numerous industry publications, recommended practices, and inspection codes recommending Profile Radiography (PRT) as the preferred method of inspection for pipe diameters of NPS 1” and smaller, equipment owners continue to utilize digital ultrasonic thickness gauging, which is often unreliable.

Digital Ultrasonic Testing (DUT)

Most owner-user facilities utilize embedded DUT technicians to obtain thickness and corrosion data on their equipment and piping systems. In these cases, DUT is often selected because of outdated past practices and as a means to minimize costs. However, when using DUT,  specialized equipment (i.e., special curved or miniature shoes/wedges, as well as diameter specific calibration blocks) is required to accurately assess SBP. Unfortunately, in a career spanning almost three decades, I’ve witnessed that most do not bother obtaining such items prior to inspection. In areas in which you wish to inspect that are insulated, inspection ports are cut in the insulation to facilitate taking DUT readings.