Acoustic Emission Testing for Corrosion Monitoring and Deferral of Storage Tank Turnarounds

Abstract

Storage tank turnarounds have both financial implications and impact supply chains. Owner-operators have deployed different on-stream corrosion monitoring and inspection techniques to assess storage tank conditions and explore opportunities for reducing downtime and postponing internal inspections. One of those opportunities is Acoustic Emission Testing (AET), which has been widely used to assess the extent of tank bottom corrosion and qualify storage tank turnaround deferrals. This article reviews the effectiveness of AET for inspecting tank bottoms in two ways; namely, benchmarking regulations in different countries and comparing AET and Magnetic Flux Leakage Testing (MFLT) results through a case study. The article also proposes a set of alternatives to using AET for tank bottom inspection and the deferral of internal inspection.

Introduction

Storage tanks play a vital role in the supply chain operations of the petroleum industry. Sometimes, the operational needs dictate deferring a storage tank outage for routine internal inspection and maintenance activities. In such instances, owner-operators will normally carry out evaluations as part of their risk management practices to aid in making a sound technical decision and ensure safety and the environment are not jeopardized.

Previous studies and field experience have revealed that the risk of failure to above-ground storage tanks highly depends on tank bottom conditions, and the dominant damage of tank bottoms is deterioration caused by corrosion on the product-side and/or the soil-side.^[1] AET has been used by owner-operators for years as a tool to assess tank bottom conditions and to help qualify the deferral of scheduled internal inspections. The purpose of this article is to:

• Benchmark the regulations for AET as a practice to assess the condition of tank bottoms and support the postponement of internal inspections.
• Review the effectiveness of AET through real-world examples and a case study, comparing AET and Magnetic Flux Leakage Testing (MFLT) results.
• Discuss a set of alternative decision-making tools to using AET that owner-operators may consider to assess tank bottom conditions and make decisions on internal inspection deferrals.

Overview of AET