An Overview of Heat Treatment in the Refining, Power, and Petrochemical Industry - Part 2: The Importance of Heat Treatment to Mechanical Integrity

Introduction

Heat treatment is an important process in the refining and petrochemical industry. It gives us the ability to alter the metallurgical characteristics of piping and equipment to better suit their intended applications. Oftentimes, this means altering a material’s hardness, strength, toughness, ductility, and elasticity.

There are many mechanical integrity aspects of heat treatment that ensure the desired outcome is not only achieved, but that it is achieved safely and without negatively affecting the asset. When done properly heat treating adds beneficial properties, most often essential characteristics to the component.

In Part 1 of this two-part series, we discussed the basics of heat treating. We discussed the purposes, application types, and methods to give the reader a better understanding of what goes on when heat treating. Knowing the basics allows you to further learn the impact that heat treating has on the assets in your inspection programs.

In Part 2 of this series, we’ll dig deeper into the benefits of heat treating, specifically relating to mechanical integrity, as well as the quality control measures that take place during the heat-treating process. We will discuss common damage mechanisms whose susceptibility can be greatly reduced or even eliminated with heat treatment. We’ll also touch on how heat treating is used to reduce risk in risk-based inspection (RBI) programs and expand threshold limits for integrity operating windows (IOWs). We will also cover the importance of the heat treatment plan, including the engineering that takes place when developing the plan.

Why is Heat Treatment Important in the MI World?

For the inspection and reliability world, the short answer is to prevent cracking. Cracking can be caused by a number of different scenarios, and they’re not all within our control; but a large element that is mostly within our control is stress, hence the name “stress relieving.”

In the refining, power, and petrochemical industries, heat treating is commonly used to reduce residual stresses developed as a result of welding or forming a material. It allows the material to relax, which is especially important for thick materials and those found in environmental cracking regimes.