How Valves Flow Into Your Integrity Program - Part 2: Mechanical Integrity Considerations

Introduction

Understanding valves, their anatomy, and how they operate, gives the inspector a better sense of what potential problems exist. At the same time, knowing which problems are more common to a specific type of valve allows the inspector to connect these dots and formulate an inspection plan that ensures continued reliability of valves.

In part one of this two-part series, we discussed the basics. We introduced the main valve types used in the industry and the two classifications of valves that belong in mechanical integrity (MI) programs: Emergency Isolation Valves (EIVs) and Critical Check Valves (CCVs). We summarized the industry standards and references that apply to EIVs and CCVs, and we discussed a process for identifying these valves and managing them within the MI program.

In this article, part two, we’ll go further in depth with the inspection and testing of valves, including EIVs and CCVs. We’ll discuss common damage mechanisms that affect different valve types and the inspection methods capable of detecting certain failure mechanisms before they happen.

Ideally, all valves should work when needed; but the truth is that valves fail. While many valve failures may have minimal impact on process safety, there are a number of valves whose failures can potentially domino into safety problems or larger failures of a process unit. EIVs and CCVs are highlighted in industry standards and references because they’re vital to process safety, and they should be included in mechanical integrity programs to be inspected and maintained. However, the owner/operator’s inspection group oftentimes has limited experience in this field.

Valves often seem to fall into the “gray zone” of equipment – they don’t explicitly belong to one functional group or another. Along with a handful of other miscellaneous assets, valves tend to slip through the cracks of expertise for owner/operators. They’re typically maintained by third party valve repair facilities who are experienced and able to specialize in valves.

With this series, we hope to close the gap by discussing the common failure mechanisms of valves and give the inspector an idea of what to look for during an inspection. For externally detectable failure mechanisms, we will discuss the on-stream inspection methods used to detect premature valve failure and provide guidance for minimizing or mitigating these failures.