So, You’ve Got IOWs – What’s Next?

Introduction

The refining and petrochemical industries have recently seen an increased focus on integrity operating windows (IOWs). The first edition of API RP 584, “Integrity Operating Windows” (2014), and the subsequent release of the second edition (2020) have helped to raise awareness of IOW programs and how IOWs fit into an overall fixed equipment mechanical integrity (FEMI) program. While considerable time has been given to the work processes necessary to develop a set of IOW limits, less time and focus have been placed on how to manage those limits once they’ve been determined. This article will provide a brief background on IOWs before focusing on integrating IOWs into an existing FEMI program.

IOWs are defined as established limits for process parameters that affect the integrity of fixed equipment and piping. When operating parameters deviate from these limits, degradation is more likely to occur. IOWs should be considered a specific subset of a larger group of unit operating parameters (product quality, environmental limits, etc.). If operations are kept within these limits, degradation should be predictable; however, this does not necessarily mean low rates of damage [1].

API 584 defines IOWs in three categories [2]:

• Critical – requires the operator to take immediate predetermined actions to return the process variable within the IOW limits to prevent significant defined risks of potential equipment damage or hazardous fluid release or result in an emergency or rapid non-orderly shutdown.
• Standard – requires predetermined operator intervention or corrective action by a subject matter expert (SME) if the duration of the exceedance is more than a specified time. Typically, the duration of exceedance could cause an increased degradation rate or introduce new damage mechanisms beyond those anticipated.
• Informational – often less restrictive limits for Critical and Standard IOW limits, are for trending by the SME and, in some cases, may not be controllable by operations. An IOW Informational limit is a parameter that may be used to predict a change in corrosion potential.