IOW Theory

The Integrity Operating Windows (IOWs) are defined as limits on process variables, beyond which the operating facility integrity deteriorates rapidly, leading to unsafe conditions. Impact can be a shortening of the remaining lifecycle of the asset and an activity such as a S-RBI review to assess the Remnant Life (RL) can be considered.

During design, potential Degradation Mechanisms are foreseen and usually addressed. However, operational variations or process changes over time can make the original design susceptible to degradation. The benefit of operating within integrity limits (typically the Integrity Operating Window) is that the Remaining Life of Equipment is as per design, ensuring safe and efficient operations.

The basis of these IOWs are data, process and engineering knowledge, and operating design windows. An IOW variable is considered a Barrier, if operationally controlled to Ensure Safe Production (ESP) within its window and covered by a proactive monitoring plan. Materials and Corrosion Engineers (MCEs) should be responsible for IOW monitoring.

In the image below the ESP limits are shown. These limits have to do with Process Control and Alarm Management. The IOW is defined as the green band between the Integrity High and Low limits. Thus, both the ESP Target and Integrity limits are applicable when defining IOW variables. The Integrity limits can be classified as Standard, Critical or Monitoring - in the below example they are Standard. The IOW variable should be monitored for exceedance of the ESP Integrity and Target limits to give an indication of the Barrier’s status. These two limits thus form part of the IOW definition.Visualization of ESP Limits. The Target and Integrity limits are applicable when defining the IOW.

Defining IOWs in IMS

IOW are defined in the CL - see Creating and Defining IOWs and also Defining Barriers (and linking to IOWs).