Whilst manual inspection remains a valuable tool for measuring the plant health, this blog post explains the benefits of continuous monitoring over periodic inspection.
Turning corrosion and erosion data to into true process insights
Uncontrolled corrosion and material degradation undeniably leads to hefty safety, environmental, reliability, and operational consequences. Standards, developed by the American Petroleum Institute (API), guide on recommended techniques to manage unknown corrosion risk and try to understand its impact on equipment health. API-580 details Risk-Based Inspections (RBI) and API RP 584 details Integrity Operating Windows (IOW). Both are powerful standards offering techniques to manage inspections and limit asset degradation respectively.
RBI analysis is used to identify and understand risk, drivers, and determine in which stage of the lifecycle the operators’ assets are in. This tool can also indicate if more extensive or frequent activities are required and determine how to mitigate future risks. During this process, inspection-related techniques, such as radiography, guided wave, eddy current, or others are used. Alongside this, inspection locations are specifically defined and prioritized based on historical data, metal loss mechanisms, and other inputs. Nevertheless, most fixed equipment assets will likely only be inspected every few years, leading to extremely sparse data to try and trend and an understanding of plant health that may be several years out of date.
In parallel, IOWs define established (usually empirical) limits for process variables that can affect the integrity of the equipment if the process operation deviates from them. They support stringent integrity management programs by managing possible changes/deviations in the process, noting the process variables are usually well monitored in typical process plants.
Both techniques are proven and used widely across the industry. Unfortunately, there are downsides or limitations to both that hinder their performance and ability to measure asset integrity. Performing frequent and extensive inspections to feed RBI models implies not only hefty expenses but also mobilizing and exposing personnel to hazardous areas.
Additionally, the lack of repeatable and accurate data offered by traditional corrosion measurement technology hinders the IOW definition and measurement process. IOW limits are usually set by an empirical understanding of how an average asset will handle typical corrosion risks or process conditions – it is extremely challenging to optimise the IOWs for the particular plant or process unit and so the high risk conditions flagged by the process variables might not actually be damaging the plant, or, perhaps worse, unflagged process conditions might be damaging the plant health rapidly without detection.
Preventing safety and environmental accidents
Preventing safety and environmental accidents requires not only complying with regulations but also harvesting actionable information. A complete and consistent Asset Integrity Management system ensures compliance with a variety of standards, such as those written by API.
Unfortunately, RBI methods based on calculated probability of failure assume that the risk of failure can be truthfully assessed, the notion that the focus must be on failure rather than on unmanaged degradation, and that periodic internal inspection is a vital step in failure prevention. Often, the time from the point of degradation to failure is uncertain and short, leading to unforeseen consequences.
From a historical point of view, these notions are understandable. For more than a century, failures were unexpected, common, and poorly understood. Moreover, internal inspection was the only means available to prevent them. Current corrosion and erosion monitoring techniques are driven by the availability of non-intrusive, wireless, and battery-operated capabilities. These technologies enable, from the actual failure start, instantaneous information harvesting and seamless delivery to all key decision makers.
Increasing uptime and safety with non-intrusive corrosion and erosion monitoring
Online non-intrusive corrosion monitoring is already popular across industry with the availability of data-to-desk monitoring systems that provide previously unachievable quality and frequency of online wall thickness measurements. This is especially important in certain process units due to the high risks posed by the process which, if realised, could cause danger to the environment or personnel.
This blog post shows that continuous monitoring enables greatly enhanced visibility into the health of the fixed assets and piping, in real time, and from a safe area. Intentional or unintentional changes to the process can be monitored and impacts to plant health monitored to better plan necessary maintenance.
The return on investment from deploying continuous monitoring technologies is large. Avoidance of costly unplanned shutdowns can save millions of dollars annually. Some high-profile facilities have failed to restart entirely following a catastrophic failure caused by unknown corrosion risk and impact. Risk-based inspection techniques are proactive, but are based on limited datasets, and a lot of theory. Integrity operating windows attempt to control the risk of corrosion impacting the plant health, but in this current environment, can operators afford to limit operating capabilities to that of a standard model? In order to drive the plant to its maximum capability operators not only need to inspect it every few years, and not only infer its ability to deal with corrosion risk, but rather continuously monitor its health in real time. It is recommended to apply both continuous monitoring and periodic inspection methods in tandem for the most comprehensive view of asset health and corrosion status.