Continuous Asset Integrity Monitoring to Detect Corrosion with Installed Ultrasonic Sensors Saves More than $4 Million

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Refineries face a significant challenge in managing the Amine Treating Unit (ATU) for Environmental Compliance and Safety, often part of the Sulfur Recovery and Tail Gas Treating Units (SRU and TGTU). The ATU's role is to convert remaining sulfur compounds into hydrogen sulfide (H2S), which is then reprocessed by the SRU. However, corrosion and erosion issues are often encountered during this process, affecting asset integrity planning. We will present the sweet solution for dealing with sour gas and explore how an asset owner successfully harnessed the potential of wireless, installed ultrasonic sensors to precisely monitor and trend their asset's corrosion rates, resulting in substantial maintenance cost savings of $4.8 million.

The Challenge

Traditional manual ultrasonic inspections pose cost inefficiencies, risk unexpected leaks, and cause downtime, underscoring the demand for a real-time monitoring solution.

Figure 1: SRU & Tail Gas

The challenge arises from the presence of "sour" gas within the ATU, a gas that induces corrosion over time. This corrosion primarily occurs due to the gradual accumulation of Heat Stable Amine Salts (HSAS), which is further exacerbated by localized wall loss resulting from pressure fluctuations. The corrosive attributes of H2S, including alterations in pH levels, increased solution conductivity, and the destabilization of protective sulfide layers, further compound the issue. In this specific case, it was identified that a poorly designed horizontal nozzle in the exchanger served as a source of turbulence, intensifying corrosion rates in specific areas.

Figure 2: Piping & Instrumentation Diagram With Affected Areas Highlighted

The sporadic nature of erosion-corrosion damage makes accurately determining corrosion rates and identifying potential problem areas challenging. Traditional manual ultrasonic thickness inspections, performed at varying intervals over the years, resulted in limited success and unexpected leaks, causing downtime.

The Solution

Automated wireless ultrasonic sensors provide real-time monitoring and trend analysis to proactively address corrosion and erosion.

Figure 3: Thickness Data (Y-Axis) Collected Over 12 Months (X-Axis) (Upper Graph). Ultrasonic Waveform Makes Precise (+/1.001in) Thickness Readings From Sensor (Lower Graph).

To address sporadic erosion-corrosion damage, the asset owner transitioned from regular manual inspections to a monitoring approach using microPIMS®, an intrinsically safe system by Eddyfi Technologies. This advanced system is equipped with ATEX Zone 0 Haz-Loc certification, extended battery life, and utilizes long-range sub-Gigahertz wireless connectivity.

Working with inspection, corrosion, and operations teams, the asset owner mapped out high-risk areas and conducted baseline screening and inspections to identify monitoring locations. microPIMS sensors were deployed at strategic positions, allowing them to program daily wall thickness measurements and track them over time. The installation process was swift, taking just one day, and each sensor was set up in under 20 minutes per location. By implementing microPIMS sensors for monitoring, the asset owner achieved rapid and precise corrosion rate trending at each sensor location, with accuracy up to within 0.025 millimeter (.001 inch). Figure 3 illustrates the data collected over a year.

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  • Refineries can extend asset life, prevent costly unplanned outages, save millions in maintenance expenses, and optimize operational efficiency, all while ensuring environmental compliance and safety.

More than six unplanned outages that had occurred at the ATU over a 15-year period were traced back to a corrosion issue costing an estimated $12 million dollars in maintenance and causing $200 million dollars in downtime. By effectively monitoring and addressing corrosion in the TGTU using microPIMS, the asset owner extended its safe operation by an estimated 4.62 years, saving approximately $4.8 million dollars in maintenance costs. The initial $40,000 investment in a microPIMS starter kit resulted in a 98% return on investment and a payback period of less than 3 months.

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