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Would you step outside to guess the weather or check the radar?
For crude distillation unit (CDU) overhead corrosion, many refiners still rely on snapshots: coupons, ultrasonic tests, and boot water pH. Unfortunately, corrosion doesn’t wait for your next reading. It forms in hidden spots, like storms rolling in without warning. Digital twins act like a corrosion radar that continuously track conditions and predict risks before they strike.
Corrosion in the CDU is one of refining’s most costly and hazardous problems. Overhead lines and condensers are continuously exposed to corrosive compounds. According to NACE, corrosion costs the oil and gas sector more than $1.3 billion annually. Unexpected failures can trigger shutdowns, safety incidents, and regulatory penalties. Other mechanisms, such as amine hydrochloride salts and wet H₂S cracking create hidden risks even where equipment looks sound.
Traditional monitoring tools tend to be reactive, intermittent, and localized. For example, corrosion has been observed even at boot water pH 7, because the first condensing droplets upstream were far more acidic — a blind spot that routine testing missed. Neutralizers like ammonia also dissolve more slowly than hydrogen chloride (HCl) that leave early condensation dangerously acidic. It’s like seeing clear skies overhead while a storm brews on the horizon.
So how do you stay ahead of the storm? The solution is moving from lagging indicators to predictive, real-time monitoring. That’s where digital twins come in. A corrosion digital twin integrates plant data with first-principles simulation to dynamically model CDU overhead conditions, track risks, and guide proactive action.
Digital twins, powered by platforms such as the Petro-SIM® process simulator and OLI engine, replicate CDU overhead systems. By feeding in live data such as temperature, chloride levels, injection rates, and lab analyses, the model continuously updates. All corrosive species must be modeled together for accurate forecasts.
Key performance indicators (KPIs) reveal when and where corrosion is most likely to occur:
Digital twins let refiners test crude blends, injection strategies, and operating adjustments virtually before making costly real-world changes. In one case, the digital twin revealed a dew point pH as low as 2.9, shock condensation in elbows and vertical runs, and uncovered that boot water pH was artificially elevated by sour stripper water, which masked the true severity of corrosion risk.
Armed with predictive insights, operators adjusted ammonia dosing and wash water. In one refinery, this approach reduced corrosion rates from 30 to 50 mil/year to safer levels, while avoiding unplanned shutdowns, which saved millions. That’s the payoff of using a radar instead of waiting for the storm to hit.
Once proven in CDU overheads, digital twin corrosion monitoring can be scaled to other high-risk units. This supports safety, predictive maintenance, compliance, emissions reduction, and strengthens risk-based inspection strategies while extending equipment life. Regulators now recognize continuous monitoring as a replacement for scheduled inspections. For refiners advancing through the energy transition, digital twins also help process more corrosive biofeeds and hydrogen-rich fuels while Bringing Decarbonization to Life®.
To explore the full case study and technical details, please read the article.