Case Studies › Downstream Refining
Case StudyRefinery CoolingUSIndependent · No Chemistry Sold

Every cooling report read “all green” — and the refinery’s heat exchangers kept failing every year

A refinery’s cooling program looked healthy on paper. Cycles, chemistry, program residuals, product usage, and general corrosion rates all sat in the green — quarter after quarter. Yet the site was still replacing failed heat exchangers every year and overbuilding systems to survive the changeouts, at a cost of millions annually. Everyone had accepted it as “just the type of water here.” An independent review found the real story hiding behind the green dashboard, rebuilt the metrics and baseline chemistry, cut treatment cost by nearly a third, and eliminated the failures.

Unit Served
Refinery cooling system
Key Issue
“All green” reports, annual HX failures
Hidden Finding
127 mpy pitting behind <3 mpy general
Treatment Cost
Reduced 32%
Outcome
HX pitting failures eliminated
Challenge — What Was Happening

Everything appeared to be operating “in the green.” Cycles of concentration, water chemistry, chemical program targets, inventory and product usage, and general corrosion rates all read on target — yet the refinery kept failing heat exchangers.

The site was replacing failed exchangers every year and overengineering systems just to survive the changeouts. The losses ran into the millions annually, and the problem had been written off as “just the type of water here.”

The supplier reported everything as fine and routinely delivered value projects that helped the customer — while total cost kept climbing. No single number on the dashboard pointed to the real problem.

Intervention — What We Did

Ran a 3-year water-quality and operational review, cross-checking service reports against what the system chemistry should actually produce.

Performed an onsite system evaluation with operator and service-company interviews to reconstruct real operating practice — then re-ran the corrosion data properly.

Applied advanced saturation modeling and a full risk review, including seasonal and manganese variation in the supply water — then rebuilt the metrics and baseline chemistry working with both the supplier and the customer. No plant capital required.

What The Reports Showed
  • Every service report and quarterly review showed every metric green
  • General corrosion under 3 mpy — a “good” number by any standard
  • Program residuals, tracer, and product usage on target
  • Account staffed by a very new service team (<2 years) with one senior advisor
Operating Conditions
  • High-phosphate program — all orthophosphate, no cathodic inhibitor
  • Copolymer dispersant with PTSA tracer, on target
  • Tolyltriazole for yellow-metal protection
  • Sodium hypochlorite, free Cl₂ held at 0.5–0.8 ppm
  • Isothiazolinone non-oxidizing biocide
Root Cause Finding

The service company had never run a pitting analysis on the corrosion coupons. General corrosion read a healthy <3 mpy — but the first proper pitting analysis showed 127 mpy of localized attack, fast enough to drill through a heat-exchanger tube wall in under a year. That is what was failing the exchangers, and it never appeared on a single “green” report.

Copper corrosion had never been measured correctly either. Done properly, the admiralty brass showed 0.9 mpy with active dezincification. The cause: free chlorine held at 0.5–0.8 ppm was destroying most of the tolyltriazole, leaving the yellow metal largely unprotected. The phosphate program was all orthophosphate with no cathodic inhibitor, and seasonal manganese swings in the supply water were driving additional risk the program never accounted for.

  • Moved to higher cycles of concentration to cut water use and blowdown
  • Rebalanced the inhibitor to orthophosphate plus a cathodic inhibitor
  • Reduced the free-chlorine target to 0.3–0.5 ppm to stop destroying the azole
  • Upgraded to chlorine-tolerant (halogen-stable) azole for durable yellow-metal protection
  • Added a phosphonate for manganese control
  • Upgraded the polymer to a quad-polymer dispersant for the challenging conditions
  • Wrote supplier- and customer-side operations manuals for treatment and testing
  • Helped upgrade lab equipment and method, and trained both teams in correct testing and upset response
32%
Treatment cost reduced — heat-exchanger pitting failures eliminated, water use down 20%
Treatment Cost
Reduced 32%
Mild Steel Corrosion
<1 mpy, 0 pitting
Admiralty Brass
<0.1 mpy, no dezinc.
Water Usage
Reduced 20%
Results Delivered
  • Eliminated — heat-exchanger failures from pitting corrosion
  • Corrected — mild steel to <1 mpy general with zero pitting
  • Protected — admiralty brass to <0.1 mpy, no dezincification
  • Reduced — treatment cost 32% and water use 20%
Economics
  • Stopped the recurring annual heat-exchanger replacements that ran into the millions
  • Ended the overengineering built solely to survive changeouts
  • Lower chemical spend and lower water use, together
  • Program correction required no plant capital — metrics and chemistry rebuilt with the existing supplier
Even when everything reads “green,” it’s worth having an independent set of eyes review the whole picture. Even without a technical chemistry problem, there is almost always room to improve — and always a reason to make sure you’re getting everything you can out of your plant. Green reports are only as good as the tests behind them.

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