Statistical Tool for Wall Thickness Assessment Gets a Three-Part Deep Dive
According to Inspectioneering Journal, a three-part series on Extreme Value Analysis (EVA) is underway, with the first installment published in the March/April 2026 issue. Authored by W. David Wang, Ph.D., P.E., founder of Asset Integrity Global LLC, the series challenges the common practice of using the lowest measured wall thickness reading as the basis for fitness-for-service decisions. Wang argues that observed minimums almost always exceed the true minimum, making that approach statistically inadequate. EVA offers a method to estimate the true minimum with confidence bounds, without requiring expanded inspection coverage.
What It Means for Subcontractors
- Mechanical integrity and inspection contractors may face client pressure to justify inspection scope. A defensible statistical framework like EVA can support run/repair/replace decisions without automatically calling for more coverage and cost.
- Broader inspection sweeps mean more cleaning, more downtime, and more resource demand. EVA gives teams a tool to optimize scope while maintaining integrity assurance.
- Parts 2 and 3 of the series will cover heat exchanger tube applications and additional equipment types. NDE and inspection service providers working in refinery, petrochemical, or pipeline environments should follow the series at inspectioneering.com. Note that publication timing of later installments has not been confirmed as of press time.
