Corrosion Rate & Remaining Life: Wall-Thickness-Based Life Assessment
What is Corrosion Rate & Remaining Life Assessment?
Remaining life estimation for in-service equipment and piping extrapolates the wall-thinning trend: corrosion rate CR = (t0 - t1) / elapsed time, and remaining life = (t1 - t_min) / CR, where t_min is the minimum wall thickness required by the design code. The tool takes original wall thickness, measured wall thickness and service time and returns the corrosion rate and remaining life. The output directly feeds RBI risk ranking and inspection planning in a mechanical integrity program.
When to Use It
Use it for periodic inspection of in-service piping and pressure vessels in refining, chemical and power plants, for RBI data input and for trending of corrosion monitoring locations (CMLs). It is also useful for revisiting remaining life when corrosion rates spike and for optimizing shutdown and inspection intervals. When multiple thickness readings exist, take the thinnest value and the fastest rate for a conservative estimate, and re-assess after any change in process conditions.
How to Use It (Step by Step)
Enter the original wall thickness, the latest measured thickness, the elapsed service time and the minimum required wall thickness. The tool computes the corrosion rate, compares it with the remaining thickness and outputs the remaining life plus a suggested next inspection date. Review the basis: measuring points must be at the same physical locations to be comparable, and the linear-extrapolation assumption should be revalidated whenever media, temperature or inhibitor treatment changes.
Key Formulas / Example
Corrosion rate: CR = (t0 - t1) / dt, where t0 is the original thickness and t1 the measured thickness after dt years. Remaining life: RL = (t1 - t_min) / CR, where t_min follows the design code such as ASME B31.3. For example, with t0 = 12.0 mm, t1 = 10.5 mm after 5 years and t_min = 8.0 mm, CR = 0.3 mm/yr and RL = (10.5 - 8.0) / 0.3 = 8.3 years.