Compare previous and current ultrasonic thickness readings to estimate metal loss, percentage reduction and average thickness loss rate.
Repeated ultrasonic thickness measurements can be compared to determine how much wall thickness has been lost between inspections.
The percentage reduction is calculated from the original measurement:
When the inspection interval is known, the average loss rate can also be estimated:
A single ultrasonic thickness reading provides the measured wall thickness at a particular location and inspection time. Comparing readings from the same location over time can reveal changes in wall thickness.
For meaningful trending, measurements should be taken using consistent procedures, locations, equipment and inspection conditions whenever practical.
The calculator converts the measured thickness difference into an average loss rate when an inspection interval is provided.
For example, if a component loses 0.6 mm over one year, the simple average rate is 0.6 mm/year. This is a mathematical trend based on the two readings, not a guarantee that future loss will continue at the same rate.
If a minimum allowable thickness is entered, the calculator compares it with the current UT reading and reports the remaining thickness margin.
A positive margin means the measured thickness is above the entered minimum. A zero or negative margin requires engineering review against the applicable design or inspection requirements.
When the measured loss rate is positive, the calculator can make a simple constant-rate projection toward the entered minimum thickness.
This is only a mathematical projection. Actual deterioration rates can change with operating conditions, corrosion mechanisms, process changes and inspection uncertainty.
Those decisions require the applicable engineering standard, design data, inspection procedure and component-specific assessment.
For useful thickness trending, record the inspection location, measurement date, instrument information and measured thickness. Repeating measurements at established thickness-monitoring locations helps make comparisons more meaningful.
Where localized corrosion is present, multiple readings may be needed rather than relying on a single measurement.
How is ultrasonic thickness loss calculated? Subtract the current UT thickness reading from the previous reading.
How do I calculate percentage metal loss? Divide the thickness loss by the previous thickness and multiply by 100.
Can repeated UT readings estimate a corrosion rate? Yes. Thickness loss divided by the time between measurements gives an average thickness loss rate.
What does remaining thickness mean? It is the latest measured wall thickness at the inspection location.
Why might a later UT reading be thicker? Measurement variation, probe position, surface condition, calibration and other inspection factors can cause a later reading to be higher.
Can this calculator determine whether equipment is safe? No. It calculates measurement-based thickness loss and trends. Safety and fitness-for-service decisions require the applicable engineering assessment.