Ultrasonic thickness gauges work by sending a short pulse of high-frequency sound through the material that needs to be checked. The instrument then measures the time it takes for an echo to be received from the back wall, and uses this data to calculate the thickness of the material.

These instruments are often used to measure the thickness of boilers, bunkers, casings, castings, gantries, gas tanks, pipelines, pressure vessels, tankers and tubes.

If you need to comply with certain statutory requirements, or simply want to measure the effect or abrasion or corrosion, then a thickness gauge can help.

Single-echo thickness gauges measure the time taken for one back wall echo to pass through the material and surface coating under test. While this is a reasonable approach, the thickness reading will not be accurate, as the sound has also passed through the aforementioned surface coating.

Coatings such as bitumen, epoxy and paint all have a velocity of sound, which is around one third of steel. As a consequence, readings taken with a single-echo thickness gauge will be higher than they actually are.