Penetrant leak testing (PT) is a non-destructive testing method used to detect leaks in closed structural systems. The technique enables locating leaks open to the surface through which liquids or gases can pass. It is particularly useful for thin-walled components that cannot be subject to pressure testing or when rapid detection of a localized leak is required.
The test involves applying a penetrant to one side of the component, usually the internal side or the side exposed to pressure. After a specified dwell time, which allows the liquid to migrate through any discontinuities, a developer is applied to the opposite surface. The developer absorbs any penetrant emerging from a leak, revealing the exact location of the defect.
Penetrant leak testing is used for inspecting the tightness of: thin-walled tanks and hermetic enclosures, welded joints in pressure equipment, enclosures and objects with limited internal access, as well as components in the chemical, food, energy, and precision industries.
Before testing, the surface must be meticulously cleaned of dirt, oil, paint, or other substances that could interfere with the penetrant or the developer. The surfaces should be dry and degreased.