What is considered the most universally used black light in liquid penetrant examination?

In liquid penetrant examination, the most universally used black light is the enclosed mercury-vapor arc lamp. This type of light is specifically designed to emit ultraviolet (UV) radiation necessary for the detection of surface irregularities in non-porous materials. The UV light causes the fluorescent penetrant, which has been applied to the surface of the material, to glow, highlighting any defects that may exist.

Enclosed mercury-vapor arc lamps are favored in this context because they produce a strong, consistent output of UV light, enabling clear visibility of fluorescent materials in various inspection scenarios. Their performance efficiency and availability also contribute to their universal acceptance in industrial and testing environments.

While LED lights are gaining traction in various applications due to their energy efficiency and longevity, they may not yet produce the same intensity and quality of UV light as enclosed mercury-vapor lamps. Similarly, incandescent bulbs and high-pressure sodium lamps do not provide the specific UV wavelength range needed for effective liquid penetrant examination, making them unsuitable for this specialized use.