What is Vacuum Box Testing and Why Request It?
The objective of the vacuum box technique of bubble leak test is to locate leaks in a pressure boundary that cannot be directly pressurized. This is accomplished by applying a solution to a local area of the pressure boundary surface and creating a differential pressure across that local area of the boundary causing the formation of bubbles as leakage gas passes through the solution. This testing helps companies save costs associated with lost time and production incurred from repairing leaks after startup.
How the Method Works
A vacuum box with a viewing window large enough to view the complete area and to allow sufficient light to enter the box for proper examination is then placed over the surface. The box, which by means of its construction and a suitable gasket, being capable of producing and holding a pressure differential of at least 8 psi, is then evacuated. A calibrated gauge is placed in the system to verify the required pressure differential to detect vacuum seal or other types of leaks in the equipment. The area is then viewed for evidence of through-thickness leaks by the formation of bubbles on the surface.