Vacuum box testing is a non-destructive examination used when trying to locate weld seam leaks. A vacuum box and a compressor create a high- or low-pressure vacuum while a detergent solution is applied to the test area. The detergent bubbles, making leaks visible within the created pressure envelope. Clev Dynamic utilizes systems compliant with ASTM E515. All inspections are conducted within the parameters of ASME Section V Article 10, Appendix II or to client specifications.
The aim 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
Vacuum box testing provides for the detection of through-thickness leaks and is most commonly used for testing welds. Cracks, pores, and lack of fusion are typical causes of leaks detectable by this method. A bubble-forming solution is applied to the surface to be tested by flowing, spraying, or brushing the solution over the examination area. Household soap or detergents designed specifically for cleaning are not permitted as substitutes for bubble-forming solutions. A commercial leak detection solution is used that is compatible with the temperature conditions during the test. As a standard technique, the temperature of the surface of the part to be examined should not be below 40°F (5°C) nor above 125°F (50°C) throughout the examination.
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.
Clev Dynamic Inspections Limited understands the need for high operator proficiency in order to get the best results from Vacuum Box testing and so, all of our Inspectors receive ongoing training and are experienced in the field. Contact us today for more information or quotation.