What is leak-down testing and in which system is it commonly used?

• A. Pressurizing a system and monitoring pressure decay to find leaks; commonly used in pneumatic and hydraulic systems.
• B. Measuring temperature changes to detect leaks.
• C. Using soap solution to locate leaks.
• D. Inspecting for audible hissing sound.

Answer: (B)

Leak-down testing involves sealing a system, applying a known pressure, and monitoring how the pressure decays over time to detect leaks and locate where they occur. Because pneumatic and hydraulic systems operate under pressure, this method directly measures the rate of pressure loss, making it effective for pinpointing leaks and validating component integrity. By holding pressure and watching the gauge, you can gauge the leak's size and determine the path of least resistance; a slow or no decay means the system is tight, while a rapid decay indicates a leak somewhere in the test area. Other approaches—measuring temperature changes, applying soap solution, or listening for audible hisses—are different leak-detection techniques that don't provide the quantitative pressure-decay information that leak-down testing yields.