Which test is used for high-sensitivity leak detection in brazed joints?

• A. Helium leak testing.
• B. Pressure testing with inert gas or water.
• C. X-ray inspection.
• D. Dye penetrant testing.

Answer: (A)

High-sensitivity leak detection relies on using a tracer gas that can reveal even the smallest openings. Helium is ideal for this because it’s inert and has atoms so small they can pass through micro leaks that other gases wouldn’t detect. In a helium-leak test, the part is exposed to helium and a sensitive detector, usually a mass spectrometer, watches for helium escaping from the joint. This setup can measure extremely tiny leak rates, making it perfect for brazed joints where even minute leaks would matter.

Other methods can still catch leaks, but they’re not as sensitive. Pressure testing with inert gas or water can show overall integrity or gross leaks, but very small leaks may not cause a noticeable pressure change quickly enough. X-ray inspection helps view internal features and joints, but it doesn’t reliably prove leak tightness. Dye penetrant testing detects surface-breaking flaws, not leaks hidden inside a sealed joint. Helium leak testing directly targets the leak path and gives a quantitative, highly sensitive readout, which is why it’s the preferred choice for high-sensitivity leak detection in brazed joints.