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What is Welding Air Leakage Test?

Date:2025-06-10
welding air leakage test (also called a pressure decay test or leak test) is a non-destructive testing (NDT) method used to detect leaks in welded joints by pressurizing the component with air (or another gas) and monitoring for pressure drops or visible/heard leaks.
Methods for Welding Air Leakage Testing
Bubble Test (Soap Solution Test)
Apply a soapy water solution to the welded area.
Pressurize the component with low-pressure air (typically 1–5 psi).
Bubbles form at leak points.
Pros: Simple, low-cost, effective for small parts.
Cons: Manual inspection, not suitable for high-pressure systems.
Pressure Decay Test
Seal the welded component and pressurize it to a specified level.
Monitor pressure drop over time using a gauge or sensor.
A significant drop indicates a leak.
Pros: Quantitative, good for closed systems.
Cons: Requires calibration, sensitive to temperature changes.

Vacuum Leak Test
Evacuate air from the component and check for pressure rise.
Alternatively, use a vacuum box with soap solution on the outside.
Pros: Effective for large structures (e.g., tanks, pipelines).
Cons: Requires vacuum equipment.
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Ultrasonic Leak Detection
Use an ultrasonic detector to pick up high-frequency sounds from escaping air.
Pros: Detects tiny leaks, no need for liquid solutions.
Cons: Requires skilled operation, background noise interference.

Helium Leak Testing (Mass Spectrometry)
Pressurize the component with helium and use a detector to locate leaks.
Pros: Extremely sensitive (detects very small leaks). Cons: Expensive, requires specialized equipment.
          • Standards & Acceptance Criteria
          • ASME BPVC Section V: Covers leak testing standards for pressure vessels.
          • ISO 9978: For leak detection in radioactive systems.
          • AWS D1.1: Specifies acceptance criteria for welded structures.
          • Acceptable Leak Rates depend on application (e.g., HVAC vs. high-pressure gas lines).
          • Best Practices
          • ✔ Clean surfaces before testing (oil, dirt can mask leaks).
          • ✔ Use appropriate pressure (avoid over-pressurizing thin materials).
          • ✔ Document results for quality control.
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