Leak testing is a crucial inspection method used by professionals to determine if an object or system is operating within acceptable leak limits. This technique helps identify potential flaws that could lead to the escape of liquids or gases, ensuring safety and efficiency in various industries.

Leaks occur when there's a defect—such as a hole, crack, or imperfection—in an object, allowing the contents to escape. Leak testing uses pressure to detect these issues, making it an essential part of regular maintenance and quality control processes.

Typically, leak tests are conducted on systems or objects designed to contain liquids or gases. These tests are non-destructive, meaning they don’t damage the object being tested, which makes them ideal for ongoing monitoring and evaluation.

Non-destructive leak testing is just one of many NDT methods available. It’s widely used because it allows inspectors to check for leaks without compromising the integrity of the object. If you're interested in learning more about NDT, be sure to check out this detailed guide.

What Is Leak Testing?

Leak testing involves using pressure to detect defects in an object that may be causing leaks. The basic principle is that substances flow from areas of high pressure to areas of low pressure. By applying controlled pressure and monitoring the flow, inspectors can pinpoint the location and severity of any leaks.

This type of testing is typically performed on closed systems where even small leaks can have significant consequences. The success of the test depends on the material and design of the object being tested, as different materials respond differently to pressure changes.

Common defects that leak testing identifies include:

• Cracks
• Holes
• Weak seals
• Other imperfections that allow gas or liquid to escape

Industries such as automotive, consumer goods, medical devices, packaging, and sealed electronics frequently use leak testing as part of their quality assurance protocols.

Advancements in Leak Testing

Recent technological advancements have significantly improved the accuracy and efficiency of leak testing. Innovations in sensors, valves, and data collection systems have made it possible to detect even the smallest leaks with greater precision.

The integration of the Internet of Things (IoT) has also transformed how leak testing is conducted. Now, inspectors can remotely collect, monitor, and share data, enabling real-time decision-making and faster response times. This not only improves maintenance but also enhances overall operational efficiency.

Leak Testing Methods

There are several common leak testing methods, each suited for different applications:

• Burst Test: Applies increasing pressure until the object fails, useful for determining structural limits.
• Chamber Test: Used for sealed packages or devices that lack an opening for direct pressure application.
• Pressure Crack Test: Detects "weeping" in valves using a downstream sensor.
• Pressure/Vacuum Test: Compares pressure between the test object and a reference volume to detect leaks.
• Pressure Decay Test: Measures pressure loss over time to identify leaks under positive pressure.
• Vacuum Decay Test: Similar to pressure decay, but under negative pressure conditions.
• Occlusion Test: Identifies obstructions in gas flow paths that may indicate leaks.

Most leak tests operate at low pressures, typically around 15 psi or 25% of the design pressure, whichever is lower. This ensures safety while still providing reliable results.

Key Considerations in Leak Testing

While leak testing is a powerful tool, it requires careful planning and execution. Here are some important factors to consider:

Acceptable Leak Rate

Different industries have varying standards for what constitutes an acceptable leak rate. Some leaks may not require immediate action but should still be monitored. Understanding these thresholds is crucial for effective maintenance planning.

Manufacturing Purpose

Before conducting a leak test, it's important to understand the original purpose of the object. Some components are designed to allow fluid passage, while others must remain completely sealed. Knowing this helps determine the appropriate testing approach.

Material Properties

The material of the object can greatly affect the outcome of a leak test. Brittle or highly flexible materials may react unpredictably to applied pressure, so these properties must be taken into account during test planning.

Medium Characteristics

The substance being contained—whether liquid or gas—also plays a role. Different media have different molecular sizes and behaviors under pressure. Choosing the right testing method and pressure range is essential for accurate results.

Leak Testing Equipment

A variety of tools and devices are used to perform leak tests. Here are some common examples:

Air LeakAGE Inspection Devices

Photo credit: Zaxis

Air leak testing devices provide real-time data to inspectors, supporting multiple testing methods including vacuum decay and pressure decay.

Compact Pressure Decay Leak Tester

Photo credit: Zaxis

This compact device is ideal for reducing connection volume and improving test sensitivity, especially in tight spaces.

Large Display Leak Tester

Photo credit: Zaxis

Larger displays offer enhanced visibility and faster testing capabilities, making them suitable for complex or high-volume operations.

Leak Standard

Photo credit: Zaxis

Leak standards are used to calibrate testing equipment and ensure consistent results across different systems and environments.

Leak Testing Standards and Codes

Leak testing is often governed by industry-specific standards and codes to ensure consistency and reliability. Here are some of the most commonly referenced standards:

ASME (American Society of Mechanical Engineers)

• ASME B31.3: Pressure Testing and Leak Testing Requirements for Process Piping

ASTM (American Society for Testing and Materials)

• ASTM E432-91(2017)e1: Standard Guide for Selection of a Leak Testing Method
• ASTM E493 / E493M - 11(2017): Standard Practice for Leaks Using the Mass Spectrometer Leak Detector in the Inside-Out Testing Mode
• ASTM E499 / E499M - 11(2017): Standard Practice for Leaks Using the Mass Spectrometer Leak Detector in the Detector Probe Mode
• ASTM E1003 - 13(2018): Standard Practice for Hydrostatic Leak Testing
• ASTM A1047 / A1047M - 05(2019): Standard Test Method for Pneumatic Leak Testing of Tubing
• ASTM E1603/E1603M-11(2017) Standard Practice for Leakage Measurement Using the Mass Spectrometer Leak Detector or Residual Gas Analyzer in the Hood Mode
• ASTM F2164 - 21: Standard Practice for Field Leak Testing of Polyethylene (PE) and Crosslinked Polyethylene (PEX) Pressure Piping Systems Using Hydrostatic Pressure
• ASTM F2786 - 16(2021): Standard Practice for Field Leak Testing of Polyethylene (PE) Pressure Piping Systems Using Gaseous Testing Media Under Pressure (Pneumatic Leak Testing)
• ASTM E2930 - 13(2021): Standard Practice for Pressure Decay Leak Test Method
• ASTM WK76995: New Practice for Field Leak Testing of Polyamide-12 (PA12) Pressure Piping Systems Using Gaseous Testing Media Under Pressure (Pneumatic Leak Testing)

ISO (International Organization for Standardization)

• ISO 20484:2017(en): Non-destructive testing — Leak testing — Vocabulary
• ISO 20485:2017(en): Non-destructive testing — Leak testing — Tracer gas method
• ISO 20486:2017(en): Non-destructive testing — Leak testing — Calibration of reference leaks for gases
• ISO 27895:2009(en): Vacuum technology — Valves — Leak test