What is Leak Test?

What is Leak Test?

Leak test is a non-destructive testing (NDT) method that is used to identify leaks in a sealed system or component such as piping, vessels, tanks or other enclosures.

Leak Testing is a quality control measure that is performed to ensure that a system or component is not leaking fluids or gases that it is designed to contain and hence an in-service failure can be prevented before placing the part to operate.

Leak tests are performed using various methods, such as pressure testing, vacuum testing, or tracer gas testing. The most common approach involves in a leak test is simply pressurizing the part with a gas (such as air or helium), and monitoring for any drop in pressure over time, usually a defined time period. If the pressure drops, it indicates that there is a leak in the system or component that is giving passage to escape the gas or liquid used for leak testing.

Types of Leak Test

Several Leak testing methods are used to detect and locate leaks or defects in a sealed system or component. The common types of leak tests methods are:

  1. Pressure Decay Test: This method involves pressurizing a sealed part with a gas and monitoring for any drop in pressure over time. If the pressure drops, it indicates that there is a leak in the system or component.
  2. Vacuum Decay Test: This method is similar to the pressure decay test but involves applying a vacuum to a sealed system or component and monitoring the pressure for any changes over time.
  3. Bubble Test: In bubble test a liquid solution is applied to the part and monitoring for any bubbles that may indicate a leak.
  4. Helium Leak Test: This method involves pressurizing a system or component with helium gas and using a helium detector to locate any leaks.
  5. Mass Spectrometry Leak Test: This method is a highly sensitive technique that uses a mass spectrometer to detect any helium or other tracer gas leaks from a system or component.
  6. Ultrasonic Leak Test: This technique uses an ultrasonic leak detector to locate any leaks in a system or component by detecting the high-frequency sound waves generated by the escaping gas or liquid.

How do you perform Leak Test?

The general steps for performing a leak test are:

  1. Prepare the Part: The system or component to be tested is prepared by ensuring that it is clean and free from any debris or contaminants that may interfere with the test results.
  2. Choose the Test Method: The appropriate leak test method is chosen based on the system or component being tested, the sensitivity of the test required, and the available equipment and resources.
  3. Pressurize or Vacuum the System: The system or component is either pressurized with a gas or vacuumed to a certain level, depending on the type of test being used.
  4. Monitor for Leaks: The system or component is then monitored for any drop in pressure over time, bubbles, or other signs of leaks. The monitoring may be performed manually or using specialized equipment.
  5. Identify and Locate Leaks: If a leak is detected, it is identified and located using specialized equipment such as a helium detector or an ultrasonic leak detector.
  6. Repair and Retest: Once the leaks have been identified and located, the system or component is repaired, and the test is repeated to ensure that the leaks have been eliminated.
  7. Record the Results: The results of the leak test are recorded, and any necessary documentation is completed for quality control and regulatory compliance purposes.

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Jiten Karmakar is an NDT Specialist, holding ASNT NDT Level III and ISO 9712 NDT Level III Qualifications. He is having vast hands-on practical and theoretical experience with all major NDT Methods and technique.