Basic Principles of Leak Testing

The flow of gas or liquid through the wall of the object due to manufacturing defects like crack, or bad seal may create a pressure difference, which generates the flow of gas or liquid. This always flows from the higher pressure to lower pressure.

These leaks are detected when the gas or liquid flows from positive pressure i.e. inside an object to the outside at atmospheric pressure. In the rarest of cases, the leak can flow in the opposite direction i.e. atmosphere to inside an object.

The constant demand for technical products and changing consumer needs has created a requirement of hermetically closed elements. While manufacturing such products it is made sure that the external atmosphere is checked from under-pressure or overpressure by assuring that the product is sealed tightly. Leak testing is implemented with an aim to spot the unwanted porosity in the objects. It is a quality control step to ensure product integrity. Products like TV, pressure vessels, cathode tubes, pumps, Chemical or nuclear plants, beverage cans, etc. undergo leak testing.

Different Types of Leaks Include –

  • Manufacturing defect i.e. loophole in the production process
  • Imperfect part assembly of the products
  • Virtual leaks due to cavity in the chamber walls

The Principal of Leak Testing by Pressure

The leak can be caused due to two reasons – Difference in Pressure and Pressure Change.

The difference in Pressure: the amount of air per unit volume is based on the volume of atmospheric pressure. Whenever the atmospheric pressure is high, the amount of air is also high. In order to maintain a balance atmospheric pressure, the air flows from high point to low point. Considering this principle air is transferred at a different pressure to spot the leaks.

The Pressure Change: Air is charged inside the object in order to increase the pressure causing a pressure difference between the inside and outside of the object. In case of a defect in the object, the inside air will flow to an outward direction. Causing a change in air pressure helps in keeping a traction of leakages.

Methods of Leak Testing By Pressure 

Internal Pressure Change Method

It involves monitoring the pressure differenceafter a time interval of applying pressure inside the object. This method suits best for an object that has an air charge port and a small amount of deformation.

External Pressure Change Method

For this method, the object and masterwork are placed in a chamber and pressure is applied in volume between the chamber and object. Thus, the pressure inside the object is changed due to intrusion of air inside the object. This method is optimal for objects that do not have air charge port and has small amount of deformation.

Tank Pressuring Method

In this method leak is detected by applying pressure inside the object using compressed air stored in a tank. Objects that do not have any pressurization port with relatively large internal volume can undergo this method.

Major Applications of Leak Testing 

  • Automotive Components
  • Medical devices
  • Industrial Products
  • Packaged foods and beverages


The leak testers can be customized and designed to carry to step of quality control. This step is vital to deliver top class products to the customers. Experts at Mikrobuild leak testers for their customers, putting their experience in automation since 2008.