Quality Magazine

Training Trends:

May 9, 2003

On the surface, leak testing may appear simple and straightforward. In reality, however, the determination of the leak testing system that is ideally suited for an application can be deceivingly complex. The following are three must-ask questions that should be answered before making a decision on a leak tester.

What is an automatic production leak tester?

Automatic production leak testers are those types of testers that perform the leak test cycle without operator attention or interpretation.

Today’s sophistication in leak testing no longer allows a simple leak test. Typical testing normally requires:

  • Test programs for various part models
  • Dual leak and flow testing sequentially or simultaneously
  • Various test pressures or vacuum or both
  • Special testing techniques

A complete automatic cycle performs the leak test from start to finish, displays quantitative results and the accept or reject status. Accept or reject limits are programmable by the user.

The most common types of leak tester are:

  • Electronic memory pressure or vacuum decay leak testers
  • Flow type testers
  • Differential type pressure decay leak testers

Fully automatic production leak testers typically perform leak cycles of less than 0.9 to 30 seconds. These testers communicate with programmable logic controllers (PLC). These testers:

  • Monitor for testing trends
  • Have maintenance programs
  • Store test data
  • Change programs automatically
  • Output alarms of calibration tampering
  • Automatically compensate and calibrate
  • Temperature compensate
  • Have parts grading
  • Have dual station and dual pressure capability

What should I look for in a leak tester supplier?

Be sure that the leak tester supplier selected is experienced and can offer the leak testing technique that fits your application and requirements—not just the technique that he offers.

In other words, be sure that the supplier is not offering just one technique and must sell it as "the best way." The leak tester supplier should offer and support the following techniques:

  • Pressure decay
  • Vacuum decay testing
  • Differential pressure decay
  • Mass flow testing
  • Differential pressure flow testing
  • Chamber testing
  • Pressure increase testing

The pressure decay and vacuum decay testing are the most popular because of ruggedness and simplicity.

With these techniques available, a supplier can honestly evaluate requirements and recommend the best technique for a specific application.

Remember, when a purchase is made from a qualified and trusted supplier, a measure of security and guaranteed performance can be expected.

Look for quality registrations such as ISO 9001, CSA (Canadian standards) and CE MARK (European requirement). These registrations will ensure additional quality, documentation and solid software.

Correct tooling and design is most important to the success of a leak test project. A supplier should be well experienced in this area.

What specifications should be provided to the supplier?

If testing parameters are available, provide them to the supplier in a format as follows:

  • Test volume
  • Production rate
  • Reject leak rate
  • Test pressure
  • Test part
  • Part material
  • Number of the part model

If the test parameters are not available, explain the test application or any problems to the supplier. He should have years of application experience and be able to help set the parameters and recommend a system that is right for the application at hand.

For a new product, a number of variables should be considered when setting the leak test specifications. Answers to the following questions will be helpful:

  • How is your product used in the marketplace?
  • Is the leak specification set to prevent liquid or air leakage?
  • Type of liquid used in the product
  • Material of the product
  • Working pressure of the product
  • What are the consequences of a leaking product?

Life threatening

Damage to people or surroundings

Possible fire or explosion

Product deterioration

Cost to the user

Product malfunction

Frustration, inconvenience

Customer relations

Unsightly or displeasing environment

Next month Training Trends will explore major considerations when purchasing a leak tester.

For more information, contact Uson L.P. (Houston) at (281) 671-2000.