Air Tightness Tester FAQ

Ask

Why is the leak standard for an air tightness tester not zero?

Answer

An air tightness tester measures leakage values. However, no product in this world is completely leak-free; all so-called leakage is relative.。The principle of air tightness tester testing is based on pressure sensor monitoring. Even if the product does not leak, temperature, volume, and product deformation can also cause data fluctuations, so the value will naturally not be zero.

Ask

What are the temperature requirements for an air tightness tester?

Answer

Theoretical ambient temperature: 5-40°C, relative humidity no greater than 85%. It mainly depends on whether the product being tested is sensitive to temperature. If it is sensitive, testing in a temperature-controlled workshop is best. If the product is greatly affected by temperature, allow an interval between each test.  Based on experience, every 5°C increase will cause a change of about 2-5 Pa.

Ask

What should I do if the air tightness leak detector has insufficient pressure?

Answer

Insufficient pressure — here is the main analysis of what is happening. 1. A major leak in the product prevents the pressure from building up, which also results in insufficient pressure; 2. Check the upstream air supply pressure to see whether it is between 0.4 and 0.6 MPa.

Other reasons:

Cause 1: Air supply pressure too low or fluctuating

Countermeasure: Ensure the air source is stable above 0.4 MPa. Note: To provide a stable air supply, do not connect pneumatic tools such as air guns to the air source during testing.

Reason 2: Whether the set value of the test pressure regulating valve has changed.

Countermeasure: Perform a self-check on the air tightness tester. Check whether the real-time pressure setpoint changes under Pressure Setting > Pressure Regulation, and adjust the setpoint of the precision pressure regulator.

Reason 3: The test fixture of the air tightness tester is not properly sealed.

Countermeasure: Check whether the sealing fixture is in a sealed state.。

Reason 4: The test air pipe line of the air tightness tester is not sealed.

Countermeasure: Check the test air hose and connectors.

Reason 5: Insufficient pressurization/inflation time

Countermeasure: extend the inflation time.

Reason 6: Insufficient inflation time for the volume

Countermeasure: Extend the volume filling time.

Reason 7: Faulty pressure sensor in the air tightness tester

Ask

Is a negative reading normal in air tightness testing?

Answer

Look at the testing principles adopted by air tightness testers: direct pressure air tightness testers and differential pressure air tightness testers.

1. The probability of a negative reading on a direct pressure air tightness tester is very low. When there is no leak, a negative reading may appear if the test time is very long (or if the product under test or the fixture deforms and keeps being compressed).

2. For a differential pressure air tightness tester, since it uses a comparative testing method, the pressure at the test port and the reference port may not be consistent, which can also result in negative values. Generally, the negative values are very small. A few Pa is normal.

Ask

What are the relationships between the leak rate units of an air tightness tester: scc and kPa, sccm and Pa, sccm and scc, scc and cc/min?

Answer

Air tightness testers generally use differential pressure sensors or direct pressure sensors, so the test results are naturally in pressure units, such as: Pa, kPa, bar, MPa. These are collectively referred to as pressure decay values, or leak values.   However, some air tightness testers display test results in sccm, scc, cc/min, which are collectively referred to as leak rates. The leak rate is derived by calculating the correspondence between pressure decay and flow using the air tightness test formula. For details, please refer to the air tightness tester calculation formula.