An air tightness tester is also called a sealing tester, leak testing instrument, or leak detector.It is an advanced non-destructive testing method in which the product is inflated (with compressed air or nitrogen), stabilized, and tested, after which the leak detection system derives the pressure decay (pressure attenuation) value, leak rate, etc. through a series of analytical sampling and calculations, thereby making a judgment on the product. Currently, common test methods include the direct pressure method (pressure method), differential pressure method, sealed cavity method (quantitative method, volumetric method), flow method, and mass flow method.
The direct pressure method, also known as the pressure method, is suitable for testing workpieces with low sealing test accuracy requirements or low pressure, such as IP65 waterproof tests.
Leak testing principle: Compressed air or nitrogen is fed into the internal cavity of the workpiece under test at a specific pressure via a pressure regulating valve. Once the set pressure is reached, the gas path between the workpiece under test and the air source is shut off, and this state is held for a specific period to allow the pressure to stabilize. During the stabilization period, the instrument first determines whether the workpiece has a gross leak based on the leakage condition, and then enters the testing phase. The pressure sensor records the current real-time pressure reading. After a period of testing, the real-time pressure reading is read again and compared with the previously recorded pressure reading. If the workpiece under test has a leak, the difference between the two pressure readings is the pressure decay of the workpiece during the test cycle; the larger the value, the more severe the leak. If the difference is within the allowable range, the workpiece under test is deemed acceptable. Otherwise, it is deemed unacceptable.
Its testing principle is shown in the figure below:
The differential pressure air tightness testing method, also known as the comparison method, is suitable for common air tightness tests such as IP waterproof testing, including: automotive and motorcycle oxygen sensors, fuel pumps, gearboxes, motors, wiring harnesses, battery packs, controllers (VCU), engine assemblies, cylinder blocks, cylinder heads, intake manifolds, radiators, reversing radars, mobile phone accessories, smart band accessories, watch accessories, tuners, die-cast aluminum parts, valves and pipe fittings, etc.
The differential pressure test method builds on the direct pressure test by adding a differential pressure sensor. It features a small range and high resolution, and is mainly used for workpieces that require high sealing test accuracy.
During inflation, all valve groups shown in the figure below are fully open, and the pressure at both ends of the differential pressure sensor is the same. When stabilization begins, the valve groups close, and the pressure transitions from fluctuation to stability. The pressure at the reference part end of the differential pressure sensor remains constant, while the other end is connected to the test workpiece. When a leak exists at the test end, the pressure at the test end drops. The differential pressure sensor compares the pressures at both ends to calculate minute leaks.
Its testing principle is shown in the figure below:
The sealed cavity method, also known as the quantitative method or volumetric method, is suitable for testing workpieces without inflation holes, such as wristbands, cameras, mobile phones, watches, automotive lights, outdoor lights, Bluetooth earphones, tire pressure sensors, electric toothbrushes, flashlights, stage lights, and walkie-talkies.
The test method involves placing the workpiece to be tested into a sealed chamber. After the test is started, the Wanken leak detection system opens air circuit switch valve 1 and switch valve 3 to inflate the gas quantification device. Once a specific amount of air pressure is reached, air circuit switch valve 1 and switch valve 3 close, and air circuit switch valve 4 opens, releasing the gas from the quantification device into the test chamber. If the workpiece has a large leak, the pressure will drop rapidly, exceeding our set lower limit, and the system will trigger an alarm. If the workpiece has a micro leak, the pressure will decrease slowly, which can be detected by the Wanken high-precision leak detector.
Its testing principle is shown in the figure below:
Suitable for IP65 waterproof testing and workpiece flow testing, such as: infusion tubes, capillary copper tubes, speakers, waterproof breathable membranes, etc.
The air inlet source pressure must exceed the test pressure by more than 1 bar. After being regulated by the pressure regulating valve, the gas passes through the flow sensor and enters the test workpiece. The direct pressure sensor monitors in real time whether the internal pressure of the test workpiece reaches the required level. If the requirement is met, the value of the gas passing through the flow sensor is the flow rate of the workpiece at that pressure.
Its testing principle is shown in the figure below:
Suitable for gearbox housing assemblies, battery packs, controllers (VCU), automotive radiators, automotive motors and other large-volume workpieces with small leaks, and can also reduce the impact of temperature and other environmental factors on testing.
The test method is as follows: during inflation, air is first supplied to the air storage tank end. Once the set pressure is reached, the air supply line is cut off, the inlet valve is closed, and the switch valve at the workpiece end to be tested is opened. After stabilization, testing begins. If there is a leak at the test end, the gas in the test chamber will flow toward the test end. At this point, a mass flow meter can be used to measure the leak rate from the air storage end to the test end. The total leakage of the entire system is then calculated using a formula.
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