Helium leak test
The detection of leak rates in the molecular range requires a special search gas method using a mass spectrometer. The smallest search gas traces are detected in the high vacuum chamber of the leak test stand. The accuracy of the Helium leak test system starts where that of the dry air leak test method ends: approx. 0.1 to 1.0 std. cm³/min. Leak rates, corresponding to 10-6 Torr liter/sec, can easily be detected in the relatively short cycle time of mass production lines.
Typical testing components which cannot be tested successfully with the dry air leak test method as follows:
- Torque converter
- Aluminium wheel rims
- Refrigeration compressor
- Barrels
- Heat exchanger
- Thermo valves
- Gas meters
Volumetric measurement leak test & Volume-dependent leak test
Volumetric measurement leak test
The volume of combustion chambers can be accurately determined (±0.1 cm³) using dry air and differential pressure measurement leak test technique. An exact quantity of air is introduced into the test cavity from a reference chamber. The resultant pressure after expansion is a precise parameter of the size of the volume to be measured. Either the absolute volume or the deviation from a nominal volume can be measured and displayed.
Typical testing components as follows:
- Volume of combustion chamber volume/size of cylinder head
- Volume of piston crown
- Cavity size of viscous couplings
Volume-dependent leak test
Closed hollow bodies with no opening for air to enter are leak tested in a bell jar. After they are placed in the jar, the cavity between the test part and the interior of the bell jar is pressurized. This pressure is generated by an expansion volume from which pressurized air expands into the bell jar during the filling phase. The ratio of the expansion volume to the volume of the cavity, and the pressure in the expansion volume before the filling phase, are chosen in such a way that the test pressure will be reached in the cavity unless the test part has a gross leak (volume measuring principle). In the measuring phase, any fine leaks will be detected via the pressure decay method and gross leaks via pressure monitoring. To detect gross leaks, it is important for the ratio of the volume in the test part to the remaining test volume to be sufficiently high.
Typical testing components as follows:
- Binoculars
- Sensors
- Electronic Components
Internal leak test & Dynamic pressure test
Internal leak test
For internal leakage, two testing spaces are tested for leak tightness in relation to each other. One example is the dividing surface between the water jacket and the oil chamber in an engine. As the oil chamber generally has the larger
test volume, it is initially pressurized with test air while the water jacket remains unpressurized. In this phase, a measuring device with two channels is used to detect whether there is any leakage between the chambers.
Typical testing components as follows:
- Cylinder Housing
- Engine Assemblies
Dynamic pressure test
For checking the passage cross section in bored or cast channels: If the passage is occluded or severely narrowed due to casting defects, this can be checked via a “pressure window” using the dynamic pressure method. Special test procedure for testing of bores and bore cross-sections. Possible tests are either under the conditions like "checking whether passage is obstructed" or "checking whether minimum cross section is present".
Typical testing components as follows:
- Cast parts
- Bores
- Cooling ducts
Ventilation device membrane test & Radial shaft sealing test
Venting device membrane test
As in functional clothing, venting devices are used, for example, to protect components from external splashing and to dissipate internal moisture into the surrounding environment. When filling via the venting device, the first step is to check whether the membrane is present or has been incorrectly or doubly applied. This check is performed using a “pressure window” or “leakage window”. After an OK result is achieved, filling of the test part continues and the classic leak tightness test is carried out, which means it targets to testing the presence and permeability of pressure equalization membranes.
Typical testing applications as follows:
- Battery Boxes
- Electronic Components
Radial shaft sealing test
Extending the measuring circuit makes it possible to test one or more radial shaft seals (depending on the design of the leak test panel) in parallel with the oil chamber leak test. The radial shaft seal is sealed externally by the customer and checked for leak tightness to the oil chamber. At the end of the test, the customer connects the radial shaft seal to the oil chamber via external valves which are controlled by the leak test panel. This ensures that the radial shaft seal no longer leaks during the oil chamber leak test, meaning that these leaks can be assessed entirely separately.
Typical testing applications as follows:
- Radial shaft seal test 1, 2, 3
