Pressure Impulse Test RigCopyright: © Maximator
Pressure impulse testing is used to investigate the service life of internally pressure loaded parts, such as hydraulic components. The testing system at ifas is suitable for testing components up to a pressure of 1200 bar and, compared to conventional systems on the market, offers extended instrumentation which, in addition to service contracts, also allows it to be used in fundamental research, for example for evaluating additively manufactured components and new types of sensors.
The system is based on a constant pressure supply with 120 kW drive power. The output pressure is adjusted depending on the test parameters. By means of a servo-hydraulically operated pressure intensifier and various auxiliary units, a cyclically varying pressure profile is applied in the high-pressure section of the system, which is used to load the test object. The pressure control in the test section is based on a redundant arrangement of pressure sensors, so that a load-induced excessive deviation of a transducer can be detected and leads to shutdown of the system. Further protection by means of a pressure relief valve in the high pressure is also ensured.
The test objects are arranged in a test chamber on a distribution tree. This is of modular design so that the shape of the distribution tree can be adapted according to the required number and size of the objects to be tested. Due to the high possible pressures, the test objects are connected to the manifold tree by means of specific high-pressure fittings. For applications with moderate pressure requirements, adapters for standard fittings are also available. Telemetry modules for remote maintenance and test monitoring ensure maximum system availability.
Possible load cycles
By default, the system runs sinusoidal cycles at a frequency of up to 25 Hz. However, it is also possible to run trapezoidal cycles at a slightly reduced frequency, as well as cycles according to DNVGL-CP-0185 at up to approx. 2 Hz. The highest pressure occurring in the cycle can be up to 1200 bar. The test frequency that can be achieved depends on the component and must be examined on a case-by-case basis. HLP 32 is used as the operating medium. Cooling of the high-pressure part ensures a medium temperature that is representative for hydraulic applications.
Measurement technology and documentation
The system has two redundant pressure sensors for controlling the load pressure and component-specific cycle counters. The pressure amplitudes are statistically evaluated over the entire test period, so that the reproducibility of the tests can be verified at any time. Usual fluctuations of the pressure amplitudes are in the range of a few per mille.
The system at ifas also has additional interfaces for recording measured values. First, the component temperature can be recorded at up to 10 measuring points in parallel over the entire test duration.
In addition, other electrical signals (voltage, current, resistance bridges) can be recorded during the test and synchronized with the test. This allows on the one hand a deeper insight into test objects, e.g. by measuring the occurring superficial strain by means of applied strain gages, and on the other hand the measurement of the sensor data of a sensor under test. To reduce the amount of data, the aforementioned values can be recorded at defined cycle numbers during a specified interval with high temporal resolution. Changes in the properties over the test duration are thus easily traceable.