The hydraulic power unit is the central component of a hydraulic test bench. Pressure sensors are qualified on an impulse pressure hydraulic test bench by means of an “accelerated life” test.
A failure of the facility would increase the development time because tests could not be carried out as planned. Moreover, delivery of certain types of pressure sensors would be restricted during this time as the tests necessary to ensure series quality could not be carried out. This in turn would have a direct impact on sales in this product group and would compromise product availability.
The existing hydraulic power unit is already equipped with sensors (temperature, pressure and level sensors). This information is used to control the system and to stop the machine in the event of limit violations. The power unit features two tanks for hydraulic oil cooling.
Another particularity of the power unit are the two redundant pumps which are identical in construction. In existing systems with two redundant pumps, it is crucial to ensure an equal usage of the pumps in order to increase their total operating hours and to avoid damage to one of the pumps (such as seized bearings) due to excessive idle time.
Comprehensive condition monitoring of the hydraulic power unit
The aim is to monitor the wear in the hydraulic system and the running time of the pumps in order to optimise them. Limit violations are to be detected early by automated alarm management.
The signals of the existing sensors in the system are captured via the Y-path/retrofit. Two variants were installed:
Tank
The other sensors were installed and set up according to their relevant operating instructions.
Pump
Return line
moneo RTM is centrally installed on a server. Using the IO-Link master, the sensor values are sent to moneo RTM for visualisation and evaluation.
Comprehensive condition monitoring of a hydraulic power unit with moneo RTM
Through retrofitting (capturing of sensor values from controller) and additional recording of characteristic values of the hydraulic power unit, all requirements of a comprehensive condition monitoring solution could be met.
The dashboard provides the user with an overview of the current sensor values in the installation. The following dashboard provides an overview of the process-relevant parameters.
Separate dashboards provide more information, such as the current characteristic values of the pump:
The analysis function allows users to access the stored history data of the sensors. For example, this simplifies troubleshooting. Various sensor values can be viewed and analysed over time.
The following analysis clearly shows that the vibration value (v-RMS) and the hydraulic oil temperature correlate. For example, the vibration value can be used as an early indicator of a limit violation of the hydraulic oil temperature.
Static thresholds are set for various process values of the hydraulic power unit. If a process value is exceeded or not reached, a ticket is created in moneo, which can be further processed via ticket processing rules.
For the hydraulic power unit, the following process values are used for limit value monitoring:
This function can be used to easily define what should happen after a warning or alarm has been triggered, e.g.:
Using calculated values and templates, additional information can be generated from measured values.
To record the operating hours, the operating hours counter template was used. As long as the speed of the pump is greater than 50 rpm, the time counter remains active.
The 0...10 V analogue value of the temperature sensor must be scaled to the corresponding temperature value (0 V = 0°C and 10 V = 100°C).
The level sensor transmits only the measured value without offset via the IO-Link interface. This must be added to the measured value.