Hydraulic Hose Pressure Test System
In order to verify against Society of Automotive Engineers (SAE) professional standards for high pressure hydraulic hoses, the client had developed a test system capable of pulsing hydraulic fluid through its own hoses and logging the results. Pressures for this system would range between 10,000 and 20,000 psi and durations upwards of one million times per hose. The pressure needed to be precisely controlled throughout the pressure pulse for both the rising and falling edges, as well as maintaining peak pressure all to within 10% of the target pressure. In addition to the pressure control, it was also necessary to maintain the temperature of the oil to within five degrees Celsius of the user specified value.
The current system was running legacy data acquisition hardware that had been phased out and was no longer supported. Additionally, the previous contractor did not deliver drawings for the electrical panel that contained hundreds of connection points. While upgrading the hardware, it was also desired to have the tester communicate its status and test data via the company’s network to a host computer capable of logging the data and displaying recent information on a website to be view-able by any authorized person logging in from outside the company network.
Control of the system and information display is provided through a National Instruments touch panel PC. The touch panel PC provides control of the three separate pressure segments, each capable of testing hoses to different specifications. The PC is also used as a means to calibrate each of the analog sensors in the system.
National Instruments’ CompactRIO hardware is used to acquire data at two rates and control several motors and valves. High speed data is needed to accurately capture the pressure information for each pressure pulse as well as monitor the several ESTOP buttons located around the system. Less critical information is captured at a lower speed to free up system resources. To meet the high speed acquisition rate, the FPGA hardware on the cRIO was used. An FTP server is also running on the cRIO to allow the network host computer to retrieve test data files.
In addition to monitoring physical ESTOP buttons, the system is able to gracefully shutdown a test in the event that an out-of-range condition occurs such as over temperature or over pressure. To ensure quick response to any potentially dangerous situation, the high speed capability of the hardware FPGA is used to monitor for the majority of the critical events. The FPGA is also used to monitor the status of the real-time application through a watchdog timer that requires a reset once per second. Failure of the real-time application to reset the FPGA watchdog stops all tests in progress. If a non-critical alarm event occurs, the information is displayed to the user, but testing is allowed to continue.
Because of Optimation’s services, the test system is now able to autonomously log data to a central server. By mirroring the data logging of the clients existing systems, operator training time is reduced by not requiring special data logging instructions for one unique tester. The common data format and storage location also allows for faster data analysis and quicker identification of trends for each production run. Upgrading to commercially available data acquisition hardware has reduced any potential system downtime due to a hardware failure. If the legacy hardware had failed without replacement parts available, the system would have been offline for weeks, delaying production, as the system was upgraded to operate on newer hardware.