Customer had a 30-year old hydraulic hose cyclic pressure tester that is used to life cycle test automotive and off-road equipment hose assemblies. These assemblies are combinations of application dependent bent metal tube with crimp connected rubber and poly fiber hoses. Test pressures would vary between 200 psi and 3000 psi.
Simply put, the test center had a functional test chamber with solid mechanics and a solid hydraulic design with a long history of low / non-existent annual maintenance costs. The test engineer could hook up an external oscilloscope and watch the hydraulic pressure cycle 25-30 x per minute. The tester worked. What kept it working was a custom designed, hand made bread board of electronic parts purchased at Radio Shack in the mid to late 70s . Other than the Radio Shack parts it was all simple relay logic, with one pressure test wave form.
Customer needs this machine to verify manufacturing process changes, functionally test sample materials and endurance test parts for customer quality inspection programs. Aside from the fact that the Radio Shack parts stopped working and no replacement parts could be found the customers of this machine had progressive and expansive expectations of machine needs since the early 1980s.
Components reused with minimal changes were the hydraulic circuits, piping, servo valve, test chamber and oil heater. The 480VAC power elements where reused. All relay logic and pushbuttons were stripped from panel. Replacement platform was as follows:
- For control of hydraulic servo valve and pressure profile was done using a Delta Computers model RMC 75 controller with Ethernet IP interface for connection with the Rockwell compact logic processor
- Data/Test Cycle setup, programming and machine sequence was done using a Rockwell Compact Logics processor, L33
- Operator Interface Display using a Proface 12” Display unit.
All components where inter-connected using Ethernet IP protocol. The Delta Computers RMC Controller has a built-in interface to Rockwell Logix as a Generic Ethernet Module with data ranges configured. These functions allowed the memory of the Logix platform to use a custom structured UDT to containerize a specific test profile and target number of cycles that would be passed down to / into the RMC 75 Controller for directing the servo valve position and pressurized oil flow rate.
Pressure monitoring sensors (0-3000 psi range, Baumer # PBM4 Series) where installed in the test chamber to monitor the pressure on the supply and drain manifold headers. The general idea of this machine is to test 10-20 hose assemblies in parallel with the failure of one hose ending the test. Failure modes ranges from a small pin hole leak, a complete failure of a hose to metal tube crimp location or a burst metal tube section. When the Drain manifold pressure sensor fails to reach target pressure when drain solenoid is closed, there is a leak and test is stopped. Bottom of chamber is a catch basin with gravity drain return to tank. Normal return is a pressure hose connection from drain manifold.
User is also able to setup single pressure cycle (simple) or more complicated multi-step linked “pressure-time” segments into one “test cycle”. Actual pressure can be monitored on the Proface Display screen. However, the Delta RMC controller has a better pressure display screen that has a faster update than the Rockwell PLC/Proface display does.