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Coping With Defective Pressure Nails

Most transducers in fluid power systems are short-term pressure spikes, commonly referred to as pressure spikes.

Most transducers in fluid power systems are subjected to short-term pressure overloads, commonly referred to as pressure spikes. If these spikes are severe enough, a permanent positive zero shift may occur at the output of the Melt Pressure Sensor transducer.
After investigating these spikes, we developed a laboratory method to determine the magnitude of the actual pressure increase that caused a particular field failure. The method shows that the pressure increases in a system much more than the nominal system pressure.
Using this procedure, for example, we determined that two transducers rotated by one of our users for our fault analysis were subjected to pressure spikes of 19,500 and 21,500 psi. The user said he found our results difficult to accept and found a little miracle. The system included convenient relief valves, a padded hydraulic ram and had only 1350 psi working pressure. When we told the user that the pressure increased by 14.4 and 15.9 times the system pressure, logic dominated our findings.
To solve this problem, we bought a digital storage oscilloscope and disk recorder at the user's facility to test the hydraulic systems of casting machines experiencing transducer failures. The recorder featured an auto-trigger function that allowed measurements at 0.5usec / point resolution. Test results revealed a pressure rise of more than 5500 to 20,000 psi. Working pressure was kept between 1250 and 1350 psi during the test period.
Results from Tests
The results of these tests and other tests performed at the same location six months later led us to several conclusions:
• Pressure increases occur in hydraulic systems. The most severe are caused by rapid changes in system flow that can be caused by components such as pumps, pistons, ramps, valves and control devices.
• Air trapped in the hydraulic fluid increased the magnitude of the sudden pressure spikes. Air evacuation from the system can reduce peaks by up to 60%.
• Pressure spikes in excess of 20,000 psi can be generated in a system with rated operating pressure of only 1300 psi.
• The typical pulse duration of the Melt Pressure increase is approximately 0.25ms. Most safety valves, pressure relief components, and drain plugs cannot respond to such short-term transients.
• The size of the spike delivered to the Melt Pressure Transducer depends on its location in the system.
• Melt Pressure Sensor Pressure reducers effectively reduce the size of the head that the transducer must withstand. Snubbers stop or absorb shocks and vibrations that damage pressure gauges.
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