Insane Hydraulics

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Cylinder Mounted Pilot-to-Open Check Valve Interactive Pressure Graph

The following interactive graph plots out theoretical pressures of a hydraulic sytem composed of a differential area cylinder and a pilot-to-open check valve (please refer to the diagram below the graph). It is assumed that there is no back pressure in the return line.

The term "Equivalent Pressure Differential" (horizontal axis) refers to the caculated pressure differential across the check valve - the valve is considered open when this pressure is higher than the check-valve cracking pressure (5 bar in this example).

The main purpose of this chart is interactivity, i.e. to demonstrate in a clear and graphical way how changing the key parameters of such a system (valve pilot ratio, cylinder area ratio, load induced pressure, trapped pressure and cylinder orientation) affects the numbers and can create conditions for overpressure and cylinder locking. The lines are plotted out beyond the magenta line for a clear illustration of the lines slope (pressure development tendency), obviously in a real system the pressures would be immediately affected by the check-valve's opening.

I will be uploading a detailed article explaining the subject, and also a much more extensive simulator page, which will include all the cylinder related maths with imperial and european units so that it can be easily applied to real life dimensions. (This means that this paragraph will soon be replaced by something like "Click here to read a detailed article on the subject, and follow this link to a more detailed calculator).

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Load Pressure refers to load induced pressure
Trapped Pressure refers to the pressure trapped inside the respective cylinder chamber by the check-valve (possible when the system reaches end of travel).
Green and Red numbers on the left side of the graph indicate C1 and C2 pressures when piloted check valve opens (points where the green and red lines cross the magenta line).