hydraulic splitter sizing

[turnkey4099]

I agree with the main part of your post. This shoot forward thing tho has nothing to do with slack in the pins or slide. It is instead the release of energy stored in the mechanism - aka flex of beam, hose expansion, cylinder body expansion, ram compression, flex of the pins, fluid compression, torsion on the pump and engine shaft, etc. It all amounts, as you describe, to an extremely short movement. If the system relaxation occurs instantly there is an extremely short duration pressure spike on the unloaded side of the cyl. Look at it with an unfilled pressure gauge and youll see more of a pressure jump than there is. A fluid filled gauge would give better perspective. Many parts of the system would suffer if this instant release situation were prevalent, however it is very rare that this energy is released precipitously and so the detrimental effect falls in the noise. Maybe the splitter lasts 10 minutes less because of it. Altho a true effect, it is inconsequential here.
larry

Yes, I did not allow for the flex, hose expansion, etc. It is all part of the sudden movement. One point though. Fluid compression?? You can't compress fluid unless there is an air bubble or air entrained in the fluid...at least not at the pressures common in hydraulic systems (ca. 2500 psi).

Harry K

 

[SPYDERLK]

Yes, I did not allow for the flex, hose expansion, etc. It is all part of the sudden movement. One point though. Fluid compression?? You can't compress fluid unless there is an air bubble or air entrained in the fluid...at least not at the pressures common in hydraulic systems (ca. 2500 psi).

Harry K

Everything compresses. Its just a matter of how much. Not much for hyd fluids - - about 1% at 2500psi. Below copied off Google.
Hydraulic fluid is not perfectly rigid. The ratio of a fluid's decrease in volume as a result of increase in pressure is given by its bulk modulus of elasticity. The bulk modulus for hydrocarbon-based hydraulic fluids is approximately 250,000 PSI, (17,240 bar) which results in a volume change of around 0.4% per 1,000 PSI (70 bar). The formula for calculating the volume change of a hydraulic fluid under pressure using its bulk modulus is Pressure/Bulk Modulus. [Ex: 1000/250000= .4%]. When the change in volume exceeds 10 cubic inches (160 cubic centimeters) decompression must be controlled.
......Interesting huh!?
larry