Yellow Pages Basic Hydraulics |

Oil FlowA hydraulic pump produces flow. Flow is the amount of fluid coming out of the pump. PressurePressure occurs when there is resistance to flow. Pascal's LawPressure applied at any point upon a confined liquid is transmitted undiminished in all directions (Fig.1). This means that when more than one hydraulic cylinder is being used, each cylinder will pull or push at its own rate, depending on the force required to move the load at that point (Fig. 2). Cylinders with the lightest load will move fi rst and cylinders with the heaviest load will move last (Load A), if the cylinders have the same capacity. To have all cylinders operate uniformly so that the load is being pulled or pushed at the same rate at each point, control valves (see Valve section) must be added to the system (Load B). ForceThe amount of force a hydraulic cylinder can generate is equal to the hydraulic pressure times the “effective area” of the cylinder (see cylinder selection charts). Use the formula F = P x A to determine either force, pressure or effective area if two of
the variables are known.Cylinder Oil CapacityThe volume of oil required for a cylinder (cylinder oil capacity) is equal to the effective area of the cylinder times the stroke. Usable Oil CapacityThe amount of hydraulic oil in the pump’s reservoir which can be used to activate one or more cylinders. Cylinder SpeedPressure applied at any point Cylinder speed is determined by dividing the pump fl ow rate by the cylinder effective area. |

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