TRU T ST R ED U . STED All Williams ® Cylinders and Pumps undergo 100 % functional quality control testing. THE SCIENCE OF HYDRAULICS ENGINEERING SCIENCE PERTAINING TO LIQUID PRESSURE AND FLOW Hydraulic History • The thinkers and experimenters, such as Galileo, Newton and Pascal, discovered interesting phenomena many years in advance of actual practical applications of their theories • Pascal discovered and formulated the “Law of Hydraulics” about the year 1650, but nearly 150 years passed before that law was exploited in a practical application • Pascal’s law, which states “that an external force exerted on a unit of area of a confined liquid will be transmitted undiminished to every unit area of the interior of the vessel,” is the basis upon which every hydraulic device functions PRINCIPLES OF HYDRAULICS • W hen a mechanic pumps the handle of a hydraulic pump, they are exerting force with a small piston on an area of a confined liquid • That force is transmitted by the liquid, through a hose or pipe to the interior area of the hydraulic cylinder, including the effective area of the piston • The piston is forced to move • A very simple example of this is shown here: • In variations of the above example, the principle of hydraulics is not changed - The small piston may be moved by a lever, or by the rotary power of an electric motor or gasoline engine; the fluid flows through a pipe, a tube, or a hose; check valves, relief valves and control valves may be introduced into the system along with a reservoir of fluid and return lines; and, the ram may be a of a number of different types or shapes. But the action remains the same. The applications of hydraulic equipment are limitless INPUT/OUTPUT MEASUREMENTS • The force in-put and force out-put of hydraulic devices can be very simply measured and calculated - The pressure produced by the piston on a confined liquid is measured in pounds per square inch, or psi - If ten pounds of force is exerted on an area of ten square inches, the pressure will still be 1 psi – but if 10 pounds of force is exerted on one sq. inch, the pressure will be 10 psi • The force produced by liquid pressure against a piston will be measured in pounds or tons - If there is a pressure of 100 psi exerted on a piston with an area of 10 square inches, the total force will be 100 (psi) x 10 (sq. in) or 1,000 pounds A one pound weight which is placed on an area of 1 sq. in. produced a pressure on that area of 1 psi HOW HYDRAULIC FORCE WORKS Piston Travel • When the small piston is “pushed down” in the pump cylinder, the amount of fluid it will Stroke displace will only be enough to move the larger piston a short distance. Therefore, while tremendous force advantage is gained, there is a sacrifice in “distance”. • There is another principle involved in the hydraulic process. - When a man pushes against a wall with his hand, the force he exerts is opposed by the resistance of the wall. If he pushes against no resistance he would not be able to exert force. His hand would pass freely through the air. - A hydraulic cylinder is the same. A pump may be rated with a pressure out-put of 10,000 psi, but unless there is a resistant force against the cylinder requiring 10,000 psi, the pump will develop only enough pressure to move the resistant force. - A cylinder rated at 10 tons at 10,000 psi and which is exerting a force of 1 tons, will require considerably less than the 10,000 psi potential out-put of the pump. The pressure will be 1/5 or 2,000 psi in the system. BASIC HYDRAULIC SYSTEM SETUPS Single-Acting Cylinder Application Single Acting Cylinder JHW6C10T06 or JHW6C10T10 (Longer Stroke) Pressure Gauge JHW8604W Male Coupler JHW8RH38DM Hand Pump JHW5HS2S100 or Foot Pump JHW5AS150 (Longer Stroke) Double-Acting Cylinder Application Double Acting Cylinder JHW6CD55T06 Needle Valve JHW8V38N Electric Pump JHW5E505H1G Pressure Gauge JHW8604W Male Coupler JHW8RH38DM 6' Hydraulic Hose JHW8H3825D06 6' Hydraulic Hose Gauge Adapter JHW8H3825D06 JHW8FG38MF 2 Male Connector JHW8FN38M Gauge Adapter JHW8FG38MF
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