Fluid Power – How Hydraulics Can Move Mountains

Many people may not realize the potential power that they hold in a glass of water.  If you really look closely at the power of fluids, like water, you’ll see how they have the ability to literally move mountains.  Examples are everywhere in nature.  One of the best examples of how powerful a fluid can be is the Grand Canyon.  With enough time, water can carve out vast parts of our landscape.  And it didn’t take long for humans to harness fluid power in the form of hydraulics.

Hydraulics is a term used for the application of fluid power in a liquid form.  After all, gas is also a fluid.  When you look at gas as a fluid power, it is referred to as pneumatic.  Hydraulics is most commonly used in machinery.  The advantage of using hydraulics in machinery is the ability to move, cut, carry, lift, dig, or mix a very large load.  In machinery the hydraulics form a system made up of a pump to move the fluid, hoses or pipes for the fluid to move through, and a hydraulic actuator that performs work.  The two most common types of actuators in hydraulics are cylinders and motors.

Before we can get into how the hydraulic motors and cylinders work, we need to understand two aspects of hydraulic power: pressure and flow.  Pressure is the amount of force that is being transmitted through a fluid and can be calculated as pounds per square inch (PSI).  If you apply 1000 pounds onto one square inch of area, you have 1000 PSI.  Flow is the amount of volume and speed in which you are moving the fluid, and is many times calculated as Gallons per Minute (GPM).  If you are pumping 20 gallons of fluid every minute, your flow is 20GPM.  In hydraulics, horsepower is calculated from pressure and flow. Calculate Hydraulic Horsepower

A hydraulic cylinder is basically a rod that is inside a sealed tube.  As the tube is filled with fluid, it forces the rod out of the tube.  Cylinders are everywhere in machinery and can push and pull very large loads of weight.  Think of a fork truck and the cylinders used to lift the load.  The force that the cylinder can exert depends on cylinder size and the amount of pressure being applied.  The amount of speed that the rod moves out at is determined by cylinder size and the flow of the fluid.  Calculate Cylinder Force  Calculate Cylinder Speed

A hydraulic motor is very similar to a pump.  A pump is being turned by electrical, mechanical, or even human power to create pressure and flow in the fluid.  A motor converts the pressure and flow back to a rotating output.  Many times motors are mounted to wheels, augers, or mixers.  Think of the drum on a cement truck.  That is a heavy load being turned.  The amount of torque the motor is able to produce depends on the motor displacement and the pressure of the fluid.  The speed of the motor also depends on the motor displacement, but depends on fluid flow.  Calculate Hydraulic Motor Torque  Calculate Hydraulic Motor Speed

Now you have the basics of how hydraulics work and why they are used on heavy machinery.  The next time you drive by a construction site and see the large machinery, think about the river in the Grand Canyon and how powerful fluids really can be.

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