Week1/Lesson 1 - Introduction Fluid Power Engineering Week1/Lesson 1 - Introduction

Welcome to the world of Fluid Power In this lesson we shall Learn what Fluid-Power Engineering is Explore some of the uses of fluid power in industry Compare and contrast a fluid-power circuit and an electrical circuit Learn a bit about the components that make up a fluid-power system Look at some simple fluid-power circuits

Where is fluid power used? The industrial applications of fluid power are: In stationary settings to deliver powerful/fast motion control For mobile systems like cranes, back-hoes, concrete pumps, forest-harvesting equipment, earth-moving equipment, mining For aeronautical systems Pneumatics for motion control in automated systems in industry In short, any place where a great deal of power or force is needed in a small package

Hydraulic cylinders to raise bridge Large-scale, stationary system Hydraulic cylinders to raise bridge

Mobile systems Back-hoe Stick cylinder Bucket cylinder Boom cylinders A diesel engine in the main body drives a hydraulic pump to provide pressure and flow to the cylinders A back-hoe is a very common application for fluid-power systems. It has three links: 1) The boom, near the base of the machine, 2) the stick, pivoted off the boom, and 3) the bucket, which is the end effector of the back-hoe. (End effector is a term in robotics for the piece of equipment at the end of a bunch of links. It is the part that is specially shaped to do the work of the machine.

Mobile systems Machine for use in tree-harvesting application Note its similarity to the back-hoe This machine has the same three joints. The end effector is different. In robotics, end effectors often are different because each machine is built for a different purpose.

Mobile systems Machines for use in mining application

Mobile systems Core-drilling machine to take sample cores for drilling Note its similarity to the back-hoe

Aeronautical system Aeronautics is another big user of hydraulic actuation systems… This is due to their compact size and the amount of force they can generate in this small package To the left a rendition of the actuation system for the control surfaces in an airliner wing

Aeronautical systems Another aeronautical use…helicopters

Pneumatics Industrial-automation example Pneumatic cylinders You can tell that the cylinders are pneumatic because of the clear plastic tubes leading to them. Air pressure is lower than normal hydraulic pressure, so these easily cut, routed pneumatic tubes are possible. Industrial-automation example

Pneumatics Pneumatic actuation used in automated system for automobile manufacture

Pneumatics – mobile use Pneumatic braking system for a vehicle

Comparison with electric circuits Hydraulic fluid, like electricity, flows in a circuit. It is pumped from a reservoir, a tank that is… …it flows through various pipes/tubes/hoses… …it can be directed into different directions… …it drives an actuator – a cylinder or a hydraulic motor… …then it flows back into the reservoir

Comparison with electric circuits The reservoir is like a an electrical ground The pump is analogous to a battery The tubes are like wires Valves are like switches Pressure is like voltage Flow-rate is like current So it makes sense to use our knowledge of electrical circuits to analyze and design fluid circuits

Analogy with electric circuits We have a standard way of drawing electric circuits with their components A cartoon-like drawing shows the various components and how they are arranged in the circuit Such a drawing shows the function but not the physical details of the components

Fluid-power symbology Likewise, electric circuits are drawn in a certain way, like cartoons, with components representing the physical components that make up the circuit Pump Valve Cylinder Reservoir We need to master this language of expressing fluid-circuit components before we can understand how the circuit works

Analogy with mck-systems in Vibrations Another example, in Vibrations, stick-figure drawings are used to represent the function of system components but not their details Focusing on the details and not the function is confusing So part of the study of fluid power is to master the symbology so that it can be understood but also so that you can make your own drawings of hydraulic circuits to perform tasks for which you design them

Fluid Power uses special symbology The details of the construction of a device… Port A Port B Rod Piston Cylinder …are hidden in the cartoon-like representation of the component… The cartoon shows the function, but not the details of the component

A simple circuit In this position, fluid flows on… Let’s look at our simple circuit and see how it works: In this position, fluid flows on… …into the rod end of the cylinder… Reservoir The fluid pushed out of the cap end of the cylinder flows back to the reservoir The pump pumps fluid from the reservoir… Reservoir The valve has three positions… …and the cylinder retracts The two reservoirs are actually the same reservoir for the system

Shift valve to center position In the center position of the valve… …the valve blocks the flow from pump to cylinder and from cylinder to reservoir So pump flow is shut off and cylinder is locked and can’t move

What’s use of this circuit? The cylinder is connected to some kind of load… …so as the cylinder extends and retracts, it moves the load with it… …like opening and closing the drawbridge in the first example shown

Arrows pointed in toward center designate a hydraulic motor A pump can also drive a motor Cylinders are linear actuators (they move in a line), but there are also rotary actuators too, called hydraulic motors Arrows pointed in toward center designate a hydraulic motor The one-way pump can drive the hydraulic motor either forward or reverse, depending on the valve position A motor might drive a vehicle, a grinding machine, or some other device at a certain speed

Example - Cylinder motion Before we finish this lesson, let’s look at a simple analysis of cylinder motion A hydraulic system is to be designed to lift a 1500-kg mass upward at a rate of 1 m/sec. The pump is selected to deliver fluid at 70 bar. Find AP , the area of the piston DP , the diameter of the piston Q , the flow rate through the system Phyd-min , the minimum hydraulic power (p·Q) needed from the pump As a first pass, ignore all leakages and energy losses in the system

Example - Solution First set the upward force on the piston equal to the weight: 𝑝∙ 𝐴 𝑃 =𝑚∙𝑔 𝐴 𝑃 = 𝑚∙𝑔 𝑝 The Excel solution uses the cell-naming functionality of the spreadsheet. This solution methodology is recommended because it enhances the checkability of the analysis. Ap = m*g/p = 1500 kg * 9.81 m/sec^2/70 bar 1 Pa = 1 N/m^2 and 100,000 Pa = 1 bar A bar is about 14.5 psi, so about 1 atm So 70 bar ≈ 1000 psi The actual system is a bit more complicated than this, but it is useful too to make first passes and then add the complications in a layered approach.

Outside learning In this course we shall also use outside sources of material A very useful resource is the “Big Bad Tech Channel”on YouTube by Jim Pytel of Columbia Gorge Community College in The Dalles, Oregon. This channel contains 44 videos on various aspects of fluid-power systems Turn the closed-captioning on (if available) to be able to understand better the details of the lectures Watch: Introduction to Fluid Power Systems How a hydraulic system works – Aviation hydraulic systems Airbus hydraulic system: how does it work – A320 hydraulic system Parker Aerospace Hydraulic Systems Overview: An animated fly through Rexroth for the Wood Industry

End of Week 1/Lesson 1