Fluid Power Basics
Written by: Bud Trinkel, Certified Fluid Power Engineer
Edited by Mary Gannon and Richard Schneider, Hydraulics & Pneumatics magazine.
Fluid Power Basics starts with background information about simple air and hydraulic circuits, principles of fluid power operation and physical laws governing fluid power. Subsequent chapters cover different types of hydraulic fluids, fluid rating, operating parameters, and how to apply them. Next, a discussion on plumbing of fluid power systems covers tubing, pipe, and hose installations. A short section on vacuum and its applications is followed by basic circuit information. Coverage then shifts to discussing different components that make up a complete hydraulic or pneumatic system: reservoirs, filters, pumps, flow meters, gauges, and relief valves.
A detailed discussion of directional control valves covers check and prefill valves; decompression circuits; sliding plate, spool and poppet designs; in-line and sub-plate mounted valves, as well as screw-in and slip-in cartridge valves. One chapter is dedicated to an explanation of proportional and servovalves.
Subsequent chapters cover all types of flow controls and their use in a circuit. Next are pressure controls except relief and unloading valves. This chapter includes sequence, counterbalance, and reducing valves. Shuttle valves, quick exhaust valves, and other special-purpose valves are explained. There is a chapter on accumulators that shows and explains how the different types work and common applications.
The book also covers all types of actuators, including cylinders, rams, motors, and rotary actuators. Application of these components in different circuits gives a general overall view of how they are used.
Circuit diagrams are intended to show the function of the components and do not necessarily show all the components to make a safe and reliable system. Drawing practices and symbols according to ISO standards have been used when possible.
I began my fluid power profession as a salesman of cylinders and valves. I had used the same cylinders as a designer of plastic injection molds, diecast dies, and related tooling. In my ten years in design, I never had to think about what it took to make the cylinders operate. The people who built the fixtures or ran the tooling took care of getting the valves and hooking them to the cylinders. Not until I started my sales career did I realize the tool shop depended on fluid power salesmen to tell them what they needed. It may surprise you to know that salesman design more than 90% of all fluid power circuits in the United States.
The first two cylinder air circuits I designed took several hours and some of these didn't even work. Fortunately, the company I started with was committed to training, so design time decreased and working circuits increased. In a few years air logic controls and a full hydraulic pump and valve line brought more challenges and more knowledge about fluid power.
I quickly found teachers of fluid power were in demand at schools with adult evening classes. Many people worked with fluid power but had little or no training in how it worked. I can testify to the fact that teachers always learn more than their students. I often think about some of the early classes and questions I could not answer.
This material is the text for a basic fluid power course I have been teaching for several years. It is dedicated to people who bought fluid power products even if the circuit didn't work the first time. It is also dedicated to many students who asked questions I'd never thought of, and to students who came up with ideas I might have passed over because I was sure it could not be done.
Bud Trinkel, CFPE
Fluid Power Consultant