Earlier, I mentioned how electric and hydraulic actuators are similar in execution and principle, and in this blog post I’d like to finish off the mini-series on the similarities between hydraulic and electric symbols.
The most obvious similarity is the conductor,which is a hose in hydraulics or a wire in electrics. The physical manifestation can vary—such as with tube or track—but the symbol is a simple line. The most basic valve in hydraulics is the check valve, which blocks fluid in one direction, while allowing free flow in the opposite. A diode can block electrons from traveling in one direction but also allow them to flow in the opposite direction. If you’ll notice on the drawing, the symbols are just as similar as their function.
An electrical resistor is used to reduce the flow of electrons, and just like the hydraulic flow control, they can provide fixed resistance as well as variable resistance. The symbols are somewhat similar, but their execution differs only in that one flows electrons and the other fluid molecules. In the hydraulic realm, flow control valves are often pressure compensated to ensure they flow at their desired setting regardless of downstream pressure changes, and this concept can be achieved in electrics as well, although it’s not always required.
Electric battery technology has come a long way, and it’s astounding how much power can be stored for slow to moderate rate of release over an extended period of time. There is no hydraulic equivalent to an electric battery; that much energy just cannot be stored and released over an extended period of time. For short bursts of high power, however, hydraulics can use the accumulator.
The hydro-pneumatic accumulator cheats and uses compressed nitrogen as the medium of energy storage, because liquid is nearly incompressible. The electric version of an accumulator is the capacitor, which can also provide very high bursts of power, but over a short period of time.
Two components similar in practice but dissimilar in symbology are the transformer and intensifier. The electrical transformer uses inductance coils with differing windings to change voltage, and the hydraulic intensifier uses a tandem cylinder with different sized pistons to turn low pressure into high pressure. With either example, it should be clear that power cannot not be higher after the change than before. For example, you cannot take a given voltage/pressure and double it while keeping the same input of amperage/flow; it will actually be less than half after we deduct for inefficiencies.
There are many more functional comparisons between electrics and hydraulics, but my list of examples is limited by my knowledge of electronics. Still, you can see how if you’re an electrician or electrical engineering, you’re much better at hydraulics than you think you are. Like I said previously, we’re not so different, you and I.