When you flip the diagonal line to lean outward from the valve body, the coil now shifts the valve by pulling on the armature pin, although it is rare to see the symbol drawn this way. The first operator is the symbol for a solenoid coil that magnetically pushes on the armature pin, which makes sense as the diagonal line leans towards the valve body. Starting with Figure 1, there are three ways to draw an electric operator for solenoid valves, which most people recognize. This chapter of hydraulic symbology covers most of what needs to be known to read and create the average hydraulic schematic, since actual electrical symbols are somewhat different.
Understanding electrical symbology becomes more important as machinery becomes more sophisticated, and you may come across schematics that are hybridized with electronics or even electric actuators like linear or servomotors. In fact, over the past few decades, most advancement in hydraulics has been in how it’s controlled rather than improvements in the foundational components such as valves, pumps and actuators. Any book or lesson in fluid power worth its weight in gold will discuss the importance of electrical and electronic control of hydraulics.
