You can find hydraulic systems in many different types of machinery, including aircraft and construction equipment. These systems use an incompressible fluid to push pistons or rotate vanes inside a motor in much the same way that pneumatics use compressed air. Knowing how these systems are classified can help you understand whether you have the right one for your application and which types of parts or repairs you will need.
Open or Closed Systems
Hydraulic systems can either be closed-loop, the fluid flows between the pump and the motor continuously, or open-loop, where the fluid enters a reservoir before the pump inlet. These systems are used in multiple applications so it is essential to know whether you need an open-loop for less heat production or a closed-loop for more precise component responses. Not all hydraulic fluid is designed to handle the same pressures and temperatures because the pump and motor types vary according to size and application. These differences mean that hydraulic fluid, such as EPF-262 fluid Houston TX, will have a boiling point and flash point listed to help you choose the right one for your systems and application.
Fixed or Variable Displacement
Hydraulic systems can also be classified by whether you can change the amount of displacement produced by the pump. Screw pumps and gear pumps are fixed displacement, meaning that you cannot change the amount of displacement, but you can change the drive speed. Internal and external gear pumps are the most common ones in use because they can be the least expensive and easiest to maintain.
Variable displacement systems, such as axial piston, rotary vane and radial piston pumps, allow you to change the amount of displacement. By reducing or increasing the displacement in systems with pistons, you can change the distance that the piston or vane moves. This variation is helpful in equipment like trash compactors where the piston will need to move further when the bin is emptier.
Hydraulic systems are generally classified by where the fluid travels, open or closed-loop, and whether you can change the pump’s amount of displacement. These classifications will inform the applications and the type of fluid recommended for the pump.