Most of the time we forget that hydraulic systems are very simple. No matter where they operate – on a space shuttle or the power steering unit of a car – a hydraulic system is nothing more than a fluid under pressure, flowing and doing work.
That said, there are a few components in most hydraulic systems that aid in fluid control and productivity, and there are some basic fundamentals that every operator should follow to help maximize the performance of the overall hydraulic system.
This week, we’ll look at the hydraulic reservoir, the pump, and the electric motor.
The hydraulic reservoir
Item A in the hydraulic system sketch above is the hydraulic reservoir. This component stores hydraulic fluid and protects it from contamination. While it may not be the heart of the system, it is certainly one of the most important components. Here are some of the design criteria:
The reservoir must be sized to 3 to 5 times the fluid capacity of the hydraulic system to facilitate proper oil delivery and cooling.
It contains a baffle to help remove contaminants (water and particulate) and dissolved air.
It has a strainer, not a filter, to help preclude large contaminants from entering the pump inlet, causing a restriction. Strainers are typically sized between 80 and 100 micron.
It also has a breather to filter the air that enters the reservoir due to changing fluid levels. Breathers should be able to remove both moisture and particulate.
Its pump suction inlet should be sized correctly so as not to promote fluid cavitation.
Fluid return piping should be away from the suction line to reduce the turbulent flow and aeration.
As you can see, the reservoir needs to be designed correctly for the system to operate properly.
The pump and electric motor
Items B and C in the sketch above are the electric motor and the pump, respectively. The pump and motor must be carefully matched, as the combination is truly the heart of the system. Some pump and motor considerations:
The motor is typically electric but may be other modes as well to include air, fluid and combustion-driven.
If the pump is designed for a certain output, say 10 ml/rev, then the motor must be equally rated to ensure the development of the needed system pressure and fluid delivery.
The pump speed must be controlled to avoid development of excess vacuum at the inlet causing fluid cavitation.
Typical pumps include piston, vane, and gear. Their choice depends on the amount of fluid needed in the application.
Gear Pump - constant displacement used up to 3000 psi.
Vane Pump - Used in high oil flow low-pressure systems.
Piston Pump - Provides viable displacement to vary output and pressure.
Getting right the pump/motor combination is critical to ensure proper system performance.
That’s it for this week. Join us next week when we take a look at the valves, the actuator and the hydraulic fluid itself – as well as what you need to know to keep your system running at full speed.
If you have any questions about this week’s tip, leave a comment in the section below.
What parameters should be followed to test a hydraulic pump?
That flow and pressure a achieved as designed.
Strainer is rarely found in tanks. It reduces the pump efficiency significantly.
Great! It's simple and easy to understand!
Very well, precise and understood writing, easy to understand.
Excellent information and thanks for the clarification on the hydraulic pumps.
Nikolay - A strainer is a basic and important component of all hydraulic systems. If it is designed correctly and the oil is in good condition it will not reduce the pump efficiency. The purpose of a strainer is to prevent large contaminants from enter the pump. If it is not found in your tank that is most likely because some one has removed it. Check the pick up tube for threads. If they are there, the strainer has been removed. If the strainer is reducing pump efficiency, it may be coated with contaminants and need to be cleaned. Thanks.
very good information rick and i wait for the part 2
It Would Be Very interesting to know a little more about the operation of the valves, especially the servo
Heber - Possibly a future topic. Thank you.
Another measure for hydraulic pump condition is casing drain flow back to the reservoir. Increasing flow indicates increasing wear within the pump.