Last week, we started looking at the key components in a hydraulic system – including the hydraulic reservoir, the pump, and the electric motor – and outlined some basic fundamentals that operators must know to keep the system at peak performance.
This week, we continue this discussion by looking at the valves, the actuator, and the hydraulic fluid.
There are several valves in a hydraulic system, but they are all designed to accomplish the same task – direct the flow of oil through the system and enable work to occur.
Let’s look at these remarkable components:
The relief valve (item D above) sets system pressure. It is usually placed directly after the pump, but it may be placed in other areas as well. If the system pressure exceeds the normal threshold, the valve will open, directing oil flow back to the reservoir.
The directional control valve (item E above) routes the fluid to the actuator. It contains a spool with three different positions. One position sends fluid to a side of the actuator, allowing it to extend, while a different position sends to the opposite side of the actuator, allowing it to retract. There is also a neutral position that will send fluid back to the reservoir, allowing the actuator to rest.
The flow control valve (item F above) controls the speed of the actuator by regulating the volume of oil to the actuator.
The check valve (item G above) keeps oil from flowing in the wrong direction, particularly when the actuator changes direction.
The actuator (item H above), also known as the workpiece, is the location where energy must be converted to mechanical energy and motion It is most often a cylinder and may be single (one-direction) or double (two-direction) acting.
The fluid is one of the most critical components in a hydraulic system, as it is the lifeblood of system. The proper oil will help maintain long component life, keep systems clean and free of contamination, and help enhance system performance. Hydraulic oil is typically between 32 and 68 cSt at 40 C. It must provide:
Wear protection – delivered through anti-wear additives in the formulation
Oxidation stability – delivered through antioxidants in the formulation
Good foam and air separation characteristics
Demulsibility – or a good ability to separate from water which is critical in helping minimize water contamination
Rust protection – an ability to displace moisture on metal surfaces
Varnish protection – delivered through detergent and dispersant additives in the formulation
The fluid must also be compatible with the other system components, typically the metals used in component design and the seals. Some of this protection is inherent in the base stocks used or is provided by additives used in the formulation.
Now, admittedly, this tip series covers the simplest hydraulic systems and there are some hydraulic components not covered in these articles. We didn’t mention a pressure gauge, oil level/thermometer gage, or an accumulator; those discussions are a bit more advanced and we’ll cover them in future.
I hope you enjoyed this tip series. If you have any questions at all, please leave a comment in the section below.
Thank you for this info. It's so helpful.
Jose - Actuators do not generate force but rather react to the force applied by the fluid. I hope this answers your question.
Excelente repaso de conceptos básicos en sistemas hidráulicos.
good for me
Una duda en los actuadores encontré que no son dispositivos capaces de generar una fuerza a partir de fluidos y de la energía eléctrica y por que motivo o cual es la razón que dicen sobre esta situación de los actuadores.