excuse me, what direction should i take?

We talked about what creates the flow in a hydraulic system, now I would like to get into what controls that flow.  A valve is the device that controls the direction, pressure, or the speed of the hydraulic fluid.  There are several different types of valves. Hydraulic circuit valves are grouped by the function they perform. 

The route by which the fluid takes through a valve is called the way. There are one, two, three and four way valves A pressure relief valve is a one way valve. When the pressure starts to get to high in the circuit the fluid pushes against a poppet inside the valve. This poppet is connected to a spring which intern gets depressed and opens up a port for the fluid to flow through thus reducing the pressure in the circuit.

an example of a electrical
directional control valve.

Directional valves control the direction of the fluid through the circuit. These can be two, three, or four way valves. The valves have an internal spool that changes position thus opening and closing certain pathways for the fluid to flow though. The mechanism to change the position of the spool can be manual, mechanical, hydraulic, or electric. The most common mechanism are electric solenoids.

Pump, pump, pump it up

In hydraulic circuits, the pump is the device that creates the flow of hydraulic fluid. The pump converts energy supplied to it from a motor or engine into rotational force. Hydraulic pumps are either positive displacement pumps or variable displacement pumps. Displacement refers to the flow of fluid through the pump per rotation. In a positive displacement pump, the flow rate cant be changed. 

In contrast, the flow rate in a variable displacement pump can be changed. This change allows for the saving of power and energy which otherwise would be lost doing normal changes in work loads. Different types of pumps include gear, vane, piston, rotary vane, and bent axis pumps. Bent axis pumps are the most efficient pumps, however, the gear pumps are the simplest and cheapest type. 

Flow rate of the pump is proportionally related to the actuator speed; the actuator speed depends on the flow rate of the pump, faster pump faster output. Most pumps are used in an open system, which means the reservoir is not pressurized. If the reservoir is pressurized then it’s a closed system. Examples of machines that couldn't operate without the use of hydraulic pumps are cranes, loaders, backhoes. Power steering in cars also use hydraulic pumps.

hydraulic circuits

hydraulic circuit

In hydraulic circuits we can see the combination of both electrical and mechanical components being used together to accomplish a task. There are 6 basic components a hydraulic circuit needs to have to be able to operate. You need hydraulic fluid, a reservoir tank to house the fluid, pipes and or hoses to allow for the flow of the fluid, a pump to move the fluid, valves to control the pressure and direction of the flow and actuators to change the hydraulic force into useful mechanical force.

A good example of the use of a hydraulic circuit that everybody would know but might not be aware of are in airplanes. The hydraulic circuit is used to control the landing gear, brakes, flaps and stabilizers.

 According to Albert W. Kemp, author of Industrial Mechanics, an actuator is: “a device that transforms fluid energy into linear or rotary mechanical force.” Cylinders and hydraulic motors are other example of actuators. If you have ever had a flat tire and had to use a tire jack you have used a cylinder. A tire jack uses two cylinders that are of different sizes to create the leverage you use to jack up your car. 

hydraulic mount

In this video you will see a hydraulic cylinder being assembled and then mounted on to a rail. Then it will demonstrate the linear motion that the hydraulic fluid will produce when it is actuated. The video clearly shows that a cylinder is made of several different metal components, but it doesn’t show how these components are sealed together using o-rings. Without these o-rings the components would not seal properly together and hydraulic fluid would leak out everywhere. 

The mounting to the rail will allow the cylinder to lift something that is in front of it that might be standing vertical to a horizontal position above it. The video then goes on to show you a cut out of the cylinder while it is in motion. This part illustrates how the hydraulic fluid would be pushed against the plunger. The rod attached to the plunger would then be pushed out of the cylinder to create the linear motion to move whatever is attached to the cylinder. The way the cylinder is mounted onto the rail creates longer linear motion from the cylinder because it is also in motion. This allows you to use a smaller cylinder to get the same amount of work done. 

examples of elctromechanical components



internal workings of a speaker

According to the McGraw-hill dictionary of Scientific & Technical Terms, electromechanics pertains to the mechanical devices, system, or process, which is electrostatically or electromagnetically actuated or controlled. In this blog I would like to introduce and explain to you the different kinds of electromechanical devices and illustrate how they are used today in different industries.Simply put, electro-mechanics is any mechanical component controlled by electrical inputs. 


Examples of common items that are electromechanical devices include speakers, alternators, and typewriters. In the illustration on the right, the loudspeaker cone is the mechanical component. Additionally the electrical components are the wire coil and the permanent magnet. Other electromechanical devices that may be lesser known are amusement rides, hydraulic systems, high-speed automation production lines, robotics and other systems that use programmable logic controllers (PLC). PLC’s are really the brains of the electrometrical device PLCs differentiate from other computers by that they are very reliable.

+ On the second row from the top is an example of a PLC.

They are able to withstand the harsh conditions of various industries in which they are utilized. Examples of industries that use electromechanical devices are the steel industry, automotive industry, the food industry, and the movie industry, just to name a few. As you can see, electromechanical devices are used in a variety of different industries but in completely different ways.