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How Hydraulic Valves work?

10/8/2013 4:33:40 PM | by Anonymous

Hydraulic Valves

A hydraulic valve directs the flow of liquid mediums from its input to its output ports. The direction of flow is determined by the positioning of a spool that is driven by a linear force motor. Hydraulic valves operate and move systems through liquid pressure. In most applications, using liquid to move machineries is the more commonly used method. As compared to drier methods, the liquid will not cause the same wear on systems. It does not require as much movement parts and often provides a smoother, more precise motion than means that require more mechanics. Hydraulic systems also come caveats. They require being both water and air tight to function appropriately. Even smaller cracks or leaks can lead to disastrous outcomes for the system. All in which results in making the valve the most important part of the hydraulic system since there is a need to open and close with great precision. Additionally, it holds the liquid pressure with perfection and best accuracy.


The root word or hydraulic may come from “hydro”. However, that does not mean that hydraulic systems function using water. Water is considered to be too corrosive and abrasive and does not have the proper qualities to be used in hydraulic systems. Some qualities would include having appropriate level of water pressure. Instead, various types of oils are used in place of water. These oils not only help to run the system smoothly without causing wear and tear on the inside of the pipes. They also have excellent compression qualities as compared to using water.


In hydraulic systems, the selected liquid has to be very dense and mostly incompressible. Denser liquids have molecules that are fitted closely in nature and do not require much space to branch out. When put under high pressure or a large force is applied, the liquid will not change in shape or shrink in size. This is due to the tightly packed molecules and more pressure will change neither the space nor their chemical composition. On the other hand, when compressible liquids are placed under pressure, it will collapse. They will draw their molecules closer together until the pressure is finally released. Incompressible oils simply transfer the energy of the pressure onward through the entire body of the liquid.


This would mean that the pressure can be transferred along the liquid and be utilized to turn cranks, move pistons and perform many other type of work. The force that is extended throughout the channeled body of liquid will require pipes to hold it. The pipes holding it has to be very strong and stable. They can also be in a variety of shapes and sizes. This would make hydraulics useful in awkward spaces.


Hydraulic valves are used to allow liquid to enter and leave specific spaces in the system. These valves are used in conjunction with hydraulic pumps to control the flow of liquid. Some valves are automatic. When the fluid reaches a certain level of pressure on the inside of the cylinder, the hydraulic valves will then close. This ensures that the system has the required amount of pressure in that particular part. However, having too much pressure can also result in potential damage to the system. The valves also need to have a very reliable seal to prevent any leakage of fluids towards the pump and to lower the pressure again. Other valves are also computer controlled. They can be sealed and released at varying degrees that is dependent on the task.


The valve control also performs spool positioning, pressure and temperature measurement. Additionally, it also indicates alarm conditions. The valve controller will receive a command for the position from the field bus through the system controller. It will then be driven by the linear force motor until the output signal of position sensor equals the input value of the position command. At the same time, the temperature and pressure of the valve are monitored. An alarm clock indicates that if one of these sensors exceeds the pre-determined safety value.

 

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