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HYDRAULIC FLUID
Hydraulic fluid must be essentially non-compressible to be able to transmit power instantaneously from one part of system to another.At the same time,it should lubricate the moving parts to reduce friction loss and cool thr components so that the heat generated does not lead to the fire hazards.It also helps in removing the contaminants to filter. The most common liquid used in hydraulic systems is petroleum oil because it is only very slightly compressible.the other desirable property of oil is its lubricating ability.Finally ,often,the fluid also acts as a seal against leakage inside a hydraulic component.The degree of closeness of the mechanical fit and the oil viscosity determines leakage rate. Figure below shows the role played by hydraulic fluid films in lubrication and sealing.
THE FLUID DELIVERY SUBSYSTEM
It consists of the components that hold and carry the fluid from the pump to the actuator .It is made up of the following components.
RESERVOIR
It holds the hydraulic fluid to be circulated and allows air entrapped in the fluid to escape. this is an important feature as the bulk modulus of the oil, which determines the stiffness of hydraulic system deteriorates considerably in the presence of entrapped air bubbles. It also helps in dissipating heat.
FILTER
The hydraulic fluid is kept clean in the system with the help of filters and strainers. It removes minute particles from the fluid, which can cause blocking of the orifices of servo-valves of cause jamming of spools.
LINE
Pipe, tubes and hoses, along with the fittings or connectors,constitute the conducting lines that carry hydraulic fluid between components. Lines are one of the disadvantages of hydraulic system that we need to pay in return of higher power to weight ratio.Lines convey the fluid and also dissipate heat.In contrast, for Pneumatic System, no return path for the fluid, which is air, is needed.since it can be directly released into the atmosphere.There are various kinds of lines in a hydraulic system.The working lines carry fluid that transmit controlling pressures to various directional and relief valves for remote operation or safty . lastly there are drain line that carry the fluid that inevitably leaks out ,to the tank.
FITTINGS AND SEALS
Various additional components are need to join pipe or tube sections, create bends and also to prevent internal and external leakage in hydraulic systems. although some amount of internal leakage in built-in, to provide lubrication, excessive internal leakage causes loss of pump power since high pressure fluid returns to tanks, without doing useful work. External leakage,on the other hand, causes loss of fluid and can create fire hazards, as well as fluid contamination. Various kind of sealing components are employed in hydraulic system to prevent leakage.A typical such component, known as the O-ring is shown below.
Hydraulic fluid must be essentially non-compressible to be able to transmit power instantaneously from one part of system to another.At the same time,it should lubricate the moving parts to reduce friction loss and cool thr components so that the heat generated does not lead to the fire hazards.It also helps in removing the contaminants to filter. The most common liquid used in hydraulic systems is petroleum oil because it is only very slightly compressible.the other desirable property of oil is its lubricating ability.Finally ,often,the fluid also acts as a seal against leakage inside a hydraulic component.The degree of closeness of the mechanical fit and the oil viscosity determines leakage rate. Figure below shows the role played by hydraulic fluid films in lubrication and sealing.
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| LUBRICATION AND SEALING OF HYDRAULIC SYSTEM |
It consists of the components that hold and carry the fluid from the pump to the actuator .It is made up of the following components.
RESERVOIR
It holds the hydraulic fluid to be circulated and allows air entrapped in the fluid to escape. this is an important feature as the bulk modulus of the oil, which determines the stiffness of hydraulic system deteriorates considerably in the presence of entrapped air bubbles. It also helps in dissipating heat.
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| RESERVOIR |
FILTER
The hydraulic fluid is kept clean in the system with the help of filters and strainers. It removes minute particles from the fluid, which can cause blocking of the orifices of servo-valves of cause jamming of spools.
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| GRAPHYCAL SYMBOL OF FILTER & RESERVOIR |
LINE
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| DIFFRENT LINES IN HYDRAULIC SYSTEM |
FITTINGS AND SEALS
Various additional components are need to join pipe or tube sections, create bends and also to prevent internal and external leakage in hydraulic systems. although some amount of internal leakage in built-in, to provide lubrication, excessive internal leakage causes loss of pump power since high pressure fluid returns to tanks, without doing useful work. External leakage,on the other hand, causes loss of fluid and can create fire hazards, as well as fluid contamination. Various kind of sealing components are employed in hydraulic system to prevent leakage.A typical such component, known as the O-ring is shown below.
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| SEALING BY O-RING |
Awesome diagrams!
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