First of all, most of hydraulic system valve (such as pressure relief valve, directional valve and others) are design with a very precise and small clearance. Oil cleanliness is very crucial to ensure that the component will not be premature fail, wear and tear. Failing to comply with the cleanliness requirement, your system will having so much problem.
Secondly, to avoid high maintenance cost. Trust me, hydraulic system parts mostly are not cheap. When premature failure, wear and tear happen, the maintenance cost can shoot up to twice, thrice and more than that.
To ensure the oil cleanliness is always within specs, a good filtration system is needed. Basically, for the common hydraulic system, the filtration system will be consists of:
- Circulation Filtration System
- Pressure Line/ Supply Line Filtration System
- Return Line Filtration System
Of cause, the more complicated and critical your hydraulic system, the more filtration system need to be put.
Circulation Filtration System.
The main function of the circulation filtration system is to keep the hydraulic system clean. The oil will be continuously circulated by the pump while the system is in operation. Normally, the circulation system use vane pump or gear pump to circulate the oil. The pressure normally not exceeded 6 bar. The standard filter element rating is around 13 micron.
Pressure Line / Supply Line Filtration System.
This filtration system normally is attached to the main pump. The main purpose is to filter the oil before delivered into the system (valves, cylinders,hydraulic motors). It plays major roles to protect our hydraulic system components. Common practice for the location of the filter are either located in hydraulic main pump suction line or in hydraulic main pump pressure line (some people call discharge line or delivery line). The advantage for putting the filter in suction line is we can give extra protection to the pump since the oil is filtered before it enter into the pump. The disadvantage of this practice is it can cause cavitation and damage our pump internal components if not been replaced on time once clogged. Why? Because once the filter clogged, the flow rate of the oil will be decreased and causing the air bubbles created. These bubbles will hit the internal parts of the pump and burst. The energy produced during bursting will make the pump internal parts wear and tear faster. The advantage of putting the filter in pressure line is the risk for your pump cavitation due to clogged filter element is eliminated. The disadvantages are your pump did not have any extra protection and need filter element that can resist high pressure. Normally the filter element rating are around 6 to 10 micron.
Return Line filtration system.
Return line filtration system acts like the last defender for our oil reservoir. It located at the end of the hydraulic system loop. During designing and installation stage, it is a compulsory that all the oil needed to return back to tank must go through this filtration system. Failing to do so, you will be facing problem to control the oil cleanliness. The main function is to trap any dirt from wear and tear hydraulic component inside the system to enter the reservoir back. The filter element for this system will normally clogged faster than other two filtration system. Therefore, the frequency of changing is much more higher. It is crucial to ensure the clogged filter element is replaced on time. Normally the filter element rating is 20 micron.
Filtration system plays big role in hydraulic system. The finest rating for the filter element, the more you need to spend for the cost. However, this system is still needed and the cost consumption is one we need to face it in order to keep our hydraulic system in clean and smooth condition.
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