When designing a hydraulic circuit, an open or closed-circuit filtration system needs to be decided on to optimise the circuit’s performance by maintaining fluid cleanliness and preventing premature wear. This all contributes to increasing the lifespan of the circuit. With regards to maintaining a filtration system, working closely with the filter manufacturer is important as every circuit is unique.
A closed circuit design
This type of design will either make use of a suction line filtration or a charge pressure filtration for partial or full flow. The suction line filtration occurs when the filter is placed in the circuit between the fluid reservoir and the inlet to the closed-circuit pump. Refer to the manufacturer’s recommendation for bypass vs non-bypass filter in the suction line. When a filter needs to be changed a contamination monitor will send an alert when the vacuum level is reached.
Charge pressure filtration is achieved when the filter is designed into the charge circuit of the closed-circuit pump. This can lessen high inlet vacuum during cold start-up conditions, and fluid filtration is immediate ahead of a pump’s control and the hydraulic loop. Charge pressure filtration can be divided into either partial flow or full flow. Partial flow filtration occurs when the charge pressure relief valve is located upstream of the filtration, while full flow filtration has the charge pressure relief valve downstream. Partial flow filtration has a portion of the charge pump oil which flows through the filter while the remaining oil flows over the charge pressure relief valve back to the reservoir. The full flow allows
An open circuit design
In an open circuit design suction filtration is not recommended as there is high possibility that high inlet vacuum can occur. It is recommended to place a screen in the reservoir covering the pump inlet. When it comes to open circuits the most preferred method is return line filtration which allows all the fluid in the system to pass through the filter as it returns to the reservoir.
Choosing the correct circuit design provides protection from contamination of the hydraulic system which can occur during assembly and operation. A contaminated system causes unnecessary wear and tear which affects the lifespan of the components, and therefore it is important that only clean fluid enters the circuit.
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