Open and Closed Circuit Hydraulic Pump Systems 101

If you are familiar with hydraulic systems, two common hydraulic circuits used are open loop and closed loop. Each type of circuit has its advantages and disadvantages. Understanding the difference between open loop vs. closed loop hydraulics is essential to ensure you are using the best circuit design for your hydraulic system.

What Is an Open Loop Hydraulic Circuit?

An open loop circuit is where the inlet to the hydraulic pump and the return flow on the hydraulic motor or actuator are connected to the hydraulic fluid reservoir. The system can include relief and other control valves that direct fluid to the actuators and then back into the reservoir.
 

Advantages of an Open Loop Circuit

• Ideal for hydraulic systems that operate at lower pressures
• Only option for circuits that contain actuators other than motors
• Cost less to configure and design
• Easier to maintain
• Fairly straightforward to diagnose and find problems

Disadvantages of an Open Loop Circuit

• Fluid reservoir must be large enough to allow for proper fluid cooling
• Hydraulic system could generate excessive heat if the reservoir is too small

What Is a Closed Loop Hydraulic Circuit?

A closed loop circuit is where the return on the motor is connected to the inlet on the hydraulic pump. A small gear pump is used as a charge pump to pump cooled fluid into the closed loop circuit.
 

Advantages of a Closed Loop Circuit

• System uses a much ; only needs to contain enough fluid to supply the
• Well-suited for drive applications and hydrostatic transmissions
• Works well with higher pressure s and pumps
• Systems run at much higher pressures than most
• Less fluid required; majority of fluid contained inside the
• Direction of fluid flow can be reversed without requiring
• Pump case drain fluid replaced by fluid supplied to the pump via the charge pump
• Allows system designers more flexibility in designing system controls

Disadvantages of a Closed Loop Circuit

• Costs more to configure and design
• Can be more challenging to diagnose and find problems
• Replacement pumps, motors, and parts can cost more
• High-pressure hydraulic fluid filtration necessary

Which Circuit Is the Best?

Deciding whether an open loop or closed loop hydraulic system is best depends on the system design and its intended functions. An open loop pump configuration is best for systems that will be supplying non motor actuators such as cylinders or rotatiors. Conversely, closed loop systems are better for wheel and track drive motors on mobile machines and mobile equipment.
 
For further assistance or help to decide whether open loop vs. closed loop hydraulic systems are best for your application, please feel free to contact White House Products, Ltd. at +44 (0) 1475 742500 today!

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