# Objectives

The typical hydraulic system is made up of many components. This has the potential to create various competing flow paths.

It is important to understand where flow should be travelling through a system, and in the case of troubleshooting, where flow could be travelling if a component is not functioning correctly.

The typical hydraulic system is made up of many components. This has the potential to create various competing flow paths.

It is important to understand where flow should be travelling through a system, and in the case of troubleshooting, where flow could be travelling if a component is not functioning correctly.

We will explain the concepts behind series and parallel circuits.

We will explain the concepts behind series and parallel circuits.

And we will look at how to determine the pressure in a branch of a circuit, as well as the total system pressure.

And we will look at how to determine the pressure in a branch of a circuit, as well as the total system pressure.

Finally, we'll use this information to establish the path of least resistance.

Finally, we'll use this information to establish the path of least resistance.

# What is a Parallel Circuit?

Even basic hydraulic systems usually have more than one possible flow path.

Pump > Motor > ReservoirPump > Relief Valve > Reservoir

That is to say, once the pump has drawn in fluid from the reservoir, there is more than one potential path through valves and actuators for fluid flow back to the reservoir.

The flow paths or branches are said to be in parallel with each other.

# For Example...

Consider the most basic log splitter.

It has one flow path from pump to reservoir via the flow control valve and cylinder.There is another path to reservoir through the relief valve, if it were to open up.

# What is a Series Circuit?

If there is a flow path from one component to another those components are considered to be connected in series.

Check Valve > Orifice > Ball Valve > Motor

Each component can exert a restriction on the circuit and each restriction, (essentially a load) in series with the next, has a cumulative effect on the total pressure at the beginning of the branch.

# For Example...

Directional/Flow Control Valve
Cylinder
Directional/Flow Control Valve
Cylinder

An example of a series circuit would be a directional control valve which leads to a cylinder. The noticeable loads in series would be the cylinder pushing a log and the directional/flow control valve.

# Pressure Drops

If you were to take a pressure reading of an active hydraulic circuit immediately before a load...

You would see that the second reading is lower than the first reading. The difference between the two readings is known as a pressure drop.

You would see that the second reading is lower than the first reading. The difference between the two readings is known as a pressure drop.

The pressure drop is equivalent to the resistance to flow imposed by the load.

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