What Is a Hydraulic Flow Divider? What Does It Do?

In our hydraulics and pneumatics lecture notes, hydraulic systems section, we’ve dedicated this post to hydraulic flow dividers. In this article, we’ll cover the differences between two styles of hydraulic flow divider and what needs to be done to resolve issues that can arise from incorrect applications.

Hydraulic Flow Divider

As machining processes and manufacturing efficiency increase, hydraulic components are becoming increasingly smaller, more expensive, and more complex. For flow dividers, what used to require a fairly bulky pair of mechanically coupled gear motors has now been reduced down to a cartridge valve.

What Does a Hydraulic Flow Divider Do?

Why is a hydraulic flow divider used? There are often two actuators that need to be synchronized with each other. When designing a linkage mechanism between two actuators, it’s not possible or practical to keep things synchronized. Another option is to control the oil flow to each actuator. The total available flow can be split in half (or in other ratios) so that the total motion on each side is a specific, predictable amount.

Types of Hydraulic Flow Dividers

The principle a gear-type flow divider operates on is positive displacement. This means there’s a specific volume displaced for every rotation. It’s unaffected by pressure (mostly). Join the shafts of two gear motors together, “T” the inlets together, and separate the outlets, and you have a gear-type flow divider.

The operating principle of a spool-type or cartridge-type flow divider is pressure compensation. This means that, with a spool on each side, it shifts to balance the pressure needed for the oil to take both paths. Since fluid follows the path of least resistance, there must be equal resistance on both sides to allow the same amount of flow on each side.

How Are Hydraulic Flow Dividers Selected?

Of course, every approach has its advantages and disadvantages. The cost of a new spool/cartridge-type flow divider is lower than that of a gear type. Gear-type dividers are much larger and heavier, but they’re more tolerant of contamination.

An important disadvantage of spool-type hydraulic flow dividers is their sensitivity to pressure fluctuations. In the event of a leak on one leg, all flow-dividing capability is lost, and the spool-type divider can essentially become a “T.” Another potential issue with spool-type dividers is heat generation. They operate by creating a pressure drop, which generates heat. If they don’t generate heat, they don’t work. Under ideal conditions, both styles can potentially be accurate to within 2% or better.

Generally speaking, if we have no concerns regarding cost, dimensions, or weight, a gear-type flow divider will always be the best-performing type of hydraulic flow divider. In situations with minimal overrunning loads, choose the spool-type divider, or make sure the overrunning loads are controlled by another method, such as counterbalance valves, or that the divider is placed in a “meter-out” position. Carefully consider the amount of heat that will be generated by the created flow and pressure drop.

Another important point is the possibility that a spool-type hydraulic flow divider may, in some cases, slow the actuators down compared to a gear type. If an overrunning load is a significant part of a cycle time, then trying to use a spool-type divider to control this load ultimately won’t be an acceptable solution.

If you’re aware of the disadvantages of a spool-type flow divider and ultimately decide the advantages are more valuable, using a compact cartridge-style flow divider will give your company a cost advantage. This can create a competitive advantage for your product. Otherwise, go with the gear-type flow divider.