Which hydraulic flow dividers are suitable for synchronizing cylinders?

Gear-type (rotary) flow dividers are the most widely used and generally the best-suited option for synchronizing hydraulic cylinders, typically holding accuracy within about 1–3%. Piston-type dividers suit high-pressure, high-accuracy work, while spool-type (pressure-compensated) dividers are a lower-cost choice where moderate accuracy of roughly 5–10% is acceptable. The right choice depends on load balance, operating pressure, required accuracy, and budget. When two or more cylinders must lift, push, or tilt a load together, even a small difference in speed can twist a platform, bind a guide, or overload one side of a structure. Flow dividers are one of the simplest and most reliable ways to solve this problem. This guide explains which types work for cylinder synchronization, how they compare, and what to consider before you specify one.

Why is cylinder synchronization difficult? 

In theory, two identical cylinders fed from the same pump should move at the same speed. In practice they rarely do. Several factors cause them to drift apart:

• Unequal loads: oil takes the path of least resistance, so the lightly loaded cylinder moves first.
• Internal leakage: worn seals let different amounts of oil bypass the piston in each cylinder.
• Manufacturing tolerances: small differences in bore, rod diameter, and seal friction change effective area and speed.
• Oil temperature and viscosity: hot oil leaks more, and the effect is rarely identical on both sides.
• Plumbing differences: unequal hose lengths and fitting restrictions alter flow to each branch.

A flow divider forces the incoming flow to split into controlled, proportional streams regardless of the pressure each branch sees. That is what makes it effective for synchronization.

How a hydraulic flow divider works

A flow divider takes one inlet flow and splits it into two or more outlet flows, usually in equal portions, although unequal ratios such as 2:1 are available for cylinders of different sizes. Unlike a simple orifice or flow control valve, a good divider maintains the split even when outlet pressures differ.

There are three main designs used for cylinder synchronization: gear-type, piston-type, and spool-type.

Gear-type (rotary) flow dividers

A gear-type divider is built from two or more gear sections on a common shaft, each section acting like a small hydraulic motor. Oil entering the divider drives all the gear sections, and because they are mechanically linked, each section must pass the same volume of oil per revolution. The result is a positive, volumetric split.

Advantages

• Good accuracy, commonly within 1–3% under normal conditions
• Works well even when the cylinders see very different pressures
• Can handle a wide flow range
• Available in two, three, four, or more sections
• Robust and widely available

Limitations

• Pressure drop across the divider generates heat
• Efficiency is reduced because of the pressure intensification effect between sections
• Accuracy falls at very low flow rates, where internal leakage becomes a larger share of total flow
• Larger and heavier than spool types

Gear-type dividers are a strong default for mobile equipment, lifting platforms, dump bodies, material handling systems, and general industrial machinery.

Piston-type flow dividers

Piston-type dividers use a rotating group, much like a small axial piston motor, to measure out equal volumes. Because of the tight tolerances in piston construction, leakage is low and accuracy can be very good.

Advantages

• Highest accuracy among the divider types, often better than 1–2%
• Suited to high operating pressures
• Better performance at low flow rates and with low-viscosity fluids
• Good efficiency compared with gear types

Limitations

• Higher purchase cost
• More sensitive to contamination, so fluid cleanliness matters
• Less common in light-duty applications

Choose a piston-type divider where precision matters, such as press platens, heavy lifting equipment, and industrial test rigs.

Spool-type (pressure-compensated) flow dividers

Spool-type dividers use a pressure-compensated spool and fixed orifices to proportion the flow. If one outlet pressure rises, the spool shifts to keep the pressure drop across each orifice similar, which keeps the split roughly even.

Advantages

• Compact and economical
• Lower pressure drop than rotary dividers in many designs
• Simple construction with few moving parts
• Often available with built-in relief or check features

Limitations

• Accuracy is lower, commonly in the 5–10% range
• Not ideal for precise synchronization over long strokes
• Performance depends on flow range and may suffer outside the design window

Spool dividers are a good fit for lightly loaded, cost-sensitive systems such as agricultural implements or simple lifting devices where small position error can be tolerated.

Quick comparison of divider types

Values are typical and vary by manufacturer, so always confirm against the datasheet.

Key factors when selecting a flow divider

Required accuracy

Decide how much position error your machine can tolerate. A tilting platform may accept a few percent, while a press may not.

Flow range and operating pressure

Match the divider to the pump flow and system pressure. Running far below the rated flow reduces accuracy, and exceeding pressure ratings shortens life.

Load variation

If cylinders see widely different loads, a positive-displacement divider (gear or piston) generally performs better than a spool type.

Number of cylinders

Two cylinders may need one divider with two outlets. Three or four cylinders can use a multi-section divider or cascaded units, though accumulated error increases with each stage.

Heat and efficiency

Every divider drops pressure and creates heat. Check that your cooling capacity can handle the added load, especially in continuous-duty systems.

Installation and setup best practices

• Place the divider close to the cylinders to reduce hose volume differences.
• Use matched hose lengths and fittings on each branch.
• Add cross-port relief valves to protect the divider from pressure spikes when a cylinder reaches the end of its stroke.
• Filter the oil well, because contamination increases internal leakage and wear.
• Bleed all air from the circuit before commissioning, since trapped air destroys synchronization.

Why flow dividers alone do not hold perfect sync

No flow divider is perfectly accurate, and small errors accumulate over repeated cycles. Cylinder internal leakage, end-of-stroke conditions, and temperature changes all add drift. For this reason, many systems add a rephasing method, such as

• Cylinders bottoming out at full stroke to reset position each cycle
• Re-phasing check valves or ports that let oil bypass at stroke end
• Position sensors with proportional or servo valves for closed-loop control

When very tight synchronization is needed over a long distance, a closed-loop electro-hydraulic system is usually a better answer than a divider alone.

Common mistakes to avoid

1. Choosing a spool divider for a high-accuracy application
2. Running the divider well below its minimum flow
3. Ignoring pressure spikes at the end of the stroke
4. Using mismatched cylinders without adjusting the divider ratio
5. Neglecting filtration and fluid cleanliness
6. Forgetting to account for heat generation

For most cylinder synchronization jobs, gear-type flow dividers offer the best balance of accuracy, durability, and cost. Piston-type dividers are worth the extra investment when precision and high pressure are critical, and spool-type dividers work well where budgets are tight and small errors are acceptable. Whichever type you choose, good installation, clean oil, and a plan for periodic rephasing will make the difference between a system that stays aligned and one that slowly drifts out of step.

1. What is the most accurate type of flow divider for synchronizing cylinders?

Piston-type flow dividers are generally the most accurate, often achieving better than 1–2% error, with gear-type dividers close behind at about 1–3%.

2. Can a flow divider keep cylinders perfectly synchronized?

No. Flow dividers greatly improve synchronization but cannot eliminate drift caused by leakage and temperature, so many systems include a re-phasing feature or closed-loop control.

3. Why does my flow divider generate heat?

The divider creates a pressure drop as oil passes through it, and that energy is converted to heat. Larger drops and higher flows produce more heat.

4. Can I use a flow divider with cylinders of different sizes?

Yes, if you select a divider with a matching split ratio, such as 2:1, so that each cylinder receives flow in proportion to its volume.

5. When should I use servo or proportional valves instead of a flow divider?

Use closed-loop servo or proportional valve control when you need very tight position accuracy, long strokes, or variable speed profiles that a flow divider cannot reliably deliver.