// Catalogue

Pilot Operated Valves for Big Flow Control

Pilot-operated valves use a small pilot stage to shift a much larger main spool, so a compact coil or air signal can control big hydraulic and pneumatic flows. TSA Hydraulics Engineering supplies them within the Directional Control family of our Valves range.

A pilot valve borrows the system’s own pressure to do the heavy lifting. Clever, until the pressure drops and the valve refuses to shift. Internal or external pilot and drain decide how it behaves, so check the code letters. Send us the full model code, and we will match a factory original or an equivalent with the same pilot setup.

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// Buying guide

How a Pilot Operated Valve Works

The valve has two stages stacked together:

The pilot stage, usually a small solenoid valve, directs a little oil or air.
That pilot flow pushes on the ends of the main spool.
The main spool shifts and controls the full flow between the ports.

Because the coil only moves the small pilot spool, it stays compact and cool, even on large valves. Most hydraulic directional valves from NG10 (CETOP 5) upward are pilot operated.

Internal or External Pilot?

Internal pilot: the pilot oil or air is taken from the main pressure port. It is simple and neat, but the valve needs a minimum pressure to shift, often around 5 bar on hydraulic valves and 2 to 3 bar on air valves.
External pilot: the pilot supply comes from a separate line. This is needed when the main pressure can drop too low to shift the valve.

Here is a classic trap. A valve with a tandem or open centre unloads the pump in neutral, so the pressure falls and an internally piloted valve cannot shift out of centre. The fix is an external pilot supply, or a back pressure check valve in the pressure line.

Internal or External Drain?

On hydraulic valves, the pilot stage also needs a drain path back to tank. With an internal drain, it shares the main tank port. If that tank line carries back pressure, such as from a cooler or filter, use an external drain through a separate line, or the valve may not shift cleanly.

Smoother Shifting

Large spools can shift hard and send a shock through the pipework. Many pilot-operated valves offer:

Pilot chokes: small adjustable restrictors that slow the main spool.
Stroke limiters: screws that limit how far the spool travels, trimming the flow.
Soft shift options: built in damping for smoother starts and stops.

Air Pilot Valves

In pneumatics, a pilot valve can be switched purely by an air signal from another valve, a push button or a limit valve. With no electrics at the valve itself, these valves suit wet areas, simple machines and places where sparks are a risk, such as some mine sites and paint shops.

Quick Troubleshooting

Valve will not shift: check the pilot pressure, and whether the pilot is internal or external.
Shifts slowly or unevenly: check the pilot chokes, and check the drain line for back pressure.
Shifts with a bang: add or adjust pilot chokes.
Coil works but nothing moves: dirt may be blocking the pilot stage.

Pilot Operated Valves Specifications to Check

Size: pneumatic port size
Spool symbol and centre type
Internal or external pilot, and internal or external drain
Minimum and maximum pilot pressure
Pilot actuation: solenoid, air, hydraulic or manual
Pilot chokes or stroke limiters, if fitted

Why Buy From TSA Hydraulics Engineering

As a pilot-operated valves supplier, we read the pilot and drain letters in the code, not just the size and spool. You get clear prices in AUD, OEM or equivalent options, and help sourcing pilot-operated valve replacement parts such as pilot valves, coils and seal kits. We tell you upfront whether a valve is genuine or an equivalent.

// FAQs