You're selecting a new hydraulic distributor. You already know you need the CETOP 03 standard, a 24V power supply, and a flow rate of 60 l/min. You look in the catalog, and there's a wall of letters waiting for you: 4WE6E , 4WE6G , 4WE6J ... What do they mean?
This single letter in the product code represents the most important parameter of the entire valve – the spool type (flow pattern) . It determines what happens to the oil when the coils are de-energized (in the neutral position). Choosing the wrong letter is a guaranteed disaster: from sagging charges, to ruptured hoses, to a literally burnt-out hydraulic pump.
In this guide, BRhydraulic experts will decipher the 4 most popular industrial slider designs for you. We'll explain how they work and which machines they should be used for.
1. Scheme E (Slider Cut Off / Closed Center)
This is the simplest and most common slide valve in industrial systems with variable displacement pumps.
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How it works in neutral position (no current): All four ports (P - supply, T - return, A and B - outputs to the actuator) are completely cut off and blocked .
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What this means in practice: Oil from the pump cannot flow through the valve into the tank (port P is closed). At the same time, the cylinder is hydraulically blocked (ports A and B are closed), so the load hangs stably in the air.
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Application: Industrial presses, injection molding machines and systems in which the pump itself reduces its flow to zero when the pressure in the system increases (multi-piston pumps).
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⚠️ Warning: Never use an E-spool in simple gear pump (constant displacement) systems without an additional relief valve! The pump will immediately fail without a place to push the oil.
2. Scheme G (Pump Unloading / Tandem Center)
This is an absolute standard in smaller systems powered by cheap gear pumps.
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How it works in neutral position: The actuator output ports (A and B) are blocked, but the supply channel from the pump (P) is open and connected directly to the drain to the tank (T) .
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What this means in practice: The actuator is locked and holds the load. However, the oil pumped by the actuator can flow freely through the valve and return to the reservoir without pressure buildup.
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Applications: Hydraulic power units (power packs) with constant displacement pumps, smaller workshop presses, and splitting machines. The G slide allows the pump to "rest" (run without load) when the machine is idle, preventing oil overheating.
3. Diagram J (Motor slide open)
Moving on to rotary drives. Hydraulic motors operate under their own rules due to their powerful inertia.
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How it works in the neutral position: The supply port (P) is blocked. However, the receiver ports (A and B) are open and connected to the tank drain (T) .
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What this means in practice: If you're driving a heavy drum or drill and suddenly release the button, the hydraulic motor will try to keep spinning under momentum (actually becoming a pump). The J-spool allows it to draw oil from port T and push it out the other side, allowing the motor to coast to a smooth stop.
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Application: Drive of hydraulic motors (e.g. drilling rigs, winches with mechanical brake, wrapping machines).
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⚠️ Warning: Using an E (closed) slide on a hydraulic motor will cause the pressure to burst the hoses or destroy the motor shaft when stopped!
4. Scheme H (Full Flow / Open Center)
This is the "maximum open" slider.
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How it works in neutral position: All ports (P, T, A, B) are connected to each other.
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What this means in practice: Oil from the pump flows freely into the reservoir, relieving the system. At the same time, the actuator ports remain open for overflow.
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Application: Systems in which the actuator or motor must move completely freely under the influence of external forces (e.g. free-falling arm under its own weight or floating arm in agricultural machinery).
Summary
When ordering a distributor, always check the seventh or eighth character in the manufacturer's code.
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Holding weight and having a variable pump? Select E.
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Holding weight and having a gear pump? Select G.
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Driving a motor with high inertia? Select J .
Looking for a valve for your project? At BRhydraulic, we stock CETOP 03, 05, 07, and 10 manifolds with every possible spool configuration. Check out our category. Hydraulic slide solenoid valves and choose the equipment that suits your machine.