SUN HYDRAULICS CORP
PSDLLBN812
Electro-Proportional

This electro-proportional, direct-acting reducer/reliever valve reduces a high primary pressure at the inlet (port 2) to a constant reduced pressure at port 1, with a full flow relief function from port 1 to tank (port 3). The valve is biased to the relieving mode. Energizing the coil connects port 2 to port 1. Increasing the current to the coil will proportionally increase the reduced pressure at port 1. If pressure at port 1 exceeds the setting induced by the coil, pressure at port 1 is relieved to port 3. Draining port 4 makes the valve insensitive to pressure at port 3. This valve is open in the transition from reducing to relieving which provides good pressure control and dynamic response. Optional full manual control is available.

• Maximum pressure at port 3 should be limited to 3000 psi (210 bar).
• All spring ranges are tested for correct operation with 5000 psi (350 bar) inlet pressure.
• Direct acting concept provides highly reliable operation in contaminated systems, especially at dead headed conditions.
• Pressure on the drain (port 4) is directly additive to the valve setting at a 1:1 ratio and should not exceed 5000 psi (350 bar).
• Leakage specified in Technical Data is out of port 3 with a supply pressure of 2000 psi (140 bar) and the valve set at mid range. This leakage is directly proportional to pressure differential and inversely proportional to viscosity expressed in centistokes.
• The transition from reducing to relieving is slightly open. The result is very good pressure control with oil consumption of about 0.1 gpm (0,4 L/min.).
• For optimum performance, an amplifier with current sensing and adjustable dither should be used. Dither should be adjustable between 100 - 250 Hz.
• Full reverse flow from reduced pressure (port 1) to inlet (port 2) may cause the main spool to close. If reverse free flow is required in the circuit, consider adding a separate check valve to the circuit.
• Uses for the 'L' manual screw adjustment include: emergency valve setting during power failure or alternatively boosting the valve setting
• With the 'L' adjustment screw, all ranges are factory set at zero (adjustment screw fully backed out). With the coil de-energized, clockwise adjustment of the screw will increase the spring bias load up to the maximum setting for that range. With the coil energized, any mechanical pressure setting is directly additive to the coil induced value.
• By controlling the pressure at the drain (port 4), the effective setting of the valve can be increased over the nominal valve setting.
• Incorporates the Sun floating style construction to minimize the possibility of internal parts binding due to excessive installation torque and/or cavity/cartridge machining variations.

Additional Resources

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• Sun Expands Corrosion-Resistant Solutions
• Sun Cartridges with EPDM Seals
• Weatherized Solenoid Valves for Harsh Environments
• Configure Your Bluetooth Embedded Amplifier with AmpSet Blue™
• Series 4 PLUS Cartridges Offer Higher Flows with Lower Pressure Losses
• QuickDesign with SmartConnect Offers Drag-and-Drop Schematic Tool
• Electro-Proportional Basics Explained
• Proportional Amplifiers and Ancillary Products
• Manufacturing Sun Cartridge Cavities
• Solenoid Coils for Switching and Proportional Valves
• Reducing and Reducing/Relieving Valves
• Electro-Proportional Cartridge Valves
• Electro-Proportional Terms and Definitions
• Cavity Information (S-171) and Tooling
• Sun's Floating Style Screw-In Cartridge
• Fluid and Temperature Recommendations
• Sun Model Code Explanation; 999-901-334
• Performance Data
• Cartridges: Materials of Construction
• Units of Measure, Settings, and Conversions

• Please verify cartridge clearance requirements when choosing a Sun manifold. Different valve controls and coils require different clearances.