MOOG D691-072D

Product Introduction

D691-072D is high-flow two-stage electro-hydraulic proportional servo valve equipped with patented MOOG SERVOJET flapper-less pilot drive architecture and fully integrated on-board control electronics. Simultaneously realizes independent closed-loop flow control and pressure closed-loop control via dual analog command input signals, combining proportional flow regulation and pressure limiting functions within single valve body.
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Description

Technical & Hydraulic Specifications

  • Valve Architecture: Two-Stage SERVOJET® flapper-less pilot stage + main spool flow control stage
  • Mounting Standard: ISO 4401 Size 05 four-port manifold mounting interface
  • Maximum Supply Operating Pressure: 350 bar (5000 psi)
  • Rated Flow Capacity @ 70 Bar Pressure Drop: 220 L/min
  • Dual Independent Control Command Signals: Flow command ±10 VDC; Pressure command ±10 VDC / 4–20 mA dual signal compatibility
  • Spool Step Response Time (0–90% Full Stroke): ≤12 ms
  • Hysteresis Performance Index: ≤1.5% full rated spool stroke
  • Flow Gain Linearity Deviation: ≤5% full operating range
  • Maximum Null Drift Deviation: ±2% full stroke across full operating temperature band
  • Permitted Hydraulic Fluid Temperature Range: -40 °C to +150 °C
  • 90° Phase Lag Dynamic Response Frequency: 45 Hz at 30% rated stroke signal
  • Fluid Cleanliness Standard Requirement: ISO 4406 Code 16/13 maximum particulate contamination
  • On-Board Electronic Supply Voltage: ±15 VDC dual isolated analog power supply

Functional Features

  1. Dual independent closed-loop control channels: spool position flow loop and load pressure feedback pressure control loop
  2. Integrated on-board signal conditioning electronics with differential spool position feedback and pressure signal amplification circuits
  3. Separate analog output monitoring ports for real-time spool position actual value and load pressure actual value signal transmission to upper controller
  4. Hardware enable signal threshold circuit (valve activation above +8.5 VDC enable input signal)
  5. Built-in pressure limiting override function to cap maximum hydraulic load pressure independent of flow command signal
  6. Thermal over-temperature protection circuit cutting pilot stage drive current upon electronic housing overheating

Working Principle

Dual analog command signals (flow setpoint, pressure setpoint) input to valve integrated electronics module; LVDT spool position sensor provides real-time flow feedback signal, external pressure transducer load pressure signal provides pressure closed-loop feedback. On-board electronics calculate differential error signals for flow and pressure loops simultaneously, output calibrated drive current to SERVOJET pilot stage linear force motor. Pilot stage hydraulic flow displaces main control spool to modulate actuator port flow volume; pressure override circuit prioritizes pressure limiting control when load pressure exceeds setpoint value to protect mechanical tooling. Integrated electronics continuously transmit spool position and pressure actual feedback signals to external motion controller for system closed-loop synchronization.

Material Composition

  • Main Valve Body: Forged high tensile carbon steel, hard chrome plated internal flow passages
  • Main Control Spool: Precision ground martensitic stainless steel with plasma nitride surface hardening
  • SERVOJET Pilot Stage Force Motor: Rare-earth permanent magnet silicon steel laminated stator assembly
  • LVDT Spool Position Sensor: Sealed stainless steel tube with PTFE hydraulic fluid isolation sleeve
  • Pressure Feedback Interface Seal: High-temperature FKM fluorocarbon elastomer O-rings
  • Electronic Enclosure: Die-cast aluminum alloy IP65 sealed housing with ribbed passive heat dissipation fins

Structural Characteristics

  • Standard ISO 4401 Size 05 bottom manifold mounting flange with calibrated mounting bolt torque specification
  • Side dual sealed multi-pin electrical connector terminal block for flow command, pressure command, feedback monitoring and power supply wiring
  • Axial integrated LVDT spool position sensor coaxial with main control spool
  • External pressure transducer mounting port integrated on valve side body for direct load pressure feedback signal acquisition
  • Ribbed die-cast aluminum electronic housing bonded to valve main body for shared hydraulic fluid temperature heat dissipation

Advantage Highlights

  1. Single valve hardware realizes synchronized flow + pressure dual closed-loop control eliminating separate pressure reducing valve components
  2. SERVOJET flapper-less pilot stage design delivers superior contamination resistance versus traditional flapper-nozzle two-stage servovalves
  3. Wide -40 °C to +150 °C fluid temperature operating range compatible with high-temperature hot forging hydraulic oil systems
  4. On-board integrated electronics remove requirement for external separate servo valve amplifier hardware
  5. Dual analog monitoring output signals simplify upper motion controller closed-loop signal wiring layout
  6. High 220 L/min rated flow capacity suitable for large tonnage hydraulic press rapid actuator stroke movement

Applicable Industries

Large tonnage metal forging hydraulic presses, high-tonnage injection molding machinery, aluminum extrusion hydraulic control lines, heavy-duty composite material forming equipment

Installation Requirements

  1. Mount to precision machined ISO 4401 Size 05 steel manifold with mounting bolt torque calibrated to 45 N·m
  2. Install 3 μm absolute rating inline hydraulic filter upstream of valve supply inlet port
  3. Dual-shielded twisted pair cabling mandatory for flow/pressure command and feedback analog wiring, single-end shielding grounding at motion controller cabinet
  4. Mount pressure transducer directly to valve integrated side pressure feedback port to eliminate long pressure signal tubing delay

Usage Precautions

  1. Maintain hydraulic fluid particulate contamination level below ISO 4406 16/13 to prevent SERVOJET pilot stage flow path clogging
  2. Do not exceed 350 bar maximum supply pressure to avoid permanent main spool body deformation
  3. Perform bi-annual LVDT zero offset calibration and pressure feedback signal gain adjustment per factory maintenance manual
  4. Replace all FKM sealing elastomers every 4000 operating hours to prevent high-temperature hydraulic oil leakage
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