I. Explanation of Model Numbers

D631: 631 Series Two-stage Mechanical Feedback Servo Valve

Z: Non-explosion-proof, standard industrial environment

820: Flow code 80 L/min (Δp = 35 bar); Last digit 0 = Standard Leak Valve Core

C: Internal Pilot + FPM (fluorine rubber) seal (high-temperature type)

Sentence: Z820C = 80L/min High Flow + Internal Pilot without External Connection + FPM High-Temperature Seal + Standard Leakage Universal Type

II. Core Parameters (Δp = 35 bar)

Rated Flow: 80 L/min

Maximum Pressure: 315 bar

Frequency Response (−3dB/90°): 40–50 Hz (Standard Response for High Flow)

Step Response: 35–40 ms

Hysteresis: ≤0.3%

Resolution: ≤0.1%

Zero Leakage: ≈0.50 L/min (Standard Leakage, Type 0)

Pilot Method: Internal Pilot (No X Port Required)

Seal / Temperature: FPM (−20 to +120°C)

Filter: NAS 6–7 / ISO 4406 14/11

III. Comparison of 820C and 803C (Two Brothers of 80L Internal Pilot) Table

Parameters: D631Z820C, D631Z803C

Flow rate: 80 L/min, 80 L/min

Pilot: Internal, Internal

Leakage type: 0 = Standard leakage (≈0.50 L/min), 3 = Low leakage (≈0.30 L/min)

Sealing: FPM high temperature, FPM high temperature

Power consumption: Slightly higher (standard leakage), Lower (energy-saving)

Price: Economical (general model), More expensive (energy-saving model)

Applicability: Regular continuous operation, Long-term standby / Energy-saving priority

Sentence: 820C has standard leakage and is cheaper; 803C has low leakage and is more energy-efficient.

Four. Quick Overview of 80L Series (820/803/804)

Z820C: 80L, Internal pilot, FPM, Standard leakage (0), Economical general model

Z803C: 80L, Internal pilot, FPM, Low leakage (3), Energy-saving high-end model

Z804C: 80L, Internal pilot, FPM, High leakage (4), Large flow rate quick response

Five. Application Scenarios (Z820C)

Heavy-duty presses, large injection mold locking / injection, die-casting machines

Metallurgical conventional rolling, large hydraulic cylinder synchronization, platform positioning

High temperature (≤120℃), ordinary hydraulic oil, continuous operation

Internal pilot, cost control, stable and reliable closed-loop system