ISO 4411:2019

Overview

ISO 4411:2019 - "Hydraulic fluid power - Valves - Determination of differential pressure/flow rate characteristics" specifies standardized methods to measure the pressure differential produced by fluid flow through any path in a hydraulic valve under steady‑state conditions. The standard defines test installations, measurement procedures and how results must be presented so that valve differential pressure/flow characteristics are comparable across manufacturers and test laboratories.

Key topics and requirements

• Test installations and circuit: requires a controllable flow supply, relief protection and defined locations for pressure and temperature measuring points. Straight, uniform‑bore tube lengths are specified to establish flow profiles (for example, lengths of at least 10d and 5d at upstream/downstream tapping points).
• Pressure‑tapping: single static pressure tappings are used and must not be located at the lowest point of a tube. Subplate-mounted valves can use standard pressure‑tapping plates.
• Measurement classes: three accuracy classes (A, B, C) are defined. Permissible systematic errors during calibration include, for example, flow rate ±1.0 / ±2.0 / ±3.0 % and differential pressure ±1.0 / ±3.0 / ±5.0 % for classes A, B and C respectively.
• Test fluid and properties: use a valve‑manufacturer‑approved fluid; record mass density (ρ) and kinematic viscosity (ν). For class A/B accuracy, density and viscosity must be measured from samples taken immediately before testing.
• Temperature control: fluid temperature must be controlled; permitted temperature variation depends on accuracy class (see ISO 4411 Table 3).
• Steady‑state measurements and procedure: only record readings after steady‑state is reached; measure upstream and downstream pressures and calculate pressure differential (including tare correction where required).
• Presentation of results: standard prescribes the format and units for presenting differential pressure/flow rate curves and accompanying measurement data.

Applications and users

ISO 4411:2019 is intended for:

• Hydraulic valve manufacturers for product development and specification verification.
• Independent test laboratories performing comparative valve tests.
• OEMs and system integrators specifying valve performance for hydraulic systems.
• Procurement and quality departments requiring consistent test evidence for acceptance or certification.

Practical applications include specifying pressure loss for directional control valves, flow‑control devices and pressure‑sensitive components used in mobile and industrial hydraulic systems.

Related standards

Relevant normative references in ISO 4411:2019 include:

• ISO 4401, ISO 6263, ISO 6264, ISO 10372 (mounting/interface standards)
• ISO 5598 (fluid power vocabulary)
• ISO 9110‑1 and ISO 9110‑2 (measurement techniques)
• ISO 5781 (mounting surfaces for certain valves)

Keywords: ISO 4411:2019, hydraulic fluid power, valves, differential pressure, flow rate characteristics, test procedures, measurement accuracy, pressure tapping, steady‑state testing.