ISO 4926:2020

Overview

ISO 4926:2020 is an international standard that specifies the composition and characteristics of a non-petroleum-based reference fluid used for compatibility testing of hydraulic braking systems and their components in road vehicles. Published by the International Organization for Standardization (ISO), this third edition replaces the 2006 version with significant technical revisions aimed at improving fluid formulation and compliance with related standards.

The standard ensures consistent testing conditions by defining a precise chemical makeup of the reference fluid, which plays a crucial role in evaluating hydraulic brake system performance, safety, and component compatibility. This reference fluid is essential for manufacturers and testing laboratories involved in hydraulic brake system development and certification.

Key Topics

• Reference Fluid Composition
  The fluid is composed of specific glycol ethers and additives in defined mass fractions:

  • Borate of triethylene glycol monomethyl ether (around 50%)
  • Triethylene glycol monomethyl ether (27.5%)
  • Tetraethylene glycol monomethyl ether (10%)
  • Triethylene glycol monobutyl ether (10%)
  • Diisopropanolamine (2%)
  • Tolyltriazole (0.5%)
    This precise formulation enhances testing reliability and safety.

• Chemical and Physical Requirements

  • Water content: ≤ 0.20% measured per ASTM D 6304 (Coulometric Karl Fischer Titration)
  • Reserve alkalinity: 15.5 ml according to ASTM D 1121
    These parameters ensure the fluid maintains stability and compatibility during testing.

• Compliance with ISO 4925
  The reference fluid complies with ISO 4925, the specification for non-petroleum-based brake fluids, reinforcing standardized quality for hydraulic braking applications.

• Application Scope
  ISO 4926 targets compatibility testing of hydraulic braking systems, crucial for verifying brake fluid behavior with system seals, metals, elastomers, and other components in road vehicles.

Applications

• Hydraulic Brake System Development
  Automotive engineers and manufacturers use the ISO 4926 reference fluid to assess material compatibility and fluid performance during product development cycles.

• Component Testing and Quality Assurance
  Testing laboratories apply this reference fluid in standardized procedures to validate seals, hoses, valves, and master cylinders for tolerance to brake fluids and environmental factors.

• Regulatory and Certification Processes
  Compliance with ISO 4926 supports regulatory approval by providing a recognized benchmark fluid for compatibility tests, facilitating safer and more efficient hydraulic braking systems.

• Research and Innovation
  Researchers developing new non-petroleum-based brake fluids and additives leverage this standard’s defined fluid composition to benchmark and compare novel formulations.

Related Standards

• ISO 4925: Specification of non-petroleum-based brake fluids for hydraulic systems, setting broader quality criteria for brake fluids used in road vehicles.

• ASTM D 6304: Standard Test Method for Determination of Water in Petroleum Products, Lubricating Oils, and Additives by Coulometric Karl Fischer Titration, referenced for water content measurement.

• ASTM D 1121: Standard Test Method for Reserve Alkalinity of Engine Coolants and Antirusts, referenced for reserve alkalinity determination critical to brake fluid stability.

Summary

ISO 4926:2020 ensures reliable compatibility testing of hydraulic braking systems through a clearly defined, non-petroleum-based reference fluid formulation. By adhering to this standard, manufacturers, testers, and certifiers ensure hydraulic brake system components meet crucial safety, performance, and durability requirements. This contributes to improved vehicle braking safety standards worldwide while supporting innovation in eco-friendly brake fluid technologies.