ISO 6743-4:2015

Lubricants, industrial oils and related products (class L) - Classification - Part 4: Family H (Hydraulic systems)

ISO 6743-4:2015 establishes the detailed classification of fluids of Family H (Hydraulic systems) which belong to class L (Lubricants, industrial oils, and related products). It is intended to be read in conjunction with ISO 6743‑99. This classification system does not include automotive brake fluids or aircraft hydraulic fluids.

Lubrifiants, huiles industrielles et produits connexes (classe L) — Classification — Partie 4: Famille H (Systèmes hydrauliques)

L'ISO 6743-4:2015 établit la classification détaillée de la famille H (Systèmes hydrauliques) qui appartient à la classe L (Lubrifiants, huiles industrielles et produits connexes). Elle est destinée à être lue conjointement avec l'ISO 6743‑99. La présente classification ne s'applique pas aux liquides de freins pour automobiles ni aux fluides pour systèmes hydrauliques utilisés en aéronautique.

General Information

• Status: Published
• Publication Date: 19-Jul-2015
• ICS: 75.120 - Hydraulic fluids
• Technical Committee: ISO/TC 28/SC 4 - Classifications and specifications
• Drafting Committee: ISO/TC 28/SC 4/WG 3 - Joint ISO/TC 28/SC 4 - ISO/TC 131 WG: Classification and specifications of hydraulic fluids
• Current Stage: 9020 - International Standard under periodical review
• Start Date: 15-Oct-2025
• Completion Date: 15-Oct-2025

Relations

• Consolidates: ISO 17072-1:2011 - Leather - Chemical determination of metal content - Part 1: Extractable metals
• Effective Date: 06-Jun-2022
• Revises: ISO 6743-4:1999 - Lubricants, industrial oils and related products (class L) - Classification - Part 4: Family H (Hydraulic systems)
• Effective Date: 24-Sep-2011

Overview

ISO 6743-4:2015 is an international standard developed by the International Organization for Standardization (ISO) that provides a detailed classification system for hydraulic fluids, categorized under Family H of class L-lubricants, industrial oils, and related products. This standard is essential for industries that utilize hydraulic systems for various applications, ensuring consistent classification and specification of hydraulic fluids for optimal performance and safety.

This third edition updates the previous 1999 version to include environmentally acceptable fluids, addressing the growing demand for sustainable industrial practices. It is designed to be used alongside ISO 6743-99, which provides general classification guidance.

Important Note: ISO 6743-4:2015 excludes automotive brake fluids and aircraft hydraulic fluids, focusing solely on industrial hydraulic system fluids.

Key Topics

• Classification System for Hydraulic Fluids
  The standard establishes a structured classification with symbols and codes to identify specific hydraulic fluid categories. Each fluid category is designated by symbols starting with "H" (for hydraulic systems), followed by specific letters indicating the fluid's composition and application.

• Fluid Categories Covered

  • Mineral Oils and Refined Oils: Including non-inhibited mineral oils (HH), improved anti-rust and anti-oxidation oils (HL), anti-wear oils (HM), and oils with enhanced viscosity/temperature properties (HV).
  • Environmentally Acceptable Fluids: Including triglycerides (HETG), polyglycols (HEPG), synthetic esters (HEES), and polyalphaolefin/hydrocarbons (HEPR).
  • Specialized Hydraulic Fluids: For systems requiring anti-stick/slip properties (HG) or those involving water-based fire-resistant fluids (HFAE, HFAS, HFB, HFC).
  • Synthetic Hydraulic Fluids: Including phosphate ester-based (HFDR) and other synthetic compositions (HFDU).

• Viscosity Grading
  Fluid viscosity grades are indicated in accordance with ISO 3448, allowing users to select fluids based on viscosity requirements for specific applications.

• Symbols and Coding
  The unique coding system promotes clarity and uniformity, making it easier for manufacturers, users, and regulators to communicate fluid specifications.

Applications

ISO 6743-4:2015 is widely used across various industrial sectors where hydraulic systems are integral to machine operation and control. Typical applications include:

• Industrial Hydraulic Machinery
  Fluids classified under this standard ensure reliable performance in manufacturing equipment, presses, and metalworking machines.

• Construction and Marine Equipment
  Hydraulic oils designed with enhanced viscosity and temperature tolerance support the robust demands of heavy machinery and marine operations.

• Environmentally Sensitive Operations
  The inclusion of environmentally acceptable hydraulic fluids aligns with regulatory requirements and ecological considerations in forestry, agriculture, and waterway equipment.

• Fire-Resistant Hydraulic Systems
  Water-based emulsions and synthetic hydraulic fluids classified for fire resistance are critical in applications where safety from ignition risks is paramount.

• Multi-Functional Lubrication Systems
  Specialized fluids with anti-stick/slip properties cater to machines that combine hydraulic and plain bearing lubrication, enhancing operational stability during low-speed movements.

Related Standards

For comprehensive understanding and application, ISO 6743-4:2015 should be used in conjunction with related standards within the ISO 6743 series and other pertinent documents:

• ISO 6743-99: Provides general classification principles for class L lubricants and oils.
• ISO 11158: Specifies requirements for fluid categories HH, HL, HM, HV, and HG.
• ISO 12922: Covers specifications for water-based fire-resistant hydraulic fluids (HFAE, HFAS, HFB, HFC) and synthetic fluids (HFDR, HFDU).
• ISO 15380: Specifies standards for biodegradable and synthetic hydraulic fluids like HETG, HEPG, HEES, and HEPR.
• ISO 3448: Defines viscosity grades for industrial liquid lubricants.

Implementing these standards ensures fluid selection matches machinery requirements for efficiency, longevity, and compliance with environmental and safety regulations.

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Keywords: ISO 6743-4:2015, hydraulic fluid classification, industrial lubricants, hydraulic systems, environmentally acceptable hydraulic fluids, hydraulic oil standards, ISO 11158, ISO 12922, ISO 15380, industrial oils, hydraulic fluid viscosity, fire-resistant hydraulic fluids

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 6743-4
Third edition
2015-08-01
Lubricants, industrial oils and related
products (class L) — Classification —
Part 4:
Family H (Hydraulic systems)
Lubrifiants, huiles industrielles et produits connexes (classe L) —
Classification —
Partie 4: Famille H (Systèmes hydrauliques)
Reference number
©
ISO 2015
© ISO 2015, Published in Switzerland
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form
or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior
written permission. Permission can be requested from either ISO at the address below or ISO’s member body in the country of
the requester.
ISO copyright office
Ch. de Blandonnet 8 • CP 401
CH-1214 Vernier, Geneva, Switzerland
Tel. [phone]
Fax [phone]
[e-mail]
www.iso.org
ii © ISO 2015 – All rights reserved

Contents Page
Foreword .iv
1 Scope . 1
2 Normative references . 1
3 Explanation of symbols used . 1
4 Detailed classification . 2
Bibliography . 4
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the meaning of ISO specific terms and expressions related to conformity
assessment, as well as information about ISO’s adherence to the WTO principles in the Technical
Barriers to Trade (TBT) see the following URL: Foreword - Supplementary information
The committee responsible for this document is ISO/TC 28, Petroleum products and lubricants,
Subcommittee SC 4, Classifications and specifications.
This third edition cancels and replaces the second edition (ISO 6743-4:1999), which has been technically
revised with the following change:
— the table of classification now includes environmentally acceptable fluids.
ISO 6743 consists of the following parts, under the general title Lubricants, industrial oils and related
products (class L) — Classification:
— Part 1: Family A (Total loss systems)
— Part 2: Family F (Spindle bearings, bearings and associated clutches)
— Part 3: Family D (Compressors)
— Part 4: Family H (Hydraulic systems)
— Part 5: Family T (Turbines)
— Part 6: Family C (Gears)
— Part 7: Family M (Metalworking)
— Part 8: Family R (Temporary protection against corrosion)
— Part 9: Family X (Greases)
— Part 10: Family Y (Misce
...

NORME ISO
INTERNATIONALE 6743-4
Troisième édition
2015-08-01
Lubrifiants, huiles industrielles
et produits connexes (classe L) —
Classification —
Partie 4:
Famille H (Systèmes hydrauliques)
Lubricants, industrial oils and related products (class L) —
Classification —
Part 4: Family H (Hydraulic systems)
Numéro de référence
©
ISO 2015
DOCUMENT PROTÉGÉ PAR COPYRIGHT
© ISO 2015
Droits de reproduction réservés. Sauf indication contraire, aucune partie de cette publication ne peut être reproduite ni utilisée
sous quelque forme que ce soit et par aucun procédé, électronique ou mécanique, y compris la photocopie, l’affichage sur
l’internet ou sur un Intranet, sans autorisation écrite préalable. Les demandes d’autorisation peuvent être adressées à l’ISO à
l’adresse ci-après ou au comité membre de l’ISO dans le pays du demandeur.
ISO copyright office
Ch. de Blandonnet 8 • CP 401
CH-1214 Vernier, Geneva, Switzerland
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail [e-mail]
Web www.iso.org
Publié en Suisse
ii © ISO 2015 – Tous droits réservés

Sommaire Page
Avant-propos .iv
1 Domaine d’application . 1
2 Références normatives . 1
3 Explications des symboles utilisés . 1
4 Classification détaillée . 2
Bibliographie .4
Avant-propos
ISO (the International Organization for Standardization) is a worldwide federation of national standards
bodies (ISO member bodies). The work of preparing International Standards is normally carried out
through ISO technical committees. Each member body interested in a subject for which a technical
committee has been established has the right to be represented on that committee. International
organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.
ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the meaning of ISO specific terms and expressions related to conformity
assessment, as well as information about ISO’s adherence to the WTO principles in the Technical
Barriers to Trade (TBT) see the following URL: Foreword - Supplementary information
L’ISO 6743-4 a été élaborée par le comité technique ISO/TC 28, Produits pétroliers et lubrifiants,
sous-comité SC 4, Classifications et  spécifications.
Cette troisième édition annule et remplace la seconde (ISO 6743-4:1999) qui fait l’objet d’une révision
technique incluant le changement suivant:
— introduction des fluides acceptables pour l’environnement dans le tableau de classification.
L’ISO 6743 comprend les parties suivantes, présentées sous le titre général Lubrifiants, huiles industrielles
et produits connexes (classe L) — Classification:
— Partie 1: Famille A (Graissage perdu)
— Partie 2: Famille F (Paliers de broche, paliers et embrayages associés)
— Partie 3: Famille D (Compresseurs)
— Partie 4: Famille H (Systèmes hydrauliques)
— Partie 5: Famille T (Turbines)
— Partie 6: Famille C (Engrenages)
— Partie 7: Famille M (Travail des métaux)
— Partie 8: Famille R (Protection temporaire contre la corrosion)
— Partie 9: Famille X (Graisses)
— Partie 10: Famille Y (Autres applications)
— Partie 11: Famille P (Outils pneumatiques)
— Partie 12: Famille Q (Fluides de transfert de chaleur)
iv © ISO 2015 – Tous droits réservés

— Partie 13: Famille G (Glissières)
— Partie 14: Famille U (Traitement thermique)
— Partie 15: Famille E (Huiles pour moteurs à combustion interne
...