ISO 18418-2:2022

Gasoline engines - High pressure liquid fuel supply connections - Part 2: Pipe assemblies

This document specifies dimensions and requirements for high-pressure fuel pipe assemblies and assembled pipe sets made of seamless stainless steel or surface-treated steel tubing to be used with 60°concave cone connectors on gasoline (spark-ignition) engines.

Moteurs à essence — Connexions pour des lignes de combustible liquide à haute pression — Partie 2: Lignes assemblées

General Information

• Status: Published
• Publication Date: 31-Oct-2022
• ICS: 43.060.40 - Fuel systems
• Technical Committee: ISO/TC 22/SC 34 - Propulsion, powertrain and powertrain fluids
• Drafting Committee: ISO/TC 22/SC 34/WG 2 - Injection equipment
• Current Stage: 6060 - International Standard published
• Start Date: 01-Nov-2022
• Due Date: 11-Dec-2022
• Completion Date: 01-Nov-2022

Relations

• Revises: ISO 18418-2:2014 - Gasoline engines - Medium pressure liquid fuel supply connections - Part 2: Pipe assemblies
• Effective Date: 23-Apr-2020

Overview

ISO 18418-2:2022 specifies dimensional and performance requirements for high-pressure fuel pipe assemblies and assembled pipe sets used on gasoline (spark-ignition) engines with 60° concave cone connectors. It covers assemblies made from seamless stainless-steel or surface-treated steel tubing for modern gasoline direct-injection (GDI) systems (commonly operating around 35 MPa). The standard defines how pipes, ends and connector nuts are dimensioned, identified, packaged and verified for safe service.

Key topics and technical requirements

• Materials: Acceptable stainless-steel and surface-treated steel tube grades are referenced to ISO 9329-4, ISO 15510 and ISO 8535-1 for material properties and treatments.
• Dimensions & tolerances: Requirements for connector nuts, thread sizes (e.g., M14×1.5, M16×1.5), centreline geometry, developed length, and drawing/data requirements (Cartesian coordinates for bend points).
• Pipe end design: Details for spherical sealing faces to mate with the 60° concave cone (see ISO 18418-1 for cone geometry), and requirements for chamfers, shoulders and minimum thread engagement.
• Cleanliness: Internal bore cleanliness shall be assessed per ISO 19724 and designated using the component cleanliness code (CCC) unless otherwise agreed.
• Bending and formability: Minimum bend radius is 2.125 × outside diameter; ovality of bent portions must not exceed 15%.
• Operating pressure & safety: Permissible operating pressure must include an adequate safety margin below fatigue strength under pulsating pressure and be agreed between supplier and customer.
• Tightening & sealing: Tightening torque and sealing performance are determined empirically for each tube/nut/material combination; leakage testing uses operational fuel and maximum expected pressure.
• Designation, packaging & ID: Standardized tube designation formats and packaging rules to protect mating faces and prevent debris ingress.

Practical applications and users

• Automotive OEMs and powertrain engineers specifying high-pressure fuel lines for GDI systems.
• Tier‑1/2 suppliers manufacturing or assembling high-pressure fuel pipe assemblies and connector nuts.
• Quality, test and validation teams performing sealing, fatigue and cleanliness testing on fuel systems.
• Aftermarket and repair organizations that need replacement components specified to international dimensions and safety practices.

Benefits & keywords (SEO)

Adopting ISO 18418-2 ensures interchangeability, consistent high-pressure fuel pipe assemblies, reliable sealing with 60° concave cone connectors, controlled cleanliness, and predictable mechanical behavior for gasoline direct injection (GDI) systems.

Related standards

• ISO 18418-1 (60° concave cone geometry)
• ISO 7876-4 (vocabulary)
• ISO 8535-1 (high-pressure steel tubes)
• ISO 9329-4 / ISO 15510 (stainless steel specifications)
• ISO 19724 (cleanliness assessment)

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 18418-2
Second edition
2022-11
Gasoline engines — High pressure
liquid fuel supply connections —
Part 2:
Pipe assemblies
Moteurs à essence — Connexions pour des lignes de combustible
liquide à haute pression —
Partie 2: Lignes assemblées
Reference number
© ISO 2022
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
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ISO copyright office
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Phone: [phone]
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Website: www.iso.org
Published in Switzerland
ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Material properties .1
5 Dimensions and tolerances .1
6 Cleanliness . 3
7 Minimum bend radii . 3
8 Pipe end connections . 3
8.1 General . 3
8.2 Type of connection ends . 3
8.3 Pipe end assembly for 60° concave cones . 4
9 Operating pressure . 5
10 Ovality of bending portion . 5
11 Tightening torque and sealing performance . 5
12 Designation . 6
12.1 Stainless-steel tube . 6
12.2 Surface-treated steel tube . 6
13 Packaging and identification .6
Bibliography . 7
iii
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
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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).
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www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 22, Road vehicles, Subcommittee SC 34,
Propulsion, powertrain and powertrain fluids.
This second edition cancels and replaces the first edition (ISO 18418-2:2014), which has been technically
revised.
The main changes are as follows:
— high-strength steel tubes are required as fuel pressure increases;
— additional specification of tubes, already in use worldwide, are added.
A list of all parts in the ISO 18418 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
iv
Introduction
Some spark ignition (SI) engines use direct injection (DI) fuel systems which supply gasoline under
pressure to a rail and to the injectors via pipe assemblies with a 60° concave cone connector. Such
components are similar to ISO 2974 and ISO 13296 for the diesel injection systems except for the
relationship between the outside and inside diameters of the pipes due to the lower pressure range.
GDI fuel systems typically operate in a pressure range of around 35 MPa and are labelled “high
pressure”. In the context of all injections systems, including diesel, this same pressure range is
considered as medium pressure, as diesel injection operates at much higher pressures, however the
term “high pressure” is used in this document.
v
INTERNATIONAL STANDARD ISO 18418-2:2022(E)
Gasoline engines — High pressure liquid fuel supply
connections —
Part 2:
Pipe assemblies
1 Scope
This document specifies dimensions and requirements for high-pressure fuel pipe assemblies and
assembled pipe sets made of seamless stainless steel or surface-treated steel tubing to be used with
60°concave cone connectors on gasoline (spark-ignition) engines.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 7876-4, Fuel injection equipment — Vocabulary — Part 4: High-pressure pipes and end-connections
ISO 8535-1:2016, Diesel engines — Steel tubes for high-pressure fuel injection pipes — Part 1: Requirements
for seamless cold-drawn single-wall tubes
ISO 9329-4:1997, Seamless steel tubes for pressure purposes — Technical delivery conditions — Part 4:
Austenitic stainless steels
...