EN 3658:2008

Aerospace series - Tube bend radii, for engine application - Design standard

This standard provides details of bend radii used in the manufacture of rigid tubes. It also provides details of the minimum length of straight permissible between such radii during manufacture.
This standard applies to rigid tubes conforming to EN 3717 and produced only in ASD materials.

Luft- und Raumfahrt - Biegeradien von Rohren, für Triebwerksanwendung - Konstruktionsnorm

Diese Norm enthält Festlegungen über Biegeradien, die bei der Fertigung von Rohren zu verwenden sind. Sie enthält auch Einzelheiten über die gerade Mindestlänge, die zwischen solchen Biegeradien in der Fertigung zulässig ist.
Diese Norm gilt für Rohre nach EN 3717, die ausschließlich aus ASD-Werkstoffen hergestellt werden.

Série aérospatiale - Rayons de cintrage des tubes, pour application moteurs - Norme de conception

Aeronavtika - Krivinski polmeri cevi za uporabo pri motorjih - Standard za projektiranje

General Information

• Status: Published
• Publication Date: 25-Mar-2008
• Withdrawal Date: 29-Sep-2008
• ICS: 49.080 - Aerospace fluid systems and components
• Technical Committee: ASD-STAN - Aerospace
• Drafting Committee: ASD-STAN/D 3/S 3 - Hydraulics
• Current Stage: 9093 - Decision to confirm - Review Enquiry
• Start Date: 21-Jan-2024
• Completion Date: 14-May-2025
• Ref Project: SIST EN 3658:2008 - Aerospace series - Tube bend radii, for engine application - Design standard

Overview

EN 3658:2008 - "Aerospace series: Tube bend radii, for engine application - Design standard" (CEN) defines design rules for bend radii and minimum straight lengths when manufacturing rigid tubes for aero-engine fluid systems. It applies to rigid tubes that conform to EN 3717 and are produced in ASD materials. The standard gives consistent, manufacturable criteria intended to support mandrel bending, structural integrity and dimensional acceptability in engine applications.

Key topics and technical requirements

• Scope & applicability: Applies only to rigid tubes for engine fluid systems that meet EN 3717 and are made from ASD-specified materials.
• Uniform bend radius: To enable continuous bending operations, all bends in a given tube configuration should use the same radius and be measured to the tube centreline.
• Radius basis: Standard bend radii are based on a multiple of the tube outside diameter (D):
  • Steel: radius = 2.5 × D
  • Titanium: radius = 3.0 × D
  • Specific preferred radii for common tube sizes are provided in the standard (see Table 1).
• Plane of bending: Each bend radius must lie in one plane only (no compound 3D bending for a single radius).
• Minimum straight length between bends: To accommodate mandrel bending and clamp widths, a minimum straight length Z is required. Typical guidance:
  • For most diameters: Z = 3 × outside diameter (D)
  • For tube diameters ≤ 16 (where necessary): Z may be 2 × D (not preferred). See Table 2 for details.
• Wall thickness after bending: Outer-wall thinning occurs during bending. Minimum allowable wall thickness after bending (T1) must be ≥ 90% of nominal wall thickness (T).
• Ovality limits: Maximum allowable ovality after bending (difference between max and min diameters at a section) must not exceed 10% of nominal outside diameter.
• Units: All dimensions are given in millimetres.

Applications and users

EN 3658:2008 is used by:

• Aerospace design engineers specifying rigid tubing for engines (fuel, oil, hydraulics)
• Manufacturing/production teams performing mandrel bending and tool design
• Quality and inspection personnel verifying bend radii, wall thickness and ovality
• Suppliers and procurement teams drafting part specifications and acceptance criteria

Practical benefits include improved manufacturability, consistent bending operations, reduced rework, and clearer procurement requirements for engine fluid system tubing.

Related standards

• EN 3717 - Aerospace series - Tubes - Selection for engines fluid systems (normative reference)
• ASD prestandards and ASD‑STAN documentation for aerospace tube material and fabrication guidance

Keywords: EN 3658:2008, tube bend radii, aerospace, engine application, rigid tubes, mandrel bending, ovality, wall thickness, EN 3717, ASD materials.

Standards Content (Sample)

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Aerospace series - Tube bend radii, for engine application - Design standardAeronavtika - Krivinski polmeri cevi za uporabo pri motorjih - Standard za projektiranjeSérie aérospatiale - Rayons de cintrage des tubes, pour application moteurs - Norme de conceptionLuft- und Raumfahrt - Biegeradien von Rohren, für Triebwerksanwendung - Konstruktionsnorm49.080Aerospace fluid systems and componentsICS:SIST EN 3658:2008enTa slovenski standard je istoveten z:EN 3658:200801-junij-2008SIST EN 3658:2008SLOVENSKI
STANDARD
EUROPEAN STANDARDNORME EUROPÉENNEEUROPÄISCHE NORMEN 3658March 2008ICS 49.080 English VersionAerospace series - Tube bend radii, for engine application -Design standardSérie aérospatiale - Rayons de cintrage des tubes, pourapplication moteurs - Norme de conceptionLuft- und Raumfahrt - Biegeradien von Rohren, fürTriebwerksanwendung - KonstruktionsnormThis European Standard was approved by CEN on 21 December 2007.CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this EuropeanStandard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such nationalstandards may be obtained on application to the CEN Management Centre or to any CEN member.This European Standard exists in three official versions (English, French, German). A version in any other language made by translationunder the responsibility of a CEN member into its own language and notified to the CEN Management Centre has the same status as theofficial versions.CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland,France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.EUROPEAN COMMITTEE FOR STANDARDIZATIONCOMITÉ EUROPÉEN DE NORMALISATIONEUROPÄISCHES KOMITEE FÜR NORMUNGManagement Centre: rue de Stassart, 36
B-1050 Brussels© 2008 CENAll rights of exploitation in any form and by any means reservedworldwide for CEN national Members.Ref. No. EN 3658:2008: E
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