EN 3691:2001
(Main)Aerospace series - Pipe coupling 8°30' in titanium alloy - Unions, bulkhead, long, welded end
Aerospace series - Pipe coupling 8°30' in titanium alloy - Unions, bulkhead, long, welded end
This standard specifies the characteristics of unions, bulkhead, long, welded end for pipe couplings 8°30', in titanium alloy, for aerospace applications.
Nominal pressure: up to 28 000 kPa
Temperature range: - 55 C to + 135 C
Luft- und Raumfahrt - Rohrverschraubung 8°30' aus Titanlegierung - Gerade Schottverschraubungen, lang, mit Anschweißende
Série aérospatiale - Système de raccordement 8°30' en alliage de titane - Raccords droits pour traversée de cloison, type long, à souder
Aerospace series - Pipe coupling 8°30' in titanium alloy - Unions, bulkhead, long, welded end
General Information
Relations
Overview
EN 3691:2001 specifies the characteristics and requirements for aerospace series pipe coupling 8°30' in titanium alloy - specifically unions, bulkhead, long, welded end fittings used in aerospace fluid systems. The standard covers dimensional data, materials, surface treatment, marking and installation guidance for couplings designed for high-pressure service up to 28 000 kPa and a temperature range of -55 °C to +135 °C.
Key topics and technical requirements
- Scope & operating limits: nominal pressure up to 28 000 kPa; temperature range -55 °C to +135 °C.
- Configuration, dimensions & mass: detailed dimensional data referenced in figures and Table 1 of EN 3691 (codes correspond to sizing and pressure classification). Unspecified dimensions may be manufacturer-defined if EN 3275 type II qualification/acceptance is met.
- Materials: titanium alloy per referenced aerospace material standards (EN 3311 or EN 3314 for TI‑P64001 variants).
- Surface treatment & lubrication:
- Weld end: no surface treatment, minimum 10 mm (outside and bore).
- Threads and sealing faces: lubrication per EN 2491 (molybdenum disulphide dry lubricant); prior abrasive blasting with non‑metallic grit.
- Lubricant film thickness: 0.005 mm to 0.013 mm.
- Sealing & geometric configuration: coupling geometry follows related standards (EN 2656, EN 3274, EN 3275) for 8°30' coupling ends (welded and thread forms).
- Marking & designation: marking per EN 2424 style A; designation format and code examples specified (e.g., UNION, BULKHEAD EN3691 0805).
- Installation & technical specification: installation details illustrated (figure 3) and technical acceptance per EN 3275, type II.
Applications and users
EN 3691:2001 is intended for components used in aerospace fluid systems where high strength, corrosion resistance and weight savings are critical. Typical applications:
- Aircraft hydraulic, fuel and pneumatic lines
- Bulkhead pass-through fittings and welded tube systems
- High‑pressure fluid transfer in airframes and propulsion auxiliary systems
Primary users:
- Aerospace designers and systems engineers
- OEMs and suppliers of titanium pipe fittings and fluid-system components
- Quality, procurement and certification teams ensuring parts meet aerospace standards
- Maintenance and repair organizations specifying replacement components
Related standards
Normative references cited by EN 3691:2001 include:
- ISO 5855-3, EN 2424, EN 2491, EN 2656, EN 3267, EN 3274, EN 3275, EN 3311, EN 3314
EN 3691:2001 (pipe coupling 8°30' titanium alloy) should be used in conjunction with these standards for full specification, testing and acceptance of aerospace coupling components.
Standards Content (Sample)
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Aerospace series - Pipe coupling 8°30' in titanium alloy - Unions, bulkhead, long, welded endLuft- und Raumfahrt - Rohrverschraubung 8°30' aus Titanlegierung - Gerade Schottverschraubungen, lang, mit AnschweißendeSérie aérospatiale - Systeme de raccordement 8°30' en alliage de titane - Raccords droits pour traversée de cloison, type long, a souderAerospace series - Pipe coupling 8°30' in titanium alloy - Unions, bulkhead, long, welded end49.080Aerospace fluid systems and componentsICS:Ta slovenski standard je istoveten z:EN 3691:2001SIST EN 3691:2004en01-maj-2004SIST EN 3691:2004SLOVENSKI
STANDARD
EUROPEAN STANDARDNORME EUROPÉENNEEUROPÄISCHE NORMEN 3691October 2001ICS 49.080English versionAerospace series - Pipe coupling 8°30' in titanium alloy -Unions, bulkhead, long weldedSérie aérospatiale - Système de raccordement 8°30' enalliage de titane - Raccords droits pour traversée decloison, type long, à souderLuft- und Raumfahrt - Rohrverschraubung 8°30' ausTitanlegierung - Gerade Schottverschraubung, lang, mitAnschweißendeThis European Standard was approved by CEN on 20 January 2001.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 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 Management Centre has the same status as the officialversions.CEN members are the national standards bodies of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece,Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom.EUROPEAN COMMITTEE FOR STANDARDIZATIONCOMITÉ EUROPÉEN DE NORMALISATIONEUROPÄISCHES KOMITEE FÜR NORMUNGManagement Centre: rue de Stassart, 36
B-1050 Brussels© 2001 CENAll rights of exploitation in any form and by any means reservedworldwide for CEN national Members.Ref. No. EN 3691:2001 ESIST EN 3691:2004
for aerospace applications.Nominal pressure: up to 28 000 kPaTemperature range: – 55 C to
+ 135
C2Normative referencesThis European Standard incorporates by dated or undated reference provisions from other publications.These normative references are cited at the appropriate places in the text and the publications are listedhereaf
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Frequently Asked Questions
EN 3691:2001 is a standard published by the European Committee for Standardization (CEN). Its full title is "Aerospace series - Pipe coupling 8°30' in titanium alloy - Unions, bulkhead, long, welded end". This standard covers: This standard specifies the characteristics of unions, bulkhead, long, welded end for pipe couplings 8°30', in titanium alloy, for aerospace applications. Nominal pressure: up to 28 000 kPa Temperature range: - 55 C to + 135 C
This standard specifies the characteristics of unions, bulkhead, long, welded end for pipe couplings 8°30', in titanium alloy, for aerospace applications. Nominal pressure: up to 28 000 kPa Temperature range: - 55 C to + 135 C
EN 3691:2001 is classified under the following ICS (International Classification for Standards) categories: 49.080 - Aerospace fluid systems and components. The ICS classification helps identify the subject area and facilitates finding related standards.
EN 3691:2001 has the following relationships with other standards: It is inter standard links to EN 3691:2001/AC:2003. Understanding these relationships helps ensure you are using the most current and applicable version of the standard.
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