EN 3690:2001

Overview

EN 3690:2001 is a European standard that defines the specifications for aerospace-grade pipe coupling unions, specifically 8°30' bulkhead unions manufactured from titanium alloy. Developed by CEN (European Committee for Standardization) and prepared by the European Association of Aerospace Manufacturers (AECMA), this standard addresses critical requirements for pipe couplings used in demanding aerospace fluid systems.

This standard ensures that bulkhead unions in titanium alloy meet stringent performance criteria, withstanding nominal pressures up to 28,000 kPa and operating efficiently within a temperature range from -55 °C to +135 °C. The focus on titanium alloys guarantees excellent strength-to-weight ratios and corrosion resistance - key attributes for aerospace applications.

Key Topics

• Scope and Application
  EN 3690:2001 covers long bulkhead unions for pipe couplings set at an 8°30' angle, designed for aerospace fluid system components. This enhances the reliability and safety of fluid transfer within aircraft and spacecraft environments.

• Material Specifications
  Utilizes titanium alloy according to EN 3311 or EN 3314, known for robustness and lightweight properties essential in aerospace systems.

• Dimensions and Configuration
  Detailed dimensional requirements and mass specifications are provided to ensure uniformity and compatibility across aerospace manufacturers. Manufacturer options for unspecified dimensions are allowed only if compliance with EN 3275 type II qualification is maintained.

• Surface Treatment and Lubrication
  Surface roughness and lubricant application conform to EN 2491 standards, including prior surface abrasive blasting with non-metallic grit, ensuring optimal sealing and mechanical performance.

• Marking and Traceability
  Compliance with EN 2424 marking standards assures traceability, crucial for quality assurance and maintenance within aerospace supply chains.

• Installation Details
  The standard provides installation guidance to ensure secure and reliable fitting of bulkhead unions into system assemblies.

Applications

EN 3690:2001 bulkhead unions are essential components in aerospace fluid and hydraulic systems. Their design supports:

• Fuel and Hydraulic Lines
  Ensuring leak-proof connections in high-pressure fuel and hydraulic circuits.

• Environmental Control Systems
  Facilitating fluid transfer in temperature-critical environments within aircraft.

• Spacecraft and UAV Systems
  Providing durable and lightweight connectors that meet rigorous aerospace demands.

• Maintenance and Repair Operations
  Standardized unions ease replacement and compatibility during servicing, minimizing downtime.

The combination of titanium alloy materials and precise engineering specifications supports aerospace operations where safety, durability, and performance under extreme conditions are mandatory.

Related Standards

EN 3690:2001 references and aligns with other key aerospace standards for fluid systems, including:

• ISO 5855-3 – MJ threads dimensional limits for fluid system fittings.
• EN 2424 – Marking requirements for aerospace products ensuring traceability.
• EN 2491 – Specifications for molybdenum disulphide dry lubricants and coating methods.
• EN 3267 – Washers in titanium alloy for bulkhead applications.
• EN 3274 and EN 3275 – Geometric configuration and technical specifications for aerospace pipe coupling 8°30'.
• EN 3311 and EN 3314 – Titanium alloy titanium bars used for fabrication of these aerospace components.

These related standards collectively ensure material quality, mechanical performance, and standardized production processes, forming an integrated framework for aerospace fluid system components.

Keywords: EN 3690:2001, aerospace pipe coupling, titanium alloy unions, bulkhead unions aerospace, aerospace fluid systems, high-pressure pipe couplings, pipe coupling 8°30', titanium alloy fittings, aerospace sealing solutions, aerospace hydraulic components, aerospace standards.