SIST EN 2894:2019

Overview

SIST EN 2894:2019 is a European standard developed by CEN and ASD-STAN, specifying the requirements for self-locking bihexagonal nuts used in the aerospace industry. These nuts feature a counterbore design, are manufactured from a heat-resisting nickel base alloy, and are treated with a passivation process and molybdenum disulphide (MoS₂) lubrication. The nuts are classified to withstand a minimum tensile stress of 1,550 MPa at ambient temperature and maintain structural integrity up to 315 °C.

This standard ensures that aerospace components using these nuts achieve high performance, reliability, and safety under demanding temperature and mechanical stress conditions typical of aerospace environments.

Key Topics

• Scope and Classification
  EN 2894 covers self-locking bihexagonal nuts with counterbore made from heat-resistant nickel base alloys. The classification defines mechanical and thermal resistance: tensile strength at 1,550 MPa (ambient temperature) and operating temperature capability up to 315 °C.

• Material Specifications
  The nuts must comply with material standards for heat-resisting nickel alloys, including passivation for corrosion resistance (EN 2516) and molybdenum disulphide dry lubrication (EN 2491).

• Dimensions and Tolerances
  Precise dimensions and tolerances for form and position are provided based on ISO 8788 and related aerospace specifications. The bihexagonal configuration complies with ISO 4095 standards, ensuring compatibility with aerospace bolt designs.

• Surface Treatments
  Passivation and MoS₂ lubrication treatments enhance corrosion resistance and reduce friction, making the nuts suitable for high-stress and high-temperature aerospace applications.

• Marking and Designation
  Nuts are marked following EN 2424 aerospace marking guidelines. This includes details for traceability and identification to support quality assurance.

• Quality and Production Requirements
  Manufacturers must be approved production organizations per aerospace quality management systems like EN 9100. Products must be qualified according to aerospace procedures such as EN 9133.

Applications

EN 2894 nuts are essential components in aerospace assemblies requiring extreme mechanical strength, thermal resistance, and secure fastening under vibration and cyclical loading, including:

• Aerospace structural assemblies
• Turbine and engine components exposed to high temperatures
• Airframe and fuselage fastenings requiring corrosion resistance
• High-performance aerospace fasteners in commercial, military, and space applications

These nuts are chosen when reliability, longevity, and safety under thermal and mechanical stress are critical, ensuring secure fastening with self-locking features that prevent loosening in flight and harsh conditions.

Related Standards

• EN 9100 – Aerospace quality management systems governing manufacturer approvals
• EN 9133 – Aerospace product qualification procedures
• EN 2424 – Marking specifications for aerospace products
• EN 2491 – MoS₂ dry lubricants coating methods
• EN 2516 – Passivation and corrosion resistant treatments for nickel alloys
• ISO 4095 – Bihexagonal wrenching configuration and dimensions
• ISO 8788 – Tolerances of form and position for aerospace nuts
• ISO 5858 – Self-locking nuts with max operating temperature less or equal to 425 °C

Keywords: aerospace standard, self-locking nuts, bihexagonal nuts, heat resisting nickel alloy, passivation, MoS₂ lubrication, tensile strength 1550 MPa, aerospace fasteners, high-temperature nuts, EN 2894, aerospace quality management, aerospace hardware.