DIN EN 17976
DIN EN 17976:2025-03 “Railway Applications—Screw Joints in Rail Vehicles and Vehicle Components” is the first comprehensive European standard to fully replace all previous national standards, such as DIN 25201 in Germany.
DIN EN 17976:2025-03 defines, for the first time on a Europe-wide basis, uniform requirements for the design, evaluation, installation, and maintenance of mechanical and electrical screw connections in rail vehicles.
The standard takes a two-phase approach to bolt locking by differentiating between and analyzing both slackening (with a preload force above the minimum clamping force) and self-acting loosening by rotation (when slip resistance is lost), and by requiring design countermeasures.
The design of bolted joints to be slip-resistant is generally required; if this cannot be achieved through calculation, alternative securing elements must be used.
Spring-loaded fasteners are expressly recommended to increase elastic resilience and sliding resistance, provided their suitability is demonstrated in accordance with the functional requirements of DIN 267-26.
Outdated elements such as spring rings, toothed washers, and similar washer types do not comply with the standard, as they do not meet the minimum requirements and preclude CE marking.
The standard allows for the calculation of the resilience of effective spring-loaded elements, since the residual spring effect is determined in accordance with DIN 267 Part 26, in order to increase sliding and operational safety—particularly for short clamping lengths—while simultaneously realizing lightweight design potential and environmental benefits.
For electrical contact glands, only the use of individual securing elements is permitted; combined flat washer solutions (such as flat washers with locking discs per DIN 6796) and adhesives are expressly prohibited to ensure electrical conductivity and mechanical integrity.
Based on the standard, multifunctional securing elements that prevent both slackening and unscrewing are to be preferred, as they increase the functional resilience of the connection and comprehensively support modern design requirements, particularly in lightweight construction.
- Key differences and innovations introduced by DIN EN 17976:
- Holistic approach: The new standard takes a comprehensive view of the loosening of bolted connections, including the loosening and unscrewing phases.
- Preventive protection against loosening: Specific requirements and test methods are defined to ensure protection against loosening.
- Spring-loaded fasteners: The standard emphasizes the importance of spring-loaded fasteners for increasing elastic resilience and slip resistance.
- Electrical contact glands: Specific requirements for securing elements are defined for electrical applications, although adhesives are still not permitted as securing agents.
Conclusion:
The replacement of DIN 25201 by DIN EN 17976 represents a significant step toward harmonizing and improving the safety of bolted joints in rail vehicle construction. The introduction of precise requirements and test procedures increases the reliability and lifetime of bolted joints, which is particularly important in light of lightweight construction concepts and the reduction of the CO₂ footprint.