How to properly read and understand structural fasteners according to UNI EN ISO 15048 and ISO 14399

In the context of metal carpentry and large infrastructure jobs, structural bolts are critical link elements for the safety and durability of the entire structure. Understanding markings and technical specifications properly is essential to ensure regulatory and performance compliance. This article introduces main differences between SB (non-preloaded) assemblies according to UNI EN 15048 and HV (preloaded) assemblies according to ISO 14399, providing practical guide to understand product data and making an informed choice of the correct fastener.

Reference standards

• UNI EN 15048-1

This standard defines the requirements for non-preloaded structural bolt assemblies. These are applied to joints where the load is transferred by contact (marginal friction) and the bolt is not tightened beyond its yield point.

• UNI EN 14399-1 / 14399-2 / 14399-4

These standards regulate HV assemblies, i.e. high strength bolts suitable for preloading through controlled tightening. These parts are designed to ensure high internal stress values by fitting calibrated washers, lubricated nuts and suitability tests performed on consistent lots.

Both standards are recognised by the NTC 2018 and implemented in Europe by Eurocode 3 – UNI EN 1993-1-8.

Assembly parts and mandatory markings

1. Mechanical strength class

This is the class of the item itself and it refers to the yield strength and breaking load. The most used classes are:

• 8.8 (for SB)
• 10.9 (for HV)

2. CE marking and lot number

• These are mandatory for item traceability.
• They must be reported on the original sealed packaging, never opened, as supplied by the manufacturer.
• CE marking for SB applies to the bolt + nut assembly (washers are not subject to marking but they must be compatible with the assembly).

3. Manufacturer identification

Each component must carry a permanent identification mark. For HV assemblies, this may include the letters HV, HR, HB or HN depending on the configuration (according to UNI EN 14399-9).

4. Washers

Washers are often underrated, but they are essential parts, especially for HV assemblies. Washers in accordance with UNI EN 14399-6 (flat chamfered) must be positioned under the bolt head with the chamfer facing outwards. They must also comply with the hardness specified by UNI EN ISO 6507-1 (Vickers) or UNI EN ISO 6508-1 (Rockwell).

Operational differences between SB and HV

Checks and traceability

As far as HV assemblies are concerned, the manufacturer must provide:

• 3.1 certificate according to EN 10204 + declaration of performance (DOP)
• Preload suitability test performed on each lot according to EN 14399-2
• Lot labelling, manufacturer’s marking and reference standards

Structural Fasteners by VIPA

VIPA offers a wide range of structural bolt assemblies in accordance with UNI EN 15048 and UNI EN 14399. These assemblies all certified, tested and supplied in original sealed packaging with CE marking. HV assembly kits include bolt, nut and 2 washers matched in consistent lots to ensure full compliance with national and European technical standards.

Thanks to their qualified technical support and advanced logistics, VIPA is the ideal partner for companies seeking reliability, safety and traceability for structural bolting.

Conclusion

Being able to properly read and understand technical specifications of structural assemblies is nowadays an essential requirement for players involved in steel constructions. Relying on competent and certified suppliers such as VIPA means ensuring compliance with regulations, minimising risks and achieving high and durable performance. Find out more about our complete range on VIPA Shop.