What is of HV Hexagon Bolt
The marking HV is derived from the German term “Hochfest Vorgespannt”, which refers to a high-strength, preloaded bolt. Currently, HV refers to hexagon bolt and nut assemblies according to standard EN 14399-4. These bolt assemblies are used in bolt connections of preloaded, load-bearing steel structures.
| Product | High strength pre-load bolt assemblies HV |
|---|---|
| Standard: | Dast Richtlinie021/EN 14399/DIN 6914/DIN 6915/ DIN 6916 – HV bolts |
| Property class: | 10.9 |
| Certificate: | EN10204 3.1 with full traceability 10 years, otherwise specified |
| Suitability test for preloading: | EN 14399-2 |
| Surface coating available: | Plain, Dacromet, Black, Geomet, HDG, Dorken, Delta, Electro plated, TZN |
Parts of HV and HR Assembly
| Elements of HV Assembly | Elements of HR Assembly |
|---|---|
| 1 pcs of HV bolt acc to EN 14399-4(DIN 6914), Grade 10.9 | 1 pcs of HR bolt acc. to EN 14399-3, Grade 8.8, 10.9; |
| 1 pcs of HV nut acc to EN 14399-4(DIN 6915), Grade 10.9 | 1 pcs of HR nut acc. to EN 14399-3, Grade 8, 10; |
| 2 pcs of washers EN 14399-6(DIN 6916) | 2 pcs of Washers EN 14399-6 |
HV bolt assemblies also include washers pursuant to EN 14399-6. All system components (bolts, nuts, washers) must be procured from the same manufacturer.
Preloaded bolt connections are used for ensuring slip resistance, for structures located in seismic regions or structures that are otherwise subjected to dynamic loads. Reloading is also utilised for improving fatigue resistance and long-term durability.
| Product | Old standard | Current standard |
|---|---|---|
| HV bolt | DIN 6914 | EN 14399-4 |
| HV nut | DIN 6915 | EN 14399-4 |
| HV washer | DIN 6916 | EN 14399-6 |
HV bolt assembly standards were revised back in 2007. Some old bolt lists or drawings may still include the following old designations from the DIN standard:
Differences Between HV Bolts and Regular Hexagon Bolts
- The steel strength of the bolts is 10.9, nuts are of strength 10 and washers are grade HV300.
- The width across flats of the bolts and nuts is wider than usual with a stronger under the head of the bolt. This ensures improved load and fatigue resistance.
- The manufacturer may indicate batch numbers in the heads of bolts and the face surface of nuts. This ensures that the products are visually traceable for a long period of time following installation.
Batch number labelling may be used instead of 3.1 material certificates. - HV sets used are typically hot dip galvanised. Pre-galvanising thread tolerance for HV bolts is 6 g, making it over-sized after hot dip galvanising. The HV nut thread is manufactured according to the 6AZ tolerance to ensure the fit with the over-sized bolt.
- The friction coefficient is achieved by applying the necessary coating and lubrication. This enables precise preloading of the connection.
- The HV bolt assembly components are CE labeled, pursuant to the requirements of the harmonised standards on construction products.
