This European Standard specifies the general requirements for bolt/nut/washer(s) assemblies for highstrength structural bolting, which are suitable for preloading. The intended use of bolting assemblies in accordance with this European Standard is structural metallic works.
- NOTE 1 High-strength structural bolting assemblies in accordance with EN 14399-2 to EN 14399-10 are designed to fulfill the requirements of this European Standard.
- NOTE 2 High-strength structural bolting assemblies are suitable for preloading in accordance with EN 1090-2 in steel structures.
Preload Bolt Types Introduction
Preload bolt assemblies are divided into three types: HV, HR and HRC.
Difference Between HV and HR Bolt System
HV and HR systems are basically equivalent. The main difference lies in their breakage in case of stress. HV (German) bolts use a lower nut so that they will be the first to break when under tensile strength. The internal thread will tear only afterwards. HR (French) bolts use a higher bolt and longer thread lengths. This difference makes the clamping force reduce differently, promoting greater bolt elongation and thus its breakage. Moreover, HV systems use class 10.9 screws, whereas HR systems can also include class 8.8 screws.
Remember that we are talking about controlled clamping assemblies. Therefore, the preload is applied through a torque wrench. This way, you can control the tightening torque applied to the assembly. The key factor determines the tightening torque performance based on the applied preload. This factor is essential for torque retention, but it depends on many factors, which can be difficult to control.
| Material | Steel | |
|---|---|---|
| General Requirement | EN 14399-1 | |
| Thread | Tolerance | 6ga |
| International Standards | ISO 261, ISO 965-2 | |
| Mechanical properties | Property Class | 10.9 |
| European Standard | EN ISO 898-1 | |
| Impact Strength | Value | K V, min = 27 J at – 20 °C |
| Test pieceb | ISO 148 | |
| Test | EN 10045-1 | |
| Tolerances | Product grade | C except: |
| dimensions c and r. | ||
| Tolerance for lengths ≥ 155 mm: +IT 17 -1/2 IT17 | ||
| International Standard | EN ISO 4759-1 | |
| Surface finishc | Normal | as processedd |
| hot dip galvanized | EN ISO 10684 | |
| Others | to be agreede | |
| Surface discontinuities | Limits for surface discontinuities as specified in EN 26157-1. | |
| Acceptability | For acceptance procedure, see EN ISO 3269. | |
| Material | Steel | |
|---|---|---|
| General Requirement | EN 14399-1 | |
| Thread | Tolerance | 6H or 6AZ |
| International Standards | ISO 261, ISO 965-2, ISO 965-5 | |
| Mechanical properties | Property Class | 10 |
| European Standard | EN 20898-2 | |
| Tolerances | Product grade | B |
| International Standard | EN ISO 4759-1 | |
| Surface finish | Normal | as processeda |
| hot dip galvanized | EN ISO 10684 | |
| Others | to be agreedb | |
| Surface discontinuities | Limits for surface discontinuities as specified in EN 493. | |
| Acceptability | For acceptance procedure, see EN ISO 3269. | |
Quality Inspection Laboratories
- Tensile and compression testing machines (600kN and 2000kN)
- Hardness tester (Brinell and Vickers)
- Hardness tester (HV0,3-HV30)
- Charpy impact tester 300J with cooling equipment down to -100°C
- Torque – tension testing machine (M12 – M64)
- Spectrometer for chemical analysis
- Elcometers for coating thickness measurements
- Measuring tools and gauges for dimensional inspection
- Stereo, optical, and inverted axial microscopes for metallurgical analysis
- Magnetic particle testing equipment
