The BS EN 14399-9 standard provides the definitive technical requirements for metric direct tension indicators (DTI washers) used in high-strength structural bolting assemblies for preloading. Precision engineering and rigorous quality control are critical for structural integrity in EN 1090 projects, which is why sourcing fully compliant components is essential for structural engineers, quality inspectors, and technical specifiers worldwide. FULLERKREG manufactures these specialized components to exacting tolerances, ensuring optimal performance, consistent load indication, and absolute safety in the most demanding industrial applications. For procurement teams looking to secure verified, high-performance fastening components, you can explore our complete DTI washer collection. Whether you require in-depth technical consultation, certified Mill Test Reports (MTRs), or customized large-scale quotes for your next structural project, please reach out directly to our engineering sales team via email at sales@fullerkr.com.
BS EN 14399-9 DTI Washer Dimensions Table
The following table outlines the dimensional requirements for EN 14399-9 DTI washers. Key: d1 = internal diameter, d2 = external diameter, h1 = material thickness, h2 = height over protrusions, h3 = height of protrusions, d3 = protrusion tangential diameter, d4 = protrusion internal diameter.
| Bolt Designation | d1 min. | d1 max. | d2 min. | d2 max. | h1 min. | h2 max. | h3 min. | d3 min. | d4 max. |
|---|---|---|---|---|---|---|---|---|---|
| M12 | 13.00 | 13.27 | 25.40 | 26.00 | 2.50 | 4.00 | 0.50 | 20.00 | 15.00 |
| M16 | 17.00 | 17.27 | 32.40 | 33.00 | 3.00 | 4.50 | 0.50 | 26.00 | 20.00 |
| M20 | 21.00 | 21.33 | 40.40 | 41.00 | 4.00 | 5.50 | 0.50 | 33.00 | 24.00 |
| M22 | 23.00 | 23.33 | 43.40 | 44.00 | 4.50 | 6.00 | 0.50 | 36.00 | 27.00 |
| M24 | 25.00 | 25.33 | 49.00 | 50.00 | 4.50 | 6.00 | 0.50 | 40.00 | 30.00 |
| M27 | 28.00 | 28.33 | 54.80 | 56.00 | 5.00 | 7.00 | 0.50 | 45.00 | 34.00 |
| M30 | 31.00 | 31.39 | 58.80 | 60.00 | 5.00 | 7.00 | 0.50 | 50.00 | 37.00 |
| M36 | 37.00 | 37.39 | 70.80 | 72.00 | 6.00 | 8.50 | 0.50 | 60.00 | 44.00 |
Product Characteristics & Material Requirements
| Material | High-strength steel |
| General Requirements | In accordance with BS EN 14399-9 |
| Heat Treatment | Quenched and tempered |
| Maximum Hardness | 380 HV |
| Surface Finish Normal | As processed, lightly oiled |
| Surface Finish Sherardized | In accordance with EN 13811 |
| Associated Bolts & Nuts | System HR or System HV assemblies |
| Associated Washers | Must comply with EN 14399-5 or EN 14399-6 |
| Acceptability | In accordance with EN ISO 3269 |
Critical Processing Restrictions
- No electroplating: Electroplating is strictly prohibited due to the risk of hydrogen embrittlement.
- Sherardizing: Sherardizing is permitted and recognized as equivalent to hot-dip galvanizing.
- No cadmium coatings: Cadmium coatings are prohibited due to environmental regulations.
- Other coatings: Other coatings by negotiation only.
Compression Loads at Specified Gap
Note: Minimum values equal 0.7 × fub × As per EN 1993-1-8.
| DTI Size | H8 Min (kN) | H8 Max (kN) | H10 Min (kN) | H10 Max (kN) |
|---|---|---|---|---|
| M12 | 47 | 56 | 59 | 71 |
| M16 | 88 | 106 | 110 | 132 |
| M20 | 137 | 164 | 172 | 206 |
| M22 | 170 | 204 | 212 | 254 |
| M24 | 198 | 238 | 247 | 296 |
| M27 | 257 | 308 | 321 | 385 |
| M30 | 314 | 377 | 393 | 472 |
| M36 | 458 | 550 | 572 | 688 |
Feeler Gauge Thickness Requirements
The required feeler gauge thickness depends on whether the DTI washer is placed under a stationary element or a rotated element during tightening.
| Condition | Thickness (mm) |
|---|---|
| Under bolt head / nut rotated | 0.40 |
| Under nut / bolt rotated | 0.40 |
| Under nut / nut rotated | 0.25 |
| Under bolt head / bolt rotated | 0.25 |
DTI Washer Marking Standards
BS 4395 Higher Grade Part 2
Strict marking compliance required for higher grade components to ensure traceability and part identification.
Metric Series General Grade Part 1
FULLERKREG washers carry permanent markings for size, grade, and lot traceability in strict adherence to Part 1 specifications.
Associated Bolting Assemblies
- Bolts: EN 14399-3, EN 14399-4, EN 14399-7, EN 14399-8
- Washers: EN 14399-5, EN 14399-6
- Nuts: Compatible heavy hex structural nuts
Inspection & Acceptance per EN ISO 3269
- AQL (Acceptable Quality Limit) is set at 0.65
- Acceptance number Ac=0
- Reference tables EN ISO 3269:2000 Tables 5 and 6
FAQ
-
What are the exact dimensions of an M20 EN 14399-9 DTI washer?
An M20 EN 14399-9 DTI washer requires an internal diameter (d1) of 21.00 - 21.33 mm, an external diameter (d2) of 40.40 - 41.00 mm, and a material thickness (h1) of at least 4.00 mm. -
What is the maximum hardness for EN 14399-9 DTI washers?
The maximum allowable hardness is 380 HV. -
What is the difference between H8 and H10 DTI washers?
H8 and H10 designate different property classes and corresponding compression load requirements. H10 DTIs are designed for higher preloading forces. -
What feeler gauge thickness does EN 14399-9 require?
The standard requires a 0.40 mm feeler gauge when the DTI is under a stationary element and a 0.25 mm feeler gauge when under a rotated element. -
Why are electroplated DTI washers prohibited?
Electroplating introduces a critical risk of hydrogen embrittlement, which can lead to catastrophic failure in high-strength structural bolting. -
Where can I buy EN 14399-9 certified DTI washers with full dimensional compliance?
You can purchase fully certified, compliant components from the FULLERKREG DTI washer collection. For large volume orders or compliance documentation, please email sales@fullerkr.com.
Conclusion
Ensuring compliance with EN 14399-9 is non-negotiable for structural integrity in high-strength preloaded bolting. FULLERKREG provides the precision, complete traceability, and verified material reliability required for these critical connections. Contact us today to secure fully compliant components.
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