Why washer hardness matters in HSFG joints
HSFG joints rely on preload, not bearing.
The entire joint performance depends on maintaining clamping force.
Normal washers compress.
Hardened washers do not.
This difference decides whether a joint holds or slips.
What HSFG washers actually do
HSFG washers:
- Prevent embedment
- Maintain preload
- Distribute load without deformation
- Protect coating during tightening
Normal washers flatten under load and absorb part of the tightening force.
Why preload is lost
- 1. Washer compresses under load
Normal washers deform.
- 2. Coating crush
Soft washers embed into zinc layers.
- 3. Surface relaxation
Contact surfaces settle.
- 4. Vibration loosening
Loss of preload accelerates loosening.
What happens on site
- Torque is achieved
- Preload drops after hours or days
- Joint slips under load
- Inspections fail
- Retightening is required
How to prevent preload loss
Use hardened washers
Follow EN 14399-6
Match washer hardness to bolt class
Inspect washer markings
Avoid mixing washer types
Final thought
HSFG joints are engineered systems.
Every component matters.
A soft washer can defeat a high-strength bolt.