In addition to elastic deformations, settling also occurs in a screw connection, which is predominately caused by the plastic levelling of surface roughness.
The loosening of screw connections can be prevented by means of suitable design measures. This could be the use of expansion bolts or long screws, or an increase in pretensioning force using higher strength screws. In the latter case in particular, special attention must be given to the pressure on the contact surface. Using a flange screw or underlaying or packing a suitably hard washer reduces the surface pressure and prevents loosening.
This can be achieved by means of the following measures:
High pretensioning force
- By using high-strength screws and controlled tightening procedures
- By bracing spring-loaded elements
- By means of screws and/or bolts with a specially shaped head
By means of a low surface pressure
- By means of large contact surfaces
- By means of sufficient screw-in depths
By means of a low number of joints
- No plastic or quasi-elastic elements (bracing seals)