For a VCF-joint to function properly, it also must be properly assembled. The bolts must be preloaded to above the level specified. Bolts of size up to and including M16 can readily be preloaded manually by using spanners provided by VERAX. Bolts M18 and heavier require hydraulic tensioning. A special, rather advanced and quite powerful hydraulic stud tensioner of a Fourth Generation ( FG ) for high strength bolts has been developed to serve the VCF-System.

Basically a tensioner is a tubular hydraulic jack. It exerts a straight pull to the bolt, such that the nut, free-running may be screwed down to seat onto the washer. As the hydraulic pressure is relieved, the pulling force of the tensioner is taken over by the nut, accordingly as preload in the bolt.

The Fourth Generation of tensioners were designed to utilize the strength of 10.9 bolts, resulting in a 30% reduction in weight as compared with compact joints using 8.8-bolts.