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.
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.