activates and the pressure pumping apparatus is removed with full pressure remaining in the assembly where setting paste is used as the charging medium it will cure rapidly preventing any leakage and subsequent loss of tensile load on bolts 120 when a particulate solid is used as the charging medium it will retain the tensile load indefinitely as it is already at a high density fig7 illustrates a third embodiment of the present invention where a standard form of hydraulic nut 210 is charged with charging medium 250 using media exchanger 260 in the same manner described with reference to fig3 to 7 in this case the pressure of the charging medium is not required to be maintained since the force generated is maintained by locking ring 216 which is screwed into nut 211 and engaged with piston 217 which cooperates with nut 211 to form annular chamber 230 when this type of hydraulic nut needs to be removed intact at a later time the charging medium used will be of a fluid nature in order to assist with re pressurisation for loosening lock ring 216 owing to the nature of the charge medium used the sealing capacity of fasteners 10 210 of tensioning devices 110 need only be rudimentary as illustrated in fig8 and 9 the leading edges of components and sliding engagement may be altered in order to enhance the sealing ability when viscous materials are used as the charging media the use of charging media 50 150 250 and in particular the use of solid injectable media such as graphite and of particulate solids of a granular nature such as steel balls wilt allow the hydraulic tensioning fasteners and hydraulic tensioning.