Spændemidler

Spændemidler are devices designed to apply and regulate tension in a flexible element such as wire rope, cable, chain, belt, or tendon. They can increase or maintain tension to secure loads, compensate for stretch, or enable force transmission in a system. Most spændemidler operate by converting a manual, hydraulic, or pneumatic action into axial force, and include a mechanism to lock in the set tension.

Common types include screw-type turnbuckles, which have a threaded body and end fittings; hydraulic or pneumatic tensioners that use a cylinder or jack to apply force; ratchet-type tensioners that wind a strap or cable; and belt tensioners used in engines and conveyors.

In the field of civil engineering and construction, spændemidler often refers to devices used for prestressing concrete: hydraulic jacks (tension jacks) are employed to apply tensile force to steel tendons in ducts, after which the tendons are anchored to transfer the force to the concrete.

Applications span a wide range: securing cargo on vehicles or ships, rigging in theaters and outdoor stages, belt drive systems in machinery and automotive engines, suspension systems, and load-bearing structures. Selection depends on required tension, range of adjustment, durability, material compatibility, and safety standards. Maintenance includes inspecting for wear, corrosion, and slippage, recalibrating tension when necessary, and ensuring secure locking.

The term is closely related to related components such as turnbuckles, line grips, wire rope clamps, and tension springs, though it covers devices that actively adjust or apply tension rather than passive springs. See also: turnbuckle, tensioner, prestressing.