Tensioner

A tensioner is a device that applies a force to create or maintain tension. The force may be applied parallel to, as in the case of a hydraulic bolt tensioner, or perpendicular to, as in the case of a spring-loaded bicycle chain tensioner, the tension it creates. The force may be generated by a fixed displacement, as in the case of an eccentric bicycle bottom bracket, which must be adjusted as parts wear, or by stretching or compressing a spring, as in the case of a spring-loaded bicycle chain tensioner; by changing the volume of a gas, as in the case of a marine riser tensioner; by hydraulic pressure, as in the case of a hydraulic bolt tensioner; or by gravity acting on a suspended mass, as in the case of a chair lift cable tensioner. In the power sector, the tensioner is a machine for maintaining constant tension of the conductors during work of hanging the transmission network..

Applications

 * Bolt tensioners are devices designed to apply a specific tension to a bolt. The device may be either removed once the actual nut is threaded into place or left in place, in the case of a hydraulic nut.


 * The belt or chain tension on a single-speed bicycle can be maintained by either setting the fixed horizontal position of the rear sprocket or the front chainring horizontally, or by a separate tensioner that pushes perpendicular to the chain with either a fixed position or spring tension.


 * The serpentine belt and the timing belt or chain on an automobile engine may be guided by an idler pulley and/or a belt tensioner, which may be spring-loaded, hydraulic, or fixed.


 * The chain tension of a chainsaw may be adjusted with a chain tensioner.


 * A marine riser tensioner is a device used on an offshore drilling vessel that provides a near-constant upward force on the drilling riser independent of the movement of the floating drill vessel.
 * A guideline tensioner is a hydropneumatic device used on an offshore drilling rig that keeps a positive pulling force on the guidelines from the platform to a template on the seabed.
 * Overhead electrical wires may be kept in tension by springs or weights.
 * Conveyor belts
 * Chair lift and gondola lift cables
 * Certain wood trusses, such as the beam tensioner truss picture below.


 * Fencing made of wire, such as electric fences, barbed-wire fences, and chainlink fences often include tensioning devices to keep them taut.
 * Belt sanders have a mechanism, often a spring-loaded idler drum, to apply the proper tension to the sanding belt, which can be released to allow for changing belts.