Tensioner

 ( Drilling Technology ) 

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.

• 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 bicycle chain tension on a single-speed bicycle can be maintained by either setting the fixed horizontal position of the Cogset 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.
• Chair lift and gondola lift cables
• Certain wood , such as the beam tensioner truss picture below.

• Fencing made of wire, such as , barbed-wire fences, and often include tensioning devices to keep them taut.
• 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.

==Gallery==

• Turnbuckle
• Torque wrench

• Hydraulic Tensioning Glossary