Tensioner

A tensioner is a device that applies a force to an object to maintain it in tension. Often the amount of force is adjustable. There are tensioners for applying a tensioning force to drive belts and chains, fibers, and bolts.

One type of tensioner is a large industrial spring. A tensioner is used between two objects that should be kept together but that make relative, more or less unpredicted, motions towards each other. The tensioner makes sure that independent of the motion the connection remains intact, without elements becoming overstressed. An anchor chain could be defined as the easiest tensioner.

Most tensioners can be described as industrial springs. A marine riser tensioner on board a drill ship, for instance, consists of two sheaveblocks with a wire over it. Both sheaveblocks are connected by a hydraulic cylinder and the oil of the hydraulic cylinder is connected to a gas volume under pressure. When the wire rope is connected to a riser, the wire rope is kept under a certain stress, so that the riser does not buckle. If the ship moves up and down, the tension in the wire rope is changed a bit (depending on the spring characteristic).

Fine examples

• Guideline tensioner
• Marine riser tensioner