At Railtex Pfisterer will be presenting its Tensorex spring tensioner for catenary contact and messenger wires, of which over 500 units have been supplied since the first application in 1997. Designed to provide a low-maintenance alternative to weight-based tensioning systems, Tensorex is available in two versions allowing for a maximum cable expansion of 450mm or 750mm respectively.

The Tensorex unit contains a spring which acts on a cable connected to a pulley with a constant radius. A variable-radius pulley on the same axle is connected to the contact or messenger wire. The force applied to the wire remains constant as the variation in the force exerted by the spring, pre-loaded to half the value of its total travel, is compensated by the variation in the radius of the pulley.

By installing a load cell between the Tensorex unit and the structure to which it is attached, such as a mast or a tunnel roof, the tension being applied to the overhead line can be monitored, and an alarm signal sent to a control room should this be too high or too low. Although around 60% of Tensorex units supplied to date have been installed in tunnels, including Madrid Metro and Milano’s cross-city Passante (below), recent applications include the supply of 30 units to Italian State Railways for installation at Roma Termini station.

Pfisterer srl, Italy

Reader Enquiry Number 125