Since the introduction of the Austbreck Gas Tension Device (GTD), over a decade in service has seen further development and adaption evolving to a unit that has reached exceptional levels of reliability and performance.

The GTD is offered as an alternative to conventional weights and pulley units for the automatic tensioning of overhead contact line systems.


The GTD consists of a piston cylinder. Force is transmitted from the piston to the overhead contact wire by means of a piston rod and crosshead, so that compression in the piston rod is turned into tension in the line. Then the piston is pressurised by nitrogen and acts on the piston diameter that is enclosed in a large cylinder as a reservoir. The volume of this reservoir may be varied by incorporating inert filler rods into the space. In this way the pressure/volume characteristics of the gas may be matched exactly to the individual contact wire tension length. The piston sealing action is performed by an oil seal.

Advantages of the GTD

  • Accurate Maintenance of overhead line tension
  • Reduced maintenance compared with conventional weigh and pulley systems
  • Resistant to vandalism
  • Inherent damping of the line, so reducing transmitted vibration
  • Less Visual impact than weights and pulleys
  • Requires less space than weights and pulleys – important in tunnels


Three different stroke units are available – 500mm, 900mm, 1200mm with different lengths of overhead line. Tension forces may be varied to suit the tension required in the line, up to a maximum of 30kN

Weight of each unit:

  • 500mm – 95kg
  • 900mm – 125kgs
  • 1200mm – 138kg

Ambient temperature from -40c to +60c

Gas charge – commercial grade nitrogen

Optional features on request.