Spring and balance-weight tensioners have been superseded by a gas-cylinder model developed by JR Central, offering a smaller, lighter unit with improved performance.
Whereas conventional tensioners absorb the slack produced when overhead line cables expand in the heat, the gas cylinder model actively tensions in response to changes in temperature. As the cylinder warms up, the gas inside expands, pushing against a piston. This retracts sliding rods, which pull against the catenary termination. As temperature falls, the catenary shortens, but tension remains constant as gas in the cylinder contracts. Tension can be maintained at a required level of between 10 and 35 kN.
The gas tensioner is much lighter than spring or balance-weight designs. It is also much more compact, permitting its use in places where installation of other tensioners would be difficult, such as in tunnels. Adding a pressure sensor to the gas cylinder allows the operator to monitor the catenary remotely, to detect wind gusts or catenary damage.
JR Central, Tokyo, Japan
Reader Enquiry Number 140
