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At Bridge crossings and near the railway track ternary lead cables are used because they
Are of high tensile strength
Are of low coefficient of thermal expansion
Are of low specific gravity
Can withstands shocks and vibration
Are of low specific gravity
Ternary lead cables consist of lead alloyed with small amounts of cadmium and antimony. The primary reason for their usage near railway tracks and bridges is their low specific gravity compared to pure lead, which allows them to withstand continuous mechanical vibrations and cyclic stresses without suffering from fatigue failure.
Ternary lead cables consist of lead alloyed with small amounts of cadmium and antimony. The primary reason for their usage near railway tracks and bridges is their low specific gravity compared to pure lead, which allows them to withstand continuous mechanical vibrations and cyclic stresses without suffering from fatigue failure.
╧БalloyтАЛ<╧БPbтАЛ тАФ where ╧Б denotes the specific gravity (density) of the ternary alloy versus pure lead
In environments like railway tracks or bridges, cables are subjected to persistent vibrations. Pure lead is highly susceptible to intercrystalline cracking under vibration. Ternary lead alloys significantly enhance the mechanical fatigue resistance. The lower specific gravity ensures that the overall weight of the cable sheath is reduced, thereby minimizing the gravitational stress and sagging effects on the support structures.
Ternary lead contains Lead (Pb), Cadmium (Cd), and Antimony (Sb).
It offers superior resistance to mechanical fatigue compared to pure lead sheathing.
Specifically chosen for locations with high-frequency mechanical vibrations (bridges, railway tracks).
Reduces cable weight due to lower specific gravity, preventing sheath deformation.
High resistance to fatigue cracking
Lower weight per unit length
Improved mechanical stability under vibration
Higher manufacturing cost compared to standard lead
Complex metallurgical processing required
Railway track electrification projects
Bridge cable infrastructure
Underground transmission in high-vibration industrial zones
The ternary alloy typically consists of 99.25% lead, 0.2% cadmium, and 0.5% antimony.
Option A is incorrect because while tensile strength is important, the specific vibration-resistance property is derived from the alloy composition, not just strength.
Option D is a consequence of the material properties rather than the primary material specification reason.
C is correct тАФ Ternary lead cables possess a lower specific gravity and superior fatigue resistance, which are essential for surviving the continuous vibrations found at railway tracks and bridge crossings.
Always remember that in cable design, sheath selection is based on the environmental stress profile (chemical corrosion vs. mechanical vibration).