Switch Expansion Joint
The switch expansion joint (Fig. 17.5) is a device installed at the end of LWRs to allow the thermal expansion of the breathing length. Presuming a breathing length of 100 m for a BG track and a maximum temperature variation of ±35 o C from the mean temperature in India, the breathing length would shift or move by approximately ±20 mm from its mean position. Switch expansion joints, however, are designed to accomodate a total length modification of ±60 mm. The extra allowance has been made to cater to the likely occurrence of fractures in the breathing length, creep, and the wrong positioning of the SEJ. Switch expansion joints are situated at the ends of LWRs, i.e., after a length of 1 km or so. They are positioned in the facing direction in the case of double lines and in the direction of heavier traffic in the case of single lines.