Switch expansion joint in railway track to compensate temperature gradient

Nowadays we use long welded rail (lwr) means in it, we welds 13 meters rails section to each other using at welding leaving no fish plate joint behind. So we do not provide extension joints between a long rail section. Then to compensate temperature effects like extension and compression we do provides SEJ's after some distance. SEJ is basically a joint of tongue rail(inner one) and stock rail(outer one) as shown in video. It is lubricated using grafite or oil so both rails can move with each other to compensate temperature effect. Minimum expansion size of SEJ is 40 mm and maximum for zone 1 and 2 is 120 and for 3,4,5 is 190 mm. In this video you can see a Sej on 52 kg rail section and sleepers at 65cm spacing.

[@tanishsalunkechannel9897]

Will this increase train speed than before when there were fish plates?

[@Roorkeelive]

Generally speed does depends upon the rail section whether you are using 52 kg section or 60 kg section and the type of joints in a rail section I.e. lwr or cwr. Sej's are provided in lwr and cwr for contractions and extensions due to temperature not for joining 2 rail sections. Rails are joined using welding instead fish plates now a days due to welding the noise has reduced and speed has increased.