Railway Signal Engineering

  Important facts   -  1. There should be no change in gradient within 30 m in case of BG and 15 m in case of MG of the point. 2. For IRS point Stroke is 143 mm and  opening is 115+_ 3mm.For IRS clamp type point machine maximum stroke is 220 mm. 3. For TWS Point stroke is 220 mm and opening is 160 mm.Tolerance is not mentioned anywhere. 4. Chipped/ Cracked Switch -  Chipped length is the portion where tongue rail has worn out for a depth of more than 10 mm over a continuous length of 10 mm.If the total  chipped length is 200 mm within 1000 mm from toe of switch rail, this switch rail will be called Chipped Switch. 6.  Knife Edged tip- If thickness of tip is less than 2 mm over a length of  more than 100 mm anywhere upto a distance of 1000 mm from its toe, then it is knife edged tip. 7. Vertical wear - It is measured at a point where tongue and stock rail are at same level.Vertical wear  allowed is 8 mm for 60 kg IRS Point Machine - ...

  In TWS Point,Distance between tongue rail and stock rail at JOH is 60 mm.This distance is 25 mm in IRS Point.When train moves on Point,it does some lateral movement.Due to this larger gap at JOH in TWS Point,wear and tear in wheel and tongue rail is very less compare to IRS Point. TWS fitting are made for high speed (160 kmph).Stroke of TWS Point machine is 220mm. In IRS Point only closed switch is locked and Open switch is kept free but in TWS both switches are locked.Open switch is locked with Fish tail or clamp. TWS is not suitable if curve is more than 2 degrees.  In TWS Point, throw is 220 mm 220 mm = 160 (opening) + 60 (gap at JOH)  Operating Data as per IRS :S 24/2002 - Amandement No 1 Motor DC series split field. Throw of point machine -220 mm +4/-1 Time of operation (Max) -5.0 sec Current Consumption- <_ 5.5 Amp Rated Voltage- 110 V DC Max Throw -550 Kg Slipping load - <_ 700 kg Stalling load (min) - 1000 kg Threaded portion of Lock Rod is made of steel ....