Rail Types
1. What is a Rail?
A rail is a high-carbon rolled steel section which, together with another parallel rail and the intervening sleepers & fastenings, forms the track on which railway vehicles run. It is the most critical load-carrying element—wheels transmit vertical, lateral and longitudinal forces to it; hence its metallurgy, geometry and weight decide safety, speed and maintenance effort.
2. Technical Specifications & Nomenclature
| Parameter | Value / Formula | Remarks |
|---|---|---|
| Standard length (L) | 13 m (42.65 ft) for 60 kg, 52 kg & 90 R; 26 m welded panels in LWR | Earlier 11.8 m & 12.8 m existed |
| Nominal weight (W) | Expressed in kg/m or lbs/yd | 60 kg ≈ 60 kg/m ≈ 121 lb/yd |
| Section modulus (Z) | I/y_max | Bending strength ∝ Z |
| Wear allowance | 2–3 mm on head top & 1 mm on gauge face | Re-profiling limit 8 mm vertical wear |
| Chemical composition (60 kg – IRS T-12) | C 0.60–0.80 %, Mn 0.80–1.30 %, Si 0.15–0.55 %, S & P ≤ 0.04 % | Micro-alloyed (Cr, V) for 1080 grade |
| Hardness (BH) | 280–350 for plain carbon; ≥ 380 for head-hardened (HH) | HH rails used in curves ≤ 1000 m radius |
| Contact stress limit | 2100 MPa (von-Mises) | Influences rail head radius design |
3. Indian Rail Sections – Evolution & Comparison
| Rail | Introduced | Weight (kg/m) | Height (mm) | Head (mm) | Web (mm) | Foot (mm) | Status (2024) |
|---|---|---|---|---|---|---|---|
| 90 R | 1920 | 44.65 | 142.9 | 66.7 | 13.5 | 127 | Phased out (≤ 5 % network) |
| 52 kg | 1950 | 51.92 | 156 | 67 | 16 | 140 | 35 % route-km |
| 60 kg (UIC-60 profile) | 1985 | 60.34 | 172 | 74.3 | 16.5 | 150 | 60 % network; mandatory for ≥ 160 km/h |
| 60 kg HH | 1997 | 60.34 | 172 | 74.3 | 16.5 | 150 | 12 % of 60 kg; target 25 % by 2030 |
| 75 kg (experimental) | 2022 (RDSO trial) | 74.4 | 185 | 80 | 20 | 160 | Trial on DFC (Rewari–Mewat) |
4. Rail Classifications in Use
A. By Weight (Indian Railways categorisation)
- Heavy: ≥ 52 kg/m (52 kg, 60 kg, 75 kg)
- Medium: 40–52 kg/m (90 R, 75 R rarely found)
- Light: < 40 kg/m (35 R, 25 R on NG/Metro depots)
B. By Metallurgy & Heat-treatment
- Plain-Carbon (IRS T-12)
- Micro-Alloyed (MA) – 1080 grade
- Head-Hardened (HH) – Bainitic/martensitic layer 25 mm deep
- Hypereutectoid (HE) – 0.9 % C, lab trial for 200 km/h
C. By Service Application
- Straight Track (ST) rails
- Curve rails (high wear)
- Turnout rails (wing, check, crossing rails)
- Welded-rail (LWR) panels
- Conductor rail (3rd rail 750 V DC metros)
5. Manufacturing & Quality Control
- Steel route: Blast furnace → Basic Oxygen Furnace → Continuous casting blooms (320 mm × 320 mm) → Universal mill rolling → Online water quenching (for HH) → Straightening → Ultrasonic testing (UST) → Brand marking.
- New Mills: SAIL, Bhilai (exp. to 2.0 MT), JSPL Raigarh, RINPL Vizag.
- Quality norms: IRS T-12:2019 (replaced 1996), EN 13674-1:2017, BS 11-1985.
- Brand mark example:
60 Ⅱ 13 05 23 SAIL T-12 1080 HH ← △
(kg/m, II quality, 13 m, May-2023, mill, grade, heat-treated, directional arrow)
6. Historical Milestones
| Year | Event |
|---|---|
| 1853 | First rail (50 lb/yd ≈ 25 kg/m) on BB&CI |
| 1920 | 90 R becomes “standard” on MG & FG |
| 1950 | 52 kg adopted for high-speed routes (120 km/h) |
| 1985 | Decision to switch to 60 kg UIC profile (speed-cum-freight) |
| 1992 | First HH rail (imported) laid on Agra-Gwalior curve |
| 1997 | Indigenous HH rail production started at Bhilai |
| 2005 | IRS T-12:2005 specifies 1080 grade MA rails |
| 2016 | 260 m long rail panels (Bhilai) – longest in Asia |
| 2023 | 100 % UST mandatory; QR-coded stamping launched |
7. Current Status & Recent Updates (2024)
- Indian Railways consumes ≈ 7.5 lakh tonnes rail/yr (60 % HH).
- Policy: All new lines & renewals ≥ 160 km/h to use 60 kg HH; ≤ 100 km/h may continue 52 kg.
- Long-welded rail (LWR) now 260 m factory panels, field flash-butt welded to 1 km+ strings.
- DFC (E & W) completely 60 kg HH on concrete sleepers with elastic fastenings.
- Green initiative: Waste rail recycled into “R-Girders” for ROBs (Rail Over Bridges).
- RDSO developing 75 kg rail for 25-tonne axle-load dedicated freight corridors & heavy-haul (30 t) trials.
- Import substitution: Import of rails almost nil since FY 2021-22.
8. Weight vs Speed-Axle Load Matrix (IR Guideline)
| Speed (km/h) | Axle Load (t) | Recommended Rail |
|---|---|---|
| ≤ 100 | ≤ 20 | 52 kg |
| ≤ 130 | ≤ 22.5 | 60 kg |
| ≤ 160 | ≤ 22.5 | 60 kg HH |
| ≤ 200 | ≤ 22.5 | 60 kg HH + MA |
| ≥ 200 (future) | ≤ 25 | 75 kg HH (trial) |
9. Quick-Fire Data Points for MCQ
- Minimum vertical wear permitted before rail closure: 8 mm (IRPWM).
- Length tolerance for 13 m rail: ±10 mm.
- Straightness limit (edge camber): ≤ 0.5 mm in 1 m.
- Head width of 60 kg rail: 74.3 mm.
- Foot width of 90 R rail: 127 mm.
- Thermal stress in LWR at 40 °C ≈ 1.15 t/mm² → 115 t for 60 kg.
- Head-hardened depth: 25 mm minimum.
- HH rail life extension on 600 m radius curve: ≈ 2.5 × plain carbon.
- Mill trial of hypereutectoid rail: RDSO & SAIL, 2021.
Section 1: Welding Methods & Technical Specifications
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Which reaction mixture is used in Thermit welding of rails? A) Fe₂O₃ + Al B) Fe₃O₄ + Al C) FeO + Al D) Fe + Al₂O₃
Show Answer
Correct Answer: B Explanation: The reaction mixture used in Thermit welding of rails typically consists of Iron Oxide (Fe₃O₄) and Aluminum (Al) powder. -
The pre-heating temperature required before pouring Thermit metal is about A) 600–700 °C B) 700–800 °C C) 900–1,000 °C D) 1,100–1,200 °C
Show Answer
Correct Answer: C Explanation: Rail ends must be pre-heated to approximately 900–1,000 °C to ensure proper fusion with the molten Thermit steel. -
Standard gap kept between rail ends during Thermit welding is A) 25 mm ± 1 mm B) 20 mm ± 1 mm C) 30 mm ± 1 mm D) 15 mm ± 1 mm
Show Answer
Correct Answer: A Explanation: A standard gap of 25 mm ± 1 mm is maintained to allow the molten metal to flow and fuse the rail ends effectively. -
Which welding process gives the smallest HAZ (Heat Affected Zone) width on rails? A) Thermit Welding B) Gas Pressure Welding C) Arc Welding D) Flash-Butt Welding
Show Answer
Correct Answer: D Explanation: Flash-Butt Welding uses intense localized heating and pressure, resulting in the narrowest Heat Affected Zone compared to other methods. -
Which NDT technique is mandatory for 100 % inspection of field Thermit welds? A) Magnetic Particle Inspection B) Radiography C) USFD (Ultrasonic Flaw Detection) D) Dye Penetrant Test
Show Answer
Correct Answer: C Explanation: USFD is the mandatory non-destructive testing method used to detect internal flaws in Thermit welds on Indian Railways. -
Permitted hardness in Heat-Affected Zone (HAZ) of rail Thermit weld is A) ≤ 250 HV B) ≤ 350 HV C) ≤ 450 HV D) ≤ 500 HV
Show Answer
Correct Answer: B Explanation: To prevent brittleness, the hardness in the Heat-Affected Zone of a Thermit weld is generally restricted to 350 HV or less.
Section 2: Track Maintenance & Machines
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Which machine is used for deep screening of ballast? A) Tamping machine B) DTS C) BCM D) UNOMAT
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Correct Answer: C Explanation: The Ballast Cleaning Machine (BCM) is specifically designed for the deep screening and cleaning of the ballast bed. -
The breathing length provided at each end of LWR is A) 50 m B) 100 m C) 250 m D) 500 m
Show Answer
Correct Answer: B Explanation: The breathing length is the portion of a Long Welded Rail (LWR) at each end that exhibits longitudinal movement due to temperature changes, typically 100 m. -
Dynamic Track Stabiliser (DTS) is used for A) Tamping B) Lining C) Consolidation D) Screening
Show Answer
Correct Answer: C Explanation: The DTS machine is used to provide rapid artificial consolidation of the ballast bed after tamping or deep screening. -
The 37° probe in USFD equipment is primarily meant to detect A) Transverse head crack B) Bolt-hole crack C) Web lamination D) Foot fatigue
Show Answer
Correct Answer: B Explanation: The 37° angle probe in Ultrasonic Flaw Detection is specifically oriented to detect defects and cracks around the bolt holes in the rail web.
Section 3: Rails & Sleepers
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What is the standard length of a BG rail in Indian Railways? A) 12 m B) 13 m C) 15 m D) 26 m
Show Answer
Correct Answer: B Explanation: The standard length for a single Broad Gauge (BG) rail used on Indian Railways is 13 metres. -
Pre-stressed concrete sleepers are manufactured with concrete grade? A) M-35 B) M-45 C) M-50 D) M-60
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Correct Answer: D Explanation: High-strength M-60 grade concrete is used for manufacturing PSC sleepers to withstand heavy axle loads and vibrations. -
Vertical wear limit beyond which a rail must be replaced in Indian Railways is A) 5 mm B) 6 mm C) 8 mm D) 10 mm
Show Answer
Correct Answer: C Explanation: On Indian Railways, a rail is generally considered for replacement (due to wear) once the vertical wear reaches the limit of 8 mm. -
Which colour stripe on a new PRC sleeper indicates suitability for 60 kg rail? A) Yellow B) Green C) Blue D) Red
Show Answer
Correct Answer: C Explanation: A blue stripe on the side of a concrete sleeper indicates that it is specifically designed to accommodate 60 kg rail sections.
Section 4: Speed Restrictions & Operations
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The maximum validity of a Temporary Speed Restriction (TSR) without extension is A) 3 months B) 6 months C) 9 months D) 12 months
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Correct Answer: B Explanation: As per SOD 4.05, a Temporary Speed Restriction remains valid for a maximum of 6 months unless a formal extension is processed. -
The highest operational PSR (Permanent Speed Restriction) on Indian Railways at present is A) 130 km/h B) 140 km/h C) 150 km/h D) 160 km/h
Show Answer
Correct Answer: D Explanation: The Tughlakabad–Agra section currently supports the highest operational speed on the network at 160 km/h. -
Ride Index (RI) value of 2.75 measured by OMS is classified as A) Excellent B) Good C) Satisfactory D) Uncomfortable
Show Answer
Correct Answer: A Explanation: A Ride Index (RI) value below 3.0, specifically around 2.75, is categorized as “Excellent” ride quality.
Last Updated: January 2026
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