WELDING OF RAILS



WELDING OF RAILS

1.Tolerances on finished welded joints

1.1 Flash Butt joints

Welds with new rails

1.Vertical misalignment        

+ 0.3 mm at the centre of a 1m straight edge.

- 0mm

2.Lateral misalignment         

± 0.3 mm at the centre of a 1 m straight edge.

3.Head finishing (in widthSide of rail head should be finished to :

± 0.25 mm on gauge side at the centre of 10 cm straight edge

4.Finishing of top table surface

+ 0.2 mm at the centre of 10 cm straight edge.

– 0mm

5.Web zone (under side of head,web, top of base, both fillets each side) 

+ 3.0 mm of the parent contour

- 0 mm

6.Underside of rail foot shall be suitably finished without any minus tolerance to ensure proper seating on sleepers and unhindered movement of welded panels on end unloading rakes.

Welds with old rails

1.Vertical misalignment                    

± 0.5 mm at the centre of a 1 m straight edge

2.Lateral misalignment                     

± 0.5 mm at the centre of a 1 m straight edge

3.Head finishing (on sides)              

± 0.3 mm on the gauge side at the centre of a 10 cm straight edge

4.Head finishing(on top of table surface)                                 

± 0.2 mm at the centre of a 10 cm straight edge

5.Web zone (under side of head, web, top of base and both fillets on each side)    

+ 3.0 mm of parent contour

- 0.0 mm

1.2. A.T. Welded joints

1.Vertical misalignment             

+ 1.0 mm Measured at the end of 1 m straight edge.

- 0.0 mm

2.Lateral misalignment              

± 0.5 mm Measured at the centre of 1 m straight edge.

3.Head finishing on sides          

± 0.3 mm On gauge side (measured at the centre of 10 cm straight edge)

4.Finishing top table surface     

+ 0.4 mm Measured at the end of 10 cm straight edge

- 0.0mm

Note: Dispensation for joint geometry in case of old rails may be permitted by Chief Engineer.

2. Alumino thermic welding by SKV process— Some salient details.

Rail Type

Gap between rail ends(mm)

Preheating time (minutes)

Reaction time (sec)

Heating technique

75R(72UTS)

24-26

6-8

20+3

Top heating with air& Petrol

75R(90UTS)

24-26

6-8

20+3

do

90R(72UTS)

24-26

8-10

20+3

do

90R(90UTS)

24-26

8-10

20+3

do

52 kg(72UTS)

24-26

11

20+3

do

52kg(90UTS)

24-26

10-12

20+3

do

60kg(72UTS)

24-26

10

20+3

do

60kg(90UTS)

24-26

10

20+3

do

60kg(110UTS)

24-26

15

20+3

Top heating with compressed air petrol.

52 kg (90UTS)

24-26

4.0

20+3

Do

60 kg (90UTS)

24-26

4.5

20+3

Top heating with compressed air petrol and post weld treatment

Chrome Manganese Alloy Steel Rail

60 kg (UIC) Head Hardened Rail

24-26

24-26

4.5

20+3

Top heating with compressed air petrol and post weld treatment.

Wide Gap

 

 

 

 

52kg (90UTS)

74-76

10

25+5

Top heating with air petrol.

60kg (90UTS)

74-76

12

25+5

do

52 kg (90 UTS)

74-76

3.0

25+5

Top heating with Oxy-LPG

Combination Joint

 

 

 

 

60kg (90UTS) / 52kg(90UTS)

48-50

12

25+5

do

3. Important parameters of flash butt welding of rails.

Rail Section

Type of welding plant

Butting load capacity (tons)

Flashing stroke (mm0

Butting stroke (mm)

No. of preheats

Burn off time (sec)

Final flashing time(sec)

90 R (72 UTS)

AI-APHF-30

37

12

8

8

20

25-30

52 kg (72 UTS)

AI-APHF-30

37

12

10

10

10

15

52 kg (90 UTS)

ESAB

79

14

10

10

30-40

20-25

60 kg (72 UTS)

AI-APHF-30

37

12

10

12

10

40

60 kg (90 UTS)

ESAB

79

14

10

12

30-40

20-25

60 kg(110 UTS)

AI-APHF-60

60

5

5

8

5

19-24

4. Transverse test on welded test sample:
The existing para 10.2.2.1 of manual for flash butt welding of rails may be replaced as under. “10.2.2.1 The test weld sample not less than 1.5 m long with the weld in middle shall be supported on cylindrical or semi-cylindrical supports having a diameter of 30 to 50mm and distance of one metre between them. In case of 60kg 110 UTS/head hardened rail joints the test span shall be 1.25 metre. The mandrel diameter shall be between 30 to 50 mm. The mandrel axis should be perpendicular to the horizontal axis of the rail section and it should be positioned at the centre of the weld. The weld shall be in the centre of the span and loaded in such a manner that the foot of the rail is in tension. The load shall be uniformly and gradually increased. The rate of application of the load should not exceed 2.5 tons/sec. The test joints shall withstand the minimum load and shall show minimum deflection as given in Table 1 without showing any signs of cracking or failure. The minimum deflection values are corresponding to stipulated minimum breaking loads

TABLE -1

VALUES OF MINIMUM BREAKING LOAD AND DEFLECTION IN TRANSVERSE LOAD TEST

S.No

Rail Section

Span

Min.breaking load (tonnes)

Min. deflection at centre(mm)

Frequency of testing

Stationary

FBW Plant

Mobile

FBW Plant

1.

60 kg (UIC) NHH

1.25m

115

30

1 in 500

1 in 100*

2.

60 Kg (UIC) Cr. MN. Alloy steel

1.25m

110

12

1 in 500

1 in 100*

3.

60 kg (UIC) 90 UTS

1m

150

20

1 in 1000

1 in 100*

4.

52 kg 90 UTS

1m

100

15

1 in 1000

1 in 100*

5.

60 kg UIC MM (72 UTS)

1m

135

30

1 in 1000

1 in 100*

6.

52 kg MM(72 UTS)

1m

100

30

1 in 1000

1 in 100*

7.

90R MM(72 UTS)

1m

80

30

1 in 1000

1 in 100*

8.

75R MM(72 UTS)

1m

70

30

1 in 1000

1 in 100*

9.

60 R MM (72UTS)

1m

60

25

1 in 1000

1 in 100*

*Sample joints for first 1000 joints welded by a Mobile Flash Butt Welding Plant will be tested at a frequency of 1 in 100 joints and subsequently at a frequency of 1 in 500 joints. ”

4.1 Thermite welded joints.

Rail Type

Rail Section

Min. transverse breaking load in tonnes

Min. deflection in mm at the centre at the load in col. 3

72 UTS to IRS-T-12

60 R

50

15

-do-

75 R

55

15

-do-

90 R

65

15

-do-

52 Kg

85

18

-do-

60 kg

95

18

90 UTS to IRS T-12/UIC 860-0 or equivalent

 

60

15

 

90 R

80

15

 

52 Kg

90

15

 

60 kg

115

15

Alloy Steel (Cr-Mn or Cr-V type 110 UTS)

52 kg

95

10

 

60 Kg

115

10

Head Hardened rails

60 Kg

115

12

Combination joint

*52 kg (90UTS)/

70

15

(50 mm gap)

90R (72UTS)

 

 

-do-

60 kg (90UTS)/

90

15

 

52 kg (90UTS)

 

 

*90UTS portion should be used in 52 kg/90 R combination joints.

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