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Reg. 48
MATERIALS OF CONSTRUCTION

SEAMLESS FERRITIC AND AUSTENITIC ALLOY STEEL BOILER, SUPERHEATER AND HEAT EXCHANGER TUBES


(a) Material. - (i) The tubes shall be seamless and manufactured from steel produced by an open hearth or electric process or any of the oxygen processes.  The steel shall be fully killed.

(ii) The steel shall conform to the limits of chemical compositions given in Table-1 and 2.

(iii) The grain size of cold worked grade TP 321H shall be No.7 or coarser.

(b)   Heat treatment. - (i)  All tubes of grades in Table-1, except T 91, 12X1Mo and X20CrMoV121 shall be reheated and furnished in full annealed, isothermal annealed or normalised and tempered condition.  If furnished in the normalised and tempered condition, the minimum tempering temperature for Grades T1 and T11 shall be 650 degree C and the minimum tempering temperature for Grades T5, T9 and T22 shall be 675 Degree C.

(ii)  Tubing of Grades T1, T2 and T12 either hot finished or cold drawn, may be given a final heat treatment at 650 degree C to 730 degree C, instead of heat treatments specified in sub-clause (i) above, at the option of the manufacture.

(iii)  Grade T91 shall be normalised at 1040 degree C minimum and tempered at 730 degree C minimum as a final heat treatment.

(iv)  Grade 12x1Mo shall be normalised at 950 - 980 degree C and tempered at 720 - 750 degree C for a period of 1 to 3 hours.

(v)  Grade X20CrMoV121 shall be normalised at 1020 - 1070 degree C and tempered at 730 - 780 degree C for a period of 1 hour minimum.

(vi)  All austenitic tubes (Table 2) shall be furnished in the heat treated condition.  The heat treatment procedure, except for the H grades shall consist of heating the material to a minimum temperature of 1040 degree C and quenching in water or rapidly cooling by other means.

(vii)  All H grades shall be furnished in the solution treated condition.  If cold working is involved in processing, the minimum solution treating temperatures for grades TP321H and TP347H shall be 1100 degree C and for grades TP304H and TP316H shall be 1040 degree C.  If the P grade is hot rolled, the minimum solution treatment for grades TP 321 H and TP 347 H shall be 1050 degree C and for grades TP 304H and TP 316H shall be 1040 degree C.

(c) Workmanship and tolerance - The tubes shall be well finished, cleaned free from harmful defects.  They shall be reasonably straight, smooth, cylindrical and subject to the following tolerances.  Finished tubes shall be reasonably straight and have smooth ends free of burrs.  They shall have a workmanlike finish.  Surface imperfections like any discontinuity or irregularity found in the tube may be removed by grinding, provided that a smooth curved surface is maintained, and the wall thickness is not decreased  to less than that permitted.  The outside diameter at the point of grinding may be reduced by the amount so removed.

(i) Permissible variation in outside diameter:

 For all grades except 12X1Mf and X20CrMoV121

Outside diameter (mm)

                      Permissible Variation (mm)

Over

Under

Hot finished Seamless tubes

101.6 and under

0.4

0.8

Over 101.6 to 190.5 incl.

0.4

1.2

Over 190.5 to 228.6 incl.

0.4

1.6

Cold finished Seamless tubes

Under 25.4

0.10

0.10

Over 25.4 to 38.1 incl.

0.15

0.15

Over 38.1 to 50.8 excl.

0.20

0.20

50.8 to 63.5 excl.

0.25

0.25

63.5 to 76.2 excl.

0.30

0.30

76.2 to 101.6 incl.

0.38

0.38

Over 101.6 to 190.5 incl.

0.38

0.64

Over 190.5 to 228.6 incl.

0.38

1.14

 For grade 12X1Mf

Outside diameter (mm)

Permissible Variation (mm)

Over

Under

Hot finished and cold finished tubes

Under 30.0

0.30

0.30

30 to 50

0.40

0.40

Over 50.0

0.80%

0.80%

 For grade X20CrMoV121

Outside diameter

Permissible Variation (mm)

Over

Under

Hot finished Seamless tubes

100 and under

0.75% (0.5 mm  min)

0.75% (0.5 mm min)

Cold finished seamless tubes

120 and under

0.60% (0.25 mm  min)

0.60%(0.25 mm  min)

Over 120

0.75%

0.75%

 (ii) Permissible variation in Wall Thickness :

 For all grades except 12X1Mf and X20CrMoV121

Outside

Diameter

(mm)

 

Wall thickness %

 

2.4 and under

Over 2.4 to 3.8 incl.

Over 3.8 to 4.6 incl.

Over 4.6

 

Over

Under

Over

Under

Over

Under

Over

Under

Seamless hot finished tubes

101.6 and Under

40

0

35

0

33

0

28

0

Over 101.6

0

     0

35

0

33

0

28

0

Seamless cold finished tubes

 

Over

Under

38.1 and under

20

0

Over 38.1

22

0

 For Grade 12X1Mf

Outside Diameter (mm)

Permissible variation %

Over

Under

Hot Finished Seamless Tubes

108 and under

15

10

Over 108

20

5

Cold Finished Seamless Tubes

All sizes

10

10

 For Grade X20CrMoV121

Outside diameter (mm)

Permissible variation %

Over

Under

100 and under

12.5

10

 (iii) Permissible variation in length for exact length tubes.

For all Grades except 12X1Mf and X20CrMoV121

Method of manufacture

Outside diameter (mm)

      Cut length (mm)

Over                      Under

Seamless Hot finished

All sizes

   5                             0

Seamless Cold finished

Under 50.8

   3                             0

50.8 Over

   5                             0

Note : These permissible variations in lengths apply to cut lengths upto and including 7.3 m.  For lengths over 7.3 m,  an additional over tolerance of 3 mm for each 3 m or fraction thereof, shall be permissible, upto a maximum of 12 mm.

For grade 12X1Mf

Out side diameter (mm)

Length of tubes (m)

Permissible variation (mm)

    Over                   Under

Under 108

Under 9

      15                         0

9 to 12

      35                         0

108 and over

All lengths

      50                         0

For grade X20CrMoV121

Length of tube (m)

                     Permissible variation  (mm)

              Over                                         Under

6 and under

                10

                 0

Over 6 to 12 incl.

                15

                 0

(d) Test specimens. - (i) Test specimens required for the flattening and expanding/ flaring test specified in regulations 49(a), 49 (b) and 49(c) shall be taken from the ends of finished tubes prior to upsetting, swaging, expanding or any other forming operations or being cut to length.  They shall be smooth on the ends and free from burrs and flaws.

(ii)  If desirable and practicable, tensile test may be carried out on full section of the    tubes upto the capacity of the testing machine.   For large size tubes, the tensile test specimen shall consist of strip cut longitudinally from the tube and which is not straightened within the gauge length further heat treated.

(iii) If any test specimen shows flaws or defective machining it may be discarded and another specimen substituted.

(iv)      All specimens shall be tested at room temperature.

(e)  Number of tests. -  The tests specified in regulations 49(a), 49(b) and 49(c) shall be made on minimum 2 tubes for first 100 and 1 per 100 or part thereof for tubes over 100 numbers.  

TABLE 1

CHEMICAL REQUIREMENTS FOR FERRITIC STEELS

Grade

Chemical composition %

 

C

Mn

Si

S

P

Cr

Mo

V

Ni

Other  Elements

T1

0.10

0.20

0.30

0.80

0.10

0.50

0.025

max

0.025

max

-------

0.44

0.65

---

---

----

T2

0.10

0.20

0.30

0.61

0.10

0.30

0.025

max

0.025

max

0.50

0.81

0.44

0.65

----

---

-----

T5

 

0.15

max

0.30

0.60

0.50

max

0.025

max

0.025

max

4.00

6.00

0.45

0.65

----

----

-----

T9

0.15

max

0.30

0.60

0.25

1.00

0.025

max

0.025

max

8.00

10.0

0.90

1.10

----

----

-----

T11

0.05

0.15

0.30

0.60

0.50

1.00

0.025

max

0.025

max

1.00

1.50

0.44

0.65

----

----

-----

T12

0.05

0.15

0.30

0.61

0.50

max

0.025

max

0.025

max

0.80

1.25

0.44

0.65

----

---

          -----

T22

0.05

0.15

0.30

0.60

0.50

max

0.025

max

0.025

max

1.90

2.60

0.87

1.13

----

----

          -----

T91

0.08

0.12

0.30

0.60

0.20

0.50

0.010

max

0.020

max

8.00

9.50

0.85

1.05

0.18

0.25

----

Nb = 0.06 -0.10

N = 0.030 to 0.070

Ni = 0.40 max

Al = 0.04 max

12X1

Mf

0.10

0.15

0.40

0.70

0.17

0.37

0.025

max

0.025

max

0.90

1.20

0.25

0.35

0.15

0.30

0.25

max

Cu=0.20

Max

X20

CrMoV

121

0.17

0.23

1.00

max

0.50

max

0.030

max

0.03

max

10.0

12.5

0.80

1.20

0.25

0.35

0.30

0.80

 

TABLE 2

 CHEMICAL REQUIREMENTS OF AUSTENTIC STEEL

Grade

Chemical composition %

 

C

Mn

Si

S

P

Cr

Mo

V

Ni

Other

Elements

TP304

0.08

max

2.00

max

0.75

max

0.030

max

0.040

max

18.0

20.0

----

----

8.00

11.0

----

TP304H

0.04

0.10

2.00

max

0.75

max

0.030

max

0.040

max

18.0

20.0

-----

----

8.00

11.0

-----

TP304L

0.035

max

2.00

max

0.75

max

0.030

max

0.040

max

18.0

20.0

-----

----

8.00

13.0

-----

TP310S

0.08

max

2.00

max

0.75

max

0.030

max

0.045

max

24.0

26.0

0.75

max

----

19.0

22.0

-----

TP316

0.08

max

2.00

max

0.75

max

0.030max

0.040

max

16.0

18.0

2.00

3.00

----

11.0

14.0

-----

TP316H

0.040

0.10

2.00

max

0.75

max

0.030

max

0.040

max

16.0

18.0

2.00

3.00

----

11.0

14.0

-----

TP316L

0.035

max

2.00

max

0.75

max

0.030

max

0.040

max

16.0

18.0

2.00

3.00

----

10.0

15.0

-----

TP321

0.08

max

2.00

max

0.75

max

0.030

max

0.040

max

17.0

20.0

----

----

9.00

13.0

Ti = 5xC min

0.60 max

TP321H

0.04

0.10

2.00

max

0.75

max

0.030

max

0.040

max

17.0

20.0

----

----

9.00

13.0

Ti = 4xC min

0.60 max

TP347

0.08

max

2.00

max

0.75

max

0.030

max

0.040

max

17.0

20.0

----

----

9.00

13.0

Nb + Ta = 10xC min

1.000 max

TP347H

0.04

0.10

2.00

max

0.75

max

0.030

max

0.040

max

17.0

20.0

----

-----

9.00

13.00

Nb + Ta = 8xC min

1.00 max"

 
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Message from Chairman of Central Boilers Board About Central Boiler Board History of Indian Boiler Regulations Foreword Contents Chapter Wise Contents Regulation Wise List of Amendments
Indian Boilers Act 1923 Ibr Forms Home Search Help Contact Us