Section 6 Boiler and superheater tubes
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Clasifications Register Rules and Regulations - Rules for the Manufacture, Testing and Certification of Materials, July 2022 - Chapter 6 Steel Pipes and Tubes - Section 6 Boiler and superheater tubes

Section 6 Boiler and superheater tubes

Parent topic: Chapter 6 Steel Pipes and Tubes

6.1 Scope

6.1.1 Provision is made in this Section for boiler and superheater tubes in carbon, carbon-manganese and low alloy steels.

6.1.2 Austenitic stainless steels may also be used for this type of service. Where such applications are proposed, details of the chemical composition, heat treatment and mechanical properties are to be submitted for consideration and approval.

6.2 Manufacture and chemical composition

6.2.1 Tubes are to be seamless or welded and are to be manufactured in accordance with the requirements of Ch 6, 2 Seamless pressure pipes and Ch 6, 3 Welded pressure pipes, respectively.

6.2.2 The method of deoxidation and the chemical composition of ladle samples are to comply with the requirements given in Table 6.2.1 Chemical composition of seamless pressure pipes or Table 6.3.1 Chemical composition of welded pressure pipes, as appropriate.

6.3 Heat treatment

6.3.1 All tubes are to be supplied in accordance with the requirements given in Table 6.2.2 Heat treatment or Table 6.3.3 Heat treatment: welded pressure pipes as appropriate, except that 1Cr½Mo steel may be supplied in the normalised only condition when the carbon content does not exceed 0,15 per cent.

6.4 Mechanical tests

6.4.1 Tubes are to be presented for test in batches as defined in Ch 6, 1 General requirements.

6.4.2 Each boiler and superheater tube selected for test is to be subjected to at least the following:

  1. Tensile test.

  2. Flattening or bending test.

  3. Expanding or flanging test.

6.4.3 The results of all mechanical tests are to comply with the appropriate requirements given in Table 6.6.1 Mechanical properties for acceptance purposes: boiler and superheater tubes.

6.5 Mechanical properties for design

6.5.1 The mechanical properties at elevated temperature for carbon and carbon-manganese steels in Grades 320 to 460, 1Cr½Mo and 2¼Cr1Mo steels can be taken from the appropriate Tables in Ch 6, 2 Seamless pressure pipes.

6.5.2 Where rimming steel is used, the design temperature is limited to 400°C.

Table 6.6.1 Mechanical properties for acceptance purposes: boiler and superheater tubes

Type of steel Grade Yield stress N/mm2 Tensile strength N/mm2 Elongation on 5,65% minimum Flattening test constant C Bend test diameter of former (t = thickness) Drift expanding and flanging test minimum % increase in outside diameter
Ratio
≤0,6 >0,6≤0,8 >0,8
Carbon and carbon- manganese 320 195 320–440 25 0,10 4t 12 15 19
360 215 360–480 24 0,10 12 15 19
410 235 410–530 22 0,08 10 12 17
460 265 460–580 21 0,07 8 10 15
1Cr1 /2Mo 440 275 440–590 22 0,07 4t 8 10 15
21 /2Cr1Mo 410
(see Note 1) 		135 410–560 20 0,07 4t 8 10 15
490
(see Note 2) 		275 490–640 16

Note 1. Annealed condition.

Note 2. Normalised and tempered condition.

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