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Reg. 43
MATERIALS OF CONSTRUCTION

SEAMLESS CARBON STEEL PIPES FOR HIGH TEMPERATURE SERVICE FOR DESIGN METAL TEMPERATURES NOT EXCEEDING 454 DEGREE C (850 DEGREE F)


(a)  General - (i) These regulations cover both hot finished and cold drawn seamless carbon steel pipes for high temperature service.  The pipes shall conform in all respects with the requirements herein specified.

(ii)  The seamless pipes conforming to other national/international standards which are known to be commonly used as being suitable for high temperature service can also be used with the designations of the national/international standards, provided such materials are not specifically prohibited by the regulations.

(iii)   While making pipes to other national/internationals standards the allowable stresses of the respective nation/international standards shall be strictly followed while designing the tubes.

(b)   Material. - (i)  The pipes 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 following limits of chemical composition.

Grade                                 Chemical composition %

                   C                     Mn                   Si                       S                      P

PA                   0.25*               0.27                 0.10                 0.035               0.035

                        Max                 0.93                 min                   max                  max

PB                   0.30*               0.29                 0.10                 0.035               0.035

                        Min                  1.06                 min                   max                  max

PC                   0.35*               0.29                 0.10                 0.035               0.035

                        Max                 1.06                 min                   max                  max

* For each reduction of 0.01% below the specified carbon maximum, an increase of 0.06% manganese above the specified maximum will be permitted up to a maximum of 1.35%.

(b)   Heat treatment. - Hot finished pipes need not be heat treated.  Cold drawn pipes shall be given a sub-critical anneal, a full anneal, or a normalising heat treatment after the final cold finishing process.

(c)    Workmanship and Tolerance. - The pipes shall be well finished, cleaned free from harmful defects.  They shall be reasonably straight, smooth, cylindrical and subject to the following tolerance.  Pipes manufacturer shall explore a sufficient number of visual inspections to provide reasonable assurance that they have been properly evaluated.

(i)            Permissible variations in outside diameter :

Hot finished and cold finished seamless pipes

Outside diameter

(mm)

Permissible variations (mm)

              Over                              Under

10.3 to 48.3 incl.,        

0.40

0.40

Over 48.3 to 114.3 incl.,

0.79

0.79

Over 114.3 to 219.1 incl.,

1.59

0.79

Over 219.1 to 457.0 incl.,       

2.38

0.79

Over 457.0 to 660.0 incl.,

3.18

0.79

Over 660.0 to 864.0 incl.,

3.97

0.79

Over 864.0 to 1219.0 incl.,

4.76

0.79

(ii)            Permissible variation in wall thickness:

The minimum wall thickness at any point shall not be more than 12.5% under the nominal wall thickness specified.

(iii)        Permissible variation in exact length:

Seamless Hot finished and Cold finished pipes can be ordered in specified length or in random length.  If ordered in specified length, the tolerances for all sizes shall be +6.0 mm/-0.0mm.

(d)   Test specimens. - (i)  Test specimen required for flattening and expanding/flaring test specified in regulations 44(a), 44(b) and 44(c) shall be taken from ends of finished pipes prior to upsetting, swaging, expanding or any other forming operations or being cut to length.  They shall be smooth on ends and free from burrs and flaws.

(ii)  If desirable and practicable, tensile test may be carried out on full section of the pipe up to the capacity of the testing machine.  For large size pipes, the tensile test specimen shall consist of strip cut longitudinally from the pipe and which is not straightened within the gauge length and 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 44(a), 44(b) and 44(c) shall be made on minimum 2 pipes for first 100 pipes and 1 per 100 or part thereof for pipes over 100 numbers.

 
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