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Reg. 44
MATERIALS OF CONSTRUCTION

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


(a) Tensile test. -  Test pieces cut from the ends of the selected pipes shall comply with the following requirements.  The tensile test may be carried out on the test pieces cut out from the pipe in the longitudinal direction which shall not be further heat treated nor straightened within the gauge length.  As an alternative, pipes may be tested on full cross section.

 

 

Grade

Yield Strength

MPa (kg/mm2)

min

Tensile Strength Mpa (kg/mm2)

Min

%Elongation

on G.L.=50mm min for full tube testing

PA

205 (21.1)

330(33.1)

35

PB

240 (24.7)

415 (42.2)

30

PC

275 (28.2)

485 (49.3)

30

For longitudinal strip test, the minimum required elongation shall be determined by the following equation.

e  = 1944 (A 0.2/U0.9)

where  e = minimum elongation in 50.8 mm, % rounded to the nearest 0.5%.

A = cross sectional area of the tensile test specimen in mm2 based on specified outside diameter or nominal specimen width and specified wall thickness rounded to the nearest 6.45 mm2.  If the area thus calculated is more than 484 mm2 then use area as 484 mm2.  If the calculated area is less than 484mm2 then use the actual area thus obtained.

            U = specified tensile strength in Mpa.

(b) Bend test. - For pipes of outside diameter 60.3 mm and under, a bend test shall be conducted.  A sufficient length of pipe shall stand being bent cold through 90 degree around a cylindrical mandrel, the diameter of which is 12 times the nominal diameter of the pipe, without developing cracks.

(c) Flattening test. - (i) For pipes of outside diameter over 60.3 mm, a flattening test shall be conducted.  A section of the pipe not less than 63 mm in length shall be flattened cold between two parallel flat surfaces to a distance between the plates (H) as calculated by the formula given below, without showing any sign of a crack or flaw.

         (1 + e) t

H =  -----------

         e + t/D

where     t = specified thickness of pipe (mm)

            D = specified outside diameter of the pipe (mm)

            e = a constant, as given below

 e = 0.07 for carbon steel with maximum specified carbon 0.19% or more       

 e = 0.09 for carbon steel with maximum specified carbon 0.18% or less.

(ii)  For pipe whose diameter equals or exceeds 254 mm, a bend test may be conducted instead of the flattening test.  The bend test specimens shall be bent at room temperature through 180 degree without cracking on the outside of the bent portion.  The inside diameter of the bend shall be 25 mm.  Substitution of the bend test for the flattening test shall be subject to the approval of the purchaser.

(iii)  For pipe whose diameter exceeds 635 mm and whose diameter to wall thickness ratio is 7.0 or less, the bend test described in clause (b) shall be conducted instead of the flattening test.

 
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