Problem:

 For a material like CS the reference for thermal expansion coefficient definition is Table C-1 of ASME B31.3, as per screenshot below reported:

Nevertheless, we have considered an operating case using AutoPIPE Connect v12.1:

Piping Code = ASME B31.8 - 2016

Material library = B318-16

Temp amb. = 20° °C

Pipe Material  = CS (Carbon Steel)

Temp design = 125 °C

AutoPIPE shows a Thermal Expansion Coefficient i= 1.273 vs 1.3 foreseen by Table C-1 of ASME B31.8

Why?

Solution:

Note, be very careful when referencing code editions. From the above user submission, they spoke of assigning AutoPIPE's piping code = ASME B31.3 - 2016. However, they  then showed a reference for ASME B31.3 - 2020. Again, be mindful to look up and use the exact same code reference as being specified in the software.

For most of the material libraries, AutoPIPE uses the English unit system when creating the library. This is also true for ASME B318-16 library. Please see the referenced table and material group from ASME B31.3 (2016) on the left and the values entered for the same material on the right in the image below:

We can see that the values entered in the library are correct as per English unit system. See the following conversion process of these values with answer as given by program (1.273 mm/m):

Tamb = 20 deg C

T1 = 125 deg c

Convert to English Temp units: (degC*9/5) +32

Tamb =( 20 * 9/5 ) + 32 = 68 deg F

T1 =( 125 * 9/5 ) + 32 = 257 deg F

Thermal Expansion Calculation in in / 100 ft

Reference Material Library B318-16.LIB

Example: = [ (68- (-50)) * (0.00 - (-0.9)) / (70 - (-50)) ] + (-0.9)

Interpolated Thermal Expansion Coeff, values:

68 deg F = -0.015 in / 100ft

257 deg F = 1.513 in / 100ft 

Calculate expansion from Tamb to T1

= 1.513 - (-0.015) 

= 1.528 in / 100ft

Convert units: (ExpEng / 1200) x 1000

1.528 in / 100ft = 1.273 mm / m

See Also

Explain why default material values do NOT match code reference

Libraries - AutoPIPE

Bentley AutoPIPE

External Links