Explain why default material values do NOT match code reference values in AutoPIPE?
Model with ASME CC N-755-1 (HDPE) material has default thermal expansion set to 3.648 @ 70 deg F and 6.528 @ 100 deg F, shown here:
However the reference mentions that the default values should be 8.0x10^-5.
ASME B31.3 - 2014 model using SI units.
However the reference mentions that the default values should be 6.9 mm/m
As shown on WIKI here, review the reference and values used by AutoPIPE for the default values used in the material library:
Review the reference mentioned above.
Compare the results for thermal expansion,
Appendix E Table E1 = 8.0x10^-5 = 0.00008 in / in deg f
AutoPIPE Material Library = 80x10^-6 = 0.00008 in / in deg f
Note, AutoPIPE Material library values match reference source exactly.
However, this does not match the Expan. value shown on the Press/Temp/Pipe ID tab of the input grids, why?
Be careful, look at the units!
Material Library Expan value units are in / in deg f
Where Press/Temp/Pipe id tab Expan value units are in / 100ft.
Convert the Material Library Expan. value
Ambient temp was found to be 32 Deg F:
Difference between Ambient and T1 load case
70 deg f -32 deg f = 38 deg f
100 deg f - 32 deg f = 68 deg f
Multiply by Material library Coeff. of Expansion for the given temp
38 deg f * 0.00008 in / in deg f = 0.00304 in / in
68 deg f * 0.00008 in / in deg f = 0.00544 in / in
Convert In / In to In / ft
0.00304 in / in (12 in / 1ft) = 0.03648 in / ft
0.008 in / in * (12 in / 1 ft) = 0.06528 in / ft
Convert to in / ft to In / 100 ft
0.03648 in / ft * 100 ft = 3.648 in / 100 ft
0.096 in / ft * 100 ft = 6.528 in / 100 ft
Compare to Press/Temp/PipeID tab data values
both values matched exactly!!
Scan the library for the assign properties,both Spec and Matl Tables:
Remember, similar to Code tables, in AutoPIPE all library files are entered in English units, than the program converts the values to other units by using factors found in an assigned UNT file. In this example, the unit file specified = SI for both input and output.
To see the conversion factor used, open the SI.UNT file (default location: C:\ Program Files (x86) \ Bentley \ AutoPIPE CONNECT v11 ) in any word editing application (ex. MS Word, NotePAD, Ultra Edit.):
The scale factor used for converting Thermal Expansion from in/100ft to mm/m can be found on line #25 of the file, factor = 0.8333:
Using Linear Interpolation to figure out the Thermal Expansion for 402 deg F and round off the results to one significant digit. Note that the value matches the code value from table C-2 of the code, imaged above.
Noted that 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, considered an operating case using AutoPIPE Connect v12.1:
It results that Expansion Coefficient is 1.273 vs 1.3 foreseen by Table C-1 of ASME B31.8 (see figures below):
help us to understand the reason of this incongruences?
Again, 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. The attached excel sheet does the conversion and calculation of these values, with answer as given by program (1.273 mm/m):
Similar calculations can be used for the B318-12 library (shown in the last row of the calculation above). The B318-12 library values and help reference is given below. The excel sheet is attached with this email.
AutoPIPE's default material values mentioned in the Material Library do match the referenced source values. Also demonstrated was how to correctly convert values from the material library to values displayed in the Expan. column on the Press/Temp/Pipeid tab of the input grids or Operating Pressure & Temperature dialog.