chris456s
Structural
- Feb 2, 2017
- 50
I only have access to BPVC 2019 and 2015
BPVC.III.2-Annex 3-A 2019 says, for carbon steel in class 1 vessels allowable stresses comes from Sec II, Part D Table 2a and table 5A for class 2 vessels.
While 2015 Annex 3-A makes no class distinction and says carbon steel allowable stress comes from Sec II, Part D table 5A
I assume that "class" in Annex 3-A is in reference to vessel class not material grade/class since materials like A106-B that don’t use class in their grading system and appears in both tables 2a and 5a.
However, I am confused on the vessel classing system. Seems like class 1 vessels have lesser allowable and require part 4 of BPVC.III.2 to govern using part 5 only as a supplement where part 4 cannot be applied (VIII.2 - 4.1.1.2.1 and 5.1.1.3.1). This is much stricter that class 2 vessel design where the allowables are much larger and one can freely use part 5 of BPVC.III.2. So, class 1 vessel design is at a large disadvantage to class 2 design. Class 1 design will produce thicker members and may have a much more laborious calculation process. Although I find some discussion as to the design criteria for both, I do not find a strict satisfactory definition. The definitions given in Annex 1-B of BPVC.III.2 2019 just say the class 1 are vessels that use allowables from II table 2a, while class 2 are vessels that use allowables from table 5a. So, my questions are as follows:
1) are there better definitions than those given in Annex 1-B of BPVC.III.2 2019 for class 1 and 2 vessels? How to choose which class is appropriate for your project?
2) if annex 1-B is the only definition, why would anyone choose a class 1 design when the acceptance criteria is so much more strict (lesser allowables and less of an option to use part 5 of III.2)?
3) why does this distinction appear in 2019 (maybe 2017) and not in 2015? What purpose does this change serve? What is accomplished by this vessel class distinction?
BPVC.III.2-Annex 3-A 2019 says, for carbon steel in class 1 vessels allowable stresses comes from Sec II, Part D Table 2a and table 5A for class 2 vessels.
While 2015 Annex 3-A makes no class distinction and says carbon steel allowable stress comes from Sec II, Part D table 5A
I assume that "class" in Annex 3-A is in reference to vessel class not material grade/class since materials like A106-B that don’t use class in their grading system and appears in both tables 2a and 5a.
However, I am confused on the vessel classing system. Seems like class 1 vessels have lesser allowable and require part 4 of BPVC.III.2 to govern using part 5 only as a supplement where part 4 cannot be applied (VIII.2 - 4.1.1.2.1 and 5.1.1.3.1). This is much stricter that class 2 vessel design where the allowables are much larger and one can freely use part 5 of BPVC.III.2. So, class 1 vessel design is at a large disadvantage to class 2 design. Class 1 design will produce thicker members and may have a much more laborious calculation process. Although I find some discussion as to the design criteria for both, I do not find a strict satisfactory definition. The definitions given in Annex 1-B of BPVC.III.2 2019 just say the class 1 are vessels that use allowables from II table 2a, while class 2 are vessels that use allowables from table 5a. So, my questions are as follows:
1) are there better definitions than those given in Annex 1-B of BPVC.III.2 2019 for class 1 and 2 vessels? How to choose which class is appropriate for your project?
2) if annex 1-B is the only definition, why would anyone choose a class 1 design when the acceptance criteria is so much more strict (lesser allowables and less of an option to use part 5 of III.2)?
3) why does this distinction appear in 2019 (maybe 2017) and not in 2015? What purpose does this change serve? What is accomplished by this vessel class distinction?
