Upon reviewing the Hanger report in AutoPIPE, AutoPIPE automatically selects a spring, defined by the asrisk (*) in the report. When there are mutliple options for 1 spring, it seems to always select that spring which has the greatest variation in hot vs cold load, provided it is within the defined allowable range (default 25%).
This seems strange. Why doesnt AutoPIPE select the spring with the smallest variation? Wouldnt that make more sense, as it will yield a better operation of the spring? Or am I missing something?
The real answer is Money. A bigger spring with more travel (less variation) costs more. Same reason you don't use a constant spring if a variable will work. You as an engineer have to decide what variation is acceptable.
Yes I do understand that. But that wasnt my question.
Let me rephrase my initial question: why doesnt AutoPIPE select the spring with the smallest variation - why does AutoPIPE not select the technically best option when there are mutliple options, but instead selects the 'worst'?
I believe there must have been a good reason in the past when AutoPIPE algorithms were defined. Mike, do you have a good explanation? During workshops with engineers, we have been discussing this issue several times. Better technical conditions for pipe appears when spring has LESS variability between cold and hot states. Perhaps it would be a good idea to give a choice what criteria should be applied by default?
Best regards,
Maciej Rydlewicz, PhD Eng.
maciej.rydlewicz@softdesk.pl
+48 512206994
Hello HVN,
A this time (Aug 2019) AutoPIPE Spring hanger calculates the spring requirements and then starts to search the designated spring tables to determine which spring will be a suitable fit. When the program finds the first spring that meets the requirements it is selected. The program then continues to search the spring tables for other springs and lists those that meet the requirements afterwards.
Again, the first suitable spring found from the manufacture tables would be selected while other suitable springs are listed. The algorithms does not evaluate any other criteria beside spring requirements.
Regards,
Mike DattilioBentley Systems Design AnalystDesign Engineering Analysis group===================================================
Hi Mike, thanks for getting back to me. From previous posts, and my OP, I have already understood how AP works. The reason for me posting this subject; the logic in AutoPIPE's steps for selecting a spring dont make sense, to me at least. If it's programmed to take the technically 'worst' solution, it wouldnt be too difficult to program it to take the technical best solution, wouldnt it? I understand the programmers had to make a choice, somewhere in writing their script. But that was in the past.
Another disadvantage I found with the current programming logic, is that when my system has multiple hangers, all initially set to undesigned, I have to re-run the analysis a few times. Having all the hangers set to undesigned, after the first run, I modify the first hanger's setting to the one with the least load variation. I then redo the anlaysis and usually find that the other hangers, which were still set to undesigned, have different outcomes. As such, I have to rerun the anaylsis a few times, iterating to last hanger set to undesigned. Having the program reason the other way around would make more sense, and yield a better solution, I think.
I understand AP is not designed to take away the designer and engineer's engineerings judgement; AP is just a tool. However, I believe a lot of engineers dont use it that way; for such 'engineers' it would be better the have some different steps in the program.