You are right, checking is imperative indeed.
This estimation is based on certain assumptions:
1) Piping stress isos will have probable support positions marked
2) Pipe Spec, branch table, insulation thk table, valve weights, P&ID, line designation table available
3) Piping stress analysts are skilled & motivated enough
4) It is a statistical estimate. One size may not fit all. It requires adjustment based on feedback in actual workplace.
regards,
sam
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