Why is that there is a big discrepancy between the AutoPIPE Hanger Analysis calculated values and the values that are actually on the spring cans that have been in service for many years.
Highly recommend that you see AutoPIPE online help mentioned at the top of previous WIKI page for details on how the program selects a spring hanger.
Based on the settings for Hanger Analysis (i.e. Manufacturer, Design Operating case(s), etc..), modeled piping arrangement, support locations, etc..; AutoPIPE reported 5 different springs hangers that meets the selection criteria for this node location. Furthermore, the program selected the first spring hanger listed ( Fig 82, Size 16) to be used in the actual stress analysis. See the hanger report (*.HGR) below:
Therefore, the program placed the Cold load (35145.7 N) and Spring Rate (524.8 N/mm) from the hanger selection into the Spring hanger component:
So why is there such a large discrepancy, because there is more than one spring that fits the criteria. The Spring Hanger Analysis module selected the first spring can with the longest range and highest spring that satisfies the conditions.
As mentioned in the online help:
Various hanger selections that meet the criteria are reported in a file named SYSNAME.HGR, starting with the longest range and highest spring rate and finishing with the shortest range and lowest spring rate. The first spring in the list that satisfies the requirements is selected by the program.
Another source of possible error is that your piping arrangement and modeling may not match the as-built conditions. Confirm the following: piping properties, contents, load cases, support locations, support types, support gaps, analysis settings, etc...
Ultimately, if you disagree with the Spring Hanger selection, override the automated values with your own to be used during the actual stress analysis.
Spring Hanger Selection