Hello,
I have some questions regarding the hoop stress calculation by AutoPIPE.
I've tried to calculate the hoop stress myself compared to AutoPIPE Result. The result will be shown below.
The hoop stress is 33.16 MPa according to ASME B31.4 code.
However, I calculated it by hand. The result is 32.3 MPa. The calculation method is shown below.
Why are the results of two approach are a bit different?
Greetings,
When submitting a forum posting please try to include complete details. In this case you should have provided the following:
1. Code year, or image of General Model options dialog.
2. Image of Results Model options dialog
3. Image of Edit Model options dialog
4. Image of pipe property dialog under consideration
These dialogs hold clues to how the calculations are performed.
Next, please see the following AutoPIPE help section: Help ribbon> Contents button> Contents Tab> Reference Information> Code Compliance Calculations> ASME B31.4 hoop stress document.
At the moment, appears that you are using the wrong equation. I see that you are using SI units. If you refer to the help location above, you should be using equation 2 or 4, instead of equations 1 and 3.
Be sure to read the entire page to understand how corroded thickness would be considered.
Regards, Mike Dattilio Design Analysis Engineering Group Senior Analyst Bentley Systems Inc=============================================================================
The pressure is 2.792 MPa, CA= 3 mm, D= 141.3, Thickness =12.7 mm
I see your mention above. I've already rechecked the unit, and I surely say that the formula that I put is correct because MathCad will change to the same unit.
As you see the above figure, the hoop stress by autopipe appears greater than calculation by hand slightly. So I would like to know why autopipe can't calculate like calculation by hand.
Thanks in advance
Can you please post the Results model Options dialog from this model?
Also go to Press/Temp/PipeID tab of the input grids, scroll to down to node point A37, right mouse click on the grids, and choose "Show Pressure Only". This will reduce the grids to just the pressure information, Now take the screen shot and post here.
Note, from AutoPIPE help, Help ribbon> Contents button> Contents Tab> Reference Information> Code Compliance Calculations> ASME B31.4 hoop stress> Notes: If more than one operating load condition exists there may be more than one P and results are output for the operating load condition which produces the highest hoop stress at each point.
Consider reviewing WIKI here for information on "Use corroded thickness in analysis".
First note that AutoPIPE performs all calculations in English units and then converts them to the Metric units afterwards. So there may be a little difference in the conversion process.
I took a look at this issue in detail. I created a model using your exact same values reported above.
Here are the detailed calculations in both English and Metric.
AutoPIPE's results in English and Metric.
Appears that the results are correct within the 2% difference allowed in our QA manual of program results compared to hand calculation.
Answer Verified By: Mike Dattilio