Railway Pipeline Stress Analysis - design factor
Railway Pipeline Stress Analysis - design factor
(OP)
Hi everyone, I'm working on aa pipeline stress analysis crossing the railway and I'm referring to API RP 1102 (2017) and ASME B31.4 -2006.
Starting from API RP 1102
My pipe can pass the "allowable stress check“ with 0.72SMYS. Let's call F1=0.72
However, it failed for the "total effective stress check" with 0.72SMYS. Calling F2=0.72
I'm trying to find out that for the total effective stress check, I can use 0.9 SMYS instead of 0.72. (Does F2 need to equal to F1?)
The words in API RP 1102 are vague, it only mention that F2 should be consistent with standard practice or code requirement.
Then I went to B31.4, in table 403.3-1, it does mention that the "effective stress at railroad" can use the F2=0.9. However I cannot confirm if the two codes are talking about same case.
Does anyone perform the analysis before and could share some light? I don't feel very comfortable to bring the design factor from 0.72 to 0.9 for the gas pipe without a solid reference....
Thanks ahead!
Starting from API RP 1102
My pipe can pass the "allowable stress check“ with 0.72SMYS. Let's call F1=0.72
However, it failed for the "total effective stress check" with 0.72SMYS. Calling F2=0.72
I'm trying to find out that for the total effective stress check, I can use 0.9 SMYS instead of 0.72. (Does F2 need to equal to F1?)
The words in API RP 1102 are vague, it only mention that F2 should be consistent with standard practice or code requirement.
Then I went to B31.4, in table 403.3-1, it does mention that the "effective stress at railroad" can use the F2=0.9. However I cannot confirm if the two codes are talking about same case.
Does anyone perform the analysis before and could share some light? I don't feel very comfortable to bring the design factor from 0.72 to 0.9 for the gas pipe without a solid reference....
Thanks ahead!
RE: Railway Pipeline Stress Analysis - design factor
Table 403 gives you that value (0.9) for cased or uncased pipe.
I think the wording is quite clear - for effective stress you use the value in your design code - in this case 0.9.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Railway Pipeline Stress Analysis - design factor
That is seldom allowed by railroad companies. Interesting
B31.4 obviously does not apply to gas pipelines, although 1102 can be used for both.
Regardless of what 1102 allows, B31.8 conditions must also be completely satisfied.
RE: Railway Pipeline Stress Analysis - design factor
RE: Railway Pipeline Stress Analysis - design factor
More details here: actually we're going to construct the railroad over the existing uncased gas pipeline, we will have ~10ft embankment over the existing ground and also over the existing pipe. We're trying to perform the stress analysis for the new embankment to see if the pipeline is considered still safe under the new rail live load and with the deeper burial depth...otherwise we will likely propose protection concrete slab or so to protect the pipelines on site.
And then it comes to my original question, my pipeline can pass the "Barlow stress check" with the design factor of 0.72, however it failed the total effective check if we apply same 0.72 design factor. (0.9 will pass though). I felt confused because in the calculation example of 1102, the code applied 0.72 for both Barlow check and total effective check.
RE: Railway Pipeline Stress Analysis - design factor
Dear Miaaa1101 (Civil/Environmental),
Please find below my points for the thread;
- ASME CODE FOR PRESSURE PIPING, B31.4 is for PIPELINE TRANSPORTATION SYSTEMS FOR LIQUID HYDROCARBONS AND FOR OTHER LIQUIDS
- THE RELEVANT CODE FOR GAS DISTRIBUTION AND TRANSMISSION IS ASME B31.8 WHICH IS MORE STRINGENT,
- YOU CAN FOLLOW API RECOMMENDED PRACTICE 1102 AS LONG AS YOU COMPLY WİTH THE REQUIREMENTS OF B31.8
- DF VARIES WITH LOCATION CLASS ( CROSSING AT CROWDED CITY CENTER , SUBURBAN, RURAL ...) PLS LOOK 840.22
- PLS LOOK 841.145 ADDITIONAL UNDERGROUND PIPE PROTECTION
I will strongly recommend to speak / coordinate with the relevant authority for the measurements .. Protection slab could be one of the options..
RE: Railway Pipeline Stress Analysis - design factor
Two things.
As noted above you seem to be using the wrong design code. Gas pipelines fall under B 31.8 as HTURKAK and others say
And additional dead load in the form of an embankment is not straightforward. The issue usually is that this extra dead load of the embankment compresses the ground that the pipeline is in and creates additional bending and shear stresses in the pipeline - as though the pipeline was trying to hold up the embankment.
You need to employ some geotechnical engineers to assess the ground around the pipeline and work out its long term settlement under this extra weight.
That is your key issue, not really the effect of the occasional train.
The example in 1102 does use F=0.72 for both stress checks without explaining why. However it is clear from the design codes used (B31.4 or B 31.8) that those codes use F=0.9 for the equivalent stress check.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Railway Pipeline Stress Analysis - design factor
Otherwise, some references concerning the "0.9 paradox"
https://pipelineintegrity.wordpress.com/2011/04/21...
Enbridge B31.4 Crossing Design (Minnesota, USA. Possibly submitted for their Line 5 Project.)
It is a heavy pil pipeline.
Uses 0.9 for effective stress
See page 5
https://mn.gov/puc-stat/documents/pdf_files/201703...
Tabulated Analysis of the F selection paradox
https://mycommittees.api.org/standards/techinterp/...
Crossing Design (Discussion and example)
https://epcmholdings.com/pipeline-crossing-analysi...
Online calculator
https://www.allaboutpipelines.com/API%20RP%201102/...
RE: Railway Pipeline Stress Analysis - design factor
RE: Railway Pipeline Stress Analysis - design factor
Don't forget the issue of ground compaction under all that extra weight of the new embankment. Far far worse than the train.
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: Railway Pipeline Stress Analysis - design factor
The area class design factors apply to Barlow calculation and to "total longitudinal stress", each of which do not address "total effective stress" as does API RP 1102. The area class design factors 0.4, 0.5, 0.6, 0.72, 0.8, for gas pipelines and 0.72 for oil pipelines do not apply to total effective stress based on the Von Mises formula. B31.4 and B31.8 do not use Von Mises formula. They are a Tresca stress calculations, so the failure criteria is different when using the Von Mises total effective stress formula in API RP 1102, hence that is = 0.9 SMYS.
You can see this implementation on page 34 of ADNOC's pipeline specification here discussing crossing calculations. It is identical to the Enbridge calculation I posted above for their oil pipeline (it was for Line 3 Replacement project). API 1102 applies to both oil and gas pipelines, so the same DF of 0.9, or sometimes even set as high as 0.95, can be used for either type of pipeline, oil, or gas.
https://www.adnoc.ae/-/media/adnoc-v2/files/specs/...
RE: Railway Pipeline Stress Analysis - design factor
B31.8 combined stress limits are given in paragraaph 833.4
RE: Railway Pipeline Stress Analysis - design factor
RE: Railway Pipeline Stress Analysis - design factor
1503-44 is directing you in the right direction. Enbridge's crossing report too confirms this.
GDD
Canada
RE: Railway Pipeline Stress Analysis - design factor
RE: Railway Pipeline Stress Analysis - design factor