I am not sure what you really want but I am going to guess.
You want to know the criteria for which lines should be submitted for Stress analysis.
Is that correct?
If that is correct then:
Pipe Stress Criteria
The question:
What are the criteria for which lines need formal stress calculation?”
My answer:
You will get lots of opinions on this one. Here is what I use and teach.
1. “The 1500 rule”
(from David Diehl, COADE)
a. If the line size (nominal pipe size) times (x) the Operating temperature (degrees F) are below 1500 then the line "may" not need formal stress analysis.
Example 3”(x) 400 degrees (F) = 1200
b. If the line size (nominal pipe size) times (x) the Operating temperature (degrees F) are above 1500 then the line "may" need formal stress analysis.
Example 4" (x) 400 degrees (F) = 1600
2. If the line (regardless of temperature) connects to a pump, a compressor or other alignment sensitive equipment then it should be submitted for formal stress analysis.
3. The "May" noted above relates to the application of good judgment when considering other factors such as metallurgy and the wall thicknesses above schedule 80.
Pipe Stress Criteria #2
The question:
What is the minimum recommended temperature or temperature range for which flexibility analysis should be done per ASME B31.3?
My answer:
I do not have a copy ASME B31.3 (Old or current 2009) so I can't cite any specifics therein. However I would be surprised if B31.3 would give a minimum Operating temperature for the requirement of flexibility analysis. There are just too many variables.
Flexibility Analysis might come in a number of forms and should consider many situations.
Forms:
- Visual Review
- Informal Calculations (pencil, paper and a handheld calculator)
- Formal Analysis for excessive stress caused by common factors (Operating Temperature induced expansion, Dead/Live Loads)
- Special Analysis (i.e.: Analog studies for reciprocating compressors, seismic studies, Sea-Force studies for Offshore Platforms)
Many engineering companies may set some minimum analysis criteria on a project by project basis but there is always the exception for even "That" project.
Exceptions may include:
- Very large diameter pipe
- Very heavy wall pipe
- Very thin wall pipe
- Exotic Alloy Pipe
- Attachment to strain sensitive equipment (Pumps, Glass lined vessels, etc.)
- Extremely low temperature (Cryogenic) systems
- Any pipe installed in Arctic locations
- All other lines below the stated minimum level on a job installed in a place like Oman or Kuwait. Example: Installation metal temperature is in range of 130 to 140 degrees F or higher but the normal operating temperature is (-) 50 degrees F
Even if the Code makes a recommendation on this subject each Piping Lead and the assigned Pipe Stress Engineer are responsible for the proper engineering and design of the project.
I see that you are new here, so I'll take a moment and explain how this place works. Everyone here is a volunteer. We enjoy helping people with issues. If we didn't, we wouldn't spend our time on eng-tips.com. What we don't seem to do very well is respond to declarative statements with implied demands--we all get enough of them from people who are paying us for our time.
For free, if you take a moment and explain what you are trying to do, what you've done to try to solve the problem that has you held up, and ask politely if anyone can point to a way forward, you will be amazed at the amount of work members here will give you for free. All you have to do is: (1) be polite; (2) pose a question that is interesting; and (3) indicate steps you've already tried. I've seen threads that included all three of those simple things receive advice that they would have had to pay a consulting firm many thousands of dollars to get (if the the consulting firm they chose could even answer the question, most can't). I've also seen threads where someone posted a bare faced "need" never did get a substantive response.
It is your choice, but you have to realize that if you bore us we'll just not bother.
"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.
amrfd9,
It sounds like you are demanding a method to determine critical lines for pipe stress analysis. Why not take some time out (as others have in the past) and come up with a robust system to determine critical lines/systems yourself. You do not get a critical lines chart but rather a set of rules to assess the lines.
