Design Temperature of Piping System
Design Temperature of Piping System
(OP)
Hello,
I would like to know how the design temperature of a piping system is chosen?
Is the temperature of the working fluid or the smallest temperature rating of each component chosen as the design temperature?
Thank you,
Alex
I would like to know how the design temperature of a piping system is chosen?
Is the temperature of the working fluid or the smallest temperature rating of each component chosen as the design temperature?
Thank you,
Alex





RE: Design Temperature of Piping System
If it matters (i.e., you are designing close to some limit) then you had better either use modeling or other calculation methods.
Generally you just make sure that the material properties are appropriate for a range that is far wider than your expected range. If you have a material that starts to have brittle problems at -120F and strength problems at +500F then using a design temperature of winter ambient (call it -45F in Northern Alberta) or summer ambient (+120F in Death Valley, CA) is appropriate--use whichever one gives you the lower MAWP. You can look at the design temperature of the components you've selected (use the most restrictive), but I contend that I'd better know design pressure and temperature before I begin selecting components.
On the other hand, if you are designing steam piping that is going to exit a building on Alaska's North Slope then you had better be doing some serious thermal modeling. Rules of thumb will end up killing some caribou.
David
RE: Design Temperature of Piping System
The Casti Guidebook on B31.3 Process Piping has some helpful guidence.
We usually tack 50 F onto the highest temperature the pipe will encounter and use that for our design temperature. The low end is usually specified from coldest ambient at location.
Just my two cents worth.
Always remember, free advice is worth exactly what you pay for it!
RE: Design Temperature of Piping System
Just a heartfelt plea for the rational and transparent engineering derivation of design temperatures.
Steve Jones
Materials & Corrosion Engineer
http://www.linkedin.com/pub/8/83b/b04
RE: Design Temperature of Piping System
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"Pumping accounts for 20% of the world's energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies) http://virtualpipeline.spaces.live.com/
RE: Design Temperature of Piping System
I won't get into the subject of how the minimum ambient temperature relates to your minimum design metal temperature other than to repeat the prior comment that the CASTI book "Guide to ASME B31.3 Process Piping" does do a good job of discussing this topic
RE: Design Temperature of Piping System
Beyond that and directed toward other discussion, I also guess some might argue there could conceivably be some danger in just mentioning "ambient" as the only measure, at least in the case of pipelines carrying fluids such as very high pressure gases. E.g. if the pipeline carries a gas under high pressure, and the line somehow contains or develops a breech for whatever reason (to where there is a leak), as reported at h
RE: Design Temperature of Piping System
**********************
"Pumping accounts for 20% of the world's energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies) http://virtualpipeline.spaces.live.com/
RE: Design Temperature of Piping System
While joule-thompson effects can be important and could have contributed to the severity of the case you mention, the initiation of the leak was most probably due to construction damage as reported in the following.
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"Pumping accounts for 20% of the world's energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies) http://virtualpipeline.spaces.live.com/
RE: Design Temperature of Piping System
B31.3 permits variations in temperatures and pressures from operating levels, provided certain conditions are meet. Joule-Thompson cooling IMO would usually be considered outside the normal operating temperature levels, so a JT temperature need not be the "design temperature". Non-the-less, the design should accomodate the lowest temperatures that could be reached under the increased design limit provisions for transient occurrences and either by choosing a material listed for a lower temperature, by qualifying a choosen material for lower temperature use by specifying appropriate toughness requirements, or by providing crack arrestors.
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"Pumping accounts for 20% of the world's energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies) http://virtualpipeline.spaces.live.com/
RE: Design Temperature of Piping System
Alex
RE: Design Temperature of Piping System
RE: Design Temperature of Piping System
**********************
"Pumping accounts for 20% of the world's energy used by electric motors and 25-50% of the total electrical energy usage in certain industrial facilities."-DOE statistic (Note: Make that 99% for pipeline companies) http://virtualpipeline.spaces.live.com/
RE: Design Temperature of Piping System
I recently saw it in a PSV study I did. We had a well that could produce 100 MCF/d into 20 psig. At 45 psig the flow rate was near zero. We had a 350 psig MAWP on a vessel. I did a credible-scenario analysis and said that the required flow rate at set pressure was a pretty small number (thermal case was the only one credible). One of the teenaged engineers (lower case) that sat in on my presentation said that he wasn't comfortable with saying that the required capacity was very low--since 2-inch pipe at 350 psig can move 3 MMCF/d and that is the required capacity. The room agreed with him and the PSV went from fitting in the space provided to requiring 3 sizes bigger valve that required a code modification to the vessel. A costly "well-meaning mistake".
David