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Ambient and design temperature

Ambient and design temperature

Ambient and design temperature

Dear Friends,

I'm new in stress analysis and I'm doing stress analysis on a pipeline connected to a pig trap; about 25 meters of pipeline is above ground and existing part is underground. According to the site condition document "Average minimum absolute ambient temperature" of the field is 1°C, "Average maximum absolute ambient temperature" is 48°C and minimum soil temperature is 16°C in winter. It should be mentioned that maximum operating temperature is 31°C.
I have some doubts about temperatures:
1- Which of above temperature should be considered as ambient temperature in "special execution option" of CAESAR II?
2- Should I consider sunshine temperature(85°C) for above ground portion and maximum operating temperature(31°C) for UG portion of the pipeline for stress, displacement and load calculations?

I have another question:
How can I model a pig trap? Is it true to consider an anchor point at interference of pipeline and pig trap? If yes, the nozzle load is really huge. If not, how can I deal with the trap?


RE: Ambient and design temperature

Averages are of no use.
Design temperatures should include the max and min of all possible temperature excursions.
Design pressures should include the max and min of all possible pressure excursions.

i.e. Use 85C for max above ground pipe. Minimum for above ground piping should be minimum air temperature.

Operating temperatures, when within the max-min range above, are not relevant. If outside the above range, move the relevant design temperature to include it.

Although B31.4 designs can have surge pressures up to 10% higher than design pressure. Be extension, design pressure should at least equal MAOP at the design temperature.

RE: Ambient and design temperature

Model the pig launcher from the point on the underground pipeline that locates the "virtual soil anchor", the point where the soil restrains the pipe. It requires some knowledge of soil properties.

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