Pipeline stress analysis: Determination of the temperature of pipelines at normal conditions
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This post was last edited by lp3484 on 2017-12-5 09:29. I recently worked on a small liquid ammonia filling station project, and the local quality inspection department insisted on a stress analysis being conducted. The problem is that the pipeline input stage already poses a challenge for me: the system has no heat source nor any heat exchange equipment, and the medium consists of both liquid ammonia and ammonia gas; therefore, the temperature of the medium should change according to the ambient temperature. So in regions like the Northeast, how should the pipe temperature be entered? Should one use the lowest temperature in winter, T1, and the highest temperature in summer, T2, for calculation? CaesarII version 2017 is being used.
During installation, the temperature is taken as the ambient temperature, with one design temperature for high temperatures and another for low temperatures.
Dear expert, I have a question here. I entered 40 as the maximum ambient temperature for T1, and -40 as the minimum ambient temperature for T2. During error checking, it keeps saying that the conditions for T2 are outside the range suitable for this material. Why is that? Can’t the 8163 10-modified steel be used at -40 degrees? Changing it to -10 degrees still didn’t work; it worked when set to 0 degrees, but a warning was given stating that if the temperature for T2 is entered as 0, that temperature will be assumed to be the ambient temperature. What does this mean? The configuration file clearly states that the default ambient temperature is 20 degrees.
Carbon steel can generally only be used at -20 degrees; it may not work at -10 degrees, possibly due to incomplete data in the material database.
In ASME B31.3, look at the low-temperature stress relief condition. Or as described in GBT20801. Additionally, if the ammonia pipeline is made of carbon steel, an error will be reported when the temperature drops below -20 degrees.
Steel grade 10 cannot be used at -40°; the design parameters are flawed
So what kind of pipes should be used for outdoor pipelines in the Northeast region? Can’t carbon steel be used? But places like oil depots use 20# steel, right?
In my opinion, there is a problem with this design; according to GB50316 3.1.3.1, the design temperature of pipes should be set at or below the lowest temperature that the pipe material can withstand. If your environment can reach temperatures as low as -40, then the design temperature for the piping system (the low-temperature value) should be at least -40. It is advisable to specify both a design high temperature and a design low temperature; the design temperature must cover the ambient temperature at least. The material can be low-alloy steel or high-alloy steel. The selection of materials can appropriately refer to SH/T 3059.
You have overlooked the situation of low temperature and low stress