Thermal expansion issue of S30408 material tanks
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This post was last edited by cymlz0826 on 2017-6-13 09:46. Our unit is equipped with a heat low-temperature tank made of S30408 material; during normal operation, the temperature is around 240°C and the pressure is 1.1 Mpa. Its upstream is the high-pressure tank; there is a shut-off valve in the middle, and the oil in the low-pressure hot tank comes from the high-pressure tank. When operation resumes in winter, this tank is at atmospheric pressure, with a temperature of around -27°C, the ambient temperature. When the shut-off valve is opened at the start of operation, oil at a temperature of about 150°C flows into the low-pressure tank instantly, causing the pressure to rise to 1.1 Mpa. Could this damage the equipment due to thermal expansion and contraction? Last winter, when work started, it was discovered that there was a crack in this tank; the manufacturer was called in and sealed it up. The company concluded that it was a problem with the tank itself, but I wonder if it might have been caused by thermal expansion I hope some expert can help clarify this.
What is the general structure of this jar, and what is the direction of the crack in it?
Weld crackage is definitely related to thermal expansion and contraction; there are problems with your process procedures – the tank is innocent. -Why isn’t preheating performed before feeding at 27°? ? ?
This post was last edited by cymlz0826 on 2017-6-14 at 11:17. The cracks are vertical; it’s a vertical tank, and the cracks are located slightly below the weld between the head and the cylinder – less than 10 centimeters from the weld. They’re very small; you can’t see them unless you look closely.
This post was last edited by cymlz0826 on 2017-6-14 at 11:16. It’s not a weld; it’s the cylinder body of the vertical tank. My idea is to add cold oil first. Then gradually increase the temperature in a cyclic manner.
Could you explain it in detail? I’m not from a hardware-related field
Is the crack on the inside or the outside? How long has the jar been in use? Is this feeding method frequent? Due to the good toughness of S30408 and the fact that -27 degrees is not a very low temperature, the area most likely to experience problems when using sudden feed method is likely to be at the Type D weld at the oil inlet, rather than the location mentioned. Therefore, I think it may not be caused by thermal expansion, but rather factors such as the medium issues, fatigue problems, or the quality of the cylinder (welds) need to be considered.
The medium has already leaked due to cracks; this tank has been in use since 2015, and it’s filled in this way every time it’s put into operation – about 4.5 times so far. That’s what I think: there must be some defect in that cracked area. Coupled with the sudden introduction of hot oil at low temperatures, at around 150°C and a pressure of 1.1 Mpa, this caused thermal expansion, which led to cracking in the weak spots. I still think it’s better to avoid raising the temperature and pressure in this way; it would be better to first introduce cold oil and then increase the temperature gradually through circulation. Why is there a limit on the rate of temperature increase in reactors? Isn’t it because of material considerations? Although the materials may differ, thermal expansion and contraction are definitely factors at play here.