What would happen if the inlet of the bottom suction pump leaks? ? ? ?
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As is well known, the inlet section of the bottom pump in a pressure reduction tower should be under negative pressure, with a certain level of vacuum. So, if there’s a small leak in the inlet pipeline, do you think oil will leak out, or will air get in? Theoretically, air should be leaking in. Has anyone experienced it? Hehe
I’ve never worked in a vacuum distillation unit, but just because the top of a vacuum tower is under negative pressure doesn’t mean the bottom is also under negative pressure. In general, it’s normal for a distillation tower to have a pressure drop of 0.7–0.8 kilograms; so what’s more the case in a vacuum tower? Therefore, the inlet of the pump at the bottom of the vacuum tower can’t be under negative pressure ? Please invite the representative from the atmospheric and vacuum distillation workshop to give an explanation! This post was last edited by wakawakaa on 2009-2-16 17:03]
With a vacuum level of 98, minus the static pressure of the oil surface (the pressure drop in the packed tower is very small), there is generally still a vacuum level of around ten units at the bottom of the tower. For details, see the FAQ on atmospheric and vacuum distillation technology. I also came up with this question after seeing this passage.
I have worked with atmospheric and vacuum distillation processes, and it’s definitely positive pressure. Didn’t the original poster notice that the base of the vacuum distillation tower is much higher than that of an atmospheric distillation tower? The base of a vacuum distillation tower is designed to be over 10 meters high so that the material at the bottom of the tower can overcome the negative pressure and flow to the bottom pump. The inlet of the bottom pump mentioned by the original poster is close to the ground level; therefore, it should be under positive pressure. If it were negative pressure, the material would be drawn out through the top of the tower, making it easy for the tower to become empty.
For more details, see the FAQ on atmospheric and vacuum distillation: If the level gauge in the vacuum tower malfunctions, a vacuum gauge can be temporarily installed at the inlet of the bottom pump to estimate the liquid level. At normal liquid level, the vacuum level is several kilopascals. The liquid level rises by one meter, and the vacuum level decreases by a certain amount. . . . . . Actually, I’m not sure either whether it’s positive pressure or negative pressure, so I’m looking for someone who has actually encountered a leak to get some insights.
Personally, I think whether the inlet of the pressure relief tower bottom pump is under negative pressure should be determined by the pump’s net positive suction head and the location of leaks in the inlet pipeline!
It first manifests as a decrease in the flow rate of the pump; generally, this isn’t dangerous. If the pump’s flow rate increases, then it’s necessary to check the level of vacuum. After the vacuum tower returns to positive pressure, any significant leakage will be detected. I have experienced leaks in the extraction lines of the secondary stripping tower; normally the pumps operate properly. The issue was discovered when the bottom pump failed to deliver flow – this was while trying to restore positive pressure. Usually, after shutting down the vacuum pump, operators go up to the tower for inspections. It was found that corrosion at the welds of the line drawn out in the second reduction stage still occurred in 1/4 of the cases (the drawn-out line is 1Cr18NI9), but no accidents resulted.
Even if the tower is under negative pressure, there is a certain liquid level at the bottom of the tower, and liquids have static pressure. If the pump inlet is filled with liquid, there will be no negative pressure. Pumps have minimum pressure requirements at their inlets; otherwise, how could pumps be used at the bottom of a tower under negative pressure?
Let me provide a technical review on this issue. . . The key lies in the preliminary technical design. . . 1. If the designer has a good understanding of how centrifugal pumps operate, they will be able to create favorable technical conditions to ensure their proper functioning. To maintain optimal operating and suction conditions, centrifugal pumps should ideally be fed with liquid under positive pressure. However, in the case of vacuum distillation towers, the pump inlet must overcome a negative pressure of nearly one atmosphere. Therefore, to enable the centrifugal pump to draw in liquid properly, chemical engineers who have studied fluid dynamics know how to calculate the approximate distance and dimensions from the liquid level at the bottom of the tower to the inlet of the pump. . . . So I won’t say much more. . . . Hahaha. . . 2. If the liquid drawn into the pump’s inlet is at negative pressure, it is very difficult for the pump to operate safely. . . . Hahaha. . . . It would be strange if they didn’t find time for it. . . :Lol 3. So, I think under normal circumstances, a properly designed submersible pump inlet will still leak oil and catch fire. . . Of course, it is not excluded that oil leakage and ignition can occur within the suction vacuum range permitted by the pump. . . That situation is too rare. . . This post was last edited by wangsc on 2009-2-18 20:53]
Theoretically, it is under negative pressure, but due to the static pressure difference at the inlet, positive pressure will definitely occur. Once a perforation is detected, oil leakage will surely happen; coking will occur in the sand filter, and the coke deposits will block it. If a large hole appears, fire will definitely break out.