Questions regarding the drum liquid level

The liquid level is rising! When the pressure in the pipeline network exceeds the saturated steam pressure corresponding to the drum temperature, the vaporization rate of the drum decreases, steam production falls, and the liquid level rises.

Reply to 2# Hidden Pig: But in reality, the liquid level decreases.

Has the water supply amount changed? Has the steam output changed?

This post was last edited by arpcd on 2011-12-10 at 16:14. As network pressure increases, the steam output of the boiler decreases. From a material balance perspective, since the amount of steam is less than the amount of water supplied, the water level should rise. However, based on my experience in adjusting the water level of 300MW boiler units, this is not entirely true; in fact, the water level first drops and then rises. In retrospect, everyone agreed that the reason for this phenomenon was an increase in the pressure of the steam drum, which led to a decrease in the amount of steam produced. As a result, the boiling of water inside the drum slowed down suddenly, and the number of bubbles in the water decreased rapidly. The reduction in the volume of these bubbles caused the water level to drop. This is a common phenomenon known as \"false level\" in boiler steam drums. It should be noted, however, that this phenomenon does not last long, usually between 20 and 40 seconds, with a maximum of no more than one minute. If the water level continues to drop after the pressure in the drum increases, then the causes should be sought in factors such as the feedwater flow rate and the thermal load of the furnace. After all, the water level in a steam drum is influenced by many factors, but the most direct influences are the feedwater volume and the steam output; among these, the feedwater volume has the fastest impact on the water level. .

Reply to 5# arpcd: I don’t understand how the bubble volume affects the liquid level I’ve also seen similar statements, but I’ve never understood them.

When other factors related to the steam drum remain relatively constant, a decrease in the pipeline network pressure leads to an increase in the liquid level； The pipeline network pressure rises, and the liquid level drops. At this point, both the actual volume of gas released and the measured volume remain relatively constant; the factor that causes fluctuations in the liquid level is the change in the volume of bubbles of water under high pressure, a phenomenon commonly referred to as \"false level\" in operational terms. To overcome the \"false level,\" the feedwater volume to the drum is generally controlled using \"three-element control,\" which takes into account changes in the drum level, gas generation rate, and feedwater volume in order to regulate the feedwater supply to the drum accordingly.

After reading it, I still think what was said above makes sense

I think none of what was said above is correct. The steam produced by the boiler goes into the steam pipeline network, and there is definitely a check valve at the boiler’s outlet; therefore, the steam pressure is not affected by the level of liquid in the drum. If there is no check valve, steam will flow back and damage the boiler.

When other factors related to the steam drum remain relatively constant, a decrease in the pipeline network pressure leads to an increase in the liquid level； The pipeline network pressure rises, and the liquid level drops. At this point, both the actual volume of gas released and the measured volume remain relatively constant; the factor that causes fluctuations in the liquid level is the change in the volume of bubbles of water under high pressure, a phenomenon commonly referred to as \"false level\" in operational terms. To overcome the \"false level,\" the feedwater volume to the drum is generally controlled using \"three-element control,\" which takes into account changes in the drum level, gas generation rate, and feedwater volume in order to regulate the feedwater supply to the drum accordingly. The steam generated at 3.05 MPa by the drum is connected to the steam pipeline network; now the pressure in the network has risen to 3.11 MPa. How should the liquid level in the drum change under these conditions, and why? Who can be as loyal to a partner as one is to the Renminbi?

It is certain that there is a check valve at the outlet of the steam pipeline on the 9th floor. However, due to the high pressure in the rear steam pipeline, the steam drum is unable to generate steam, which in turn affects the liquid level in the steam drum. We encounter this situation often; we just need to find a way to deal with it