Why should control valves in gas-liquid two-phase flow be placed as close as possible to the connected equipment, and if possible, connected directly?
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The last edit to this post was made by Little Worker on 2016-6-27 at 09:27. As the title suggests, I’m considering the possibility that there is a pressure drop across the control valve; the gas-liquid mixture condition downstream of the valve should be even worse. Therefore, it’s advisable to shorten the pipelines as much as possible and connect the equipment directly. I’m not sure if that’s the case. Also, since control valves are part of valve assemblies, how is it possible to connect them directly to the pipe ends of the connected equipment? Does anyone have photos of this in a real installation? And why should gas-liquid two-phase flow pipes be straight? The longer length is probably because it can easily lead to water hammer. As for being straight, is it because having too many elbows can cause cracks at those points? In the case of hot water condensate pipes, from a stress perspective, shouldn’t having more elbows be better? How can this contradiction be resolved?
The water hammer phenomenon in the gas-liquid two-phase flow is quite severe, especially behind the control valve, as this causes the gas phase to suddenly turn into a liquid phase, increasing the likelihood of water hammer. Therefore, it is necessary to get as close to the device as possible. But it’s not necessary to connect directly to the device, right?
Is erosion greater compared to ordinary check valves (i.e., those without signal tubes)?
The two-phase flow pipeline should be short and straight. The reason for this is obvious: by minimizing the length of the two-phase flow path, the fluid can enter the equipment more quickly, which enhances safety. The direct reason is that the more elbows there are, the more turbulent the flow becomes, and the more intense the two-phase flow is. Moreover, elbows are the areas where water hammer is most severe; therefore, they should be avoided