Determination of operating pressure in pipeline data sheets
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I have been studying pipeline data tables recently, and there is one issue I’m not quite clear about. I earnestly ask for the expertise of everyone here. For example, 1: A metering tank for liquid caustic is placed on a platform 12 meters high. The liquid caustic is pumped from the storage area to this tank at a pressure of 0.4 MPa. After the liquid level is measured, it is transported by gravity to the mixing tank located on a platform 6 meters high. What is then the operating pressure of the outlet pipeline? Should it be written as normal pressure/0.1 MPa, or should it be 0.4 MPa just like the inlet pipeline of the tank? There is a vent on the top of the tank. I thought that since the liquid caustic soda has been sitting in the tank for some time, there should be no pressure left, only gravity acting on it. What should be specified for the operating pressure of that outlet pipeline? 2. The mixing tank (at normal temperature and pressure) is equipped with a vent line; since some of the raw materials are volatile substances, should the pressure specified for this vent line also be at normal temperature and pressure? Why does it seem like the gas phase medium always has some pressure? I see some people have written 0.05 MPa; where does this value come from?
1. The static pressure at the lowest point of the outlet pipeline (without considering the liquid level in the tank) is 0.06 MPa; if flow continues, the pressure will definitely be lower than this value, and atmospheric pressure can also be used. 2. Is the material flammable or explosive? Does the mixing tank have a nitrogen sealing system? What is the pressure during operation?
May I ask how you came up with 0.06? The materials in the mixing tank include ethanol, a flammable liquid classified as Category B; there is no nitrogen seal. During the mixing process, various raw materials are added to the mixing tank and then pumped into the reaction tank. That’s why I say the ingredient preparation process takes place at normal temperature and pressure.
A height difference of 6 meters results in a static pressure of 0.06 MPa.