What constitutes the internal pressure of a container?

The pressure inside the container is primarily determined by the pressure of the fluid entering through the inlet pipe and the hydrostatic head of the fluid within the container. When calculating the pressure inside the container, it is also necessary to consider the dynamic head of the inlet and outlet pipes of the equipment, as well as the pressure drop in the pipes. However, if the container is sealed and has no passages connecting it to the outside world, even if an inlet pipe with an operating pressure of 0.7 Mpa is connected to the container, the pressure inside the container will not increase; it remains a container at atmospheric pressure. .

The internal pressure of the container should include factors such as the pressure carried by the fluid entering through the inlet pipe, the dynamic head at the equipment’s inlet pipe, the liquid column head inside the equipment, the resulting frictional resistance, as well as the effects of the dynamic head at the outlet pipe and the pressure drop in the piping. If the container is closed and has no vent holes or gas vent pipes, the pressure inside the inlet nozzle will continue to build up without any release, resulting in an increase in pressure within the container. However, even if an inlet pipe with an operating pressure of 0.7 Mpa is connected to the container, the pressure inside the container does not necessarily increase to 0.7 Mpa. This is because the liquid inside the container may evaporate or vaporize, thereby leading to a partial release of pressure. Furthermore, if the pressure inside the container exceeds the tolerance limit of the equipment’s casing, what is likely to happen is an explosion of the container, rather than simply an increase in internal pressure. Therefore, in industrial production, it is very important to control the pressure inside containers; relevant rules and regulations as well as operational requirements must be strictly followed, and necessary safety protection equipment should be provided.

Why is what you say different from what was replied in the second floor? I’d like to ask for advice

Answer 1 is relatively concise and clear; it states that the pressure inside the container is mainly determined by the pressure of the fluid entering through the inlet pipe and by the hydrostatic head of the fluid within the container, and it mentions that even if the container is connected to an inlet pipe with an operating pressure of 0.7 Mpa, the pressure inside the container remains at atmospheric level. However, when calculating the pressure inside the container, factors such as the dynamic head of the inlet and outlet pipes of the equipment and the pressure drop in the pipes still need to be considered. Answer 2 is more detailed and comprehensive; in addition to the pressure of the fluid entering through the inlet pipe and the liquid column head, it also mentions factors such as the dynamic head of the equipment’s inlet pipe, pipeline pressure drop, the liquid column head inside the equipment, and the dynamic head of the outlet pipe. It also highlights the risk of container explosion, points out the importance of controlling the pressure inside the container, emphasizes the need to strictly adhere to relevant regulations and operational requirements, and stresses the necessity of having appropriate safety protection equipment

Assume I ignore most of the pressure drop and consider only the pipeline delivery pressure. So, for calculating the pressure inside a container, does it suffice to determine the changes in the dynamic head of pressure at the inlet and outlet of the container in order to find the internal pressure? After all, the dynamic head associated with the fluid flowing in the pipes is likely to be much greater than that of a liquid column, as well as any pressure losses. So, for high-pressure feed, since the operating pressure of the vessel is at atmospheric pressure, does that mean the outlet pipe should also be at high pressure? In fact, the discharge pipe of the container also operates at atmospheric pressure; I am referring to HG20570.9-95 for the calculation of pressure loss in the inlet and outlet pipes of equipment

My understanding is that after high-pressure feeding, the majority of the dynamic head is converted into ΔP/ρg, which is the static head (hydrostatic head), and it possesses a certain potential energy. As the diameter of the tank is much larger than that of the inlet pipe, the dynamic head tends to 0, so the dynamic head in the outlet pipe is supplied solely by the potential energy. But the problem is that with this 0.7 MPag feed, even after taking into account most of the pressure losses and converting it to a hydrostatic head, would the tank have to be extremely large? In fact, the container outlet pipes shown on many line lists are designed based on the pressure of the tank

The internal pressure of the container determines the pressure carried by the fluid that enters it. Once the operating pressure of the container and the piping system are fixed, the energy required to transport the fluid is also fixed. The value of 7 kilograms for the fluid is a calculated figure; it represents the amount of energy necessary to push the fluid into the container, based on the characteristics of the piping system. This value of 0.7 MPa applies under the condition of a container at normal pressure. In other words, the conditions calculated based on the piping system become the internal pressure conditions of the container once the fluid enters it, and it’s important to understand the sequence of events involved