Why does the air leakage rate of a vacuum system increase as the operating pressure (absolute pressure) of the vacuum system increases?

You’ve got it backwards. Logically speaking, external pressure is fixed; the lower the operating pressure, the smaller the pressure difference, and therefore the less air should leak out!

You have the causal relationship backwards. To view vertically, look at the intersection of the vertical axis and the diagonal line, from top to bottom. A vacuum is created only when the exhaust volume exceeds the system’s intake volume. Regarding the graph, assuming a volume of 200 m3, at pressures between 12 and 100 kPa, the vacuum leakage rate is 40 kg/h. A vacuum pump with a pumping capacity greater than 40 kg/h – let’s say 50 kg/h – is required in order to create a vacuum in that volume. At pressures of 2.79~11.8 kPa, the leakage rate is 30 kg, while the pumping rate remains at 50 kg, so as to achieve a higher vacuum level. Up to the limit, in the ideal state, the system has no leaks – it is a perfect vacuum. In the initial stage, the leakage amount consists of the leakage from the connections and seals, plus the gases adsorbed on the surface of the equipment, plus the gases that enter through the gaps between molecules. In the intermediate stage, it can be considered as the gases adsorbed on the surface of the equipment plus the gases that enter through the gaps between molecules. In the final stage, it can be considered as only the gases that enter through the gaps between molecules. This is why the gas leakage is greater at low vacuum and smaller at high vacuum. When no gas leaks into the system and the air from the original system is removed, an absolute vacuum can be achieved

This post was last edited by zeq521fcy_ZMKT on 2019-3-29 16:20, School*,

What I mean is the absolute pressure under vacuum conditions (below atmospheric pressure); external pressure is considered as gauge pressure, and the lower the operating pressure, the greater the pressure difference

The horizontal axis represents the volume of the vacuum system, which remains constant for a given device. The vertical axis represents the air leakage rate. Each curve corresponds to a different operating pressure (absolute pressure). As can be seen from the graph, for a given vacuum volume, the air leakage rate increases as the operating pressure rises.

:Q Please solve this problem; it goes against common sense

It is not the vacuum level that determines the leakage rate; rather, it is the leakage rate that determines the vacuum level.

This post was last edited by symc on 2019-3-30 at 17:51 :) Are you still arguing fiercely over this? :) It’s very simple – it’s a requirement imposed by human factors. As you know, the lower the pressure, the greater the pressure difference, and thus the greater the leakage rate… So, as is well understood, if you want to achieve a higher vacuum level (i.e., a lower pressure), it’s necessary to ensure good sealing and reduce leakage… Otherwise, the required pressure level cannot be achieved. What is then the purpose of a helium leak detector? It’s just for inspection, right?:D Ugh, these days, learning* means just memorizing things by rote…:sleepy:

This explanation seems reasonable. So, for the same device, is the air leakage rate at an operating pressure of 10 KPaA lower than that at an operating pressure of 30 KPaA?

Take a look at the formula. For a vacuum apparatus with a constant volume of the vacuum system, the K value increases as the operating absolute pressure rises. As the absolute pressure increases and the external pressure remains constant, the pressure difference decreases. Can this be interpreted as meaning that the air leakage rate in a vacuum system increases as the pressure difference decreases?