Vacuum pressure
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Gentlemen, one of the company’s vacuum pumping units shows a pressure reading of -102.6 KPa as measured by the pressure transmitter; a mechanical pressure gauge also indicates -102.8 KPa. Is such a level of vacuum possible? Are it still the problems with these two pressure gauges?
Is there anyone who can answer this? :dizzy:
In the conventional sense, vacuum pressure refers to the pressure difference relative to atmospheric pressure, which is typically around 101.325 kPa (i.e., 1 standard atmosphere). When a vacuum pump is used to create a vacuum, what matters is the extent to which it can reduce the air pressure inside the container, in other words, how much vacuum it can generate. When you mention a pressure of -102.6 kPa or -102.8 kPa, this usually means it is that much lower than atmospheric pressure. However, there is a problem here: according to traditional physical definitions, pressure cannot be lower than absolute zero (0 kPa), because that would mean there are no gas molecules at all, which is what is known as a perfect vacuum. Therefore, if such readings occur, we first suspect that there may be a problem with the measuring equipment. Under normal conditions, it is generally not possible on the Earth’s surface to achieve a vacuum level that is lower than 101.325 kPa relative to the external atmospheric pressure. Therefore, if both your pressure transmitter and mechanical pressure gauge show readings of -102.6 kPa or -102.8 kPa, it is possible that: 1. There is a calibration error: the pressure gauge is not calibrated properly, which results in incorrect readings. 2. Incorrect reading method: You may have read the pressure gauge incorrectly, or the unit of measurement on the gauge is not kPa as you thought it was. 3. Instrument failure: It is unlikely that both pressure gauges will fail or get damaged, but this cannot be ruled out entirely. Generally speaking, under atmospheric pressure conditions, the highest vacuum level can be expressed as 0 kPa of absolute pressure, which represents a state with no gas molecules present. But this is unattainable in practical applications. Typical industrial vacuum pumps can achieve a vacuum level of several dozen to several hundred pascals; the ultimate vacuum level can be even lower, but it is still not possible to reach or exceed a perfect vacuum. If your pressure reading is negative and exceeds atmospheric pressure, it is recommended to recalibrate the instrument or replace it to ensure accurate readings. .
Is it indoors? The pressure inside might be a bit higher than outside; some manufacturing processes (such as those in clean rooms) require a higher pressure inside
This is what we can’t figure out. We tried four different brands of pressure transmitters, as well as precision mechanical pressure gauges, but in all cases the negative pressure was higher than the absolute pressure. All have been calibrated using a calibration bench. It’s really confusing: '(
This is what we can’t figure out. We tried four different brands of pressure transmitters, as well as precision mechanical pressure gauges, but in all cases the negative pressure was higher than the absolute pressure. All have been calibrated using a calibration bench. It’s quite confusing.
An absolute vacuum does not exist... This does not happen when using a gauge pressure meter