Could the experienced technician explain the difference between vacuum valves and ordinary valves in the simplest terms possible?
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:Is there a sentence that clearly explains this issue regarding handshakes? For example, what is the difference between vacuum gate valves and ordinary gate valves, and can they be used interchangeably in the same application? Or who can replace whom? Are vacuum valves mostly used in pipelines for oxygen or other gases? Here are the answers I found on Baidu. Could any expert briefly explain the most fundamental differences and the areas where they are commonly used in practice? Vacuum valves are valves whose internal chamber is in a vacuum state, often referred to as negative pressure, with the pressure inside being lower than atmospheric pressure. They are used in vacuum pipeline systems, and include vacuum ball valves, vacuum butterfly valves, vacuum diaphragm valves, etc. The medium is of high purity. Ball valves, gate valves, globe valves, and so on can all be manufactured as vacuum valves or conventional valves. There is no difference in appearance; the difference lies in the design of the valve connection parts, which is just a matter of detail. Vacuum valves have the following characteristics compared to positive-pressure valves: the pressure is below atmospheric pressure, and the pressure drop across the valve disc must not exceed 1 kilogram-force per square centimeter. The operating temperature of the medium depends on the process of the device in use. The temperature generally does not exceed the range of -70 to +150°C. The most basic requirement for such valves is to ensure a high degree of sealing at the connections, as well as tightness in the structure and the gasket materials. Vacuum valves can be divided into four groups according to the medium pressure: 1) Low-vacuum valves: medium pressure p = 760~1 mmHg ； 2) Medium vacuum valve: p=1×10-3 mmHg. 3) High-vacuum valves: p=1×10-4 ~1×10-7 mmHg ； 4) Ultra-high vacuum valves: p≤1×10-8 mmHg.
Here’s a pseudo-understanding for reference only. The valves are all the same; in a process system, regardless of the pressure, as long as there is a pressure difference, they must be installed according to the direction specified for those valves. Is this understanding correct? It’s provided for reference only.
Vacuum valves are designed to prevent external air from entering the pipeline, as well as to prevent the housing from deforming under high vacuum conditions.
Simply put, a vacuum valve is a valve used to maintain the vacuum level in a pipeline when the normal operating pressure is negative. Ordinary valves do not have this requirement. Generally speaking, no one can replace another; vacuum valves may not be able to withstand the higher positive pressures encountered with ordinary valves ； Similarly, ordinary valves may not be suitable for applications with negative operating pressures. Incidentally, a regular vacuum valve actually uses a low-leakage gasket at the middle flange; after a vacuum degree test confirms that it meets the required standards, it is then labeled as a vacuum valve. If it is a high vacuum, a bellows seal should be used.