The relationship between water seals, oil seals, mechanical seals, and dry gas seals
Thread Content
I have just started working with rotating equipment, and I often hear terms like water seal, oil seal, mechanical seal, and dry gas seal. I know that they are all types of shaft seals, but I don’t know much about them in detail. I would like to learn more about this; please advise me, experts. Thank you
A water seal is a separation method that uses water to isolate two sections of gas from each other. A mechanical seal, on the other hand, is a device designed to prevent fluid leakage; it consists of at least one pair of end faces perpendicular to the axis of rotation, which remain in close contact and slide relative to one another under the action of fluid pressure and the elastic force (or magnetic force) of a compensation mechanism, along with the assistance of additional sealing elements. A dry gas seal is a new type of contactless shaft seal used to seal gas or liquid media in rotating machinery. Compared to other seals, dry gas seals feature low leakage rates, minimal wear, long service life, low energy consumption, simple and reliable operation, low maintenance requirements, and the fluid being sealed remains free from oil contamination. Therefore, in compressor applications, dry gas seals are gradually replacing floating ring seals, labyrinth seals, and oil-lubricated mechanical seals.
Reply to 1# mp1975: They are all types of seals; it’s just that they have different names. Water seals and oil seals are terms used based on the sealing medium, referring to seals that are used to seal water or oil respectively. Mechanical seals and dry gas seals are terms used based on the different structural designs of seals. A mechanical seal consists of at least one pair of end faces that are perpendicular to the axis of rotation; under the combined action of fluid pressure and the elastic force (or magnetic force) of a compensation mechanism, along with the assistance of auxiliary sealing rings, these end faces remain in close contact and slide relative to each other, thereby preventing fluid leakage. The dry gas seal structure is similar to a mechanical seal; the fundamental difference from a conventional mechanical seal is that one of the sealing ring surfaces of the dry gas seal is fitted with evenly distributed shallow grooves. During operation, the gas used for sealing is introduced into the groove, creating a hydrodynamic pressure effect that separates the sealing surfaces, thereby achieving a contactless seal.