Collection of discussions on oil seal products: 1. Where did the concept of bearing isolators come from?

Thread Content

I haven’t been to Haichuan for a long time; many rules have changed. Since there are new regulations and guidelines, one has to be extremely careful with what one says. :I would like to state here that this post is purely for technical discussion, and it is not intended as an evaluation of market-based brand products. In the field of rotating equipment, many people have probably heard of the term “bearing isolator”. Many people get confused about terms such as \"oil seals\" or \"bearing isolators\" when they first encounter them; in fact, they are all seals used in centrifugal equipment to protect bearings. Compared to mechanical seals, this product seems insignificant. However, the chemical industry also has certain requirements regarding the selection of lubricant seals. First, skeleton oil seals. When it comes to oil seals, what comes to mind first is certainly various types of skeleton seals. Large quantity and low price are its most obvious advantages. It can be considered a sealing element, as the rubber material, thanks to its elasticity or spring force, can make direct contact with the shaft, thereby providing effective sealing and oil-blocking capabilities in equipment. However, due to friction, such products have significant disadvantages in terms of potential damage to the shaft, as well as the inability to maintain the cleanliness of the lubricating oil after damage occurs. Moreover, commonly used skeleton oil seals will exhibit excessive wear and oil leakage after thousands of hours of operation. Long-cycle equipment is designed and purchased in accordance with the API610 and GB/T3215 standards, and skeleton oil seals are no longer permitted to be used. Second, labyrinth oil seals. In the 1980s, labyrinth oil seals began to be used in mechanical equipment abroad; their predecessor was actually the comb-tooth seal used in mechanical design. The principle involves adjusting the clearance of the leakage paths at both ends of the bearing housing, using interlocking toothed or labyrinthine structures to extend the lubricant leakage pathways thereby delaying the leakage of lubricant. Later, some foreign manufacturers, through careful design, developed these types of products in a modular design that integrates the stationary and rotating rings together. As chemical pumps of imported brands entered the domestic market, these equipment components gradually gained recognition within China’s chemical processing equipment industry, leading to imitation and localization efforts. In English, when referring to an oil seal, the word \"Seal\" is often emphasized; however, the term \"labyrinth oil seal\" is not recognized in overseas markets and among some industry experts. The contradiction lies in the fact that if the labyrinth oil seal is considered a seal, then where is the contact surface (point) for sealing? Is it the middle O-ring that prevents the rotating and stationary rings from separating? Foreign manufacturers need to redefine this issue; their explanation is that the O-ring in between serves to prevent water vapor from entering the bearing housing. On this basis, the impact of water vapor on the lubricant medium was emphasized. So it’s isolation, not sealing. The concept of \"Seal\" is hidden in this product, with the seller emphasizing the concept of \"isolator\" instead. The term “Bearing Isolator” came into use, and as the product became more widely adopted, the concept of a \"bearing isolator\" was established. Objectively speaking, this is a marketing concept on par with that of a certain diamond brand. The bearing is isolated (not being visible can be considered isolation as well), but is the lubricating oil isolated (or is it still leaking)? Is it still necessary to add lubricant regularly? Can rolling bearings achieve their designed service life? Will oil leak at the pressure oil level of a sliding bearing? Since I’m the one who posed the question, I’ll try to answer it based on my limited professional knowledge. If there are any mistakes, I welcome colleagues to point them out promptly and offer their guidance. Can labyrinth oil seals still leak oil? - Yes. Labyrinth oil seals have limits on the height to which oil can be added; generally, this limit is set at between one-third and one-half of the height of the lowest ball in the rolling bearing. If the oil level exceeds this limit or rises above the body of the oil seal, oil leakage will occur. (I heard from some experts that it’s okay to let it leak for a while; the oil level will drop once that happens.) ):dizzy: When using labyrinth seals, is it necessary to add lubricant regularly? - Add it every six months. Can rolling bearings achieve their designed service life when labyrinth seals are used? - The bearings need to be replaced every little over a year on average. In equipment with sliding bearings, how do labyrinth oil seals perform? - This... the pressure resistance of the labyrinth seal is 0, so it is generally not recommended to use a labyrinth seal directly. In summary, it is believed that everyone now has a better understanding of the concept of bearing isolators. The labyrinth seal used in these isolators is indeed an innovative and groundbreaking product, which has also played a role in facilitating the export of chemical processing equipment manufactured in China and helping such equipment to integrate with international standards. Times are advancing, and products are constantly evolving; our current petrochemical construction industry is in an unprecedented situation. Regarding the operational reliability of long-cycle equipment and the requirement for maintenance-free operation over 3 or even 4 years, the new products will surely be better able to meet these demands and perform well. However, over the past few decades of use, the labyrinth oil seals in bearing isolators have also gradually shown design flaws. I will discuss each aspect of this section in detail with you in the follow-up entries of this collection, and I welcome feedback from my colleagues as well.