![]() ![]() Non-contact seals can be divided into three distinct categories: gap, traditional labyrinths or compound labyrinths, often referred to as Bearing Isolators. While the magnetic face-type seals are thought to offer greater life expectancy than lip seals, the real-world life expectancy of either type of contact seal is mostly still unknown. Predicting when contact seal failure will occur, or what seal life can be expected of any particular seal installation, has remained unknowable. Their common disadvantage is in that contact seals are friction devices that will wear out and at some point fail. Magnetic seals are considerably more expensive than lip seals.īoth types of contact seals have the advantage of being able to seal positive pressures or static levels (i.e., heads) of lubricant. ![]() The primary advantage of magnetic seals over lip seals is that they do not damage the shaft, as all dynamic contact occurs within the seal and between the two faces. The faces are usually comprised of different materials, such as carbon and stainless steel or other metals. Magnetic seals are optically flat, essentially simple unbalanced mechanical seals utilizing magnetic attraction to load faces as opposed to mechanical springs. The primary disadvantages are short life due to wear, and that by dynamically contacting the shaft they can cause shaft wear and damage. They are also readily available in almost any size required. The primary advantage of lip seals is low cost. The elastomeric contacting element is often retained by a metal housing that is press-fit into the bearing housing about the shaft. This static contacting element is pressed against the shaft, often with the aid of a spring, to assure positive contact. Lip seals broadly refer to any design utilizing an elastomeric, usually circumferential contacting element. For a non-contact seal, contact is not the mechanism by which the seal performs.Ĭontact seals are commonly further subdivided into lip seals and magnetic seals. That is not to imply the design of non-contact seals never permit components to touch (e.g., during installation or adjustment), but rather that contact is not a requirement for proper function. Non-contact seals, conversely, do not rely on contact to perform their sealing function. If there is no contact, there is no seal. Contact seals rely solely upon contact to perform their sealing functions. There are essentially two broad categories of bearing housing seals: contact and non-contact. Some basic knowledge and understanding of bearing housing seals is thus a prerequisite topic for any practicing rotating equipment reliability professional. The proper selection and design of theses bearing housing seals has a significant impact on pump reliability. Bearings are protected from their two major causes of failure, contamination and lubricant loss, primarily by the bearing housing seals. Given that bearing failure equals equipment failure, bearing protection is an essential topic to any conversation regarding reliability of industrial rotating equipment. The practical application of reliability science has made this possible, and attention to bearing life in particular has been a major contributor to this new reality. Where 90-day warranties and annual pump rebuilds were once common, users today have an expectation of five years or longer MTBR. Industrial rotating equipment, particularly industrial pumps, have undergone a similar, though even more dramatic, transformation. ![]() Today 100,000 miles is not an accomplishment, but an expectation, and many cars even have warranties that extend that far. The probability that a car would last longer than 100,000 miles was, relative to today, small.Ī typical new car warranty then was only twelve months or 12,000 miles. The reason was simple: 100,000 miles was a major accomplishment in the late 1970’s, and there was little need to record mileage beyond that point. My first car had an odometer that rolled over at 100,000 miles. This article argues that as bearing isolators have an unlimited life expectancy and do not fail under normal circumstances, they are rarely the cause of equipment downtime. The life of a pump is often dependent on the protection its bearings receive. An Inpro/Seal Bearing Isolator installed on a pump.
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