Taking a system approach, we look at the bearing housing environment from an energy balance point of perspective. A fresh lookĪ simpler approach is required to take bearing lubrication protection to the next level. The time has come for a slightly different approach. Mag-face technology has been used to try to solve the problem, but with limited success. This technology struggles in environments where steam is present and does not effectively retain oil mist. When heavier contaminates, such as sand/dust and paper stock, enter the seal, expelling them is virtually impossible regardless of the internal geometry of the seal. One weakness is that, to get rid of contamination that enters the seal, it also allows contamination to enter the seal. This design has pros and cons, as any design does. By design, an expulsion port is required in a labyrinth seal to expel any contamination that enters the seal under dynamic conditions and to drain any residual contamination inside the seal after shutdown. Each application should be considered on a case-by-case basis.ĭynamic O-ring designs have a break-in period during which black dust collects around the expulsion port, which indicates something wearing or breaking in. Mag-face technology has its place and is preferred in some applications, but it tends to be on the fringe for many industrial pump applications. Therefore, increasing the complexity of a system by adding two or three more mechanical seals does not make sense when other technologies are available that will protect the bearings more effectively at a lower price point. Mag-face technology has had success in some applications, but the technology often performs inconsistently and is more sensitive to operating conditions than other technologies.ĭuring the last 30 years, pump reliability efforts have focused on keeping the mechanical seals alive. As with all mechanical seals, the faces must be lubricated, or they will overheat and fail. Magnetic-face (mag-face) seals are mechanical seals that use magnetic force to keep the contacting faces together instead of the springs and bellows that traditional mechanical seals use. Any application with limited work space.Conveyor belt idlers, where the replacement cost of a new idler is 25 percent of the cost of a set of bearing isolators.Engineered applications, which can have large shafts where a bearing isolator is not economically practical.Light-duty pumps and motors like those used in the food processing industry (in most situations, a set of bearing isolators do not make economic sense for these applications).Low-speed, flooded shafts, such as gearboxes.This type is applied in much smaller numbers. The other type of contact seal is the magnetic face seal.
The most widely used contact seals for industrial equipment are elastomeric lip seals.
Typically, the lubrication comes from the lubricant migrating to the contacting surface elements. All contact seals must be lubricated, or they will run hot and fail prematurely, usually damaging the components they directly con- tact. Contact sealsĬontact seals are friction devices with a finite life. With the air comes contamination in the form of moisture and dust, which migrates into the bearing housing if protection is not used. The result is air being drawn in from the outside environment as the housing approaches equilibrium. Let’s examine the technologies currently available to help end users determine which technology best meets their application requirements.īecause cool air is denser than warm air, the bearing housing quickly will consume what air is inside and begin to create a vacuum. Other manufacturers have developed their own bearing isolators with varying degrees of success. The original design evolved over the years but remains a basic, two-piece compound labyrinth seal that sets the industry standard for bearing housing protection. Pumps and motors, the most prevalent industrial rotating equipment in the world, benefitted most from the upgrade. When compared to traditional sealing methods, the bearing isolator represented a paradigm shift in bearing housing protection and equipment reliability. The rotating equipment on which they were installed had short mean times between failure relative to the bearing’s rated life. Some customers learned to adjust their maintenance practices accordingly, but it was a hard fight because these designs did not adequately protect the bearing lubrication from environmental contaminants. Before then, lip seals and traditional labyrinth seals were the only real options available for machine designers and end users. In the 1980s, Inpro/Seal pioneered and marketed the first compound labyrinth seals, bearing isolators.
Shaft seals have been around since Archimedes invented the first pump, but only in the 20th Century was shaft sealing given adequate attention.
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