![]() This may sound like a large opening in comparison to the 1-micron lubricant film inside a rolling-element bearing, but because of the path that the contaminant must take to actually reach the bearing, this gap is more than adequate.Īll contaminants trying to enter the bearing housing must go through the seal’s maze (labyrinth) of turns and angles in order to reach the bearing. In many instances, this gap can be as small as 0.003 inches, which equates to roughly 76 microns. They are also considered frictionless, as the rotor and stator are separated by a very small gap. These types of seals are non-contacting, which means that the two opposing faces do not touch each other. The two pieces interlock to effectively seal out the majority of contaminants while holding in the lubricant or process fluid. The other piece, called the rotor, is attached to the shaft and rotates with the motion of the system. One piece, known as the stator, is affixed to the machine and remains stationary. Labyrinth seals are constructed in multiple pieces. However, labyrinth seals will last longer and perform better. Generally, you will need to retrofit these on the equipment and will incur the cost of their installation. Of course, the disadvantage of using labyrinth seals is that they are more expensive. So both oil retention and contaminant exclusion are at a much higher level of performance compared to contacting mechanical seals and lip seals. These seals are excellent for excluding particle contamination and moisture, even if there’s a spray of water nearby. ![]() On the other hand, a labyrinth seal is non-contacting, so it will not have the wear-out condition. Eventually, the seals no longer function well from the standpoint of both oil retention and contaminant exclusion. These types of seals tend to wear after a period of time because they make rubbing contact with the shaft. Lip seals are a prime example, particularly the ones that are only directed inward. Some seals do a good job of retaining oil or grease but do a lousy job of excluding contamination. Shaft seals must be properly selected and maintained. These types of systems provide better particle exclusion and less lubricant leakage than standard lip seals, which contact the shaft and rub the surface during operation. The basic concept of labyrinth seals is to reduce contaminant ingression not only by restricting the clearance through which particles enter but also by creating areas of turbulent flow to exclude contaminants. One limiting factor of these types of seals is the construction material, with each elastomer having its own strengths and weaknesses. Standard lip seals will limit certain contaminants from entering and restrict some leakage, but they are subject to failure, especially in systems with high pressure or extreme ambient conditions. The need for minimizing leakage while prolonging the machine’s operating life is more critical today, as the demands for reliability and the penalties for failure continue to rise. One study by Exxon Mobil showed that the amount of oil lost is four times the capacity of the machine. Not only is it attached to a machine to keep particles and outside contaminants from getting in, but it also must keep what is inside the machine - whether it is oil, process fluid or a barrier fluid - inside. Seal & Survive, Seal School Handbook)Ī seal’s function is multifaceted. Labyrinth-type seals are common devices for contaminant exclusion, and when properly maintained, they can greatly influence the reliability of the components in which they are installed.Ī comparison of various seal materials (Ref. The Capped G-T® ring, a capped version of the G-T® ring, consists of a T-shaped elastomeric energizer fitted with a contoured sealing cap and integrated pressure-activated backup rings.Simple modifications to breathers and sight glasses can be beneficial, but shaft seals are just as important in this process.The elastomeric energizer’s profile provides more evenly distributed loading to the sealing cap for improved wear life in high duty cycle applications. The Ener-Cap® seal cap geometry provides improved stability compared to the Advancap™ and eliminates roll and spiral failure.The curved cap design resists roll and spiral failure of the o-ring energizer compared to traditional rectangular capped seals. The Advancap™ is our simplest capped seal design for general-purpose duty cycles.Greene, Tweed offers three main types of capped seals: the Advancap™, the Ener-Cap®, and the Capped G-T® ring. Capped seal designs may include thermoplastic backup rings for resistance to extrusion in high-pressure applications. The thermoplastic cap provides lower breakaway and running friction and better wear resistance than an elastomer alone in high dynamic applications, reciprocating or rotary. CAPPED SEALS Capped seals contain an elastomeric energizing element with a thermoplastic cap on the sealing face.
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