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HIGH PRESSURE SHAFT SEALS
As pressures increase, special designs
become necessary.
Also known as elastomeric lip seals, radial lip seals, and oil seals, shaft seals are used in conjunction with reciprocating, oscillating, and rotating shafts to contain lubricants (or fluids) and to exclude contaminants. In some designs, shaft seals may also act to contain pressure or to separate fluids. Shaft seals are economical, suitable for use in small spaces, easy to install, and effective in a wide range of environments.
APPLYING THE PRESSURE As a general rule, the standard “V” and “K” lip designs (such as the “VBY” and the “KBY”) are effective up to a maximum continuous pressure of 4 pounds per square inch (p.s.i.). The “S” and “T” lip designs (such as the “SBY” or the “TBY”) can handle up to 5 p.s.i.
Despite their advantages, however, these standard seal designs are not adequate when subjected to pressures of 10 p.s.i. or higher. As shown in the illustration below, higher pressures can distort the sealing lip, resulting in a greater amount of contact between the lip and the shaft. Greater contact means more friction and heat generation, and, as a result, shorter seal life. In some extreme instances, high pressures have even been known to force the seal out of the bore or to tear the elastomeric lip away from its metal case.
MAKING A STAND In response to the need for seals capable of withstanding higher pressures, designers have developed a variety of non-standard shaft seals. These non-standard designs typically feature heavier-than-normal cross-sections (to minimize lip distortion) and a greater bonding area between the lip and the metal case (to lessen the chances that the lip will be torn away). The “TCN,” “SAV,” “HP1,” and “EP2” designs (right) are good examples of high-pressure shaft seals.
The styles shown here are just a few of the hundreds of standard and non-standard designs that are available from RL Hudson. And for truly unique applications, our in-house engineering department can help you with the design of a custom seal manufactured to your exact specifications. If you’d like more information on shaft seal design and selection, ask your account or territory manager for a copy of RL Hudson’s Shaft Seals Design Guide, or click here to view it online.
