Fluoroelastomer Specialists
For all rotating machinery in plants across industries, shaft seals play critical roles in protecting bearing arrangements and contributing to the reliability of equipment and systems. Proper sealing ultimately provides an effective defense in keeping machines performing as intended.
The decision-making process in selecting an industrial shaft seal would be easy if there were simply one “universal” seal design and material appropriate for any and all applications. Unfortunately, this is not the case. An ideal seal pick will always be influenced by application operating conditions and requirements.
Turning to application criteria
Industrial shaft seals primarily function to retain lubricant, exclude contaminants (such as dust or moisture), separate media (including lubricant), and resist pressure. Radial shaft seals are the most prevalent types for general and heavy-duty industrial applications. They serve to seal the opening between a rotating and a stationary component or between two components in relative motion.
In general, their design consists of a cylindrical outer covering of sheet steel (the “case”) or an elastomer providing the requisite interference fit to seal statically against the housing bore. In addition, a sealing lip made from an elastomeric or thermoplastic material enables sealing dynamically and statically against a shaft.
The lip is designed with a sealing edge formed by molding or machining and normally pressed against the counterface surface of a shaft (with a defined radial load) by a garter spring. The edge of the sealing lip and the shaft counterface surface ultimately form the most important functional area of any radial shaft seal.
Hundreds of different radial shaft seal design and material combinations have been standardized to a large degree over the years, and custom versions can be developed as necessary.
So where to begin in selecting a proper seal? The first step is to review the inherent application and operating criteria that will impact seal integrity and performance.
Internal and external temperatures. Materials for seals are engineered to perform over an optimum recommended temperature range. Beyond the designated range, thermal stress can adversely harden or otherwise degrade seal material (most notably, nitrile rubber). Such heat aging often will appear as a series of radial cracks on the seal. Conversely, if the operating temperature is too low, the seal material may stiffen and leak. In both cases, a switch to another seal material to accommodate the extremes would offer a fix.
Read more: How to select the proper industrial shaft seal for an application
