Self-Diagnosing Seal

Seals have several important functions: Preventing contamination, creating temperature and pressure safeguards, and protecting the external environment from accidental leaks and spills. By maintaining an impervious barrier between the external and internal environments in which they are placed, they serve a critical role protecting machinery and systems from temperature and pressure fluctuations and dirt and grime. They further prevent aggressive fluids and chemicals from polluting their surroundings. In the future, intelligent seals from Freudenberg Sealing Technologies can significantly expand this important core task: The seal itself is also a sensor and applies built-in functionality, via materials and design, to become a “smart seal”.

“We deliberately decided to take this route. It promises insights with considerably more information on the seal’s service life than we can get from modeling other usage data in the system,” says Dr. Boris Traber, Manager of the company’s global Materials Predevelopment. “We’re convinced that future seals will be able to provide us with accurate condition information in real time, which means they can be central elements in predictive maintenance and Industry 4.0 – the systematic digitalization of machines and plants.”

One of Freudenberg Sealing Technologies development efforts is the creation of an intelligent rod seal. This forms a capacitor with outer layers made of an electrically insulating elastomer and an inner layer of an electrically conductive elastomer with a metallic housing wall. If the successive abrasions of the insulating layer cause the seal to wear down, the distance between the electrically conductive layer to the metallic housing decreases while the capacitance rises. This makes it possible to get a condition measurement at any time which indicates the service life of the rod seal if the wear remains constant.

This offers considerable advantages: Maintenance times can be scheduled reliably in advance. Such predictions prevent follow-up costs caused by leakage damage and lower the risk of contaminating the whole batch. Another benefit: The seal is used throughout its entire service life without being replaced prematurely. This optimizes operating costs and provides a sustainable solution.

The technical concept works

Freudenberg Sealing Technologies has already developed both sealing materials and a smart rod seal that meet all the performance requirements of a conventional rod seal, including those that involve acid and base resistance, standards, service life and manufacturability.