Heavy Industry Makes Demands on Seals

From mining and construction to forestry and pulp and paper, heavy manufacturing and process industries are increasingly relentless in the demands that they place on plant and equipment. Not only does machinery have to be more reliable than ever before, to ensure that expensive production lines or operations are kept running at their optimum rate, it is also expected to last longer while functioning under ever tougher environmental conditions, with extreme temperatures and pressures, or at higher speeds.

The increased stresses placed on production and process equipment as a result of these demands can lead to often unexpected and expensive downtime, frequently caused by the failure of minor components, of which perhaps rubber or thermoplastic seals are among the most common. With research conducted by SKF while developing its New Life Theory showing that up to 14% of all premature bearing failures can be directly attributed to contaminants entering bearings via poorly designed or specified seals, the need to develop specialised components, specifically suited to heavy industry becomes clear.
Another recent seal material that is offering benefits in heavy industry is fluoro-rubber, or FKM, which combines outstanding levels of resistance towards heat, chemicals, ageing and ozone, with very slight gas permeability. It has exceptionally good wear characteristics, even under harsh environmental conditions, and can withstand operating temperatures of up to +200°C. Fluoro-rubbers are also resistant to oils and hydraulic fluids, fuels and lubricants, mineral acids, and aliphatic as well as aromatic hydrocarbons, which can cause seals made from other materials to fail.

Although FKM is an excellent material from which to produce seals used in harsh environments, it must be handled carefully. In particular, although it is stable and harmless in most operating conditions, if it is exposed to extreme temperatures above +300°C, e.g. fire or the flame of a cutting torch, it gives off hazardous fumes that can be harmful if inhaled, or if they come into contact with the eyes. In addition, once the seals have been heated to such temperatures, they are dangerous to handle even after they have cooled and should not be allowed to come into contact with the skin.

For heavy industrial applications where downtime is critical and shaft removal is impractical, all-rubber split seals are also available. All-rubber seals are simply placed around the shaft and pushed into the seal bore, then held firmly by a cover plate, which compresses the split joint together. These seals perform most effectively with grease or heavy lubricants but can also be used successfully with the latest generation of lubricating oils.

With seals no longer being commodity products, but rather essential components in the evolution of manufacturing systems, the need for these products to be tailored to individual applications is becoming ever greater. New seal materials such as PTFE and FKM are helping engineers throughout industry to achieve optimum performance from a wide range of machinery, while reducing downtime, maintenance, and ultimately costs.

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