Without seals we would have fluids leaking all over the place and contaminants infiltrating countless machines and forcing companies to spend heaps of cash on maintenance. So it is important for seals to be durable enough to withstand all the stresses an environment can throw at them long enough for the user to get their money’s worth. Depending on the environment, seals can experience stresses from dramatic changes in temperature, corrosive chemicals, high pressures, and more.
Seals used in mobile machinery applications face many of these stresses along with poor maintenance practices and operators routinely pushing equipment beyond their maximum capacities. So companies like Freudenberg-NOK have taken to developing seals and seal materials that can hold up in these rough conditions. Freudenberg’s 94 AU 30000 polyurethane seal material was designed with a much greater operating life and resistance to water and the impact of moisture than standard PU seals. Operating at temperatures up to 120° C, the visco-elastic behavior of the new material has been fine-tuned so that the flexibility of the soft segments persist despite wide temperature ranges. The material also provides high extrusion stability, allowing the seals to operate under pressures up to 50 MPa.
Pumps, compressors and ultra high vacuum applications can also put seals through their paces. The dynamic wear conditions experienced by seals in these environments can cause leaks that lead to failure. That is why Minnesota Rubber and Plastics designed a seal made from PEEK (polyetheretherketone). PEEK seals provide long operating life with chemical resistance to attacks by both organic and aqueous environments and excellent retention of mechanical properties up to 570° F (300° C). Custom joints in the seals allow for thermal expansion in hydraulic and pneumatic applications. These joints also minimize leaks and facilitate required fluid “pass through” when various hydraulic mechanisms are actuated in a system.
OmniLip PTFE rotary shaft seals from Saint-Gobain Seals can also be found in pumping applications. These seals were designed to bridge the gap between conventional elastomer lip seals and mechanical face seals. These seals come in various different types: Type 10 seals feature shaft speeds up to 25 msec and operating pressures up to 0.5 MPa; Type 50 seals feature a dust/dirt extruder design, shaft speeds up to 30 msec and operating pressures up to 0.2 MPa; Type 60 seals are suitable where shaft runout or bore/shaft misalignment exist and feature shaft speeds up to 10 msec and operating pressures up to 0.5 MPa while Type 70 seals feature shaft speeds up to 20 msec and operating pressures up to 3.5 MPa.
For reciprocating, oscillating and high wear applications, Trelleborg’s Zurcon range of plastic-based material is a suitable choice. The Zurcon Z80 line has an operating temperature from –196° to 80° C (–321° to 176° F) continuous use, and up to 125° C (257° F) for short periods. It is compatible with all water-based and alkaline cleaning agents with steam cycles below 115° C (239° F) and compliant to FDA 21 CFR 177.1520. Zurcon Z2221 is a proprietary polyurethane material specially developed for the manufacture of sealing elements. The material displays high wear resistance, low compression set and an operating temperature range of –30° to 110° C (–22° to 230° F). Compliant to 21 CFR 177.1680, it is suitable for use in food applications where resistance is required. It is compatible with many water-based and alkaline cleaning agents and with steam cycles below 115° C (239° F).
Trelleborg Sealing Solutions
Minnesota Rubber and Plastic