Plymouth, Michigan -- Freudenberg-NOK Sealing Technologies has developed a sealing technology for roller bearings used in challenging steel-plant applications, the company announced 29 April
Radial shaft seals for roller bearings in steel plants, for example those used for work rolls, are replaced after 8,000 operating hours, at the longest. Until then, they are expected to function smoothly and reliably under harsh conditions and at high temperatures.
The seals are also expected to protect the bearing internally against excessive water penetration, offer a self-retaining fit in the housing and facilitate easy assembly and repairs.
However, because these requirements cannot be achieved cost-effectively with existing seal designs and production processes, Freudenberg-NOK developed the Merkel Radiamatic RPM 41 radial shaft seal. This, it said, has already been used in European and North American steel plants.
In radial shaft seals, springs are traditionally used as pre-tensioning elements at the seal lip because the existing elastomer materials fatigues too quickly to produce a sufficiently high pretension force over long periods.
The new radial shaft seal is claimed to be unique in relying upon a spring-less seal lip design made from a special elastomer material with a very low compression set. The design was developed to facilitate high material elasticity without affecting properties such as high wear resistance and joining strength.
Another feature of the RPM 41 radial shaft seal is its elimination of metal cages as the typical retaining element in the installation space. These metal cages are difficult to install and remove, creating the risk of damaging the housing.
Although pure elastomer or rubber/fabric designs are not suited to the self-retaining function of the seal, Freudenberg-NOK conducted a series of tests and finite element analyses to come up with an innovative alternative: a steel element that is precisely placed inside the static rubber part of the seal during the vulcanisation process.
The technology, said the company, eliminates exterior metal parts which can corrode and facilitates easy assembly/disassembly by hand which protects the installation space.