Seals made of the fluoropolymer PTFE are used where many other sealing materials (such as rubber elastomers, polyurethanes, fabric-reinforced elastomer seals, etc.) reach their limits in terms of requirements such as temperature range, chemical, friction and wear resistance. That is why PTFE is the most frequently used fluoropolymer in challenging sealing applications. Parker Prädifa produces seals made from pure PTFE and numerous modified compounds with diameters of up to 4.5 meters using economical machining techniques.
Polymer materials like PTFE, PEEK, TPU, and selected elastomers are suitable for machining such as turning or milling. This makes it possible to economically manufacture both larger and smaller volumes because no additional tooling costs for molds are incurred.
Parker Prädifa has been producing complex machined polymer seals with diameters of up to 3 meters for decades. In the light of a growing demand for increasingly large seals, Parker Prädifa has continually developed the manufacturing technology of machining further and is now able to offer diameters of up to 4.5 meters at the highest level of quality. The production of even larger diameters is currently in the pipeline.
The production of large seals for challenging applications is not simply a matter of scaling up the know-how of traditional seal design and machining. The reason is that XXL sizes not only pose particular handling challenges in the manufacturing process but do so even earlier, in the design and testing stages.
The evaluation of the performance of large-scale seals under various load and temperature conditions requires sophisticated simulation models. Particularly critical factors to be considered in the design of large seals include thermal shrinkage and expansion. In addition, even relatively low pressures may result in extreme forces acting on the seals, leading to considerable deformations or even seal failure.
As the damage caused by seal failure and leakage may be particularly severe in the case of large seals, reliable sealing functionality must be comprehensively validated prior to their utilization in the respective application. Parker Prädifa uses virtual prototyping for validation. Due to the advanced method of virtualization utilizing sophisticated FEA models, costly tests with real-world parts can be avoided and development cycles significantly reduced.
Parker Prädifa ensures the top quality of XXL sealing solutions using quality assurance technologies developed in-house. Picture: X-ray inspection of large-diameter seals.
Article contributed by
Karel Kenis, business development manager PTFE
Engineered Materials Group Europe, Prädifa Technology Division