Sealing technology manual for the process industry

Coating with PTFE varnishes PTFE coatings adhering firmly to the surface of elastomers provide a high degree of friction reduction. However, the relatively soft PTFE layer is lightly abraded in dynamic con- tinuous operation. Despite abrasion of the coating, a cer- tain amount of friction reduction is maintained since the PTFE burrows into the valleys of the roughness profile of the mating surface and fills them. The slide-active PTFE lay- er is not as elastic as the base material, however. Thus, the PTFE layer forms cracks in the event of greater elongation which may lead to leaks or cause the layer to flake off. Halogenation In this method, the surface is hardened in the micro range and thus does not get pressed as strongly into the rough- ness profile of the mating surface. The result is a better gliding property. However, the layer is abraded in the event of high dynamic stress, so that the seals lose their gliding property. The method is very well-suited for the automat- ed assembly of O-rings since the rings are dry and pow- der-free. The devices remain clean and free of abrasion over a very long period of time. Lubrication with grease or oil If requested, seals can be delivered lightly greased or oiled. It is important to note that the assembly equipment may be soiled by the greases or oils. In addition, the compatibil- ity of the greases and oils must be matched with the seal- ing materials. In a dynamic application, the seals should be lubricated only shortly before assembly, because this will achieve good long-term lubrication. RFN treatment (Reduced Friction by Nanotechnology) In this procedure developed by Freudenberg New Tech- nologies, the surface properties can be set in such a way that the adhesion and thus the jamming of the components is significantly and permanently reduced. Furthermore, the surface can be designed extremely hard and thus with low-wear and low-friction properties so that RFN-treated products are predestined for dynamic applications. Due to the special process, the materials retain their elastic behav- ior and dimensional stability. RFN treatment has approval for drinking water applications and is resistant to common CIP/SIP cleaning agents. Untreated RFN-treated Glide path (m) µ 1,2 1,0 0,8 0,6 0,4 0,2 0 0 200 400 600 800 1000 1200 Technical fundamentals 30 020040060080010001200

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