Rotary Seal Design Guide - Seals Unlimited

FlexiSeal ® RotaryEngineeringChoosing the Right DesignWhile choosing the right Rotary FlexiSeal foryour application, you need to consider:• Pressure• Shaft Velocity• Lubrication• Shaft Misalignment• Shaft Runout• Shaft Hardness• Shaft Surface Finish• Different Spring Choices• Lip Shapes• Shaft LeadPressure and Shaft VelocityUnlike reciprocating applications, seals ride ona rotating shaft in only one small area wheredynamic forces and energy are concentrated. Fora guide to aid in the choice of seal profile andmaterial for optimum seal life, see Page 2-24.LubricationWhile FlexiSeals made of PTFE have a naturallubricity and can be used in unlubricatedapplications, a film of lubricant between the seallip and the shaft reduces seal wear and frictionalheat generation, makes higher surface speedspossible, and helps prevent the seal from wearinga groove in the shaft.Shaft Misalignment and RunoutApplications with rotating shafts may developproblems associated with shaft misalignment.Because rotary FlexiSeals are spring-loaded, theynormally handle runout and eccentricity betterthan FlexiLip and FlexiCase seals. For moreinformation about problems with eccentricity andrunout, see Page 2-25.Shaft Hardness and Surface FinishCatalog EPS 5350/USAIt is critical to match the right surfaceroughness with the media being sealed, especiallywhen the surface is hardened and the originalfinish will take some time to break in. See Table11-1 for recommendations and Page 2-21 for amore general discussion on the topic.Table 11-1. Surface Roughness, R aMedia BeingSealedCryogenicsHelium GasHydrogen GasFreonAirNitrogen GasArgonNatural GasFuel (Aircraft andAutomotive)WaterHydraulic OilCrude OilSealantsSpring ChoicesDynamicSurfacesStaticSurfacesµ inch µ m µ inch µ m04 max. 0.1 max.0 08 max. 0.2 max.06 max. 0.15 max. 12 max. 0.3 max.08 max. 0.2 max. 16 max. 0.4 max.12 max. 0.3 max. 32 max. 0.8 max.Rotary FlexiSeals are available with twodifferent spring designs to energize the jacket:V-shaped cantilever springs (V Series) and cantedcoilsprings (C Series). The FFN-H flanged designincluded in this section uses the helical spring (HSeries) and should only be used for static or veryslow rotary. Details on spring features can be foundon Page 2-16.111103/28/0611-2 Parker Hannifin CorporationEPS DivisionToll Free: (800) 233-3900www.parkerseals.com