PTFE ROTARY SHAFT SEALS

Transcription

1 PTFE ROTARY SHAFT SEALS NONE WEARING LOW FRICTION CHEMICALLY RESISTANT Elring radial lip seals with PTFE lips are sealing elements delivered ready for installation and are ideal for sealing rotating shafts. Their radial contact pressure produces a sealing action on the shaft. This is achieved by a combination of correct PTFE compound, lip geometry and manufacturing process. The interference as specified in DIN 3760 ensures static sealing between the outside of the seal and the seal housing. The basic design of the seal consists of an outer casing, PTFE lip, secondary elastomer seal and metal retaining ring. The metal case and seal lip are sealed by axially pre-tensioning the elastomer static seal and in special cases by a solid sealant which is temperature and chemically resistant. In addition style HN 2580 has a dust lip. ADVANTAGES Outstanding chemical resistance to corrosive media. Suitable for high temperature applications from -60 to +220 C. Also suitable for lube service and dry running. Suitable for unhardened shafts. Excellent wear resistance of the sealing lip material. In order to cover the widest possible range of applications, two standard types have been developed. Type HN 2580 is primarily used for service in unpressurised conditions or where the pressure is only slightly above atmospheric, while type HN 2390 is ideal for pressurised media. Suitable for high peripheral speeds. Low breakaway forces after long periods of non operation. Anti-adhesive properties of the sealing lip. Special materials suitable for the foodstuffs and pharmaceutical industries. LIMITED, BRUNTCLIFFE AVENUE, LEEDS 27 BUSINESS PARK, MORLEY, LEEDS, LS27 OTG, ENGLAND. TEL: (0113) FAX: (0113) 2 27

2 OVERVIEW OF TYPES I. TYPE HN 2390 Primarily for pressurised media, but also suitable for unpressurised applications. Standard Extremely resistant to wear and pressure-stable, for use in pumps, fans and compressors. Special type: friction-optimised LIMITED, BRUNTCLIFFE AVENUE, LEEDS 27 BUSINESS PARK, MORLEY, LEEDS, LS27 OTG, ENGLAND. TEL: (0113) FAX: (0113) 2 27 Low power loss and low generation of frictional heat, as required for machine tools. Special type: protective lip For use in dirty environments, on building sites and for underfloor applications. Special type: double lip, lips facing in the same direction, with or without hyrodynamic return feed spiral groove. Good sealing action, enhanced reliability, suitable for pumps and compressors. Special type: double lip, lips facing in opposite directions For separating two media, for example in centrifugal machines and decanters. Special type: negative Small clearances and cavities to ensure easy flush clean for foodstuff and medical products; used in mixers, meat cutters etc. Special type: high pressure Good compression resistance and temperature stability, suitable for machine tools and rotary unions.

3 OVERVIEW OF TYPES AND OIL SEAL II. TYPE HN 2580 For unpressurised applications and pressures only slightly above atmospheric pressure. Standard Dust lip and extremely flexible sealing lip, used in gearboxes, machine tools and pumps. Special type: friction-optimised SECONDARY SEAL The following materials are used for the secondary seal between the PTFE lip and the housing: Standard: Special models: FPM NBR EPDM MVQ PTFE/special metal compound HOUSING MATERIALS Standard: Special models: Free-cutting steel Mild steel Aluminium Plastic (DPM) Without dust lip, but with low coefficient of friction and excellent resistance to wear for centrifugal machines and fans. LIMITED, BRUNTCLIFFE AVENUE, LEEDS 27 BUSINESS PARK, MORLEY, LEEDS, LS27 OTG, ENGLAND. TEL: (0113) FAX: (0113) 2 27

4 OIL SEAL WITH PTFE SEALING LIP TYPE HN 2390 STANDARD Standard type for a wide range of applications. This model has a reinforced sealing lip; it is used primarily for pressurised media, but is also suitable for unpressurised applications. Sealing lip material: PTFE compound HS Design: Characteristics: Single lip Reinforced sealing lip Lip effectively supported to resist deformation under pressure Good sealing action in conjunction with pressurised media Suitable for lubricated or dry running Also suitable for unhardened shafts Operating limits (1) : Max. peripheral speed m/s 20 Temperature range ºC -60 to +200 Max. compressive load bar 10 Vacuum mbar to 5x10-5 Centre offset mm 0.1 Concentricity tolerance mm 0.1 LIMITED, BRUNTCLIFFE AVENUE, LEEDS 27 BUSINESS PARK, MORLEY, LEEDS, LS27 OTG, ENGLAND. TEL: (0113) FAX: (0113) 2 27

5 OIL SEAL WITH PTFE SEALING LIP LIST OF DIMENSIONS FOR TYPE HN 2390 Designation example: Oil seal with PTFE lip for shaft diameter d1 = 75 and location hole d2 = 100: RWDR HN x 100 x 10 Shaft-Ø d 1 Outer-Ø d 2 b ± 0.2 Shaft-Ø d 1 Outer-Ø d 2 b ± 0.2 LIMITED, BRUNTCLIFFE AVENUE, LEEDS 27 BUSINESS PARK, MORLEY, LEEDS, LS27 OTG, ENGLAND. TEL: (0113) FAX: (0113) * * * * * * * 22 * 25 * 42 * * 28 * * * 45 * * * 50 * 55 * * 55 * 60 * * indicates stock sizes * 8 65 * * 45 * 65 * * * * * 80 * * * * 95 * 100 * * * 110 * * * * * * 1 * * Special dimensions and dimensions > shaft Ø 130mm on request FTL SEAL TECHNOLOGY

6 OIL SEAL WITH PTFE LIP TYPE HN 2580 STANDARD Standard type for unpressurised conditions or where the pressure is only slightly above atmospheric pressure. This model has an extremely flexible sealing lip and an additional dust lip. Standard material: PTFE compound HS Design: Characteristics: Sealing lip and dust lip both made in one piece Recess in base of sealing lip Sealing lip has low radial pretension Also suitable for soft shafts Extremely flexible sealing lip Improved frictional properties Defined seal path width Operating limits (1) : Max. peripheral speed m/s 30 Temperature range ºC -60 to +220 Max. pressure bar 0.5 Centre offset mm 0.2 Concentricity tolerance mm 0.3 LIMITED, BRUNTCLIFFE AVENUE, LEEDS 27 BUSINESS PARK, MORLEY, LEEDS, LS27 OTG, ENGLAND. TEL: (0113) FAX: (0113) 2 27

7 OIL SEAL WITH PTFE LIP LIST OF DIMENSIONS FOR TYPE HN 2580 Designation example: Oil seal with PTFE lip for shaft diameter d1 = 75 and location hole d2 = 100: RWDR HN x 100 x 10 Shaft-Ø d 1 Outer-Ø d 2 b ± 0.2 Shaft-Ø d 1 Outer-Ø d 2 b ± 0.2 LIMITED, BRUNTCLIFFE AVENUE, LEEDS 27 BUSINESS PARK, MORLEY, LEEDS, LS27 OTG, ENGLAND. TEL: (0113) FAX: (0113) * * * * * 22 * 25 * 42 * * * 50 * * 55 * * indicates stock sizes 60 8 * * * * * * 80 * * * * * * * * Special dimensions and dimensions > shaft Ø 130mm on request FTL SEAL TECHNOLOGY

8 CONSTRUCTION DESIGN OF THE SEAL HOUSING Surface roughness: Ra 1.6 µm Rz 6.3 µm CONTACTING SURFACE Condition of surface The condition of the contacting surface affects the tightness and lifespan of the seal. The recommended surface roughness should be observed as far as possible, in the interests of achieving the optimum sealing action. Score marks from machining, scratches and shrinkage cavities are detrimental to the effectiveness of the seal. We advise plunge grinding the shaft in the sealing area. Another alternative would be to work in a hydrodynamic return feed spiral groove. Hardness The hardness required of the contacting surface is dependent on numerous application parameters. If the demands made on the oil seal are not particularly stringent (pressures only slightly above atmospheric and low peripheral speeds), soft shafts Recommended roughness of the contacting surface: Ra = µm Rz = 1-4 µm Roughness Rz = µm have proved ideal for very hard surfaces, such as chromium-oxide coatings. may be adequate in some cases. This also depends on the selected PTFE compound, however. We recommend a contacting surface hardness 58 HRC for more severe conditions and higher pressures. LIMITED, BRUNTCLIFFE AVENUE, LEEDS 27 BUSINESS PARK, MORLEY, LEEDS, LS27 OTG, ENGLAND. TEL: (0113) FAX: (0113) 2 27

9 FITTING When oil seals with PTFE lips are fitted, it is essential to ensure that the sensitive lip is protected from damage. We recommend using a conical fitting tool. If the oil seal is fitted facing the moulded sealing lip, it is sometimes sufficient to provide a radius at the shaft. The surface of the fitting tool should be score-free. All edges must be chamfered. Sharp edges at transitions must be avoided. When grooves or threads are fitted, the conical fitting tool must be used with a thin-walled extension. Temporary over-stretching of the PTFE lip during the fitting procedure is allowed. LIMITED, BRUNTCLIFFE AVENUE, LEEDS 27 BUSINESS PARK, MORLEY, LEEDS, LS27 OTG, ENGLAND. TEL: (0113) FAX: (0113) 2 27 PTFE rotary shaft are press-fitted into the seal housing (interference fit). We recommend either glueing the seals into the hole or using a sealing compound (e.g. Loctite 601, 641). Recommended diameters of the fitting tapers This eliminates the possibility of leakages occurring at the outer diameter in critical systems. Shaft-Ø d 1 [mm] Taper-Ø d 2 [mm] d 1-2 d 1-3 d 1-4 d 1-5 FTL SEAL TECHNOLOGY