General information on radial seals

Transcription

1 170 General information on radial seals Radial seals is the common name for shaft seals, which seal against a rotating shaft using an elastic and resilient lip of rubber or PTFE. The lip in turn is either mounted permanently in a sealing casing of metal or constitutes an integral part of the actual sealing unit. The function principle for all radial seals is that the lip slides on a very thin liquid film, generated either by the media that is to be sealed or by a separate oil film isolated from the media. The functional reliability and service life of the seals is entirely dependent on the ability of the sealing lip to bear against the shaft, the lip material, its design and the surface finish of the shaft. Prestressing of the sealing lip is achieved either by means of a garter spring which runs around the circumference of the sealing lip, or radially acting finger springs, or alternatively a combination of both types. The radial seals must be capable of dealing with all deviations due to e.g. bending of the shaft, geometric out of roundness of large bearing play. The lips must be sufficiently flexible to be able to compensate for all these deviations. Sealing lips which are prestressed by a garter spring often generate a higher total friction on the shafts than lips prestressed by finger springs. The finger springs also have the advantage, thanks to their flexibility, of being able to exert a partially higher or lower pressure against the shafts, which means that shafts with greater deviations can be sealed off. Another advantage of the finger springs is that they cannot move out of position in the way that a garter spring can. Lower prestressing force means lower friction, which in turn results in a longer service life for the seals. The rubber mixtures developed over the last few years, which are particularly resistant to abrasive media, have considerably extended the service lives of seals under extreme operating conditions. These design advantages permit use of radial seals at surface speeds of up to 35 m/s and shaft runout of up to 3.0 mm. Radial seals are manufactured in two completely different types, either endless for installation over a free shaft end, or split for easy fitting around a shaft where it is not possible to expose the free end of the shaft. Endless seals are often built into a metal casing, while split seals have no enclosure. Radial seals can be used, for example, for sealing ball bearings in pumps, gears, compressors, rollers etc. Conventional radial seals are designed for pressureless applications. For pressurised applications, a special variant is recommended with a sealing lip of restructured and carbon-filled PTFE, which can be used in applications from pressureless up to 25 bar and +250 C. The stated limit values apply under favourable conditions. Do not utilise more than one maximum value at a time. If in doubt please contact us, we will be happy to offer advice.

2 SPECMA SEALS HANDBOOK 171 Garlock radial seal P/S-Seal Temperature range: Max. internal pressure: Max. vacuum: Max. surface speed: Max. p x v factor: from -90 C to +250 C in standard version up to 10 bar in special version up to 25 bar to 0.1 Torr 45 m/s, during dry running 5 m/s 45 bar x m/s Properties: The sealing lip is very elastic and flexible, and has very low friction against the shaft. P/S Seal also has very good dry running properties. For food and pharmaceutical applications, P/S-Seal is supplied with a special lip of white Gylon -W, which meets requirements as per FDA. P/S Seal is resistant to most chemicals thanks to its material structure. This seal is also aseptic, i.e. it can be used in sterile environments. Enclosed seal for easy installation 1. Sealing lip of GYLON (restructured PTFE) 2. Backup seal of Viton 3. Casing of stainless steel (SS2350) Special seals for high pressures, high surface speeds and aggressive environments. P/S Seal comprises a thermoelastic sealing lip of Gylon restructured PTFE, which together with a backup seal of Viton is enclosed in a casing of acidproof stainless steel Used for: P/S Seal can be used for both liquids and gases, and it can replace mechanical seals and conventional stuffing box packings as a shaft seal. Thanks to its compact installation, P/S Seal is a very economical and advantageous alternative as a replacement for these types. Examples of common applications are centrifugal pumps, gear pumps, separators, blowers, rotary compressors, agitators and shaft bushings, primarily in the chemical, food and pharmaceutical industries. Dimensions: Dimension Dimension Dimension Dimension mm Part no. mm Part no. mm Part no. mm Part no. 20 x 35 x x 50 x x 75 x x 100 x x 35 x x 62 x x 80 x x 130 x x 42 x x 62 x x 85 x x 47 x x 70 x x 90 x x 47 x x 72 x x 95 x The above standard dimensions are supplied with a sealing lip of the standard material Gylon -B (see below). Other dimensions and seals with other lip materials are available to order. Special versions: P/S Seal can also be supplied in a range of special versions for different applications, e.g. contaminated environments, vacuum etc. Reverse lip Standard version with dust lip Double lips for vacuum Tandem lips

3 172 SPECMA SEALS HANDBOOK Garlock radial seal P/S-Lip Installation dimensions, mm: Shaft diameter Up to W D H H S S 1 at 5 bar S 1 at 10 bar S 1 at 25 bar P/S-Lip can be supplied in a wide range of dimensions and in different materials, all of which are available to order. Loose sealing lip for compact installation. Installed directly in the sealing space together with a backup seal of Viton and a retainer ring. P/S Lip comprises a loose sealing lip of Gylon restructured PTFE, which together with a backup seal of Viton is clamped in place axially in the housing by means of a retainer ring. Ensures compact installation and many possible variations. Used in applications where P/S Seal cannot be used for installation-related and/or space reasons. Area of application and properties: Used in cases where more lips are required due to high pressure, a large vacuum or abrasive media. Other properties are the same as for P/S Seal. Material alternatives for P/S sealing lips. Gylon -B: Standard material. Gylon -W: White special material for food and pharmaceutical applications. Meets the requirements of FDA. Gylon -F: Special material with very good dry running properties for soft counterfaces. Gylon -BI: Special material with very good dry running properties. Meets the requirements of FDA for use in food and pharmaceutical applications. Not suitable for pressurised applications. Gylon -KF: Special material for water applications. P/S Seal in standard version with lip of Gylon -B, and in special version with lip of white Gylon -W for use in food and pharmaceutical applications. Temperature range: from -90 C to +250 C ISO Press fit H7/r6 Shaft diameter h11 backup-seal groove backup-seal Max. internal pressure: Max. vacuum: Max. surface speed: Max. p x v factor: in standard version up to 10 bar in special version up to 25 bar to 0.1 Torr 45 m/s, during dry running 5 m/s 45 bar x m/s The stated limit values apply under favourable conditions. Do not utilise more than one maximum value at a time. If in doubt please contact us, we will be happy to offer advice.

4 SPECMA SEALS HANDBOOK 173 General design and operating data for P/S-Seal and P/S-Lip Counterface: To achieve an optimum sealing function between lip and shaft and long equipment service life, the face must be plunge-cut ground and an attempt must be made to achieve the following shaft face structure: Surface finish: R a = µm R z = µm R max = 4.00 µm, plunge-cut ground. The face of the shaft must be produced with absolutely no marks, scratches or other defects which could cause leaks. The recommended hardness of the surface is determined by the pressure of the media: Hardness: up to 1.5 bar: over 1.5 bar: min. 45 HRC min. 60 HRC We recommend coating the shaft with chromium oxide in order to achieve the requisite hardness. In extreme situations in which the p x v factor exceeds 20 bar x m/s, it is recommended that the shaft should be plasma sprayed with chromium oxide, followed by grinding and PTFE facing. Installation advice: The sealing lip is susceptible to mechanical damage during installation. Therefore, ensure that the lip is not passed over sharp edges. If a mounting cone cannot be integrated into the shaft, a separate one must be used. See illustration. When the P/S seal is installed with its back towards the shaft, either a mounting cone must be used or else the shaft end must be provided with a rounded, polished edge so as to ensure that the lip is not damaged during installation. See Fig. 1. When the P/S seal is installed with its front towards the shaft, a tapered face with an angle of at least 10 is required so that the lip can be mounted on the shaft with no risk of damage. The tapered face can either be in the form of a separate mounting cone (see Figs. 2 and 3) or a cone integrated in the shaft end with the same angle. It is important for the mounting cone also to have a fine, smooth surface and to be entire free of burrs, marks and scratches. All sharp edges must be rounded off and then polished for optimum installation. Some installation examples: P/S Seal Special: bearing seal P/S Seal Standard: Shaft seal in worm conveyor Shaft dia. minus 5,0 Shaft dia. minus 5,0 Shaft dia. plus 0,4 R = min 1,0 and polished Shaft dia. plus 0,4 P/S Lip: Lip arrangement for flushing, lubricating, cooling etc. Max. permissible shaft run-out P/S Seal Standard: Screw compressor shaft seal P/S Lip: Screw pump shaft seal Speed (rpm) Max. permissible eccentricity P/S Seal Standard: Drill crown seal P/S Lip: Pump stuffing box replacement seal Shaft diameter

5 174 SPECMA SEALS HANDBOOK Garlock Klozure model 64 Klozure model 64 is a robust radial seal for large runouts and high speeds, designed specifically for difficult operating conditions in heavy equipment. The design with a double spring system means that this seal is able to withstand very large shaft runouts even at high surface speeds. The sealing lip, together with the finger spring, the garter spring and a solid steel ring, is enclosed in a metal casing which gives the seal its dimensional stability. The finger and garter springs are made from stainless steel. Properties: The elastic and stainless finger spring system helps to provide the sealing lip's uniform, even pressure against the shaft and its ability to deal with large radial runouts. The limited prestressing of the lip by the garter spring means that it is only activated and reinforced the sealing function under extreme shaft runouts. Used for: Common applications: In rolling mills for sealing support and working rolls, in continuous casting equipment, calenders, rollers and gearboxes in paper machines etc. Shaft diameter: mm Max. surface speed: Max. shaft runout: 35 m/s at 25 m/s: 3.0 mm at 35 m/s: 2.4 mm Structure: Garter spring Solid steel ring Finger spring Spacer ring Sealing lip Outer casing Material alternatives for sealing lip Klozure model 64: Mill-Right N: NBR rubber with excellent oil resistance and good wear resistance. Wide media resistance range. Temperature range: -40 C C* Colour: Black Mill-Right ES: NBR-based special rubber with excellent wear resistance and heat resistance. Temperature range: -40 C C* Colour: Blue Mill-Right V: Special quality of Viton rubber with excellent chemical and heat resistance. Very good wear resistance. Temperature range: -30 C C* Colour: Green Silicone VMQ: and ozone. Colour: Light blue Silicone FDA: and ozone. Special qualitiy which meets the requirements as per FDA in food and pharmaceutical applications. Colour: Red * Max. temperature for continuous operation is 15% lower. Tolerances and installation dimensions: Shaft diameter mm Bore diameter mm 100 ± ± ± ± ± ±0.050 >250 ± / /-0.15 > /-0.25 The stated limit values apply under favourable conditions. Do not utilise more than one maximum value at a time. If in doubt please contact us, we will be happy to offer advice.

6 SPECMA SEALS HANDBOOK 175 Shaft surface finish and hardness: Surface Surface Surface finish finish Hardness speed m/s R a µm R max µm HRC > We recommend plunge-cut grinding of the shaft. Shaft end chamfer: Shaft diameter mm End chamfer length mm < > Bore diameter Shaft diameter Seal width +0.5 Garlock Klozure model 23 Split Klozure model 23 Split is a split radial seal developed especially for large runouts and high speeds. Klozure model 23 Split must always be fitted with a retainer ring. The ends of the seal do not need to be glued. Manufactured in both inch and millimetre dimensions. Shaft diameter: mm Max. surface speed: at shaft diameter mm: 5 m/s at shaft diameter over 1500 mm: 10 m/s Max. shaft runout: at surface speed 5 m/s: 0.25 mm at surface speed 10 m/s: 0.13 mm Properties: The design of the seal, with vulcanised finger springs made of stainless steel, make installation easy even in narrow or "blind" spaces. The split version makes maintenance easier as the seal can be installed without removing machine equipment, so reducing maintenance shut-downs to a minimum. This is possible because the seal has no garter spring, which would otherwise have to be put in place afterwards. Used for: Paper machines, rolling mills, machinery in the mining industry, gears, tunnel boring machines, ship engines and as wiper rings in hydraulic equipment. Material alternatives for sealing lip Klozure model 23 Split: Mill-Right N: NBR rubber with excellent oil resistance and good wear resistance. Wide media resistance range. Temperature range: -40 C C* Colour: Black Mill-Right ES: NBR-based special rubber with excellent wear resistance and heat resistance. Temperature range: -40 C C* Colour: Blue Mill-Right V: Special quality of Viton rubber with excellent chemical and heat resistance. Very good wear resistance. Temperature range: -30 C C* Colour: Green Silicone VMQ: and ozone. Colour: Light blue Silicone FDA: and ozone. Special quality which meets the requirements as per FDA in food and pharmaceutical applications. Colour: Red * Max. temperature for continuous operation is 15% lower.

7 176 SPECMA SEALS HANDBOOK Recommended installation dimensions: Shaft diam. Cross-section Cross-section Radial mm (mm) h (mm) b play (mm)c > Shaft surface finish and hardness: Surface Surface Surface finish finish Hardness speed m/s R a µm R max µm HRC > We recommend plunge-cut grinding of the shaft. Shaft and bore end chamfers: Shaft dia- L 1 L 2 meter mm mm mm < > Installation advice: Clean the housing and shaft thoroughly. Ensure that all components are in perfect condition. Lubricate the shaft with a suitable oil. Start installation by bringing together the sealing ends on the top and then push the ends into the housing. Then push in the rest of the seal uniformly on both sides of the shaft and finish on the opposite side. Finally fit the retainer ring and tighten the bolts so that the seal is compressed fully in the housing. Shaft diameter h11 Bore diameter H8 Information regarding the retainer ring: The retainer ring can be manufactured in a split version for easy installation. For the seal to have the correct axial compression, the retainer ring should be at least 6 mm thick. If the depth of the housing is greater than b±0.1 mm, the gap can be shimmed by means of a conventional soft gasket of an appropriate thickness. Availability: All dimensions of Klozure model 23 Split are available to order. The stated limit values apply under favourable conditions. Do not utilise more than one maximum value at a time. If in doubt please contact us, we will be happy to offer advice.

8 SPECMA SEALS HANDBOOK 177 Garlock Klozure model 154 Universal Shaft surface finish and hardness: Surface Surface Surface finish finish Hardness speed m/s R a µm R max µm HRC > Klozure model 154 Universal is a split or endless radial seal for universal use. Model is split, model is endless. Both types can be supplied in both inch and millimetre dimensions. Model 154 Universal must always be installed with a retainer ring, regardless of whether it is split or endless. Properties: The flexible design of the seal makes installation easy in both readily accessible and narrow or "blind" spaces. The split version makes maintenance easier as the seal can be installed without removing machine equipment, so reducing maintenance shut-downs to a minimum. This is possible because the seal's garter spring is split and can easily be assembled in situ. Used for: Standard applications in the paper and pulp industry, steelworks, rolling mills etc. Standard applications are as seals in transmissions, gearboxes and rollers. Material alternatives for sealing lip Klozure model 154 Universal: Nitrile: NBR rubber with good oil resistance and good wear resistance. Broad media resistance range. Shaft diameter: Max. surface speed: up to 2400 mm 25 m/s Max. shaft runout: at surface speed 5 m/s: 0.80 mm at surface speed 10 m/s: 0.40 mm at surface speed 25 m/s: 0.25 mm Temperature range: -40 C C* Mill-Right E: NBR-based special rubber with excellent wear resistance and heat resistance. Temperature range: -40 C C* Viton : Viton rubber with excellent chemical and heat resistance. Good wear resistance. Temperature range: -30 C C* Silicone VMQ: and ozone. Silicone FDA: and ozone. Special quality which meets the requirements as per FDA in food and pharmaceutical applications. Colour: Red * Max. temperature for continuous operation is 15% lower. Shaft and bore end chamfers: Shaft dia- L 1 L 2 meter mm mm mm < > Shaft diameter h11 Bore diameter H8 Availability: All dimensions of Klozure model 154 Universal are available to order. P/S Seal, P/S Lip, Klozure, Mill-Right are registered trademarks of Garlock Sealing Technologies. Viton is a registered trademark of DuPont Performance Elastomers.