• Document: Mechanical shaft seal types and sealing systems
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Chapter 2 Mechanical shaft seal types and sealing systems 1. Mechanical shaft seal types 2. Sealing systems 3. Selecting a mechanical shaft seal Mechanical shaft seal types and sealing systems 1. Mechanical shaft seal types In this chapter, the basic working principles for single mechanical shaft seals will be put into a practical context. The chapter describes mechanical shaft seals used in Grundfos pumps as examples of the variety of shaft seal solutions for different applications. 26 Type A Type B Type A Type B Unbalanced O-ring seal Rubber bellows seal with rigid torque transmission system Robust O-ring seal featuring Bellows seal with torque a rigid torque transmission transmission across the design required for hard spring and around the material pairings (WC/WC bellows. Therefore it is not or SiC/SiC), even where designed for hard material lubrication is poor. pairings in applications The dynamic secondary seal with poor lubrication. is an O-ring. This involves Due to the bellows, the seal a risk of wear on the shaft does not wear the shaft, under the O-ring and of seal and the axial movement is hang-up (blocking of axial not prevented by deposits movement of the rotating or seizure on the shaft. seal ring). Stationary part Rotating part 27 Mechanical shaft seal types and sealing systems Type C Type D Type G Type C Type D Type G Unbalanced O-ring seal Balanced O-ring seal with Rubber bellows seal with with spring as torque spring on the atmospheric reduced seal face transmission element side Low-pressure, simple O-ring Due to the balancing, Rubber bellows seal like seal with the spring acting this O-ring seal type is type B but with a narrow as torque transmission suitable for high-pressure seal face. Due to the element. Therefore the applications. narrow seal face, the seal seal is dependent on the performs well in high- direction of shaft rotation. The seal is excellent for viscosity and anti-freeze The shown seal is for a high-viscosity, dirt- and liquids. counter-clockwise shaft fibre-containing liquids rotation. becauce the spring is located on the atmospheric The seal type is excellent side. for low-temperature, clean- The seal features rigid water applications with a torque transmission ceramic/carbon seal face design. pairing. 28 Type H Type K Type R Type H Type K Type R Balanced, cartridge O-ring Balanced, rolled-metal Unbalanced O-ring seal, type seal unit with rigid torque bellows cartridge seal unit A, with reduced seal face transmission system This seal type is assembled The metal bellows acts O-ring seal like type A but in a cartridge unit which both as spring and torque with a narrow seal face. makes replacement safe transmission element. Due to the narrow seal face and easy. of the unbalanced design, This seal type has only the balancing ratio exceeds Similar to the type D seal, static rubber parts, with that of seal type A. This the balancing makes this reduced risk of hang-up reduces the pressure and O-ring seal type suitable for similar to type B. temperature operating high-pressure applications. limits of the seal. Similar to type G, the seal performs well in high- viscosity and anti-freeze liquids. 29 Mechanical shaft seal types and sealing systems Type O Type P Type O Type P T

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