Use of Basic Parameter in Mechanical Seal Design and How!
To minimize emission of the process fluid into the atmosphere, modern process equipments like pumps and compressors with rotating shafts are equipped with compressed packing or mechanical seal. Compression packing functions on the basic principle of controlled leakage whereas mechanical seal tend to seal without visible leakage.
Though the initial cost of a mechanical seal is high in comparison to compression packing, the power is consumed in maintenance and downtime spent for tightening or renewing the compression packing. This over weighs the initial cost of a mechanical seal even affecting the mechanical seal suppliers in India. This has worked unattended for a longer period of time.
When mechanical seals are properly used the environment is clean and hazard free as the visible leakage is absent. Here the information is given on types of mechanical seals manufacturers in India and how a mechanical seal works.
Primarily, a Mechanical Seal has 3 design characteristics
- Seal Faces – Making the seal face flat within millionths of an inch. Here both faces are lapped flat and then pressed together to effectively seal any fluid (other than a very thin film) from leakage between them.
- An Energizer – It is done using single spring, multiple springs, wave springs, metal bellows or even o-rings or internal pressure. One of the above must be used to create a force pressing seal that faces together and prevent the leakage between the seal faces.
- Secondary Seals – Secondary seals are necessary to seal parallel to the shaft. It includes rubber boots, common to industry standard type 1, 2, 21, 6 and 6A seals. O-Rings is made of a variety of elastomers including Buna-N, Viton, Aflas, Kalrez, Chemrez, Amerirez, PTFE, SBR, Neoprene, and FEP encapsulated o-rings. In the case of high temperature metal bellows seals with flexible graphite wedges are used to seal the pump sleeve or shaft.
Finally, mechanical seal works with two very flat, lapped faces that create a difficult leakage path perpendicular to the shaft when the primary seal is achieved. The leakage minimizes by the rubbing contact between these two flat mating surfaces. As in all seals, one of the faces is a non-galling material such as carbon-graphite and the other is a relatively hard material like silicon-carbide. The materials that are not similar are usually used for the stationary insertion and the rotating seal ring to prevent adhesion of two faces. The softer face has the smaller mating surface and is called wear nose.
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