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Mechanical seal how it works, types and use of mech seals

Mechanical seal is a device used for preventing leak through rotating or moving shaft and casing. Technological growth in fine finishing of material surface led to the design of mechanical seal. Availability of wide variety of special designs and sealing surfaces (for example, laser surface texturing) its application has increased drastically. It is mostly used in centrifugal pump, and with addition of O-rings and oil seal, it can be used for high pressure as well as vacuum conditions also.
Multi purpose mechanical seal with less friction are developed by using ultra-nano-crystalline diamond protective coatings. This type of seal possess good resistance to chemical corrosion.

Working principle of mechanical seal

Hydrodynamic lubrication technology is the back bone to the mechanical seal working principle.

All mechanical seals contain four basic elements/components
1. Rotating seal ring
2. Stationary seal ring
3. Spring loading section for maintaining seal face contact
4. Static seals
Mechanical seal diagram used pump shafts
Shaft mech seal

Types of mechanical seals

1. Internal mech seal
2. External mech seal

Models of mech seals available

  • Multi Spring
  • Single Spring
  • Conical Spring
  • Cartridge
  • Teflon Bellow
  • Metal Bellow
  • Wave Spring
  • Reverse Balance
  • Cap model
  • Agitator model
  • Carbon-graphite mechanical face seal
Engineering design and challenges of mechanical seal system: One of the design challenge is, control of friction heat generation at the interface between the seal faces. The temperature of the seal increases as sliding speed increase and also depends on stationary and rotating rings material of construction. Another challenge in the design was to develop the dry seal to with stand the reverse rotation condition of the shaft or impeller of the machine during trips and emergency shut downs.
Mechanical seal mounted on sleeve to fix on pump shaft
Mech seal and sleeve system