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

The mechanical seal is a device used for preventing leak through rotating or moving shaft and casing. Technological growth in the 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 a centrifugal pump, and with the 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 is developed by using ultra-nano-crystalline diamond protective coatings. This type of seal possesses good resistance to chemical corrosion.

Working principle of the mechanical seal

Hydrodynamic lubrication technology is the backbone of 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 challenges 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 withstand the reverse rotation condition of the shaft or impeller of the machine during trips and emergency shutdowns.
Mechanical seal mounted on sleeve to fix on pump shaft
Mech seal and sleeve system