LABYRINTH SEAL

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  • Its name from fact from its construction.
  • Labyrinth seals consist of series of thin strips fixed to the casing or other stationary member and arranged so as to maintain the smallest possible clearance with the shaft.
  • The labyrinth seals have small restrictions that increase the velocity of leaking fluid only to have it dissipated in the pockets, thereby throttling the fluid. 
  • The tips of the strips are extremely thin so that if rubbing occurs the tip gets worn away without damaging the shaft. 
  • These labyrinth seals do not prevent complete leakage of fluid. These are effective in only reducing leakage.
  • In it steam in leaking must follow a winding path and change its direction many times.
  • It is constructed from thin strip at the outer circumference of shaft of turbine at both end.
  • It is installed at the inner circumferential surface of casing at both end.
  • There are several types of Labyrinth packing is subjected to a throttling action. 
  • This action produced a reduction in pressure with each groove that the steam passes.
  • The amount of leakage pass the packing depends upon the clearance between the stationary and the rotating element.
  • The amount of clearance is depend on type of turbine steam temperature and service condition.
  • The leak steam from labyrinth packing is piped to some low pressure system or to a low stage on the turbine.
  • In labyrinth packaging there are two parts 
    • Fixed parts
    • Rotating parts
  • For sealing the shaft steam is used between the fixed and moving glands.
  • Each labyrinth consist of multiplicity of seal to minimize steam leakage.
  • It consist of seal ring which are under spring force due to in casing it maintain proper position and close clearance are maintain.
  • During operation it is cooled by steam supplied or by leak of steam.
  • This steam is maintain the seal temperature constant. 
  • Each ring are decide into groups and after each group a chamber is provided.
  • Number of of chamber is depend on the steam pressure in the turbine end.
  • This chamber is work as supply or extract steam for sealing.
TYPES OF LABYRINTH SEAL


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