CORROSION

Corrosion is the main cause of Bellows failure in several applications having adverse environment and / or adverse flow medium.

External Corrosion

In the form of pitting and general metal loss.

The saline nature of plant atmosphere and / or gases / pollutants in the atmosphere in combination with moisture lead to accumulation on Bellows material resulting corrosion.

Presence of chloride will result in stress corrosion cracking on austenitic stainless steel.

Internal Corrosion

The flow medium of higher pH will lead to inter granular corrosion and cracking and lower pH will result in Trans-granular corrosion and cracking.

Hydrogen stress cracking is another cause in aged material. In hydrogen services, the hydrogen is getting diffused at areas where the hardness is greater than 360 BHN and results in cracking.

Corrosion of thin walled Bellows due to condensation of SO2 Gas to H2SO4 and accumulating in the annular space between the Bellows and Liner,

Condensation will occur because of temperature drop due to

  • Sudden plant breakdown.
  • Power failure.
  • Exposure of Bellows outside to cold conditions.