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PCC-1 Appendix 0 - Coggle Diagram

- - - - The initial relaxation occurs immediately after installation and it is caused mainly by the flow of the gasket when filling in the irregularities between the flanges.
      - It can be obseved that there is loss of up to 25% of the initial installation stress.
    - - The relaxation during hte time of service of the gasket occurs primarily in systems operating at elevated temperatures or with thermal cycles.
      - Depending on the type of gasket, the operating temperature and the frequency of the thermal cycles, the effects can take months or even years before there is leakage of flanged union.
    - - This suggests us fraction of gasket load remaining after relaxation.
      - This value suggest the amount of stress retained in the gasket after the relaxation.
      - For different materials of gasket this value varies from 0.5 to 0.9.
      - In the absence for data a typical average value of 0.7 to be used.
- - - - The assembly bolt stress should not be high enough to cause over-compression (physical damage) of the gasket or Excessive flange rotation of the flange, which can also lead to localized gasket overcompression.
    - - The specified bolt stress should be below the bolts yield point, such that bolt failure does not occur.
    - - The assembly bolt stress should provide sufficient gasket stress to seat the gasket and sufficient gasket stress during operation to mainttain a seal.
    - - The assembly bolt stress should be selected such that permanent deformation of the flange does not occur.
      - If the flange is deformed during assembly, then it is likely that will leak during operation.