Page 47 - Design Criteria.qxd

48 ® Welcome to the Next Generation of Sealing Technology
Gasket Features Observation Possible Cause Possible Remedy
Asymmetrical compression Smooth and/or Dissimilar Apply recommended surface
and/or flattening of the lands of surface finish finish 125/250 Ra. Use inner
the chevron and outer rings. Place gasket
in a groove
Metal Windings Corrosion Improper metal selection Select metal compatible for
the media
Severe discoloration, cracking Improper metal selection Select proper metal
Exceeding temperature limit
Impingement or mechanical Gasket wrongly sized Redesign gasket or use
damage Improper installation alternative gasket
Improve installatin and/or
Procedure
Extreme discoloration Filler material incompatible
Corrosion with media or process Select filler material
Filler compatible with media/
Oxidation Exceed temperature limit process and temperature
Incompatible with media
Uneven compression Flange waviness Machine flanges to
Flange out of parallel recommended flatness and
Flange rotation parallelism.
Improper installation and/or Reduce bolt stress and/or
procedures compensate for rotational
effects. Improve installation
procedures
Thickness
Over-compression Improper gasket selection Use inner and/or outer rings
Improper joint geometry Redesign joint geometry
Insufficient compression Improper installatin Improve installation
Improper gasket stiffness Use proper constructed
insufficient bolt load gasket
Improper joint geometry Improve joint geometry
Leak path scoring Foreign matter Proper clean up of flanges
and/or gaskets
Transfer or imprint of flange Improper surface finish Assess finish and re-machine
surface finish flanges to proper finish
Micro imperfections, dings, Foreign matter, tool marks on Re-machine and/or repair
scratches, interrupted surfaces flanges, hardware, i.e. set flanges. Remove any
Gasket face screws ro other implements obstruction or interrupted
surfaces surfaces
Topical residue, smearing Use of adhesives, grease Do Not use any compounds,
compounds or tape as a paste, grease or tape or any
means of gasket positioning or foreign substances.
perceived performance Note: Use of a light spray of
enhancement adhesive is permissible for
holding the gasket in place if
needed
Buckling of the sealing Omitting the use of an inner Use inner rings. Assess
element ring. Smooth flange surface surface finish. Reduce bolt
finish. Bolt up inconsistencies. loads to acceptable stresses.
Mechanical Extreme temperatures. Over- Use alternative gasket, i.e.
Damage compression Flexpro
Excessive dishing, cupping Excessive bolt load. Outer Reduce bolt load to
indentations and yielding of guide ring engaging bolts acceptable stresses.
outer ring Concentric gasket installation
Troubleshooting
Joint Leakage
Often as not, when joint leakage occurs, a simple examination of the used gasket can determine the cause of failure. Firstly, always
ensure that the spent gasket is correct to specification.
The Used Gasket . . . Telltale Signals of Trouble