Generally a gasket is replaced when it suffers imminent damage as it acts as a fuse in a piping system. Damage may be caused by different factors such as:
- Water hammer: Pressure increase due to velocity change in a fluid.
- Overpressure: Pressure above the normal working pressure of the system.
- Column buckling: Rotation of a plane of one or more waves of a bellows.
- High temperature: For expansion joints, a temperature at which the material begins to lose physical properties.
- Torsion in the systems: Any rotational movement that a joint receives is a cause of damage since bellows are not designed to receive torsion.
- Incompatibility of materials with the fluid: Unsuitable material for the fluid being worked with.
- Poorly supported pipe: A pipe must be supported according to a standard and with technical specifications according to its behavior.
- The line without fixed points: The fixed points are a restriction in all the senses, to direct the movement of a pipe.
- Joints without tensioners: Tensioners (tie rods) limit the pressure reaction force in the absence of fixed points.
- Out-of-permissible design memorandums: Values according to strength calculations and permissible stresses to determine loads.
- Poor joint selection for inadequate movement: Each expansion joint has a specific movement, which must be taken into account at the time of selection.
- Very high frequencies: The very large amplitude of a frequency fatigues the bellows material, therefore the maximum lateral movement should be checked.
In general, a properly selected seal will not generate problems and its life time is extended for more than 10 years. A gasket has certain life cycles according to an EJMA calculation that is made at the time of its manufacture and is delivered to the customer to make the projection of change or maintenance.
If a process demands a change due to damage to the gasket, it is necessary to review and diagnose what caused the gasket to be damaged. This is done by making a tour of the pipeline in which it is installed, and a thorough review of the operating conditions of the system. From this point on, a flexibility study can be carried out to determine the forces, moment stresses and thus give the pertinent recommendations.