Expansion joints are specially designed for insertion into the rigid piping system for numerical purpose. The life expectance of the expansion joint is defined by Full Load Cycles that can be achieved during its lifetime. The Full Load Cycle is the movement throughout the complete range of compression to deflection and return to the original position of expansion joint.
The maximum movement of the joint occurs at the time of full load of the system. Sometimes systems shut down periodically but does not cool completely, which leads to 50 % of design movement of the machine. The system may have daily temperature cycles, which produces the movement equal to 10% of maximum working of the machine
Working Procedure
The expansion joints relieve system strain, due to the thermal change, absorb movement, reduce mechanical noise and eliminate electrolysis between the dissimilar metal. These joints when designed, installed and applied correctly usually achieve a greater life cycle in the industry. The robust maintenance programs can provide mechanical integrity to the equipment and plant safety at the same time. Depending on the condition, the joint should be replaced right away or marked for re inspection in six months.
Cycle Life
Expansion joint that is connecting two-duct end will shift position, as gas flow temperature will cause thermal expansion in the ductwork metal. The movement may involve compression or any combination of axial shifts. The joint starts at an initial position before moving the new operating position causing certain degree of stress to the joint. The initial position resumption occurs when plant system is taken offline for maintenance.
The position movement goes to operating from initial and again goes back to the normal position in cycle. The joint becomes weakened each time the joint experiences a cycle. The material losses its original strength and changes its shape. After many cycles, the fabric begins to unravel and wear out. The total number of predicted cycle is called cycle life of the joint. Depending on design and type of this joint, the cycle life can be measured which can reach to much higher level.
It is possible to determine the increased life cycle by using graph of Cycle life that can reduce non-concurrent movement.
