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Tech Talk
Hot wall universal expansion joint . Image courtesy of Teadit .
Key steps for testing expansion joints in FCC units
Expansion joints play a critical role in managing pipe stress in various industrial applications across several industries . In Fluid Catalytic Cracking ( FCC ) units , high temperatures and pressures generate significant force on piping and connected equipment . Performing movement tests , after manufacturing and during testing phases validates the expansion joints design and confirms the limit forces , without damaging critical equipment . Plant operators and maintenance engineers should , therefore , be aware of the key steps , tools , and considerations for testing the expansion joints used in these applications .
By Angelica Pajkovic and Nelson Kavanagh , Teadit
Step 1 : Understand the purpose of movement tests Expansion joints allow flexibility within piping systems by accommodating extreme thermal loads and minimizing stress on equipment , thus preventing excessive force on surrounding structures and connections . FCC units are an integral part of refining processes that makes low octane gasoline which is blended with a higheroctane gasoline or get upgraded to a higher octane . As they operate at high temperatures ( approximately 700 ° C ( 1300 ° F )) to break down heavy hydrocarbons , expansion joints are needed to prevent load transfer to sensitive equipment , such as turbo expanders . Through pipe stress analysis , simulations loads and deflections can be determined to a reasonable level of certainty . Those loads and deflection can be applied to the expansion joints in a laboratory setting through in what is called a ‘ movement test .’ During this test , joints are subjected to controlled angular and lateral movements while the applied load is measured at each degree of motion . These tests reveal the spring rate ( the force required to move the joint ) and help verify that the joint can accommodate expected movement due to thermal expansion in FCC pipelines . This test essentially bridges the gap between theoretical calculations and real-world performance , enhancing the overall dependability of the installation . More specifically , movement testing is particularly essential for :
• Thermal expansion : High temperatures in systems like FCC units cause significant thermal expansion . Movement testing ensures that the joints compensate for this expansion without imposing undue stress on nearby components .
• Pressure resistance : Movement tests under pressure reveal how pressure influences the expansion joint ’ s internal pins , rings , and friction , which can increase due to operational loads .
• High-temperature insulation and seals : Movement testing identifies if high-temperature insulation and seal materials within the expansion joint , like braided seals or metallic sleeves , impact the reaction loads under movement .
36 Heat Exchanger World February 2025 www . heat-exchanger-world . com