Introduction to FCCU Expansion Joints
FCCU (Fluid Catalytic Cracking Unit) Expansion Joints are subjected to extremely harsh environments including high temperatures, high pressures, significant axial and lateral movement, and aggressive catalyst flow. These joints are among the most critical and complex expansion joints manufactured in the industry.
They are designed as per:
ASME B31.3 Appendix X
EJMA Standards
Licensor Specifications (Lummus, UOP, KBR, ExxonMobil, Axens, etc.)
LSI Mech Engineers is proud to be the first in India to develop and supply refractory-lined FCCU expansion joints for refinery applications.
ISOMETRIC VIEW
Design & Validation Using 3D CAD Tools
At LSI Mech Engineers, we use advanced 3D mechanical CAD software as a powerful design validation tool. These tools allow us to simulate and verify real-world movement conditions of FCCU Expansion Joints before actual manufacturing. Through dynamic movement analysis, we ensure proper functionality under extreme operating conditions. Our in-house capabilities include:
• Finite Element Analysis (FEA)
• Computational Fluid Dynamics (CFD)
• Heat Transfer Analysis
These tools enable us to analyze complex geometries and predict thermal-mechanical performance under a variety of load conditions.
Specialized Replacement Inside FCCU MEJ applications
Type of FCCU Expansion Joints
We manufacture a wide variety of configurations, including:
• Hot Wall Expansion Joints
• Cold Wall Expansion Joints
• Unlined Expansion Joints
Each type is tailored based on temperature profiles, catalyst exposure, and mechanical loading.
Hot Wall Expansion Joints
Hot Wall units feature an abrasion-resistant lining using ca-stable refractories such as RESCO AA-22 and hex-mesh for protection. These linings are not thermal barriers but provide wear protection. Drying of this lining must follow a controlled procedure. Materials such as Inconel Alloy 625LCF bellows and floating rings are used to withstand high thermal and mechanical stresses.
Hot Shell, Abrasion Resistant Refractory
Cold Wall Expansion Joints
Cold Wall units are refractory lined internally to maintain shell temperatures within safe operating limits. They use bio-soluble ceramic fiber or silica blankets, stainless steel anchors and internal liner seals to prevent insulation erosion. An external insulation layer helps prevent condensation below acid dew point, avoiding dew point corrosion and extending bellows life
Advantage
- Prevents premature bellows failure due to acid dew point conditions
- Lower pipe temperatures reduce pipe expansion
- Reduces movement requirements for the joint
Cold Shell Expansion Joint
Unlined Expansion Joints
Unlined FCCU Expansion Joints are used in high-temperature areas where abrasive catalyst is not present typically in air inlet/outlet or flue gas transfer lines. These joints do not require abrasion-resistant linings and are designed to manage high temperatures without catalyst exposure.
2-Ply Testable Bellows & Monitoring Systems
FCCU expansion joints often utilize 2-ply testable bellows, where each ply is rated for full operating conditions. If the inner ply fails, the outer ply maintains integrity, ensuring continued operation and safety.
Monitoring Types
• Passive Monitor: Activated by pressure when the inner ply fails.
• Active Monitor: Uses a vacuum system to detect failures in both plies.
This system ensures early detection of failure, preventing unscheduled shutdown and increasing plant reliability.
Pantograph Linkages
Packed Bellows Configuration
FCCU bellows are internally and externally packed with ceramic blankets, and sealed using a metal braided hose. This system ensures:
• Bellows operating temperature stays between 200-500°C
• Above 200°C: Prevents dew point corrosion
• Below 500°C: Avoids high-temperature embrittlement of Inconel 625
Advantages
• Prevents dust and catalyst entry into bellows cavity
• Reduces risk of solidification that can damage bellows or restrict movement
Top view of internal refractory in MEJ assembly
Material Selection
Bellows Material
• Inconel 625LCF (UNS N06626/W. Nr. 24856)
• Offers up to 100x fatigue life compared to conventional alloys, along with excellent corrosion, cracking, and high-temperature resistance
Pipe Body Material
• Hot Wall: Stainless Steel 304 or 321H (Operating >600°C), Low alloy steels like 1.25Cr-0.5Mo (500-600°C)
• Cold Wall: ASTM A516 Gr. 70 (Max 343°C)
Universal Gimbal Expansion Joints (Hot Shell Design)
External Hardware Components
FCCU Expansion Joints are equipped with essential hardware to ensure proper performance and safety:
Control Rods:
• Restrict axial, lateral, and angular movements (not designed to withstand pressure thrust). Typically, four rods per bellows element.
Pantographic Linkages:
• Ensure equal movement distribution across dual bellows in universal joints
• Support weight of refractory-lined connecting pipes in vertical/inclined setups
Slotted Hinges:
• Maintain equal axial movement in universal joints
• Provide pipe support in horizontal setup
Central Gimbal:
• Facilitates out-of-plane lateral movement (>10 mm)
• Supports the connecting pipe’s weight in universal untied joints with panto graphs
Central gimbal type assembly for MEJ
Slotted Hinges & Pantographic linkages provided as external hardware
