FCCU Expansion Joints

Expansion joints used in FCCU service are some of the most critical and complex types of expansion joints manufactured. For this reason, the choice of manufacturer should be carefully considered. EJS has many years of experience designing and manufacturing FCCU expansion joints. These expansion joints are exposed to high temperatures (1400F), high pressures, large movement conditions and aggressive media. Great attention and expertise is required in designing the bellows and hardware to ensure that the units perform well in service. Failure of FCCU expansion joints during operation can be extremely hazardous to personnel and very expensive to the user.

There are various types of expansion joints used in FCCU applications: Tied Universals, Hinge, Gimbal, and Pressure Balanced. All of these fall into 3 major categories: Cold Wall, Hot Wall, and Unlined FCCU joints. The bellows membrane design for all three categories is basically the same, although the bellows membrane can be single ply, multi-ply, redundant ply and reinforced.

Today the material of choice for most FCCU applications is Inconel 625LCF (low cycle fatigue). Almost identical to the original Inconel 625, this special bellows grade of Inconel 625 that was introduced in 1990, provides tighter controls over the carbon, silicon and nitrogen contents. This produces a microstructure that enhances low-cycle fatigue.

Various performance analysis calculations are used to determine the theoretical life expectancy for a given design. EJMA (Expansion Joint Manufactures Association) is the predominant standard used. The expansion joint manufacturers who make up EJMA are today's leading authorities on expansion joint design.

Expansion Joint Systems, Inc., 10025 Prospect Avenue, Suite 202, Santee, CA 92071. Tel: 619-562-7458; Fax: 619-562-0636.