The Design of Rectangular Metal Bellows

Rectangular metal expansion joints are commonly used in flue gas ductwork, turbine exhaust systems, and heat exchanger applications. The Standards of the Expansion Joint Manufacturers Association (EJMA) are widely referenced for the design of rectangular metal expansion joints. The 8^th edition, 2005 addenda, contains equations for rectangular metal bellows pressure stresses, movement stresses, beam lateral deflection, fatigue life, and spring rate. This paper evaluates the accuracy of the EJMA equations based on failure reports and FEA studies. Both linear elastic and non-linear limit analyses are used for the evaluations. Improved methods are proposed for the determination of pressure capacity, beam deflection, moment of inertia, and corner rigidity. New lateral deflection limits and acceptance criteria are provided herein. This paper also includes design considerations for the pressure stops used to support bellows rails.