CHAPTER 7 - Rubber Expansion Joints

Abstract

Stresses lead to movements of the piping system, so movement absorbing devices are incorporated in the layout. The simplest method of reducing stresses is to provide additional pipe fittings in the system, in the form of loops and bends. They are usually called expansion joints, and they are either made of rubber, with one or two convolutions, or metal, with multiple convolutions. Their purpose is to provide the flexibility to absorb movements due to thermal changes, and to absorb dynamic movements of machinery, adjoining buildings etc. Rubber expansion joints offer engineering advantages over metallic joints. Rubber expansion joints, which consist of flanged ends and a flexible section, can absorb within its free length more lateral movements, than any other similarly sized joint. Expansion bellows are joints that have several sections. The flexible section of the rubber expansion joint/bellows is often a single fold which, because of the inherent flexibility of the rubber, can deal with large lateral movements with low force, a phenomenon which would require multiple folds in a similar metal component. The major difference between rubber joints and metal bellows is in the way they absorb pressure loads. The unique advantages of rubber expansion joints make them used in industrial settings where fluid and gas handling is a primary part of the process, e.g. waste management, or air pollution control. Wherever movements or vibrations from thermal expansion or mechanical equipment expansion occur, joints provide low cost and efficient solutions to leakage problems.