What are Expansion Joints? Expansion joints are used in piping systems to absorb thermal expansion or terminal movement where the use of expansion loops is undesirable or impractical. Expansion joints are available in many different shapes and materials. Any pipe connecting two points is subjected to numerous types of action which result in stresses on the pipe. Some of the causes of these stresses are Internal or external pressure at working temperature. Weight of the pipe itself and the parts supported on it. Movement imposed on pipe sections by external restraints. Thermal expansion Metallic Expansion Joints are installed in pipe work and duct systems to prevent damage caused by thermal growth, vibration, pressure thrust and other mechanical forces. Typical applications are water pipes, heating installations and piping in power stations and in the chemical industry. This gives rise to the need for various qualities that comply with the requirements of the particular media. There is a wide range of metallic bellows designs in a variety of materials. Options range from the simplest convoluted bellows used in petroleum refineries. Materials include all types of stainless steels and high-grade nickel alloy steels.