Expansion joints are designed to absorb pipe movements and stress while isolating mechanical vibration. They will reduce system noise, eliminate electrolysis, and compensate for pipe offset or alignment. They are typically specified during the engineering of a system and are commonly seen in air conditioning or heating systems, petro-chemical plants, power generating stations, ships, steel mills, pulp & paper plants, water & sewage systems, and other industrial piping systems. Expansion joints should be installed between two fixed anchor points in a system. In order to prevent damage caused by excessive motion, control rod/limit units are recommended for all applications. Expansion joints must be inspected, maintained, and replaced over time.