Which type of joint is commonly used in pipeline connections to allow for movement?

The correct answer is the expansion joint, which is specifically designed to accommodate movement in a piping system. These joints are crucial in handling thermal expansion and contraction, as well as providing flexibility to absorb vibrations from pumps or other machinery. By allowing for movement, expansion joints help prevent stress on the pipeline, which can lead to structural failure, leaks, or other damage.

In many water distribution systems, pipelines experience changes in temperature and pressure that can cause them to expand or contract. The expansion joint can flex to absorb these changes, maintaining the integrity of the pipeline and ensuring continued efficient operation.

The other types of joints mentioned typically do not provide the same level of flexibility. Coupled joints, for example, are used mainly for secure connections and do not have the capability to accommodate movement without the risk of damage. Fused joints, also known as fusion joints, involve welding the pipes together, creating a permanent and rigid connection. Similarly, welded joints are meant to create strong and permanent connections that do not permit movement.