Which of the following is a type of joint for steel piping?

The choice of an expansion joint as the correct answer is significant because these types of joints are specifically designed for absorbing thermal expansions, contractions, and vibrations in steel piping systems. When steel pipes are subjected to temperature variations, they can expand or contract, potentially leading to stress, bending, or even failure if not properly accommodated. Expansion joints allow for this movement, thereby protecting the integrity of the piping system.

These joints can either be made of metal or flexible materials, which can adapt to the changes in length that occur with temperature fluctuations. By including expansion joints in a piping system, engineers ensure greater longevity and reliability, significantly reducing maintenance needs and the chances of leaks or structural failures.

Other types of joints listed, such as flexible ball joints, restrained joints, and push-on joints, serve different purposes. Flexible ball joints allow for angular movement and are typically used in applications where pipes must connect at angled positions, while restrained joints provide resistance against axial movement, ensuring that the sections of the pipe remain locked in position. Push-on joints facilitate easy assembly without the need for welding or special tools but do not accommodate the same thermal expansion and contraction as expansion joints.