What does the term 'thermal expansion' refer to in pressure piping?

The term 'thermal expansion' in pressure piping specifically refers to the increase in pipe length and volume when the temperature of the pipe rises. As the temperature increases, materials, including metals and plastics used in piping, tend to expand. This expansion occurs because the kinetic energy of the molecules increases, causing them to move apart from each other.

Understanding this concept is critical for designing and installing systems that can accommodate the changes in dimension due to temperature fluctuations, thus ensuring that the piping systems do not develop stresses that could lead to failure or leaks. Proper allowances for thermal expansion must be accounted for in pipe layouts and support configurations, using expansion loops, joints, or other techniques to absorb movement.

The other choices address aspects related to temperature changes in pipes but do not accurately define thermal expansion. For instance, while the reduction of pipe length due to cooling is a phenomenon that occurs with contraction, it does not capture the essence of thermal expansion, which is focused on the increase in size with heat. Similarly, the expansion of liquid within the pipe may also occur due to heating, but it’s a different concept than the physical expansion of the pipe itself. Lastly, while weakening of pipes under heat stress is a concern, it pertains to the material properties at high temperatures