Temperature can change how almost every part of a valve behaves. For example, seals and soft seats have operating limits. Metals expand. Lubricants behave differently. Meanwhile, the fluid itself may change viscosity or phase. At higher temperatures, the allowable working pressure of some valve materials can also decrease. https://www.ai-pro.in/pressure-temperature-fluid-flow-the-4-things-that-should-decide-your-valve/