Cast steel trunnion mounted ball valves are commonly used in industrial applications where high-pressure and high-temperature fluid flows need to be controlled. They are designed to provide reliable, long-lasting service in a variety of industries, including oil and gas, chemical, and power generation. 

These valves are typically used to control the flow of liquids or gases in pipelines, tanks, and other industrial equipment. They are known for their durability, high performance, and low maintenance requirements, making them a popular choice for many industrial applications.