Gate valves are categorized by their pressure ratings, often classified according to industry standards such as ANSI, API, or ASME. Common ratings include Class 150, Class 300, Class 600, and Class 900, among others. These classes indicate the maximum pressure the valve can endure at a specific temperature. For instance, a Class 150 gate valve may handle pressures up to 285 PSI at room temperature, while a Class 600 valve can handle pressures up to 1,480 PSI.