Selecting a steam control valve requires a deep understanding of thermodynamic properties. You must prioritize material integrity, specifically looking for WCB (Cast Carbon Steel) or CF8M (Stainless Steel) to handle high-temperature stress. Ensure the valve is rated for the specific pressure class (e.g., PN16, PN40, or ANSI 150/300) of your boiler system. Additionally, evaluate the flow characteristic (Equal Percentage vs. Linear) to ensure precise modulation and prevent 'hunting' in your control loop.