A Comparison of API 6D and API 6A Valves | #double Block and Bleed Ball Valve # Fully Welded Ball Valve # Swing Check Valve # Dual Plate Check Valve # Axial Flow Check Valve # Piston Check Valve # Forged Steel Valves # Forged Gate Valve # Forged Globe Valve # Forged Check Valve # Concentric Butterfly Valve # Double Offset Butterfly Valve