The most common combination valve is the umbrella-duckbill style, but other combinations include bidirectional-umbrella, duckbill-diaphragm, etc.
VA3117View Data Sheet
|Outer Diameter (mm): 11.68||Outer Diameter (Inches): 0.465||Comments: High Cracking Pressure, Lower Flow||View Products|
The VA3117 design is a general purpose combination valve. The high umbrella cracking pressure is designed to prevent flow-through below a design pressure.
VA3667View Data Sheet
|Outer Diameter (mm): 15.87||Outer Diameter (Inches): 0.625||Comments: Low Cracking Pressure, Higher Flow||View Product|
The VA3667 design is a larger general purpose combination valve. This design has higher flow and lower umbrella cracking pressure to prevent flow-through below a design pressure.