Drop through and blow through rotary valves are both used for feeding powder or granular material, but they are applied differently. The selection depends on conveying method, pressure condition, installation layout and material behavior.  What is a drop through rotary valve?  A drop through rotary valve normally receives material from above and discharges it downward by gravity. It is commonly used under silos, hoppers, dust collectors and packaging or feeding points where gravity discharge is suitable.  What is a blow through rotary valve?  A blow through rotary valve is used when material is introduced directly into a pneumatic conveying line. Air passes through the valve outlet area and carries the material into the pipeline.  Main selection differences   Drop through type is often selected for gravity discharge and general airlock feeding.  Blow through type is commonly linked with pneumatic conveying line layout.  Pressure difference, leakage control and material flowability must be checked for both designs.  Installation space and pipe connection can determine which structure is practical.   When to choose drop through  Drop through configuration is usually considered when the process needs controlled discharge from a hopper, silo or dust collector. It can also be used before downstream conveying or packaging equipment.  When to choose blow through  Blow through configuration is usually considered when the rotary valve feeds directly into an air conveying line. In this case, line pressure, air volume, material loading and pipe layout should be checked together.  Related FUWEI pages  For sizing and capacity checks, see  Rotary Valve Sizing Calculator . For positive pressure conveying options, see  Positive Pressure Conveying Rotary Valve - Horizontal Blowing  and  Positive Pressure Conveying Rotary Valve - Vertical Dropping .  Selection note  Before choosing between drop through and blow through designs, confirm material data, required capacity, conveying pressure, pipe layout and installation space. These factors are more reliable than selecting only by name.