What is airlock “blow by air”?
An airlock is, or should be, a precision machined device where the clearances between the rotor and the housing are 0.004 to 0.005 inch. The rotor is divided into a number of pockets by the rotor vanes (eight vanes would be typical). Product from the hopper above flows by gravity into each rotor pocket as it passes the hopper to which it is attached. The pockets rotate to the bottom and the product drops out of each pocket in succession into the conveyed air stream and through the convey line. The pockets completes the rotation to the top filled with the compressed convey air which expands into the airlock inlet hopper. Therefore, some convey air is lost into the airlock inlet hopper. I call convey air lost in this manner “airlock displacement blow by air.” Convey air can also be lost a second way, because of the required clearances between rotor and housing as mentioned above. I call the convey air lost in this way, “the orifice factor loss of the airlock.” Every airlock has its own o
