Material Preparation
False air is air entering a vacuum conveying line at points other than the material inlet — loose couplings, a cracked hose, a poorly seated connector. It makes the vacuum pump spend its capacity sucking in this leak instead of conveying material; fill times lengthen and the machine at the end of the line runs short. At the suction lance, however, a controlled amount of air is deliberately taken in; there it is not a defect but a necessity.
When the system is newly installed there is no false air; over time, clamps loosened by vibration, worn seals and improperly tightened hose couplings enlarge the leak. The symptom is insidious: the pump is the same, the line is the same, but fill times have lengthened over the months.
The air inlet at the suction lance, on the other hand, is there to set the material-to-air ratio. If the lance is buried completely in granulate it cannot take in air and the line blocks; that is why the ventilation balance is made adjustable.
By closing the line section by section and watching the vacuum value. In the section with the leak, the vacuum does not recover. Coupling seals, hose ends and connector steps are the first places to look.