When designing a pneumatic conveying system, choosing the correct blower is the most important factor. The blower rating is expressed in terms of required pressure and volumetric flow. If a calculation error occurs, the conveying system could end up oversized, incapable of satisfying the required flow rate or experience blockages within the pipeline. This blockage occurs where the pressure in the system is at its lowest. The volumetric flow rate from the blower depends on the diameter of the pipe being used and the velocity required to convey the given material.
Capacity control of PD blowers is limited because the blower is cooled by the mass flow through the machine. Throttling the blower will result in overheating.
Effective methods of capacity control include:
Using a Variable Frequency Drive (VFD) on the blower motor to adjust blower speed
Staging blowers on or off in systems where multiple blowers are used to attain the required flow
Changing sheave sizes on belt driven blowers.
Using a Blow Off Valve (BOV) in the blower discharge piping