Process equipment selection depends on more than equipment capacity or price. According to Alexandre Venancio, chief operating officer of Gericke USA, understanding three engineering measurements can help manufacturers make better purchasing decisions for mixers, pneumatic conveying systems, and size reduction equipment.

Venancio said many engineers routinely use values such as the Froude number, pressure drop, and particle size distribution to design process equipment, but these measurements are often less familiar to equipment buyers responsible for purchasing machinery.

The Froude number is used to evaluate mixing efficiency by comparing centrifugal forces with gravitational forces inside tumbling or rotating mixers. Engineers use the value to determine impeller diameter, mixer speed, and particle collision velocity. According to Venancio, a target Froude number between 1.0 and 2.0, depending on the application, helps suspend particles uniformly while minimizing energy consumption, friction, and material separation.

Pressure drop is a key design factor for pneumatic and vacuum conveying systems. It reflects the friction between the conveyed material and piping, along with the effects of gravity, that create pressure losses during material transfer. Because pressure drop varies by material, it directly affects the size, capacity, and cost of the blower or vacuum pump required to achieve the desired conveying rate.

Particle size distribution (PSD) is a primary measurement used when specifying milling, crushing, sieving, and other size reduction equipment. Rather than measuring individual particles, engineers evaluate the distribution of particle sizes within a sample using values such as D10, D50, and D90. As an example, Venancio explained that in a sample with a D90 of 75 µm, 90% of the particles measure 75 µm or less in diameter, while in a sample with a D10 of 28 µm, 10% of the particles measure 28 µm or less. According to Venancio, the target PSD determines the processing window and influences the complexity and cost of the equipment required to achieve the desired product specification. He noted that the wider the target PSD, the less complex and costly the process equipment.