Knowing the velocity with which your materials travel through your pneumatic conveying system is vital for building an efficient machine. It ensures you can maintain adequate speed in your gas or air stream without excessive energy costs or product degradation.
But velocity doesn’t remain consistent throughout your entire system. In fact, there are many different types of velocity at different stages. Understanding what sets each one apart is key to achieving peak performance.
To ensure you’re fully prepared to design, maintain, and optimize your pneumatic conveying system, let’s explore nine common types of velocity you’re sure to encounter.
Common types of pneumatic conveying velocities
Actual gas velocity
This term refers to the volume flow rate of a cross-section of empty pipe at the current pressure and temperature conditions. It’s normally expressed in distance/time (for example, 4,000 ft/min). The actual gas velocity varies throughout the entire system and will be different at any cross-sectional area you choose to inspect.
Material velocity
The velocity at which your materials flow through your pneumatic conveying system is known as the material velocity. This is somewhat lower than the actual gas velocity at any cross-section.
Unfortunately, there are no reliable ways to actually measure material velocity. So only estimates can be given. That’s why material velocity is usually specified as either average velocity or terminal velocity.
Enclosure velocity
Enclosure velocity is the upward velocity of gas in a filter receiver or bin vent.
Flotation Velocity
This is the gas velocity at which your materials are suspended in the air. Knowing the flotation velocity of your materials is vital for figuring out enclosure velocity.
Choking velocity
Choking velocity (UCH) is the minimum actual gas velocity required to keep your materials suspended within the gas stream in a vertical pipe. If the actual gas velocity in a horizontal pipe falls below UCH, your particles will fall out of the stream and settle along the bottoms of your pipes. This can lead to blockages.
Saltation velocity
Just as UCH is the minimum actual gas velocity required to convey materials through vertical pipes, saltation velocity (USALT) is the minimum velocity required in horizontal pipes. Failing to reach USALT in your horizontal pipes will also cause materials to accumulate along the bottoms and create blockages.
USALT is always higher than UCH, often by as much as three to six times. You can decrease the USALT requirements of your pneumatic conveying system by angling a horizontal pipe downwards, even by as little as 15 degrees.
Minimum conveying velocity
Also known as pick-up velocity, minimum conveying velocity is measured at your pneumatic conveying system’s material feed point. It’s the lowest possible gas velocity at which your materials can be picked up and successfully carried through your system. This term generally applies to dilute-phase systems.
Minimum conveying velocity is typically set at least 20% higher than USALT, which itself is always higher than UCH.
Terminal gas velocity
Just as minimum conveying velocity is the gas speed as it first enters your system, terminal velocity is the speed at which it leaves at the end. You might also hear terminal velocity referred to as ending velocity or conveying line exit velocity.
Average gas velocity
Your system’s average gas velocity is the midpoint between its minimum conveying velocity (pick-up velocity) and its terminal gas velocity.
Enhance your pneumatic conveying system with industry-leading components
Once you’re familiar with the various velocities that occur within your pneumatic conveying system, you’re ready to fine-tune your operating parameters. But while this kind of optimization is an important part of minimizing costs and maximizing profits, you also need to have a resilient system. That means installing durable, abrasion-resistant parts that meet the needs of your materials and operation.
For more than 40 years, Progressive Products Inc. has been developing and manufacturing industry-leading parts for pneumatic conveying systems in a range of industries. Each component we produce is designed to be ultra-tough, letting it stay in your system for longer without needing to be replaced. With our high-quality elbows, line fittings, couplings, and other components, you can build a system that always performs at its best.
Browse our products online to see a wide range of outstanding components or get in touch with our expert team to discuss custom manufacturing.
