Solving Pneumatic Conveying Problems With Triboelectric Monitoring

Posted by Justin Dechene on Jan 17, 2017 1:15:00 PM

Process insights become process control

The use of triboelectric particle velocity monitoring in pneumatic conveying applications is relatively new. In the past, no real viable solutions existed to measure particle velocity in dilute phase pneumatic conveying systems. Pitot tubes can be used to measure air velocity in such systems but encounter problems when introduced into dust-laden air thereby limiting them to only for occasional diagnostic uses. In contrast, triboelectric systems for particle velocity monitoring have no issue working in applications with heavy dust loads. Additionally, because they track the velocity of moving particles themselves rather than measuring airspeed they present a more accurate picture of conveying conditions within the ductwork. 

But what kinds of pneumatic conveying problems can triboelectric particle velocity monitors remedy? Let’s consider two very common problems that come up with pneumatic conveying systems. 

Blockages From Product Dropouttriboelectric instrumentation offers process control to solve common pneumatic conveying problems

The most common pneumatic conveying problem that needs to be avoided are blockages in the system. While blockages can be caused by several issues the most basic indicator of an impending blockage is a drop in air speed within the ductwork. When the airspeed drops, product drop out occurs causing blockages. 

In a dilute phase conveying system the particles are suspended in the airstream and pulled through the ductwork by means vacuum/suction force generated by the system fan. In order for the particles to stay aloft in the airstream they must travel at or above a certain speed, known as the minimum conveying velocity. If the airspeed ever drops below the minimum conveying velocity for that product the particles will begin to settle and drop out of the airstream and then buildup within the ductwork. As the ductwork becomes filled with product it in turn can cause more blockages that add further resistance to the vacuum and thus cause even more dropout to occur. 

There are multiple issues that can cause the airspeed to drop in the system. But the key is being alerted to the drop BEFORE it has time to cause large accumulations in the ductwork. By accurately monitoring airspeed with a triboelectric system operators can receive advanced warning when airspeeds begin to drop and then take immediate action to correct the underlying cause. 

Integrating the instrumentation with blower controls can even support dynamic fan speed adjustments to maintain consistent particle speed.

Excessive Ductwork WearRusted-Dust-Collection-Ductwork.jpg

While maintaining airspeed high enough to prevent dropout is usually a larger cause for concern, excessive conveying velocity can cause problems such as excessive wear on the ductwork system. Especially with heavy, abrasive materials such as sand, metals and ceramics ductwork wear can be a cause of great concern. 

Again, by making use of triboelectric particle velocity monitoring systems operators can keep a close watch on any changes in particle velocity within the system. For especially abrasive applications, Auburn Systems’ models make use of probes that use materials such as tungsten/carbide or ceramics to prevent damage to the probe while still remaining functional. 

Secondary Complications from Pneumatic Conveying Problems

Disrupted flow is obviously a primary and immediate problem - but it's often just the flash point that diffuses focus from a cascading series of consequences that are even more disruptive. These include:

  • downtime - production disruptions almost inevitably follow, resulting in substantial (although difficult to quantify) cost
  • risk - have to send someone up a lift or climbing a silo to find and resolve a stoppage?
  • quality - as examples, mixing and blending can be disrupted as flow fluctuates; diminished crushed coal fuel flow can impact production temperatures
  • operational efficiency - responding to disruptions distracts from the focus on consistent quality and improvement

New Call-to-actionConclusion

Carefully monitoring particle speed in your ductwork can prevent a number of pneumatic conveying problems. Here we have discussed just two of the most common. For these reasons and more, monitoring of particle velocity in your pneumatic system can reduce downtime and maintenance costs with only minimal investment. 

Would you like to learn more about the experiences of some of our clients that improved operations and cut costs using triboelectric particle velocity monitoring? Contact us today and we will be happy to provide more information as well as a quote for your facility!

Want to learn more about the technical evolution of triboelectric instrumentation and how the process control capabilities have developed? You'll find that here.


Topics: Process Control, Flow Control