Jake Davis, Product Engineer at DeDietrich Process Systems, sits down to discuss issues around dust, the principles for properly handling dust, and the various types of equipment that can be used. Watch the video or read the transcription below.
Why is dust a problem?
Dust is a problem in many ways. First off, it’s just plain messy. Even at your house, you're constantly having to dust all surfaces, and no matter what you do. It’s the same in manufacturing. Regardless of how it occurs, dust is going to be present. So one of the first things that are important is just to maintain a clean environment. Whether it provides some sort of hazard to an operator from a health standpoint or accumulates on the ground getting wet and causing someone to slip and fall, maintaining good housekeeping practices is important.
Another way, dust can create a problem is that some powder materials can have a corrosive nature to them. We actually design many systems here to handle and address that corrosive nature but there are many systems out there. I've been to several customers where you see dust all over and it's just sitting there, corroding and eating at their equipment. Slowly, but surely, they're gonna end up having to replace various pieces of equipment, various instruments devices here and there. Dust can have a corrosive nature and it's very important to know that about it so that you can clean and handle it appropriately.
The next thing about this is they can be toxic or just unhealthy. This plays a big role in the pharmaceutical space where operators could be exposed to various sorts of APIs or active pharmaceutical ingredients. It's very important to consider when you're designing these types of systems. Equipment should be designed to prevent an operator from being overly exposed to these types of dust, these types of powders.
Probably one of the things that have gotten a lot of traction in more recent history is combustible dust. Just about any sort of organic dust is combustible in the right conditions. You may be familiar with the fire triangle. You've got three sides to it. There's your ignition source, there's your fuel, and then there's oxygen. Well, when it comes to combustible dust, there is what's called the combustible dust pentagon, and what that does is adds two sides to the triangle. One is dispersion, essentially meaning that powder is dispersed into a dust cloud. The other is containment. So when you light up a dispersion of dust, that's when a deflagration could occur. When that deflagration gets contained inside a small space, allowing pressure to build and build and build, that's when an explosion can occur. There are devices to help address this in numerous different ways, but combustible dust can lead to all sorts of incidents. If you check out the Chemical Safety Board website, you can see how this has become an issue that just needs to be addressed more and more within companies.
How can dust be addressed?
The main principle, when it comes to handling dust, no matter what kind of dust is going to be containment, keeping dust in an area and a space that we have control over. That's going to be pretty much the basis for any sort of system that gets designed to handle various bulk solid materials or combustible dust.
What equipment is available to address dust?
When it comes to the type of equipment to handle dust or even powders, because powders are essentially where the dust comes from, the goal of each of these pieces of equipment or these designs is going to be containment. There is vacuum conveying equipment, specialty vacuum cleaning equipment, and then enclosed conveying equipment, whether it be pneumatic or mechanical.
Each of these has things that they implement to address handling these different forms of dust. Let's take vacuum conveying, for instance. There are two types of pneumatic conveying systems or conveying equipment out there. There is positive pressure, and then there's negative pressure. Those can then be differentiated into dense and dilute phases. As you could imagine, with positive pressure, you're pushing the material or the air or the product through the pipeline and if there's a leak in the pipeline, then that air goes outward, out of the pipeline. If you're conveying material through this pipeline, then it's gonna spray material everywhere.
As you can imagine with the vacuum system, you have negative internal pressure. Our goal is no leaks but we know how things can go in manufacturing facilities. There will almost always be a leak of some kind at some point in the future. With the vacuum system those leaks act internally to the system, eliminating any nuisance dust getting out of the system, it keeps everything contained.
Next, we have vacuum cleaning systems where you want to consider making things portable, what sort of dust has been spilled, how large the collection chamber is for the vacuum cleaner, and the types of filters you use There are several things that play a big role and a big factor in these vacuum cleaning systems.
The next option is an enclosed conveying system. I would refer back to positive pressure in the vacuum conveying systems that kind of fall into this category. Positive pressure aside, leaks aside, if things are tight and contained, there are ways to address the other problems that dust creates inside these types of systems. Some of these are often of a combustible nature so that's the main focus when it comes to pneumatic conveying systems. If an explosion were to occur, or a deflagration was to occur, you want to have equipment in place in these types of systems that are designed to either prevent or address an explosion when it does occur: deflagration vents, isolation valves, shutoff devices, or suppression systems. Those are all things that may specifically address certain combustible dust in these types of systems.
You also have enclosed mechanical conveying systems. All systems in the right application work very well. Mechanical conveying systems can also be a very clean, enclosed, contained system to handle powders. It's all about determining what best fits your specific application and your dust.