Jessica Stank reveals the four most common powder flow problems and how these can be tackled
Powder flow problems cause frustration and hours of expensive downtime. They can also damage machines, create backups and produce sub-par products. Some types of materials, machines and working conditions make powder flow problems more likely. There are several common powder flow control problems but just as many flow control solutions to help solve these troublesome inefficiencies. Here, we offer suggestions on how to identify issues and address material characteristics in addition to powder flow control problems and solutions.
Problem: No Flow
Under normal operating conditions, the material should flow through the system without interruption. If no-flow alerts are a regular occurrence, the system is not optimally designed for either the material or the environment. This may occur in environments with high humidity, materials with high moisture content, solid materials that are irregularly shaped, or materials with certain coatings.
The way to tackle no flow is via agitation. Depending on the cause of the no-flow problem, a few solutions are available, including: a mechanical agitator before feeder entry; vibrator added to hopper; air pads to aerate product.
Each of these are long-term solutions that will ultimately save time and money by eliminating downtime. When making these upgrades, it’s important to conduct proper testing. Consider carefully where and how to mount the devices, and how often they should operate to be most effective.
Problem: Low Flow
This powder flow problem may go unnoticed for long periods since it doesn’t directly cause downtime. However, insufficient flow can affect all downstream systems. Low flow may be caused by obstructions above the feeder, or misalignments. This may also occur if the materials are too thick or the feeder is too small.
The solution is a bigger or faster feeder. The ideal flow control solutions for this problem will either expand the feeder to increase volume at slower speeds, or speed up the feeder to push more material through faster. This can be achieved via several ways: upgrade to larger feeder; add variable frequency drive; change reducer on drive.
Problem: Decreasing Flow
Some powder flow problems do not cause a sudden stop, but rather a slow reduction in material flow. Unlike other powder flow problems that are caused by materials sticking together, this is generally caused by materials sticking to the feeder because of static build-up.
The solution is to eliminate static. This is a particularly common problem in fast-moving, dry materials, but flow control solutions to this problem are generally easy to implement. These include three key approaches: ground the feeder frame to prevent static build-up; use electro-polish on feeder; add Teflon coating to feeder
Problem: Material Flooding
If too much material is getting through or the material floods after shut-off, this can also cause production problems downstream, or result in inconsistent products. These flow control solutions create the opposite effect of the previous three, but they are implemented in similar ways.
The solution is a lower, interrupted feed. Upgrading the hopper or attached systems can stop flushing and flooding. Venting the hopper will reduce aeration. Installing a slide gate or butterfly valve at discharge point can also solve the issue. Using a smaller feeder, lowering the drive speed, and inclining the feeder are other options.
Importance Of Powder Properties
The equipment design and build industry plays an important role in preventing or solving powder flow problems. However, it’s also important to consider the characteristics of the material as well. When your equipment manufacturer has a good understanding of the material characteristics of the powder, they can build the optimal machinery to prevent powder flow problems.
Before working with an equipment manufacturer, it’s helpful to have measurements on the following powder characteristics, where applicable. Details on these characteristics can help an experienced equipment manufacturer anticipate problems. There are many physical properties of powders, and which properties are most important will depend on the process and the industry. In this case, we’re considering the physical properties of food powders for human or animal consumption. These include: density; flowability; cohesion; aeration; particle uniformity; and abrasion.
If you’ve inherited a system that constantly sees problems, or your materials have changed and it’s created new issues, consider these solutions. If you’re building a new system, take advantage of testing and proper construction beforehand and these powder flow problems will never occur. The right material testing before installation will ensure that the system is made for the materials before it arrives.
Jessica Stank is with APEC