Introduction
Manufacturers dealing with bulk materials often identify downtime and production loss as the most significant concerns in their operations. The source of this downtime typically lies in the equipment responsible for moving materials through the process.
Flexible screw conveyors are one of the most commonly used pieces of equipment for bulk material handling, especially in dry processing applications. With a history spanning several decades, these conveyors are considered reliable, simple, and low-maintenance. They work with a single moving part to efficiently convey dry materials from one point to another.
However, flexible screw conveyors are often viewed as a commodity item, interchangeable between different applications. In this article, we will:
- Identify the stage of the process where downtime is most likely to occur.
- Explain how selecting the right flexible screw conveyor can reduce this risk.
- Highlight the importance of working with an experienced equipment provider to make the correct conveyor choice.
The Key Issue: Equipment Failure During Startup
Failures in flexible screw conveyors typically occur during the initial startup. This is usually a result of incorrect conveyor specifications or the wrong options being chosen for the specific application. Whether it’s a new installation or a replacement for malfunctioning equipment, improperly applied conveyors often fail for two primary reasons:
- Material Flow Issues: The conveyor may fail to move or elevate the material properly, discharge it from the conveyor, or transport it to the next stage of the process. In these cases, the conveyor will be unable to keep pace with downstream processes, causing delays and production loss.
- Screw Breakage: A conveyor equipped with an inferior screw will likely experience breakage shortly after startup. Even replacing the screw with one of similar duty can result in repeated failures due to incorrect specifications. Even with a responsive equipment provider, the time it takes for a replacement screw to arrive—especially a long 20-foot one—adds to the overall downtime.
Getting Started with the Right Application Review and Flow Analysis
An experienced flexible screw conveyor provider will begin by asking the right questions to understand the material flow requirements. Problems with material flow typically arise from the type of product being conveyed. If the right screw type isn’t specified from the beginning, issues like improper material handling will occur, leading to production disruptions.
A reputable conveyor manufacturer will conduct a material flow analysis. This involves assessing the effective flow from the hopper through the conveyor, measuring bulk density, and discussing required convey rates.
Once the product and flow analysis are complete, the manufacturer will then choose the appropriate screw type (e.g., flat wire, round wire, beveled, or heavy-duty square bar) based on the specific material and application.
Optimizing Performance Through Additional Design Factors
Once the basic configuration has been selected, several other factors can improve the performance of the conveyor:
1. Pickup Angle and Efficiency
A key design consideration for flexible screw conveyors is the pickup angle—the angle at which the conveyor body operates relative to the horizontal. A 45-degree pickup angle strikes a good balance between operating efficiency and space constraints. Operating above 45 degrees reduces efficiency and can be problematic for heavy materials, while angles below 45 degrees improve efficiency and increase convey rates.
However, the pickup angle affects more than just efficiency—it also influences the fill factor, which determines how efficiently material enters the screw. Steeper pickup angles result in lower fill factors and reduced convey rates, while shallower angles improve fill factor but may lead to jams if the factor is too high. In these cases, alternative screw designs can help resolve the issue.
2. Avoiding Flanged Inlet Issues
Some systems use small flanged inlet feeders instead of full-sized hoppers to supply the screw conveyor. While this can work for some materials, it can cause problems for lightweight or easily fluidized materials that don’t provide sufficient headload on the auger. As a result, the conveyor may fail to operate properly, especially with steeper pickup angles. For these types of materials, using a full-sized hopper is a better solution. Full hoppers provide more headload and can accommodate agitators to ensure consistent loading of the auger.
Conclusion
Minimizing downtime in material handling requires the correct equipment selection, guided by an experienced partner in bulk material handling. An expert conveyor manufacturer understands that proper startup performance is crucial, and they will ask the right questions upfront to ensure the system functions correctly from day one. While customer input is essential, selecting the ideal bulk material conveying solution relies heavily on industry expertise to avoid costly mistakes and ensure optimal operation.