Operational bottlenecks in bulk solids handling often develop gradually, resulting in erratic discharge, recurring blockages, or inconsistent production rates. The underlying cause of these bottlenecks cannot be discerned solely through routine observation. Jenike & Johanson’s structured auditing process combines bulk material testing with engineering analysis to uncover the root causes driving poor flow behavior.
The Audit: Anatomy of a Diagnostic Investigation
Our audits begin by defining the operating conditions that influence material behavior. Bulk solids respond differently depending on their environment, so our engineers first establish the exact boundary conditions before laboratory work begins. Factors such as temperature, moisture content, consolidation time, chemistry, particle size, and pressure can all influence how a material flows through storage vessels, feeders, and transfer equipment. Capturing this information ensures that bulk material testing reflects actual plant operating conditions and produces results that match real processing environments. Site assessments also allow our engineers to evaluate auxiliary equipment, investigate problem sources, and ensure that subsequent steps are taken to solve the problem.
Following the site assessment, the investigation moves into the laboratory, where our lab technicians measure the material properties that govern bulk flow. We perform targeted bulk material testing to quantify the properties that directly affect flow performance.
Critical measurements include:
- Cohesive strength- defines the hopper opening size required to overcome the material’s ability to stick to itself and is used to diagnose arching and ratholing problems.
- Wall friction- determines the coefficient of sliding friction between a bulk solid and a wall surface, which establishes the hopper angle needed for a bulk solid to slide along a wall surface.
- Compressibility- measures changes in bulk density under different consolidation pressures, which is necessary for throughput and storage calculations.
- Permeability- assesses how easily a fluid moves through a bulk solid, which is critical for the evaluation of possible throughput for fine powders
Fortunately, bench scale laboratory testing for cohesive strength, wall friction, compressibility and permeability is scalable, ensuring engineers can evaluate large stockpiles and small hoppers with similar test procedures. Be mindful that there are many other tests that should be considered depending on the application. And in specific applications, pilot scale testing may be necessary.
Utilizing Test Data to Identify the Bottleneck(s)
Once testing is complete, our engineers compare the measured material properties with the existing equipment design. The comparison reveals the source of recurring flow problems long before physical modifications start.
One of the most common root causes of flow problems involves the storage vessel discharging in a funnel flow sequence. In funnel flow, material moves through a narrow channel above the outlet, leaving stagnant regions along the hopper walls. Over time, stagnant material can compact, absorb moisture, degrade in quality, or develop stable ratholes that restrict discharge. Bulk material testing allows engineers to determine whether funnel flow is responsible and whether the equipment should be modified to promote a mass flow sequence, where all stored material moves together during discharge. However, simply converting the storage vessel to a mass flow discharge sequence is not enough to ensure all flow problems are alleviated. The storage vessel hopper geometry must still be sized sufficiently to ensure arching does not occur at the hopper outlet and the desired flow rate is achievable. Additionally, converting a bin from funnel flow to mass flow can have a major change to material induced loads acting on the vessel. It is imperative that these are checked from a structural perspective before implementation.
Feeders represent another important area of investigation. An engineering assessment is made to determine if material is withdrawn evenly across the entire outlet or only from one section of the hopper. Uneven withdrawal forms dead zones that increase consolidation and reduce effective storage capacity. Bulk material testing provides the information needed to properly design a feeder so that it provides reliable, uniform discharge while activating the entire outlet.
Attention also extends beyond the storage vessel. Transfer chutes frequently contain hidden restrictions caused by poor chute angles, abrupt direction changes, or impact zones that encourage build-up. A detailed audit identifies where material slows, accumulates, or plugs, allowing engineers to redesign each transition point utilizing measured flow properties.
Leveraging Flow Property Testing and Process Audit Findings to Remedy Flow Issues
Flow property testing and audit results represent far more than a collection of site photos and laboratory measurements. Site assessments enable our engineers to engage with the solids handling problems first hand, discuss the problems with personnel that are interfacing with the issues day in and day out, and ensure that proper process conditions are considered for further engineering and testing stages. Flow property testing data becomes a practical engineering blueprint for modifying equipment to improve flow reliability. Recommendations are directly linked to measured material properties, helping engineers to predict how design changes will affect plant performance before purchasing of equipment and installation begins.
Data-driven engineering also removes the uncertainty associated with temporary corrective measures. Industrial vibrators, air cannons, and fluidizers may appear to solve a blockage, yet they often fail to address the true root cause. In fact, if these flow aids are deployed incorrectly, they can actually increase flow restrictiveness with certain materials, and can lead to increased mechanical fatigue.
Enhancing Bulk Solids Handling Performance
Jenike & Johanson offers engineering audits and bulk material testing that enable manufacturers to identify the root causes of recurring flow problems. Using measured material properties, our engineers develop equipment recommendations tailored to materials, processes, and operating environments, helping improve reliability and reduce costly production disruptions. For more information, contact Jenike & Johanson to discuss your application and determine the testing and engineering services best suited to your operation.
