Identifying silo problems: from symptom to cause
Stalling discharge, residual material, varying product quality or damage to the silo wall have a few typical causes. The symptom narrows them down – the measured parameters of the bulk solid together with the existing silo geometry prove them.
We measure your bulk solid, calculate the flow behaviour in your silo and make specific suggestions for improvement.
Typical silo problems and their causes
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Discharge stalls or stops
A stable arch of bulk solid holds above the outlet, or a stable rathole has emptied in funnel flow.
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Residual material remains, old material comes out late
Only a core flows; dead zones remain at the walls, age and cake.
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Problems after a standstill or the weekend
At rest the strength of the bulk solid increases; arches and caking form only after the storage time.
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Composition of the discharged material varies
Fines and coarse fraction separate at the surface cone during filling and in the flow channel during discharge.
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Material floods out uncontrollably
Fine bulk solid is mixed with air during filling or by collapsing ratholes.
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Buckles or cracks in the silo wall
Eccentric filling or discharge creates a flow channel at the wall and uneven loads around the circumference.
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Mass flow The entire bulk solid is in motion – what goes in first comes out first.
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Funnel flow Only a core flows; dead zones remain at the hopper walls – segregation and ageing.
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Ratholing Only a stable channel above the outlet empties; the rest stays in the silo.
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Arching A stable arch above the outlet stops discharge completely.
Troubleshooting in four steps
The basis is the same measurement and calculation as for technological silo design – applied to your existing silo.
- Problem and silo data Record the symptoms, the mode of operation and the approximate silo geometry.
- Measurement Yield locus, wall friction, density and, if needed, time consolidation, moisture or sieve analysis.
- Calculation Mass flow, arching, ratholing and loads for the existing geometry.
- Report and suggestions Cause, assessment of the flow behaviour and specific suggestions for improvement.
Frequently asked questions about troubleshooting
- Can the cause be determined without measurements?
- The symptom narrows down the cause but does not prove it. Only the measured parameters together with the existing silo geometry show whether, for example, the outlet is too small, the hopper too flat or the wall friction too high – and which measure will work.
- Which samples are needed?
- A representative sample of the bulk solid causing the problems, about 1 to 2 litres per sample. If segregation is suspected, samples from several areas or points in time; for wall friction, a sample of the wall material.
- Which silo details are needed?
- Approximate figures are sufficient: silo shape and dimensions, height of the vertical section, hopper inclination, outlet diameter, wall material, position of inlet and outlet, and a description of the problem and the mode of operation.
- What do I receive as a result?
- The measured values and the calculation for your existing silo geometry, a test report with an assessment of the flow behaviour and specific suggestions for improvement – for example on hopper inclination, outlet, wall material or feeder.
Finding the cause of silo problems
Describe the problem, your bulk solid and your silo – we put together the right measurements and prepare a non-binding quote for you.
- Measurement of the bulk solid that causes the problems
- Calculation for your existing silo geometry
- Specific suggestions for improvement
- Confidential, under NDA on request