Bulk Solids Radar Level Selection: Surface, Dust and Inventory Limits

Bulk solids radar selection must account for the fact that the instrument measures distance to a local, uneven and changing surface. Filling cones, discharge funnels, ratholes, bridging, dust and compaction can change the measured point while total material remains similar. A narrow beam and long nominal range do not convert that local distance directly into accurate mass. The selection process should define the operational decision, map material and silo behavior, place the beam deliberately, evaluate signal margin and state the uncertainty of any level-to-volume or mass conversion.

Define the decision supported

State whether the radar provides high-level alarm, refill scheduling, process control, trend or inventory reporting. Each use has different requirements for location, response and uncertainty. A wall-side measurement may protect against local overfill but poorly represent average volume. Define what the displayed value means and who may use it before selecting the mounting point.

Characterize the material

Record particle size, shape, moisture, dielectric behaviour, bulk density range, angle of repose, dust generation, adhesion, temperature, abrasion and electrostatic conditions. Include product changes and cleaning. Identify compaction and material-in-transit effects. Supplier experience with a material name is useful, but site filling and discharge behavior still require evidence.

Map surface states

Describe central or off-centre filling, distributor movement, multiple inlets, mass-flow or funnel-flow discharge, cones, ratholes and bridging. Use photographs, surveys and operator observations across representative cycles. Decide which surface region best supports the required alarm or inventory decision and state conditions where one point cannot represent the whole silo.

Survey geometry and beam

Provide silo height, diameter, roof, cone, nozzle, reference plane, internals, ladders, braces, filters and fill stream. Plot model-specific beam width with mounting and roof tolerances. Avoid direct impact and moving structures. Confirm antenna projection, blocking distance and maximum-level margin. A beam drawing should use as-built dimensions rather than a generic catalogue vessel.

Evaluate dust and buildup

Describe dust concentration and duration during filling, extraction, condensation and antenna deposits. Review frequency, antenna and any approved purge together. Require signal-margin evidence and plan an early-service inspection after representative production. Maintenance intervals should be revised from recorded as-found condition, not assumed to be zero or set by an arbitrary calendar.

Control echoes and dynamics

Review raw echo curves at known states and match fixed targets to geometry before suppression. Set expected rate, damping and lost-echo behavior to follow credible avalanches without delaying high alarms. Prove that false-echo mapping cannot hide a real high surface. Carry low confidence and device fault to the control or inventory system.

State inventory uncertainty

Separate radar distance accuracy from surface representativeness, silo geometry, bulk density, compaction and material in transit. Validate conversions against weight, survey or production balance where possible. Document the expected uncertainty for each use and avoid unsupported custody or commercial claims. Reassess after material, inlet, extraction or silo modifications.

Validate the intended inventory use

Before approving an inventory display, compare radar distance and calculated volume or mass with an independent survey, weighment or production balance over several representative states. Record material distribution, bulk density, filling and discharge at each comparison. Use the results to define an honest uncertainty band and any conditions in which the value should be used only as a trend. This prevents a high-quality distance measurement from being presented as commercial inventory accuracy that the surface and material model cannot support.

Engineering checklist

Define alarm, control and inventory uses.
Record material and dust behavior.
Map cones, funnels and ratholes.
Plot the beam against as-built structures.
Verify echo margin during filling.
State conversion uncertainty honestly.

Frequently asked questions

Does radar measure silo mass directly?

No. It measures distance; volume geometry and bulk density add further uncertainty.

Is the centre always the best mounting point?

No. Filling pattern, structures and the intended operational decision determine the useful position.

When should maintenance be reviewed?

After representative filling cycles and whenever diagnostics or deposits show a changed condition.

Need a project-specific review? Send process data, drawings, photographs and acceptance criteria through our contact page.