Silo Radar Level Acceptance: Surface Geometry, Dust and Inventory

A silo radar measures distance to one part of an uneven, moving bulk-solid surface. It does not directly measure average level, mass or usable inventory. Filling cones, discharge funnels, ratholes, dust and internal structures can change the selected echo while the transmitter remains healthy. Acceptance must therefore define what the measurement represents, position the beam for that purpose, verify signal behavior during representative filling and emptying, and state the uncertainty of any inventory conversion. A static empty-silo display test is not enough.

Define the operational question

State whether the signal supports high-level protection, refill scheduling, process control or inventory reporting. These duties may need different positions, response times and uncertainty. A point near the wall may be useful for overflow prevention but poor for average inventory. Identify the decision made from the value before deciding how accuracy will be judged.

Map surface geometry

Record material, particle size, moisture, bulk density range, angle of repose, filling method and discharge pattern. Identify cones, funnels, asymmetry, bridging and ratholes. Use photographs or surveys from representative states. For mass or volume, define the geometric model and density assumptions separately from radar distance accuracy.

Survey the beam path

Provide silo dimensions, roof profile, nozzle, reference plane, ladders, braces, filters, distributors and inlet location. Plot the beam width through the range and include alignment tolerance. Choose a position that avoids direct fill impact and observes a meaningful surface. A narrow beam helps target selection but does not make the local surface uniform.

Address dust and buildup

Describe dust concentration and duration during filling, extraction performance, condensation and material adhesion. Check antenna exposure and any approved purge or protective arrangement. Establish a baseline echo margin and an inspection trigger rather than assuming maintenance-free operation. Heavy deposits, a blocked purge or changing dust extraction can create gradual degradation that a simple level trend may not reveal.

Control echoes and dynamics

Capture raw echo curves at empty, intermediate and high states where possible. Identify structures and moving surface returns before applying suppression. Set damping and rate filters to follow credible material movement without amplifying avalanche noise. Define lost-echo and multiple-echo behavior. Prove that false-echo mapping does not suppress a valid high-level surface.

Verify output and alarms

Check distance-to-level conversion, units, range and direction from radar through PLC, HMI and historian. Test high alarms using a safe reference or simulation that also proves the downstream path. Map device fault, low confidence and stale communication distinctly. Inventory systems should preserve timestamps and quality so invalid values are not treated as real stock changes.

Run representative acceptance

Observe at least one relevant filling or discharge sequence and compare the radar with manual, surveyed, weight or production-balance evidence. Record process state with the echo curve. Set acceptance limits for tracking continuity, alarm response and repeatability rather than demanding agreement with an uncertain bulk-density calculation.

State the approved uncertainty

Separate instrument distance performance from surface representativeness, volume geometry, compaction and density. Document the expected uncertainty for each operational use and prohibit unsupported commercial inventory claims. Retain model, geometry, settings, diagnostics and observations, and review the application after changes to material, inlet, extraction, silo internals or control duty.

Engineering checklist

Define the decision supported by the measurement.
Map cones, funnels and material behavior.
Plot the beam against real structures.
Track dust, buildup and signal margin.
Test outputs, quality and high alarms.
State inventory uncertainty honestly.

Frequently asked questions

Can one radar show total silo mass accurately?

Not by itself. Surface shape, volume geometry and bulk density add uncertainty.

Should the radar point at the filling cone?

Only if that local surface represents the intended control decision and fill impact does not compromise measurement.

What is the best acceptance reference?

Use the strongest available combination of survey, weight, manual reference and production balance, with stated uncertainty.

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