Biomass and Wood-Chip Silo Level Measurement for Reliable Operation

Wood chips, bark, straw pellets and other biomass fuels form rough, porous surfaces with variable moisture and bulk density. Filling creates irregular piles, while fibrous material can bridge or rat-hole during discharge. Radar selection therefore depends on the exact fuel and silo geometry, and the reported level must not be confused with verified flow or precise mass.

Describe the fuel range

Record material type, chip or pellet size, fines, moisture, bulk-density range, temperature and contaminants. Include seasonal suppliers and blended fuel. Wet compacted chips can reflect and flow differently from dry loose material.

State whether the silo ever receives warm material or develops biological heating. Measurement design must fit the site's fire, gas and dust risk assessment rather than treating all biomass as equivalent.

Understand pile and outlet behaviour

Map inlets, conveyors, spreaders, multiple outlets and typical angle of repose. Light chips may create steep local piles or shift as air moves through the silo. A single radar point can see a peak while the average inventory is lower.

Bridging can isolate an outlet from the surface above. Use feeder load, screw current, weight or appropriate point detection for no-flow and blockage functions. Do not allow a healthy level trend to override contrary flow evidence.

Build sufficient echo margin

Provide range, expected dielectric behaviour and surface angle to the radar supplier. Antenna aperture, frequency, beam angle and signal processing work together; choosing the highest frequency alone does not guarantee a reliable echo from loose material.

Keep the antenna clear of the fill stream, roof members and wall buildup. Plot the full beam through low and high piles and retain access for inspection without adding a protective cover inside the beam.

Manage dust, deposits and condensation

Dust clouds and fibrous deposits can reduce signal margin, particularly in a narrow or recessed nozzle. Condensation may bind fines into a persistent layer. Check roof leakage, cold bridges and ventilation conditions when buildup accelerates.

Trend echo quality and save curves during filling, settling and discharge. Set a condition-based inspection interval from actual deposits rather than copying a clean-grain application.

Treat inventory as an estimate

Radar measures one surface point. Volume requires a model of the moving pile, and mass requires bulk density that changes with moisture, particle mix and compaction. Display appropriate precision and document the expected uncertainty.

Reconcile with weighed deliveries and feeder totals using matching fuel types and timestamps. Separate discrepancies caused by level, pile geometry, density and material still in conveying equipment.

Commission safety and operations

Verify local distance, calculated level, PLC scaling, alarms, lost-echo response and feeder interlocks. Include signal filtering and conveyor stopping time in high-level tests. Independent fire or overfill protection remains separately verified.

Inspect mounting, antenna and cable protection after early high-throughput service. Record fuel condition with each accepted echo curve so future comparisons remain meaningful. Note whether ventilation or extraction was running, because airflow can move light material and change both pile shape and surface return.

Engineering checklist

Document every fuel and moisture range.
Map moving piles, bridges and outlets.
Confirm antenna and beam for weak irregular echoes.
Control dust, condensation and fibrous deposits.
State volume and mass uncertainty.
Verify alarms with conveying response time.

Frequently asked questions

Can one radar point give exact biomass tonnage?

No. Pile shape and variable bulk density normally dominate the mass estimate.

Does a stable level prove the feeder is receiving fuel?

No. A bridge can leave material above an empty outlet; use independent flow evidence.

How should inspection intervals be set?

Use recorded buildup, echo quality and risk under the actual seasonal fuel mix.

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