Coal Bunker Level Measurement in Power Plants

Coal bunkers in power plants operate under dust, vibration, uneven filling and rapid changes in demand. A radar can provide a useful continuous level trend, but it cannot by itself prove that coal is flowing to the feeder or that a bridge has not formed. The design should separate inventory, operating control, blockage detection and high-level protection, then select evidence for each duty.

Define every operating duty

State whether the continuous level supports refill control, run-time estimation, operator trend or inventory. Define separate high and low alarms, feeder permissives and trip actions. Document response time from conveyor command to the last coal entering the bunker.

A low surface does not necessarily mean an empty outlet, and a high surface may remain above a bridge. Use feeder current, belt or gravimetric flow, chute switches or other suitable evidence when actual coal movement matters.

Map filling and discharge geometry

Record tripper or conveyor discharge positions, multiple inlets, feeder outlets, wall slopes and internal liners. Moving fill points create peaks that may pass through the radar beam. Multiple feeders create valleys and rat holes that shift with unit load.

Choose a point that represents the intended control decision rather than the geometric centre by default. Where one point cannot cover the required uncertainty, use multiple measurements or state the limitation explicitly.

Protect the measurement from impact and dust

Keep the antenna outside the falling stream and credible rebound zone. Plot the full beam against roof beams, chutes and liners through the entire range. Use a rigid mount able to retain alignment under vibration.

Fine coal dust may attenuate the echo or coat a recessed antenna. Verify antenna aperture, projection, nozzle geometry and safe inspection access. Any purge must be approved for the dust area and plant air quality.

Address fire and explosion controls

Use the site's combustible-dust classification, temperature limits and equipment-protection requirements. Verify the exact certificate, cable glands, grounding, bonding and special conditions of use. Do not infer suitability merely from an enclosure IP rating.

Coordinate instrument work with fire monitoring, inerting and hot-work procedures. Opening a bunker connection can create exposure risks independent of the electrical certification.

Set alarm margins from material movement

A high-level conveyor stop must allow for detection delay, signal filtering, control response, belt stopping distance and coal already in chutes. Test the full sequence instead of checking only the displayed setpoint.

For low level, account for the surface valley above the operating feeder. Use conservative logic and confirm that a failed or held radar value cannot silently satisfy a permissive.

Commission under representative load

Save echo curves at low, normal and high levels during filling and feeder operation. Verify local value, PLC scaling, trend, alarms and diagnostic state. Observe the actual pile and record tripper position.

Inspect early for impact, loosening and buildup. Retain accepted curves and functional-test records so later coal grade or conveying changes can be compared with a known baseline.

Engineering checklist

Separate level, flow, blockage and protection duties.
Map moving fill points and feeder valleys.
Keep the beam outside impact zones.
Verify dust-area certification and grounding.
Include conveyor stopping and material in transit.
Test alarms and diagnostics at operating load.

Frequently asked questions

Can radar detect coal bridging?

It may still see coal above a bridge; combine level with feeder or flow evidence when blockage matters.

Where should radar be mounted?

At a clear, representative point established from fill and discharge geometry, not automatically at the centre.

Why include material in transit?

Coal continues entering after a stop command, so it affects the safe high-level margin.

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