Conventional Solid Measurement Techniques- Narrow Beam Angle -Only Single Point Measurement -Affected By Dust And Moisture

Solution To All the Problems Described in Previous Slide

LOW FREQUENCY 3D ACOUSTICS3D LEVEL SCANNER

Low Frequency and Dust Penetration ChartSignal Attenuation due to Dust/Moisture concentration in air

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frequency(Hz)

Att

enu

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n(d

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Ultrasonic

Sonic ( 3-4 KHz)

3dB Loss is 50% Loss of Signal Energy

Low Frequency and Dust Penetration• Sound is a pressure wave• Dust particles and Humidity in air

attenuate the wave energy• Attenuation grows sharply over 5 kHz• Low Frequency => Effective Dust

Penetration

Principle Behind Effective Dust penetration : DIFFRACTION around a particle of size less than its wavelength

Beam Angle vs. Frequency

θ - Beam opening angle λ - WavelengthD - Antenna size D

Low Frequency => Wide Beam Angle

Low Frequency => Wide Beam Angle

F = 4.5KHzλ = 7.5cm θ = 60⁰

F = 2.5KHzλ = 13cm θ = 108⁰

F = 10KHzλ = 3.4cm θ = 27⁰

F = 20KHzλ = 1.7cm θ = 13⁰

Low Frequency Acoustics and Self Cleaning AbilityLow Frequency acoustic vibrations prevents sticking of

material to the internal working of the device Ensures long term reliable performance in harsh dusty

conditions

Low frequency has 4 major advantages

Very low attenuation Easy penetration through dust

Wide angle that covers the whole silo (70-80 degrees)Acoustic vibrations contribute towards the self cleaning

ability

• 3D Surface mapping requires a 2D array

• 2 Dimensional Array of 3 Antenna

• Estimating per echo:– Distance (R), Azimuth (Ф) and Elevation

(Θ) angles– Convert R, Ф, Θ to Silo X,Y,Z

coordinates

• Final surface reconstruction, based on– Extreme and boundary points – The Material angle of repose– The silo geometry– Acoustics principles

3 Dimensional Surface Reconstruction

Working Principle

COAL BUNKERS/ FLY ASH / CEMENT/ CLINKER SILOS WARE HOUSES/

OPEN STOCKPILES

FERTILIZER/ CHEMICAL SILOS

3D Representation of the Device

3D Representation of the Device

3D Representation of the Device

3D Representation of the Device