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Lenterra Flow Sensors - In-Line Powder Flow Measurement

About Lenterra Flow Sensor Systems

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Lenterra specialises in sensor instrumentation for in-line, real-time assessment of powder flow. 

Freeman Technology are the worldwide distributors of Lenterra products.

For more information on the two systems available, the Lenterra Flow Sensor (LFS) System and the Lenterra Wall Shear Stress (WSS) Measurement System, please see below.

 

 

The LFS system consists of a Drag Force Flow (DFF) sensor, a Lenterra Optical Interrogator (LOI) and a ruggedised laptop with bespoke software.

The system provides an in-line, real-time assessment of powder flow enabling improvements in process understanding and manufacturing efficiency in various industries. 

Image showing LFS system - Optical Interrogator box (left), metal probe (centre), laptop (right)

 

Cross-section of the Drag Force Flow Sensor showing optical strain gauges

How it works 

The DFF sensor consists of a hollow pillar mounted on a stationary base, containing two optical strain gauges, Fibre Bragg Gratings (FBGs). The LOI is connected to the FBGs via a fibre optic cable and continuously monitors the FBG spectra. When the pillar is deflected by flow, one FBG becomes extended and the other one is compressed, leading to a shift in wavelength spectra. A larger deflection results in a greater shift.

When the probe is immersed in a moving powder or material, the DFF sensor bends under the force of the flow. The magnitude of the deflection is continuously measured and quantifies the drag force flow in real-time, which is a function of material properties such as size, density, adhesion and strength, allowing operators to assess material properties in-process.

 

Features
  • In-line, real-time measurement of material properties and temperature
  • Multi-directional sensitivity
  • Chemically resistant construction
  • Fibre optic connectivity
Benefits
  • Robust Process Analytical Technology (PAT)
  • Enhanced process understanding
  • Improved product quality and consistency
  • Optimise cycle times
  • Accelerate / simplify scale up
  • Minimise 'out of specification' material and rework
  • Improve compliance
  • Reduce costs (reworks, resample, retesting etc.) 

 

Image showing movement or 'bending' of probe when powder passed over it

 
Application Example - High Shear Wet Granulation

 

High Shear Wet Granulation (HSWG) is widely employed in many industries. Effective management of HSWG processes requires an understanding of granule evolution and the impact of changing properties.

The DFF sensor delivers valuable information to assist formulation and process development, as well as for routine monitoring, control during manufacturing, and scale-up strategy. The data below illustrates how the technology can be used to robustly track a granulation process, enabling the user to monitor granule evolution without disrupting the process.

   

 
Advantages of the DFF
  • Ability to assess properties of the granulated wet mass without halting the process
  • Measured FPM signal relates to wet mass consistency and granule densification, delivering significantly more information than granule size distribution alone
  • Determine the effect of process parameters on granule properties
    (e.g. impeller speed/time, water content)
  • Able to identify and quantify minor batch-to-batch variations with comparable formulations
  • Accurately track each stage of granulation process
  • Can be used to define granulation end-point - enabling robust formulation development as well as process design and control
  • Supports efficient scale-up of wet granulation processes 

Graphic showing probe inserted into a high shear wet granulator

Force Pulse Magnitude Graph

Force Pulse Magnitude Graph including reference to point at which water was added

The principal output of the Drag Force Flow sensor for powder mixing applications, including granulation, if the Force Pulse Magnitude (FPM). FPM is the difference between the force at maximum and the preceding minimum. Each FPM, therefore, characterises a passing of one blade under the probe pin. Being a differential measurement, FPM provides a reliable characteristic of the wet mass consistency and densification, since it is independent from possible zero drift in the raw signal.

 

 Other Applications

  • Blending
  • Feeding
  • Spray drying / drying
  • Flow rates in pipes and transfer chutes

 

The WSS system consists of a RealShearTM sensor, a Lenterra Optical Interrogator (LOI) and a ruggedised laptop with bespoke software.

The system provides an in-line, real-time assessment of the wall shear stress of liquid flow enabling improvements in process understanding and manufacturing efficiency in various industries.

Image of Real Shear System - optical interrogator box in background to left, metal probe front centre, and laptop to right.
How it works

The RealShear sensor is mounted flush with the pipe, vessel wall or rotor-stator workhead providing a real-time measurement of wall stress. 

The sensor consists of a floating element attached to a cantilever beam that deflects in response to shear force as liquid flows across its surface. The cantilever transmits the shear force to two optical strain gauges, or Fibre Bragg Gratings (FBG), mounted internally.  When the beam is deflected, one FBG is extended and the other is compressed, leading to a shift in wavelength that quantifies wall shear stress and temperature. A larger deflection results in a greater shift.

Fast, continuous measurement of flow rate, viscosity and multiphase flow characteristics are provided via the LOI. 

 

Image of small metal probe

 

Graphic of Real Shear metal probe inserted into the side of a high shear blender

Features
  • In-line, real-time measurement
  • Bi-directional sensitivity
  • Chemically resistant construction
  • Fibre optic connectivity
  • High measurement rate 
Benefits
  • Enhanced process understanding
  • Improve product quality and consistency
  • Optimise cycle times
  • Accelerate / simplify scale up
  • Minimise 'out of specification' material and rework
  • Improve compliance
  • Reduce costs (reworks, resample, retesting etc.)

 

Application Example - High-Shear Mixing

High Shear Mixers (HSMs) are increasingly employed across numerous industries, providing shorter mixing times and radically improving throughput compared with conventional mixing techniques. 

The RealShear sensor can be mounted within many different types of process equipment, including rotor-stator HSMs which contain a rotor that rotates in close proximity to a stationary element (a stator). Mix components that pass between these elements experience high shear stress, which is the lateral force exerted by a surface on the material or vice versa. the assessment of viscosity, granularity or, in the case of a food product, qualities such as 'spreadability' or 'mouthfeel', is important to ensure high quality final products. Despite the close proximity of the rotor and stator, the RealShear can be used to provide in-line measurements of wall shear stress to determine when target characteristics have been achieved. 

Image of Real Shear probe attached to metal cylindrical stator element

As data is acquired in real-time, it can be used to improve process efficiency and prevent overprocessing - demonstrating its value as an effective PAT tool in the manufacture of emulsions and other liquid substances. 

 
Advantages of the RealShear Sensor
  • Wall shear stress measurements at high acquisition rate
  • Rapid assessment of the impact of process parameters, e.g. mixer speed and temperature, on material properties
  • Minimal impact on the process
  • Ability to detect minor changes in wall shear stress, flow rate and fluid viscosity
  • Enables efficient process scale-up

 

Lenterra Optical Interrogator (LOI)


Optical Sensor Interrogator offers Fast, High Resolution Interrogation

Designed for use with Lenterra's in-line, real-time Drag Force Flow and RealShear sensors, Lenterra's Optical Interrogator (LOI) is a compact, robust, fast measurement unit. The LOI delivers high accuracy, long term stability, streamlined installation, and premium performance.

Using light instead of electricity and glass fibre instead of copper wire, the sensors are nonconductive, electrically and chemically passive, and immune to electromagnetic interference.

Lenterra's fibre optic platform, based on FBG technology has the ability to significantly enhance process performance, quality, productivity and safety in numerous industries.

The LOI is controlled by any standard PC through a USB interface and utilises a fast, low noise Distributed Feedback diode laser with narrow linewidth for full spectrum scanning. Custom software is used to control the interrogator and process and store collected shear stress data. 

Image of Lenterra Optical Interrogator - metal box with socket on the front for probe attachment

 Graphs showing Force Pulse Magnitude wavelength spectra

Images reproduced with the permission of Lenterra Inc.