In this interview, AZoM speaks to Jamie Clayton, Operations Direction at Freeman Technology, about how powder testers are used from the initial stages of R&D, to support process scale-up, in the day-to-day troubleshooting of commercial scale plant, and for QC, for both raw materials and finished products.
Could you give a brief overview of Freeman Technology and the role that it plays in the field of powder characterisation?
Freeman Technology specialises in the design and manufacture of systems for powder characterisation, and their application. A primary focus is the development of solutions that directly meet industrial requirements for powder testing. The range of industries that use or handle powders - as raw materials, intermediates or final products - is diverse, from food and pharmaceuticals, through to cement, paints and coatings and additive manufacturing (AM). We provide instrumentation that allows our customers to understand which powder properties define process and product performance so that they can improve either, or both, to enhance efficiency and profitability.
Where are powder testers used? Can you provide some examples of their application and value?
Powder testers are used from the initial stages of R&D, to support process scale-up, in the day-to-day troubleshooting of commercial scale plant, and for QC, for both raw materials and finished products. If you can’t achieve the formulation properties needed to commercialise a new product, if operational reliability is poor, or if product quality is not meeting customer requirements, then a tester that generates relevant information can be extremely valuable and very quickly deliver economic returns that easily justify the associated investment.
For example, 3D printing or AM has captured the imagination of several industries, a major attraction being the ability to economically produce bespoke items or manufacture at low volume, to exacting specifications. An initial challenge was to develop effective hardware, but for many the focus has now shifted to optimising feedstocks to fully exploit the technology.
AM processes are highly demanding in terms of powder properties, including flowability. For example, powder bed fusion processes rely on uninterrupted powder flow from the feed hopper, and the uniform spreading of that powder into consistent layers just tens of microns thick. Where the aim is to develop a pharmaceutical formulation for a ‘printed’ product, or a new alloy for aerospace applications, then being able to define optimal flow properties is a major gain. Such specifications cut development times, accelerating time to market and profitability, at the same time boosting confidence in the performance of the developed product.
We also see our technology transforming the work of equipment suppliers. For companies that provide processing technology – bulk powder handling plant, for example, or packaging lines – identifying an optimal solution for each new customer/powder is crucial. By correlating process performance with powder properties, it is possible to define specifications for powders that will work well in a certain unit or design. Once these are established, powders can be robustly matched to a processing solution with a high degree of certainty and efficiency. Savings accrue from the capacity to handle more work and to deliver superior solutions.
How do the Lenterra products fit with what Freeman offers?
The Lenterra products provide in-line, real-time flow measurement and therefore ideally complement our existing at-line instruments.
We manufacture two powder testers for off-line or at-line use. The FT4 Powder Rheometer® is a universal powder tester that enables comprehensive multi-faceted powder characterisation via the measurement of dynamic flow, shear and bulk properties and is typically the tester of choice for R&D, process development and troubleshooting. The Uniaxial Powder Tester is a simple, easy-to-use, automated instrument that provides highly repeatable measurements of flowability and is particularly well-suited to QA/QC applications. In combination, the two instruments robustly address laboratory-based powder testing requirements.
However, once the benefits of comprehensive powder characterisation have been appreciated, there is a natural inclination to look towards in-line, real-time measurement. The continuous assessment of variables that are known to be process relevant is now routine across many industries but options for bulk powder measurement are limited and far from ideal for many applications. The Lenterra technology extends valuable new process monitoring capabilities to our customers and over the long term will provide a secure platform for the control of powder processes.
How do the Lenterra sensors work?
Lenterra systems measure the local forces associated with the movement of powders within a process. The Lenterra Drag Force Flow sensor is a probe that is directly inserted into a pipe or vessel while the RealShear Wall Shear Stress Sensor, as its name suggests, is mounted flush with the wall of the processing equipment.
At the core of both sensors is a hollow structured cantilever with an assembly of optical strain gauges or Fibre Bragg Gratings (FBGs) mounted on its inner surface. An FBG is a periodic structure of varying refractive index embedded in the core of an optical fibre. Laser light travelling down the fibre is either transmitted or reflected by the FBG, with any deflection of the cantilever affecting the properties of the FBG and the wavelength of the reflected light. By measuring shifts in this wavelength, it is therefore possible to determine the force associated with powder flow over or past the sensor.
The technology has many practical benefits. The sensors self-calibrate, provide no ignition hazard, are not subject to electromagnetic interference, and are constructed from stainless steel, making them chemically resistant and sterilisable. A high measurement frequency (500 Hz) enables the detailed analysis of dynamic flow. Focusing on the DFF sensor, this is very fine – just 1-4 mm in diameter - minimising flow disruption and the risk of fouling. Furthermore, the adherence of material to the probe has negligible impact on the measurements made. These advantages make the technology robust and highly suitable for continuous industrial monitoring, including for high temperature applications.
What are the benefits of using in-line technology for powder processing?
With in-line technology it is possible to evaluate a greater proportion of the in-process material than can be assessed via sampling followed by off-line or at-line analysis. Furthermore, measurements are made under process conditions. These two factors make in-line measurements highly representative, maximising their relevance. However, the biggest gain is that data are measured in real-time, making it possible to:
- instantaneously detect deviations from the process setpoint
- eliminate over-processing
- minimise the downtime associated with waiting for analytical results.
In addition, in-line technology delivers these benefits while simultaneously reducing the manual input associated with routine testing. In summary, in-line technology can significantly enhance manufacturing efficiency and boost profitability.
How are the Lenterra systems different from other process analytical technology for powder processes? And which applications are they particularly useful for?
When it comes to process analytical technology (PAT) for powder processes a classic strategy is to focus on the properties of the solid powder particles. Particle size, for example, is a popular measurement, and an important metric for powders. However, where the goal is to produce a powder with defined flowability, as is often the case, then this approach is inherently limited, as particle size is just one of many variables that influences flow behaviour. A distinctive feature of the Lenterra systems is that they directly characterise bulk powder flow, rather than quantifying individual particle properties, therefore providing data that are more relevant to process and product performance.
Lenterra systems combine this attribute with proven relevance and high sensitivity. Examining the application of high shear wet granulation (HSWG) monitoring exemplifies their value. This process is highly valued by the pharmaceutical industry for its ability to transform fine, difficult to handle blends into coarser, more stable, free-flowing granules that process at high throughput through a tablet press.
Previous studies have highlighted a direct correlation between the dynamic flow properties of granules produced by HSWG (measured off-line) and the critical quality attributes (e.g. hardness) of tablets manufactured from them.1 HSWG trials using the Lenterra DFF sensor show that it produces data that exhibit similar trends to the off-line dynamic flow properties demonstrating it has comparable relevance.2 A traditional technique for monitoring HSWG is to measure the power drawn by the agitator, which also changes with the properties of the bulk powder. However, tests have shown that relative to this approach, the Lenterra technology is far more sensitive, with the ability to differentiate between similar formulations that the traditional technique cannot discriminate.3
These capabilities extend the applicability of the Lenterra technology well beyond HSWG. It has value in mixing operations, for example, for efficient detection of the point at which blend homogeneity has been reached, and for monitoring bulk powder flow in pipes and chutes.
What are the plans for moving forward with Lenterra and Freeman Technology?
We decided to work with Lenterra because of the strength of the technology. It is an innovative solution with exciting potential which is being very much reflected in the response we’re getting from various industries. There is a natural fit with our existing products and, from Lenterra’s perspective, we bring extensive application knowledge to the partnership. Going forward we believe that Lenterra’s technical expertise in combination with our understanding of industry requirements will help the technology mature into a widely adopted solution for power processing.
We are also keen to further explore relationships between dynamic data generated with the FT4 Powder Rheometer and in-line data measured with the Lenterra technology. We have many examples of the industrial application and value of our dynamic data, and correlation with the data generated by the Lenterra systems will continue to reinforce their value to powder processors across a broad range of applications.
1Freeman, T. (2014) In Pursuit of Wet Granulation Optimization. Pharmaceutical Manufacturing. Available to view at: http://www.pharmamanufacturing.com/articles/2014/in-pursuit-of-wet-granulation-optimization/
2 Narang, AS. (2016) Process Analytical Technology for High Shear Wet Granulation: Wet Mass Consistency Reported by In-Line Drag Flow Force Sensor Is Consistent With Powder Rheology Measured by At-Line FT4 Powder Rheometer®. Journal of Pharmaceutical Sciences. 105:185-187
3 ‘Equipment Interchangeability and Comparison of Drag Force Flow (DFF) Sensor and Shaft Amperage as Process Analytical Tools (PAT) for High Shear Wet Granulation (HSWG)’ Lenterra poster from AAPS 2017.
About Jamie Clayton
Jamie Clayton is Operations Director at powder characterisation company Freeman Technology, and is based at the company’s headquarters in Tewkesbury, UK. He graduated from University of Sheffield with a degree in Control Engineering and is responsible for all daily activities of the company, including overall management of the administration, production, R&D, sales and customer support teams. Jamie also works with the company’s clients to provide application based support.
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