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Accurate control for batch processes

21 June 2024

Kieran Bennett discusses the importance of process accuracy in batch manufacturing operations and how it can be achieved.

Quality control is of paramount importance in batch manufacturing operations, with cost-effectiveness coming a close second. The design of the batch sizing control system can have a significant impact on the quality of the end product.

The essence of batch control is the measurement and transfer of a variety of fluids to one location where they can be processed and moved on to the next production phase. Measuring and verifying flow volumes is key to establishing a reliable and repeatable process where all of the ingredients are measured precisely. 

Batch sizing control requires four essential components – the batch controller, communicator software, valves and a flow sensor. In addition, there are a few optional extras, such as operator displays, input/output modules and cabinets that collectively complete the installation.

Batch control is based on a simple principle – a valve opens to allow a certain volume of liquid to flow before being closed. The opening time for the valve is managed by the flow controller and a flowmeter is used to measure the actual volume dispensed. A feedback loop can improve the accuracy of the process by comparing the theoretical volume with the measured quantity.

In hygienic applications, such as those in food and beverage settings, there is an additional requirement for all the materials and designs to be optimised for cleanliness. Hygienic designs must be specialised for clean/steam-in-place (CIP/SIP) processes; the requirements mean non-contact flow measurement designs using ultrasonics, electro-magnetic and Coriolis technologies have come to the fore.

Challenging fluids
However, these designs have drawbacks which can make them unsuitable for some applications. Many of the fluids involved in food and beverage production present challenges for conventional flow meters, with many requiring a conductive fluid with laminar flow, free from entrained gases.

Bürkert’s can offer a flowmeter that uses surface acoustic waves (SAW) technology to overcome these obstacles. Manufactured from stainless steel and with no internal restrictions, the FLOWave sensor can address many of the shortcomings of other flow measurement devices in the hygienic sector.

One of the major challenges with batch sizing is setting up the equipment. With so many variables in an installation, it can be a complex and time-consuming process to manually install all the configurations and ensure that all the components are properly set up and working in harmony. Bürkert components utilise digital communications, enabling them to recognise each other and complete a large part of the configuration automatically. A touchscreen is integral to this procedure, walking the operator through the remaining steps for a simplified process.

Once the system is operational, a crucial part of batch sizing is the ability to compensate for changes in the system that affect the quantity being dispensed. Raw materials can be expensive so over-dosing, even by a small percentage, soon adds up to significant costs that could be avoided. This is especially true in the pharmaceutical industry, where active ingredients and water for injection (WFI) all have significant costs - so accuracy in this market is crucial.

Continuous accuracy
Burkert systems use a feedback loop to measure the dispensed volume and adjust the timing of the valve accordingly. For example, if the storage vessel for the dispensed liquid does not have pressure compensation, then as more fluid is used, the pressure will drop, which will result in the dosed volumes reducing. 

The measurements from the FLOWave can be used to assess the accuracy of the batch size compared to the theoretical volume. This information is used in a continuous feedback loop, to auto-correct the opening time of the valve to compensate for changes in the system and assure continued accuracy.

This setup, which has already proven itself with applications in the food and beverage sector, is widening the functionality of the FLOWave and providing additional opportunities for manufacturers to make their batching processes more accurate and cost-effective.

Kieran Bennett is Industry Manager, Food, Beverage, Chemical & Petrochemical at Bürkert.


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