Weighing and measurement accuracy key to optimised efficiency and cost control

London – Recently installed process measurement systems highlight the value of automatic collection of weighing and measurement data when it comes to improving both the formulation and the accuracy of delivery.

Speciality chemicals manufacturer MacDermid recently required individual control panels for 12 mixing tanks with sizes from 4,000 to 100,000 litres at its plant in Birmingham. The tanks are capable of blending up to 600 separate product formulations in process routines taking between 30-240 minutes.

The majority of ingredients are gravity fed into the mixing tanks from IBCs, with hot and cold water and ammonia delivered to the tanks via fixed pipework: some pre-weighed ingredients are also added in small quantities by hand. This has enabled MacDermid to integrate four separate production areas onto one compact site.

The classic approach to monitoring the batches mixed in a tank is to use load cells to measure the tank contents. Procon used this approach to provide process control systems for the vertical mixing tanks at MacDermid.

Procon had previously supplied hermetically sealed, stainless steel, shear beam load cells for the MacDermid mixing tanks. These were removed, checked and refitted to the tanks after transfer to their new locations, to be interfaced with the new control panels and weighing instrumentation. Finished products are dispensed into 25 and 200 litre drums, as well as standard IBCs, via a volumetric filling system.

“The improved batching control capabilities, together with the increased efficiencies provided by the streamlined production and stock areas, are already bringing overall improvements to productivity and reductions in batch turnaround times,” commented Lance Phasey, managing director at MacDermid.

Control recipe
Producing over one million loaves of bread each week, Jackson’s Bakery, based in Hull, wanted a state-of-the-art recipe formulation system which could guarantee every batch was right first time. It, therefore, decided to upgrade its Stevens recipe formulation and average weight systems to the latest Vantage systems from Dataprocess Stevens.

The Vantage system is designed to provide traceability and product consistency, and to virtually eliminate scrap batches, while also controlling average weight legislation conformance. A feature of the system is a function that allows the daily production requirements to be pulled from the company’s SAGE line 500 ERP System.

This information is then displayed on the Vantage touchscreen, enabling the operators to select from the list of requirements and thereby eliminating the need for a paper production schedule or a manual transfer of production data to a database. Lot numbers for each of the raw ingredients are recorded on the system, providing a comprehensive audit trail that meets the requirements of most leading auditors.

No matter how well trained or conscientious an operator, there is always the human error risk factor. The Vantage system is said to eliminate such risk by prompting operators through the recipe formulation process one ingredient at a time. This ensures that the weighing tolerances are met and no over or under weighing occurrences can spoil a batch, which can be a costly mistake.

Information relating to lot number, batch number, ingredient usage and operator productivity is captured and sent to the ERP system, ensuring that the accounting department have the very latest information - and without the delays normally experienced with paper-based reporting.

After the batches have been weighed, mixed and baked, the finished loaves are sampled using the Vantage average weight/SPC system. This sampling process involves operators taking samples from each batch of product and placing them onto the high resolution scale connected to a terminal.

Weights are then recorded and the operators have a clear set of instructions to follow in the event of a T1 or T2 (weight limits) occurrence. After the samples have been taken, a ‘pass’ or ‘fail’ scenario is presented to the operators and the data is recorded electronically on the server PC for interrogation by trading standards at a later date.

“We have relied upon Stevens’ weighing systems since the early ’90s and in that time they have become an essential tool,” said Paul Berry, technical manager at Jackson’s. “The latest integration with SAGE line 500 means we have one source of information instead of lots of small applications all out of sync with each other. The products work extremely well and we are proud of our investment.”

Flexicon, a Danish manufacturer of peristaltic filling systems that are particularly applicable to pharmaceutical applications, was acquired by Watson-Marlow in 2008. The company has recently launched the FPC50W, a flexible aseptic filling unit with integrated systems for full or partial stoppering and crimp capping of vials.

Able to deliver fill-volumes ranging from 0.1ml to 100ml with a filling accuracy of +/-0.5%, the Watson-Marlow Flexicon technology is designed for applications involving small batches, such as those from contract fillers or from research and development trials.

The system incorporates a Wipotec weighing cell in the line to provide 100% check-weighing of all vials: its output is used to provide feedback to the peristaltic filling system, driving automatic recalibration of the filling pump throughout the batch. This compensates for any drift in the peristaltic pump delivery that might be caused by relaxation of the elastomer tube as it warms and stretches.

The filling system is suited to environments where cross-contamination must be avoided; for example, the use of sterile, disposable tubing and filling needles minimises human contact with the filling operation. In addition, the peristaltic design ensures that the entire fluid path is contained for single-use, making cleaning and validation extremely simple.

Watson-Marlow Flexicon has supplied two of the automatic aseptic filling and plugging systems for use in isolator units at a new clinical trial facility built by Huddersfield-based Extract Technology for Bioquell UK of Andover.

Bioquell selected the compact FPC50 automated vial filler and capping unit because it offered a range of benefits, including: no cleaning validation; easy product changeover; no cross-contamination; and accurate peristaltic filling of better than +/-1% for volumes ranging from 0.1ml to 100ml.

Elsewhere, Precia-Molen has recently installed a weighing system for Dengie Crops Ltd, a leading UK grower and producer of alfalfa for use in the production of animal feeds. In the production process, the feed is dried, baled, manually tested for moisture, weighed, automatically stacked and manually tagged. Bales with excessive moisture are manually removed from the stack.

Precia-Molen supplied a set of R2 weighbeams - 1,000kg x 0.2kg - and installed them beneath an isolated section of the conveyor line within the stacker cage. A touchscreen terminal, with bespoke application software, Ethernet and TOR parallel I/O module, logs the weight of each bale against pre-entered source details and marks rejected bale records.
Precia-Molen also installed an SQL Interbase driver on the PCs of the accounts and operations managers, and configured a simple query for MS-Excel to provide production data.

Mettler Toledo has recently provided Chinese food company Wing Yip with the technology to verify the precise weights of pre-packaged goods received from suppliers outside the EU.

Mettler Toledo supplied its new Freeweight.Net, a statistical quality control software system for packaging and filling control from the PC. Once integrated with the weighing technologies in place at the Wing Yip distribution centre, data was available online, via on-screen displays or accessible as reports for real-time analysis, compliance and record keeping.

The attraction of using Freeweigh.Net for Wing Yip included: establishing correct sampling plans; ensuring adherence to the quality control requirements of export countries; and verifying the frequency and methodology of quality control checking.

The technology is able to monitor product and package quality parameters and present them in a way that helps the individual producer comply with legislation to control and document product quality and profitability.

The system consists of workstations for product measurement and clarification, which are linked to an existing PC terminal for reporting and recording.
Monitoring devices can be connected to the system, without the need for additional programming. Checkweighers, metal detectors and small-batch-test instrumentation can also be integrated and centrally monitored for packaging quality control.