Data on demand

Accuracy, reliability, low maintenance, capable of automation, trouble-free, these are the features and characteristics being sought by engineers across virtually every aspect of industry. Process weighing equipment is no different, even if it has taken longer to move away from being heavily reliant on operator expertise — or lack of it.

"Weight controllers are becoming very sophisticated and people buying a weight controller are now saying let's get it to do as much as possible," said Rod Morgan, sales director, Applied Weighing.

The latest advanced systems, said Morgan, can deliver most of the functions carried out by traditional PLCs but at a much faster rate and much lower cost. This, he added, includes the ability to turn on or turn off an output when target weight is reached, combined with functions to display, monitor and control temperature, pressure and moisture.

In this arena, Applied Weighing has recently introduced a high-speed, dynamic check weigher as part of a fully automated package. The weigher is powered by a 920i process controller and can be combined with lead-on / lead-off conveyors, bar coders and metal detection equipment.

The check weigher operates within wide weight ranges and can be linked to filling machines. Packs are automatically rejected if they are outside pre-set tolerances and, if linked to a filling mechanism, will automatically adjust the filling heads.

Little programming is required and real time production information is displayed on screen, with data stored in an internal databank. Key indicators may be downloaded via LAN, Profibus or RS485 connections to help minimise cost and maximise production flow.

Weighing equipment suppliers are also at the forefront of automating the increasingly critical process of collecting, recording and collating key data on yields, throughput rates, wastage, remedial work, downtime and maintenance costs.

Software-driven, automated or semi-automated systems allow managers to analyse operations in detail, identifying 'bottlenecks' and processes that are regularly causing problems, said David Edge, product manager for Avery Weigh-Tronix.

Setting up an automated system typically means putting in the hardware to capture data from existing weighing machines, dynamic checkweighers, load cells, metal detectors and other plant as well as operator data terminals, bar code scanners and test instruments. According to Edge: "The skill lies in linking this equipment into an integrated network with the right software to provide a much broader level of plant control."

And, as bespoke software can be expensive, Edge also pointed to the availability of modular systems, such as Avery Weigh-Tronix's PlantPower system that offers a 'library' of applications for specific processes.

"As a result, the customer is only investing in the applications it really needs but can extend and adapt by adding other modules if its operation changes. This modular approach means that, even for smaller processors, cost effective software systems can be installed," concluded Edge.

Another emerging trend concerns the use of telemetry systems, according to Morgan at Applied Weighing. This technology allows central monitoring for weighing systems or any other kind of measuring device at an unlimited number of remote locations.

Applied Weighing claims its Teleonix telemetry system paves the way for real and effective co-operation between customers and suppliers on multi-site operations. Information is presented graphically and data is fully compatible with standard spreadsheets and databases.

Applied Weighing has supplied such a system (image p23) to a major cement manufacturer, which is providing access to over 20 suppliers. These companies, said Morgan, can now monitor silo levels and alert the cement company if readings fall below critical levels.

Contrary to some rumours, meanwhile, implementation of the Dangerous Substances and Explosive Atmospheres Regulations does not mean replacement of all non-ATEX equipment. If a plant was safe before 1 July, then generally it will be safe afterwards. Practical problems can start to occur, however, when non-ATEX equipment requires maintenance and spare parts, so that equipment may be more difficult to support. But replacement need not be as expensive as first thought.

Nova Weigh's new 350IS and 355IS digital weight indicators, for example, are claimed to make ATEX-compliant weighing available at prices less than might be paid for safe area instrumentation. Approved for use in Zones 1 and 21, the instruments fully meet EU legal-for-trade requirements.

Both are certified to the ATEX 100A directive for use in areas where there is a risk of a flammable atmosphere being present due to gas or dust release.

The 350IS family has models to meet all EX weighing needs, from mobile drums to reactor weighing systems in production plants. It has all the essential weighing functions, but not the numerical keypad of the 355IS. Both can be fitted with either an intrinsically safe power supply or a 200-hour continuous use, long life rechargeable battery, making the indicators suitable for mobile applications. The indicators can be linked to supervisory systems, PLCs and printers via an optional communications hub located up to 300 metres away.

Siemens has developed technology for integrating both differential proportioning and control scales into an automation system. The company's Siwarex electronic weighing system combines both scales types and electronically integrates them into an automation network.

Automation of differential proportioning scales facilitates accurate weight recording and flow measurement in the main application areas of the chemicals and pharmaceuticals industries, as well as the food and beverages sector. Differential proportioning scales are especially suitable for continuous proportioning with constantly high accuracy and offer long-term stability with low maintenance costs. The automated differential proportioning scales are of particular advantage in multi-component proportioning tasks, said Siemens.