Late adopters demand more from their drives

Integration is the key to drive system growth in the food, beverage and pharmaceutical markets, says Graham Perry, Product Manager for AC Drives at WEG UK.

Recent research by the ARC Advisory Group predicts that suppliers of process automation systems to the food, beverage and pharmaceutical industries are set to benefit from high levels of growth until 2006 at least.

The main driver of this growth is the increased demand for packaged goods across Europe.

The research forecasts that food and beverage companies that employ automation systems to fully integrate their processes are the most likely to benefit from this development.

The use of drive and automation systems in the food and beverage industry is a bit like "the curate's egg": good in parts.

Many companies use the best in automation technology, whereas others can only be classed as "late adopters".

For suppliers of drive systems this tardiness presents considerable opportunities, especially as there are no formal preconditions for entry to these markets, over and above compliance with EU legislation on RFI and the LV Directive and adherence to certain hygiene standards where applicable (see below).

It is in the automation layers above drive systems that demands become more exacting, with product traceability an increasing industry requirement.

This is not a problem as many PC based Scada systems now offer standard off-the-shelf batch options that provide exceptional reporting, control and visualisation capabilities specific to the needs of the food and beverage, pharmaceuticals industries.

These systems are the key to providing the electronic process data necessary for compliance with the latest FDA 21 CFR Part 11 requirements.

Traceability apart, the keyword in food and beverage industries is integration, an objective that is increasingly achieved via a one-stop-shop approach that matches drives with control and sensing equipment.

A number of suppliers, WEG among them, have adopted this approach, selling not only products, but also compatible systems capability.

However, this development hasn't prevented some key OEMs continuing to supply machinery and equipment with drives from their preferred suppliers.

The minimum requirement for any drive supplier seeking to do business in the food and beverage sector is a range of drives that are capable of meeting customer needs right across the process spectrum, up to near servo performance.

In terms of performance, open loop vector is the minimum requirement, with closed loop as an option.

Some drive requirements are fairly mundane: the control of pumps, fans, mixers, blenders, conveyors, fillers, labellers all being quite straightforward.

However, this is not the case with end of line packaging systems, which require closed loop vector, or even servo control to provide the accurate ramps, process following, master / slave and positioning operations necessary for their precise, high speed operation.

At present, the majority of drives supplied for food and beverage applications are IP20 or IP21 rated units, housed in centralised control cubicles which are provided as complete packages by drive suppliers or OEMs.

However, control panel space ("control panel real estate") is becoming increasingly expensive, leading to a takeup (albeit slow) of distributed drives.

These units are mounted out on the process and actually on or adjacent to the motor.

To meet hygiene regulations they are housed in IP54 (min) enclosures, which are designed not to trap particulates, and offer the capability to be washed down with aggressive cleaners.

WEG's IP56 rated stainless-steel Shark package, housing a high performance WEG CFW-09 vector drive, is a good example of a unit designed specifically for use under these demanding conditions.

Enclosures such as the Shark are only necessary for equipment going out into the plant, but their use is becoming more common, driven by the growth in distributed control as a means of reducing equipment, cabling and installation costs through higher levels of plant integration.

In drive terms, achieving increased integration actually means executing tasks that were previously handled by a centralised PLC or PC.

A few years ago this would not have been impossible but today a number of drive manufacturers such as WEG offer drives with built-in PLCs.

These units are the key to more cost effective and easily expandable systems, as they enable control programs to be broken down and invested into individual intelligent drives.

There is no downside to this approach as the control programs for the drives are written in industry standard IEC61131 ladder to ensure compatibility.

Leveraging the benefits of intelligent drives for higher levels of plant automation are proprietary fieldbus systems.

Although key to the flexibility demanded from modern processing plants, the uptake of fieldbus systems is definitely not universal.

Even in the plants with high levels of integration it is rare to find a fieldbus architecture extending down to device level, and experience with open systems is that they are not yet working properly.

Currently, the most widely used fieldbuses with drive systems in food and beverage applications are Profibus and DeviceNet, both of which are offered as standard options by most manufacturers.

However, Profibus and DeviceNet interfaces cater for centralised control strategies, requiring a network master controller, typically a PLC.

The master device is entirely responsible for controlling communications over the network, and slave devices tend to be "dumb" devices with no local intelligence.

Although centralised systems remain in the ascendancy, the demands of distributed control have spawned the use of high-speed proprietary fieldbus networks for drives and deterministic open fieldbuses such as CANopen.

CAN (Controller Area Network) is a data communication network designed to fit distributed real-time control applications.

It was originally developed and applied by the automotive industry to solve the cabling problems inside vehicles.

However, it also provides benefits of high speed (up to 1Mbit/s) high reliability and low cost in processing and industrial applications.

Despite the increasing number of established fieldbuses already in use in food and beverage plants, it is becoming more and more apparent that the final say with the technology rests with a relative newcomer: industrial Ethernet.

A major benefit of using Ethernet is that through the TCP/IP it is the main network for both Intranet networks, internal within a food plant, and the Internet - for connection between plants.

A sizeable majority of food and beverage plants already use Ethernet networks for their IT operations, so the adoption of industrial Ethernet should, theoretically, pose no problems.

However, one issue that must be overcome before true plant integration based upon a single network is to be achieved, is that of communication between engineers and IT personnel.

This reservation apart, Industrial Ethernet seems to be gaining strength daily, its potential benefits even being recognised by the various competing fieldbus groups.

As a result, users can now avail themselves of Profibus on Ethernet, Modbus on Ethernet and Fieldbus Foundation (H2) on Ethernet.

More are sure to follow.

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