Networks and Communications
Anchored to an Information-Rich Future
Anchor Products Moves into the Future with ControlLogix
A 55-metre tall blue glass clad monolith rising out of the Waikato Valley in New Zealand's North Island houses the world's largest whole milk powder plant.
The massive new plant is part of Anchor Products' Te Rapa milk processing site, owned and operated by the manufacturing arm of New Zealand's largest dairy manufacturer, The New Zealand Dairy Group. The result of a two-year and approximately 89 million euro expansion project, the new Te Rapa Dryer 5 milk powder plant is designed to accommodate projected growth in the North Island milk supply through to 2005.
Dryer 5 has a processing capacity of five million litres of whole milk per day and can produce up to 23 tonnes of milk powder per hour and is the first manufacturing plant in the southern hemisphere to adopt the Allen-Bradley ControlLogix integrated control platform on such a scale.
Strategic Move
ControlLogix data-communications and wide integration strengths, backed by the Allen-Bradley open communication architecture, fits with the dairy giant's long-term control strategy.
Central to this strategy is the application of predictive automation based around technologies developed by Anchor's alliance partner, Pavilion Technologies of Austin, Texas.
"Access to real-time production data is an essential element in achieving optimal plant performance and profitability," explains Ian Steele, Anchor Products' engineering services division manager. "It's the key to our future operational strategies. A rich database of historical plant data provides us with the basis for applying Pavilion Technology's predictive neural-based control models. This in turn will run our processes and provide real-time economic analysis of plant performance."
Anchor's automation architecture - a futuristic control system to optimise access and use of plant-floor data - was conceptualised by the company in 1990. Heading up the neural system is a powerful plant historian computer, the Site Independent Routing and Reporting Processor (SIRRP). Via its onboard web server, SIRRP provides process data from all its plants to the Anchor management team. It also stores and develops the data archive needed for predictive control.
In turn, SIRRP is supported by distributed plant-level data networks - the essence of the neural-based architecture. "The ControlLogix platform and the Ethernet/ControlNet/DeviceNet data communications topology was an ideal fit with our neural model," says Steele, "both from a pure process control, and communications and backplane architecture point of view."
Widely Distributed
The Dryer 5 control system practically realises the Anchor neural architecture. It comprises a total of 12 ControlLogix controllers, almost 3,000 ControlLogix I/O points and 1,640 DeviceNet nodes. These are widely distributed across the new plant's three operation sectors (the "dry" end, the "wet" end, and powder handling) and three "service" areas (refrigeration, water, and wastewater).
At the operator interface end, ten PC-based HMI stations running RSView32 operator interface software provide access to the plant's 60,000-plus process tags.
The flexible nature of the ControlLogix architecture proved to be one of the system's greatest benefits. Steve Hayward, Anchor's automation and electrical systems manager, stresses the importance of flexibility. "Most of the plant areas you see out there are totally different to when they were commissioned," he says. "There's product improvements, new routes in and different product mixes being implemented all the time - flexibility is essential."
The ability to share I/O and databases across different controllers located in different chassis was a key benefit of ControlLogix. This was particularly so in dealing with shared process facilities such as the plant's six-bay milk reception area.
Multiple Controllers
ControlLogix also permits multiple controllers to be sited in a single chassis. This was used to advantage in the system's Dryer and Evaporator control chassis where multiple controllers were installed for reasons of control algorithm integrity and capacity. "To achieve this with legacy PLC platforms we would have had to install another three racks," explains Hayward. "The beauty of the ControlLogix platform is that it is so tightly integrated, with easy communications across the backplane."
Phil Lancaster, engineer with the Dryer 5 project's system integrator Computer Systems Engineering (CSE), believes the ControlLogix platform affords huge development timesavings. Although this was CSE's first major ControlLogix project, he estimates the company may have saved as much as 30 percent in total project development time.
"ControlLogix has provided huge advantages," enthuses Lancaster. "Features such as user-defined data types make writing routines to automatically generate tags and code very simple." He cites valve control development as a case-in-point. "You create one valve of a particular type, and you've automatically created dozens of points. Traditionally you'd have had to manage these in a database of some description."
Integrated Open Networks
Access to system data via widely integrated, open data networks was an Anchor-essential for the new dryer control system. Efficiency of data throughput was also crucial, with Anchor demanding speedy I/O updates and HMI screen refresh cycle times of less than one second. The Allen-Bradley efficient three-tiered communications architecture proved ideal.
Two separate networks of switched Ethernet are routed about the plant to provide controller to HMI data communications. The first network routes data from the 12 ControlLogix processors to two pairs of duty/stand-by RSView32 active display servers; the second carries data from the servers to the ten RSView32 HMI clients. RSLinx, Rockwell Software's server-resident communications engine, facilitates all HMI data transfer.
Two networks of 5M bit/s ControlNet form the 'control layer' of the data communications system - the first for controller to remote I/O rack communications and the second for peer-to-peer messaging.
Lancaster stresses the importance of the deterministic nature of ControlNet at the peer-to-peer and I/O communications levels. "You know exactly how fast things are going to update," he explains. "This is important with certain types of data such as pulse inputs and analogs."
A device-level DeviceNet network completed the three-tiered open communications architecture. Around 60 DeviceNet scanners support the Dryer's 1,640 DeviceNet nodes. Hayward estimates this would equate to almost 5,000 discrete I/O, realising enormous savings in point-to-point I/O cabling and hardware.
DeviceNet had been used at the Te Rapa site on an earlier project, but the Dryer 5 project extended the network's use outside the switchroom, with the vast majority of DeviceNet nodes - some 1,100 - linked to Dryer 5's DeviceNet-enabled process valves. Via the Dryer 5 DeviceNet network, important process valve information may be accessed including stroke times, actuator frequency and valve diagnostics.
Facility-to-Facility Linking
No facility within a plant is an island; linking from Dryer 5 to other existing Te Rapa plant areas was also a must. Using the ControlLogix powerful Gateway and network interface modules, data links have been realised from the Dryer 5 ControlLogix system to other Allen-Bradley PLC-controlled Te Rapa plant areas, either via ControlNet or via the DH+ and Remote I/O networks.
Linking into the plant's three existing dryer DCS control systems has proved more challenging. Here, the CSE design team developed an ingenious PC-based gateway, linking the ControlLogix system to the legacy-DCS. The gateway forms a bridge between the new dryer's control Ethernet and the DCS's serial interface.
To the future
In the longer term, Anchor Products Te Rapa plans to widen its 'data net' by extending the Ethernet/ControlNet/DeviceNet architecture deeper into the site's existing manufacturing and service areas. "Dryers 1, 2 and 4 are still viable plants and are going to be on-line for sometime," says Hayward. "We plan to incorporate the ControlLogix architecture in these areas as part of our ongoing upgrade strategy."
The ControlLogix system and its powerful data communications capabilities has provided the practical means to collect this data — and ultimately realised the 'neural-link' to the information-rich system conceptualised by Steele and his team a decade ago.