From humble production origins in 1824, when John Cadbury used a mortar and pestle to make cocoa and drinking chocolate in a grocery shop in Birmingham England, Cadbury’s has grown to one of the world’s largest international producers of chocolate by combining sophisticated technology with the highest standards of quality, technical skills and innovation.
In this tradition of excellence, Cadbury's Port Elizabeth launched Project Olympus, an undertaking to build a world-class chocolate manufacturing plant incorporating state-of-the-art facilities and best practices in manufacturing and production. To monitor and control this South African flagship, Cadbury's chose to completely integrate the plant using technologically advanced 32-bit, open automation Adroit scada system.
Brendan Wilson, now engineering project manager for Cadbury's, was the Project Control Technician for Project Olympus, says, "We carefully considered the best players in the scada field before deciding on Adroit. Adroit is a local product whose development team sit in South Africa and could therefore provide us with levels of support that a foreign scada company could not." During the installation process, Adroit's Technical Director, Mike Lamusse, personally sat in the control room at Cadbury's to assist with the project and ensure the smooth installation of the system, a perk, which Wilson says, would not be available to Cadbury's if they had chosen an overseas product. Wilson also liked the fact that Adroit has no separate development dongle, allowing Cadbury's to maintain its system at no additional cost.
DLRA Projects, now incorporated into Streamworks, were the control system suppliers and engineers for the 10-month project, and made use of Port Elizabeth-based contractors, Comptech, to assist in the project. The objectives of this impressive undertaking were to increase the chocolate making capacity of the plant by increasing production efficiency, reduction of the size of the plant floor and a decrease in the amount of manual intervention required in the process.
The Adroit scada provides a window into this largely unmanned plant, which sports three stories of production processes interspersed with an additional three mezzanine levels. Labour is only utilised at the beginning of the process for product loading and towards the end where sampling occurs for quality assurance purposes. The major processing areas consist of the powders handling system, fats melting and storage (in a 'hot room'), reactor stream (used to process 'paste' or 'crumb' from the raw material), refining the paste into flake, conching the flake into chocolate and the storage of chocolate in the 'hot room' for distribution to customers. White paste is processed from raw materials, refined into flake and conched into white chocolate at the same facility. Using the Adroit system, Cadbury's can monitor and control recipes, on/off switching and other mission critical processes from a remote control room using a single operator.
Seven Allen Bradley PLC 5s control the plant. Based on the principle of distributed automation, one PLC supervises the remote operation of the remaining six, which are logically split amongst the process areas of the plant at Crumb Tower. The system also interfaces with the powder handling system and the refiners via an eighth PLC. The PLCs are networked using an Allen Bradley standard DH+ network-to-network device.
The Adroit scada at Cadbury's replaces an existing Turbolink system (the predecessor to Adroit) and consists of 50 000 tags (an unlimited system) of which Cadbury's are currently utilising approximately 7600. By making extensive use of Allen Bradley DeviceNet distributed I/O technology, Streamworks were able to greatly reduce the amount of cabling between the field equipment and the PLC I/O allowing Cadbury's to place the PLC I/O in close proximity to the field instrumentation. From the DeviceNet communication is fed to the Adroit scada via Ethernet.
The scada sits on the main Cadbury's network (intranet) logging into various local and network drives. Using the VB scripting tool that comes standard with the Adroit package, Cadbury's developed an intranet Web page for operations staff and management depicting critical production data such as tank weights and batch numbers.
Sean Allen, control technician for Cadbury's says, "Graphics are a very important reference point at Cadbury's and the standard Adroit package provides brilliant vector graphics." Twenty-five process control and graphic visualisation screens and an additional six maintenance screens were constructed for plant depiction. In addition to the standard graphics and those provided by System's Integrators, Comptech, Cadbury's also included photographs of plant machinery and equipment associated with runs and trip feedbacks. The photographs have been converted to bitmap format and incorporated into the overall plant on-screen depiction for enhanced recognition of production processes and faults. Seven graphic screens were also created to facilitate loading parameter data sets for chosen recipe names. Recipe data is pre-configured and stored in a Microsoft Access database.
Allen continues, "Adroit is a cost-effective product that provides a very versatile, easy to use and user friendly scada system. It also has excellent logging." The Cadbury's control system is batch orientated and one of the key features of the system is its ability to track batches as they are processed through the system. Trending and on-screen alarming on the batch system allows Cadbury's to check for faults and rectify them. Trending data is written to the Microsoft Access database and pulled into Excel for reporting purposes, batch reports are produced on the completion of every batch and the information is stored on the machines for up to a month and backed up periodically. Cadbury's is currently implementing Opus Business Reporting Tool to provide greater flexibility in its operations reporting and analysis.
The system's three various modes of operation for the individual major process areas can be selected by the operator. Automatic control mode initiates a process sequence by an autostart command after the operator has entered valid values for the recipe and number of batches. Manual control mode provides the facility for an operator to perform separate steps in the full automatic sequence in a controlled manner. This function is utilised, for example, to fill a batch weigh tank to a specific level or to start a reactor vacuum system under a full set point control. All necessary safety and process interlocks for these sequences have been put in place. Lastly, maintenance mode gives access to start and stop individual prime control devices such as motors and valves.
The stand-alone scada system runs on Windows NT makes use of a dual server hot standby configuration for redundancy and is backed up by a UPS. In addition to the installation in the Crumb Tower, Cadbury's has installed Adroit scadas at the boiler house and the production facility.
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