South African Instrumentation and Control features editor, Andrew Ashton, interviewed Andrew Craig, automation manager, FlavourCraft, to establish the thought processes behind this decision.
[SAI&C]: Please give us an overview of your company, your products, your customers, and your position and responsibilities.
[Andrew Craig]: FlavourCraft is a privately owned South African flavour house. We supply flavourings and food formulations to the savoury and confectionery food markets. I am responsible for plant automation and the integration of the plant systems with the rest of the business.
[SAI&C]: What are the primary requirements of your plant control systems, functions like recipe management and reporting must surely be important?
[Andrew Craig]: Our processes are mostly short batches of a few hours duration, and each batch is different. Recipes and set-points are sent to the plant for consistent machine operation. Plant performance is monitored and reports are created on equipment and operator downtime. Trends and alarms are captured to help with plant troubleshooting. The goal is to reduce cycle times by machine and operator optimisation without compromising on quality.
[SAI&C]: When you designed your plant architecture what were the system-level criteria during solution evaluation, and which system did you choose?
[Andrew Craig]: We needed decentralised I/O. The old days of taking lots of wiring looms to a central switch room and PLC are gone. Now the wiring is run locally to small I/O stations and the information is transported to the central PLC using a single fieldbus cable. Beckhoff supports almost every flavour of fieldbus, we standardised on Profibus since the Ethernet industrial standards were not readily available from all manufacturers. Smart devices like motor drives can now be interrogated for lots of information to run the plant better. We have a scada system and we needed easy integration with this using an industry standard like OPC, which Beckhoff supports.
[SAI&C]: What particular capabilities did you consider important for integration?
[Andrew Craig]: The Beckhoff choice allowed us the flexibility to build both the small and large systems we required all with the same components and programming languages. We can start small and grow big or even split I/O stations into many pieces with very little PLC work. Cost is important and Beckhoff uses standard PC CPUs in their PLCs and I/O stations which really brings the costs down, this also means that their processing power jumps every year as the CPU speeds increase.
[SAI&C]: With respect to the food and beverage industry, and its unique problems, how has your control architecture allowed you to meet these requirements?
[Andrew Craig]: Beckhoff components are low cost and easy to install. We generate many new recipes a week and we are growing at a fast pace. This means a continual growth program which requires quick and easy plant upgrades. The I/O block idea connected with a fieldbus really suits this kind of expansion. Beckhoff has almost all the fieldbus types and terminals that allow us to interface all the devices we need to. The cost factor is also very relevant, since we may install a plant and then overhaul it within a year to cope with a new customer requirement.
[SAI&C]: Scalability sounds important, will your current system be able to accommodate your future expansion needs?
[Andrew Craig]: Beckhoff uses the same program for all their PLCs and it is written using the IEC61131-3 international standard for PLC languages. We can add and remove systems to the PLC with downtimes of less than an hour. If there is too much load on one PLC then we can easily move the I/O station and software to another PLC in a few hours.
[SAI&C]: You have a lot of PLC and control experience. How has the new technology made life easier for instrumentation engineers?
[Andrew Craig]: There is great variety in the range of components available from Beckhoff. By using specific cards rather than generic digital and 4-20 mA loops we get better diagnostics and eliminate many potential errors along the way. A good example is a temperature card, using traditional methods one would use a probe to generate a signal, say 4-20 mA, this would then be transmitted and would need reconversion to value. Now we have the probe connected straight to the card, which gives us the value directly. Also, the temperature value in the PLC is always scaled by 10, whereas traditionally there would be two scaling steps with variable scaling that would cause lots of errors. Installation and troubleshooting are also easier since these terminal cards have an error indication specific to what they are measuring. Many problems can now be sorted out without resorting to looking at the values in the PLC.
[SAI&C]: How do you find the service and technical support for your chosen supplier?
[Andrew Craig]: Beckhoff has a South African branch with staff who have many years of experience using the systems. Service and support has always been good. It also helps that we are in the same time zone as the parent company in Germany so in an emergency they can get a hold of the developers and get quick answers.
[SAI&C]: You are now using embedded controllers as your PLC and PAC in the plant, have you found them more useful than standard PLCs?
[Andrew Craig]: The beauty of an embedded PLC is that it has access to standard services available on a Windows server. We currently send e-mails and SMSs direct from the PLC. A web server on the PLC is also available. Standard PC applications can also run on the PLC if required to interface with external software such as databases. Another advantage of an embedded PLC is that many features can be added without upgrading the hardware, one need only install a new library.
South African Instrumentation and Control thanks Andrew Craig for his time and the insight provided in his answers.
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