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Dairy plant automation
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Monday, 27 December, 2010, 15 : 42 PM [IST]
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C S Sashi Kumar, BV Venkeshaiah, H Arun Kumar, and G Mahesh Kumar
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“The small, local dairy with largely manual operations has become obsolete and has been replaced by large centrally located units with factory style production. Processes in small dairy are supervised by a small number of skilled persons who starts and stops machine, operates valves, cleans the equipment at the end of run all by hand. So there was need for mechanization and automation of processes in dairy plant. Processes in the small dairy were supervised and controlled by a few skilled people who carried out most operations manually and also cleaned the equipment at the end of the run, by hand. As dairies expanded, both the number and size of the machines grew, as did the number of manual operations required. Cleaning, in particular, was a laborious business -- every machine that had been in contact with the product had to be disassembled and cleaned by hand at least once a day"
India stands number one in the world with respect to milk production with an estimated output of over 108.5 million tones in the year 2008-09. This is the right time for Indian formers to think for further improvement of milk quality by adopting clean milk production practices. This quality improvement is not only for the economical betterment of the dairying community but also to gain better milk price at international standards. In this direction semi or fully automated plants are being used in the country, particularly in the dairy plants which are producing ultra high heat treated units (UHT), the milk which can be stored at room temperature without refrigeration.
In this contest an attempt as been made to know about dairy plant automation.
Automation is defined as "Systematic supervision of a component of a process with the help of mechanical or electronic systems which replace human observation, decision and action."
The fully automated milking processes were first generated in the mid-seventies. The growing costs of labour in several countries were the main reason to start the development of automatic milking. In automatic milking systems (AM-systems) cows are milked by a robotic milking system without direct human supervision. The first milking robots were installed on commercial dairy farms in the Netherlands in 1992. The breakthrough of automatic milking came at the end of the nineties and at spring 2002, more than 1250 farms worldwide milked their cows automatically.
Automation is a fast-moving sector. Only a few decades ago, process control systems were based on electro-mechanical relays, wired together in a logical pattern. They were replaced by hardwired electronic control systems, which were faster and more reliable, as they contained no moving parts. The next improvement was programmable control systems with the logic expressed in data bits stored in an electronic memory, not in the physical arrangement of the wiring. This not only made it easier to modify the program whenever necessary, but also reduced the cost of the hardware. Now the new processors can be used to control a single machine, or build up a total control and management system to make an entire plant more productive.
The purpose of automation is to increase process efficiency, safety, productivity and product quality. The dairy industry is uniquely positioned for easy adoption of computer automation because:
Automation is generally achieved by means of automatic process control system that has been programmed with set of instructions. Control system communicates with every component critical for successful operation of process.
Why do we need automation?
Several aspects must be considered when designing automation. Therefore, the final production solution of a plant is always a compromise between product-related, process-related and economic aspects, in which external demands on the plant must be satisfied. These external requirements relate to factors such as legislation, type and amount of product, product quality, hygiene, production availability, flexibility, labour and
economy.
The product-related aspects include raw materials, product treatment and quality of the end product, while the process-related aspects include selection of process equipment to satisfy external demands. Even if the processing units in a plant are chosen primarily to achieve the stated product quality, various compromises must be made, particularly if many different products are to be manufactured.
The most effective benefits of automation are indicated below:
Safety: It is guaranteed by the fact that the control system always operates and monitors the process in exactly the same way during each production run. Unwanted mixing of different products, as well as overfilling of tanks and other errors resulting in product losses and production disturbances is avoided.
High product quality: The fact that all stages in the process are always operated in exactly the same way means that the end product will always have the high and uniform product quality with respect to physico-chemical, microbial and sensory characteristics.
High reliability of production: In manually controlled plant risk of stoppages is high because even skilled operators have difficulty in supervising large-scale processes adequately. Such risks can easily be eliminated by process control/automation.
Production economy: Precise control of the process means that product losses and consumption of service media, cleaning solutions and energy are kept to an absolute minimum. The production economy of a well-designed and adapted control system is therefore very good.
Flexible production: Flexible production can be achieved by programming the automation system with different production, alternatives and production recipes. Production can be changed simply ' by altering a recipe instead of re-, programming.
Production control: The automation system can also provide relevant data and information for production in the ' form of reports, statistic analyses, etc. These data are tools for more, precise management decisions.
Process control equipment: Automation or process control begins with various parameters being controlled with the help o| process control equipment, which include;
Transmitter. It is the sensor that is continuously sensing! The parameter being controlled and as the name implies, it transmits the signal corresponding the magnitude of: the measured variable.
Controller: The device that serves to maintain the process variable Value at the set point is the controller. The controller receives the information about the measured variable and compares with a signal corresponding to the preset value of the parameter.
Actuator or Control Element: If the magnitude of the ' difference between the desired and measured value is greater than allowable limit, the controller sends signal to the actuator, which physically responds to the controller signal and carries out the instructed function and controls the controlled variable.
The cycle of comparison and correction of the measured variable is repeated until the measured variable is within the preset limits of the desired value. The most widely controlled parameters in a dairy plant are pressure,
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