Module 6. Process control and automation
Lesson 15
PLANT AUTOMATION
15.1 Introduction
This lesson will discuss the concept plant automation. Various topics related to automation such as advantages and disadvantages; architecture of plant automation; automation tools are elaborated here. The topics discussed in this lesson will be useful to the students for understanding the state of the art technology being used for dairy plant automation.
Over the last few decades unit operations pertaining to procurement, processing and distribution in the dairy and food sector is inclining towards mechanization and automation very rapidly. The main driving force at the beginning for mechanization was economic reasons, such as labour costs. Gradually, safety considerations, mandated by legislatures, entered the scene. Nowadays food safety policies became the major factor for the mechanization and automation of the process of food production.
15.2 Automation Meaning and Definition
The word ‘Automation’ is derived from Greek words “Auto” (self) and “Matos” (moving). Automation is a technology concerned with the application of mechanical, electronic and computer based systems to operate and control production. In general, automation could be considered as a process that started with machines doing the heavy work, while humans maintained the function of telling the machines what to do. However, automated systems achieve significantly superior performance than what is possible with manual systems, in terms of power, precision and speed of operation.
“Automation may be defined as a set of technologies that results in operation of machines and systems without significant human intervention and achieves performance superior to manual operation”
15.3 Types of Automation Systems
Based on the flexibility and level of integration in manufacturing process automation systems can be categorized as follows
15.3.1 Fixed automation
Fixed automation is a system in which the sequence of processing operations is fixed by the equipment configuration. This type of automation is very commonly used in case of process using mechanized machinery to perform fixed and repetitive operations in order to produce a high volume of similar parts or products.
Typical features of fixed automation are:
1. High initial investment for custom-engineered equipment
2. High production rates
3. Relatively inflexible for the accommodation of product variety
The economic justification for fixed automation is found in products that are produced in very large quantities and at high production rates. Example of fixed automation includes Distillation Process, Conveyors, Transfer lines etc.
15.3.2 Programmable automation
In programmable automation, the equipment is designed with the capability to change the sequence of operations to accommodate different product configurations using electronic controls. Set of instructions in the form of programmes loaded into the system to control the sequence of operation. This type of automation is being used where the parts or products are typically made in batches. The system must be reprogrammed with the set of machine instructions to produce each new batch of a different product. In Cheese blenders, Paper Mills etc. Programmable automation is widely used.
Some of the features that characterize programmable automation include:
1. High investment in general purpose equipment
2. Lower production rates than fixed automation
3. Flexibility to deal with variations and changes in product configuration
15.3.3 Flexible automation
It is an extension of programmable automation. This system is widely used for the production of varieties of products from the same equipment or system. This system is capable of producing a variety of products with virtually no time lost for changeover between the products. After processing, products are automatically transferred to next machine.
The features of flexible automation can be summarized as follows:
1. High investment for a custom engineered system
2. Continuous production of variable mixture of products
3. Medium production rates
4. Flexibility to deal with product design variations
15.3.4 Integrated automation
Integrated automation system is a complete automation of the manufacturing plant. The process functioning is controlled through computer system and under coordination through digital information processing. It includes technologies such as computer-aided design and manufacturing, computer-aided process planning, flexible machining systems, automated storage and retrieval systems, automated material handling systems such as robots and automated cranes and conveyors, computerized scheduling and production control. It may also integrate a business system through a common database. In other words, it symbolizes full integration of process and management operations using information and communication technologies. Typical examples of such technologies are seen in Advanced Process Automation Systems and Computer Integrated Manufacturing (CIM)
15.4 Necessity of Automation
Even though food safety and security concerns are the major driving force for implementation of automated system in the food processing plants; the industry faces other additional emerging drivers that further accentuate the importance of implementing automation as soon as possible. Integrated automation can help food and beverage manufacturers address these below emerging trends while providing important safety benefits.
1. Customer or consumer demands
2. Labour availability and reliability issues
3. Labour laws
4. Regulatory requirements
5. Supply-chain management
15.5 Advantages of Automated systems
Automated systems have got the following advantages over the manual controlling systems
1. Production of consistent quality goods
2. Reduction in production costs
3. Flexibility to meet market demands
4. Adoption to constantly changing legal demands
5. Ensures high and consistent product quality
6. Increases production
7. Reduces losses
8. Guarantees a safe operation
9. Ensures manpower savings
10. Allows for efficient production planning, execution and reporting
Overall, the aim of automation in a dairy or food processing plant or any production unit is to meet the company need to produce goods safely, in a cost-effective manner, with high and consistent quality and in the appropriate quantities to meet market demand. A typical automated system in a diary plant different level of automation is shown graphically in fig. 15.1 given below.
Fig. 15.1 Typical automated system in the dairy plant
15.6 Architecture of Automation System
Fig. 15.2 Architecture of automation system
ERP – Enterprise Resource Planning
MES – Manufacturing Execution System
PC – Production Control
Various components in an industrial automation system can be explained using the automation pyramid as shown above. Here, various layers represent the wideness (in the sense of no. of devices) and fastness of components on the time-scale.
15.6.1 Sensors and actuators layer
This layer is closest to the processes and machines, used to translate
signals so that signals can be derived from processes for analysis and
decisions and hence control signals can be applied to the processes. This forms
the base layer of the pyramid also called ‘level 0’ layer.
15.6.2 Automatic control layer
This layer consists of automatic control and monitoring systems, which drive the actuators using the process information given by sensors. This is called as ‘level 1’ layer.
15.6.3 Supervisory control layer
This layer drives the automatic control system by setting target/goal to the controller. Supervisory Control looks after the equipment, which may consist of several control loops. This is called as ‘level 2’ layer.
15.6.4 Production control layer
This solves the decision problems like production targets, resource allocation, task allocation to machines, maintenance management etc. This is called ‘level 3’ layer.
15.6.5 Enterprise control layer
This deals less technical and more commercial activities like supply, demand, cash flow, product marketing etc. This is called as the ‘level 4’ layer.
15.7 Conclusions
Automation can address the critical issues of product safety and security both proactively and reactively with its integrated logistics, material handling and warehousing systems. Proactively, automated systems reduce the number of people with direct access to products. This alone can improve product reliability significantly while reducing the risk of catastrophe. Reactively, automated systems include up-to-the minute track-and-trace functionality. This key feature of automation can easily facilitate any recalls that may be required. But beyond enhancing food safety and security, a fully integrated automation system can provide many compelling business benefits. Advanced automation systems increase visibility into food-manufacturing operations by improving the transparency and traceability of vital business information. The result is lower labour costs, increased productivity, reduced scrap and waste, and meeting, and even anticipating, the continually increasing societal and legal demands.