Understanding Batch Process Management
Published on : Sunday 05-07-2020
Chandrashekhar Limaye elaborates upon how Batch Process Management has evolved to versions that are more flexible, easier to use and less expensive.
What is common to manufacturing of disparate products such as chocolates, tomato ketchup, shaving cream, shampoo, toothpaste, fragrances, adhesives, medicines, paints, inks, polymers, lube oils, pesticides, surfactants, etc? They are all batch processes. Each product in every category has a unique recipe, operating procedure and may be a common set of equipment for a class of products in which it is manufactured. For example, a paint manufacturing plant manufactures 20 different types of paints with the same set of equipment, but each product will have its own recipe and operating procedure. Traditionally, these products were being manufactured manually. Their requirement for instrumentation was only a pressure gauge, temperature gauge, weighing scale and a lab for testing the quality. With increasing scale, complexity of process, multi-locational manufacturing, regulatory compliances, paucity of skilled and experienced manpower, competition, they felt the need for automating their operations.
Evolution of Batch Process Management
During the initial period, automation involved transfer and charging of liquid raw materials and solvents from respective storage tanks to the batching tanks, mixers or reactors, remote monitoring of parameters like temperature, pressure, level and flow and remote operation of valves and motors. It was easy to achieve this using the available PLC/SCADA systems or DCS. Automatic temperature control of batch reactors was attempted using the conventional PID control techniques, without much success. Heavy investment in the automation system, field instrumentation and upgrading the manpower did not yield the desired results. The quality of the product, batch cycle time, productivity still depended on the knowledge and skills of the operator. Less than half of the process operations could be automated, and the rest continued to be manual. An operator was required to carry out field operations as well as go to the control room for carrying out the automated operations.
To reduce the dependence on human skills, it was necessary to transfer the recipes and procedures to the automation systems. It was partially achieved by providing recipe and sequencing functions in the PLC/SCADA or DCS along with some customised software. However, due to frequent changes in formulations and addition of new products, the recipes and sequences were required to be changed. For carrying out these changes, services of the automation system engineers were frequently required. The dependence on the automation system vendor was not only expensive, but it was also prone to exposure of the confidential product formulation information to the automation system vendors. Another major problem was
that the SCADA or DCS stored the historical data on a time basis and not on a batch basis. It was difficult tracking a batch performance on time based historical trends. There was no means of recording the raw materials consumed, key parameters in critical phases, operator actions. If a batch was spoiled, there was no means of tracing the reasons.
ISA S88 Batch Standard
In order to address above problems and to bring about a uniformity in various approaches in managing the batch processes, ISA – the International Society of Automation, developed a batch standard ISA S88 in 1995, which was updated in 2010. It is still the only standard widely followed globally. S88 has broken up batch operation in three parts, a process model defining the process stages, process operations and process actions, a physical model defining the manufacturing equipment and a procedural model defining the recipe procedures. Let me explain by taking an example of a paint manufacturing process. The process involves charging of various oils, solvents, emulsions, resins and additives in predefined proportions, in a predefined sequence in a mixer, mixing them for predefined time at specified agitator speeds, testing the quality of the product and discharge. Operation of weighing and charging of each raw material is a processing action and defined in the process model. It may be an automated action or a manual action.
The physical model begins with the enterprise (e.g., Kansai Nerolac Paints) which may contain a site (e.g., Jainpur plant) which may contain areas (e.g., Water Based Paints block) which may contain process cells (e.g., Mixers) which must contain a unit (e.g., Mixer M-101) which may contain equipment modules (e.g., Agitator) which may contain control modules (e.g., a Motor) Some of these levels may be excluded, but not the Unit. The procedural control model consists of recipe procedures (e.g., the formulation giving names and quantities of raw materials) which consist of an ordered set of unit procedures (e.g., Operating procedure) which consist of an ordered set of operations which consist of an ordered set of phases.
Model Based Approach
A Batch Management System based on ISA S88 allows the physical model to be created based on the P&I diagrams and a database of all materials. Programs are developed in the PLC/DCS for each processing action, whether auto or manual. A recipe module allows creation of new recipes, modification and deletion of existing recipes. A recipe contains the formulation i.e. names of raw materials with their quantities, usually in percentage of the total batch size, set points of parameters to be controlled such as temperature or rpm and the sequence of steps or phases of execution. There is a facility to start, stop, pause, resume and abort the sequence. Once the batch is started it executes the sequence as defined in the recipe, the processing actions in each phase are carried as defined in the process model and programmed in the PLC/DCS. The physical model and the process model are one-time developments and do not change unless there are changes in the equipment or processing actions. Only item that changes with each product is its recipe. The recipes can be easily developed in the recipe module by a chemist in the user company and does not require a control system engineer.
System Architecture of a Typical Automation System with Advanced Batch Management The S88 Batch Management System is a separate system at the supervisory level in the control system hierarchy. It uses an open database like SQL Server for storing the materials data and the recipe information. At the edge level, you may have a Hybrid DCS or a PLC/SCADA based Automation system. As the batch sequence is executed phase by phase, important batch data such as the raw material quantities added, status of important process parameters, quality parameters, time stamp, etc., is pushed to the SQL database. By querying the batch data, Batch Management system develops various reports such as the Batch Log Sheet (Electronic Batch Record), Raw Material Consumption, Energy Consumption, Equipment Utilisation, Variance from the benchmark figures, etc. The data can be analysed to compare performance of various batches for the same product for the key performance indicators (KPIs), e.g., maximum temperature, viscosity, specific energy consumption, etc. It is also possible to integrate the Batch Management System with the ERP system online.
Some automation system manufacturers claim to have systems with Batch Management built into the Controller or SCADA. However, such system have several limitations and are not as flexible and user friendly compared to the Batch Management systems with full-fledged Batch Server with open data base at the supervisory level and fully complying with ISA S88 standard.
Specifications for Batch Management
While preparing the specifications for the automation systems for batch processes, the requirements should be clearly specified. If it just mentions Recipe based batch management system, one can get away with offering the fixed recipe and batching functions normally available in most PLC/SCADA or DCS as standard. When you need a flexible batch management with detailed reports, you must specify that it should be an ISA S88 based system along with the details of the recipe, batch and reporting functions, and integration with ERP, etc.
Although the S88 standard was available since 1995, it was not very popular since the Batch Management Systems based on it were far too expensive and its implementation required a lot of customisation, which in turn required highly skilled engineers for implementation and support. The automation systems in those days were also not so open and flexible, which made adapting to such Batch Management systems difficult. Over the period, the automation systems as well the Batch Management systems have evolved to versions that are more flexible, easier to use and
less expensive.
Cost Effective Batch Management Solutions from Supertech
Supertech, a Master Alliance Partner with Schneider Electric for Control Systems and Hybrid DCS and CPG segments offers cost effective Batch Management solutions using the EcoStruxure Hybrid DCS from simple to complex systems depending on customer requirements and budget. Batch Management is based on Wonderware InBatch, Recipe Manager Plus or SUPERBatch.
SUPERBatch is an ISA S88 based Batch Management software developed indigenously by Supertech and has been used effectively in a variety of applications in Paints, Resins, Adhesives, Specialty Chemicals, Pharma API, F&B, Consumer Packaged Goods, etc. Some of these systems have been integrated with MES and ERP and others are ready for such integration. Major benefits achieved by the users are consistency in quality, reduced batch cycle time, better utilisation of equipment, improved productivity, reduced energy consumption, less manpower, reduced dependence on human skills, traceability, and analytical tools for improvement. SUPERBatch is also available on Schneider Electric Exchange portal. (For details, please click on the following link: https://shop.exchange.se.com/en- US/apps/46961/superbatch/overview)
Chandrashekhar Limaye is the Director of Supertech Instrumentation Services (India) Pvt Ltd, which provides turnkey Automation Solutions to the Process Industries. Before launching Supertech in 1995, Mr Limaye spent 18 years in the process industries. His specialisation is the application of advanced instrumentation and control systems. Supertech delivers solutions in Process Automation, Batch Management, Intelligent Motor Control, Energy Monitoring, MES and SAP Integration in Specialty Chemicals, Resins, Paints, Polymers, Pharmaceuticals, Food & Beverages, Lube Oil Blending, and Agrochemicals throughout India and abroad. Mr Limaye is a senior life member of ISA (International Society of Automation) and past District Vice President ISA District 14 (Asia Pacific) and is associated with educational institutions in India, guiding their curriculum development.
