New Trends in Process Automation

On Sep 25, 2013

Mr. Rajeush Ballamwar,
Founder Director, Prolific Systems
& Technologies Pvt. Ltd.

Definition : Discrete & Continuous Process Automation
Discrete Automation in manufacturing involves the assembly of component parts to construct products that can be measured in units, such as automobiles, household appliances and computer systems. This contrasts with continuous process automation, which typically produces a continuous stream of product, such as chemicals, paper, foods and beverages, etc. Discrete as well as continuous process automation may use both programmable logic controllers (PLCs) and distributed control systems (DCSs) to operate and control the motors, conveyors, robots, inspection systems and similar devices, which work together to complete the manufacturing process as well chemical and other continuous processes.

Preamble
Whether it is Discrete Automation or a Continuous Automation, the objective of them is the same. It is expected to bring about benefits of, among others,

Productivity
Reliability of Manufacturing
Manufacturing Process Consistency
Yield Improvement
Purity Improvement
Labour Cost reductions
Waste Reductions and
Energy Usage Savings

Though the importance of each one of them can vary depending upon the Industry vertical one operates in and the sensitivity of the issue from buyer’s perspective. To quote, Steel and Cement industry will eye on Energy usage savings as primary factor, whereas Pharma industry may look at consistency, purity as crucial factors. In order to understand latest trends in process automation, let me focus on Energy usage optimization and consistency + purity aspect by way of Discrete and Continuous Automation with the help of 2 real-time examples.

Importance of Energy Saving through Discrete & Continuous Automation
Energy has been there for ages either in potent or in motion form. And its conversion to an electrical power was a big and important milestone in the history of mankind. With that, an electrical energy has become a commonplace need in today’s world with the invention of variety of electricity-run gadgets and appliances. With such rapid development in usages of Electricity, the need of monitoring and conserving electrical energy is being felt more severely than ever before. Why energy saving? is well known because of following reasons.

Utility Costs account for 15% or more of the manufacturing costs.
Much higher in Energy intensive segments.
Awareness levels are low and now on the rise.
Often a neglected area.
Savings directly add to the bottom line.
Social and ecological responsibility as most of the power today is generated using limited fossil fuels.

As we all know, Consumption = requirement + wastage. Some wastage is avoidable. We can look forward to maximizing efficiency of the electrical circuits and thus reduce or minimize wastage.

The major loads that consume electricity are of industrial and of utility nature. Major among them are Fans, Pumps, Blowers, Agitators, HVAC (Heaters, Ventilators, Air Conditioners) & Lighting etc.

Today, there are various techniques that enable measurement or monitoring of the electrical power that gets consumed by these mostly industrial equipments. Prominent among them is the energy meter or also known as load manager. A sophisticated one also called a power analyser. It is an electronic device that captures parameters associated with quantum of power used and quality of power drawn by the loads. The parameters viz Voltage, Current, Power Factor, Energy in KWH, Active/Reactive Power and even harmonics give an idea of the loading of the electrical appliance. These meters today are offered by variety of manufacturers including the domestic ones.

These digital energy meters are available for single/three phase variants. Most of these come with in-built communication ports for connectivity with computer and other digital controllers (read, PLC). Let us look at how energy monitoring has helped a pharmaceutical company to manage their 21 chillers & compressors.

Figure 1: Shift Report

Existing System.
No prior automation in energy management. With rising electricity and operation costs, the need was felt for achieving higher efficiency in usage of utilities. As a result, it was decided to cover the 21 chiller systems spread across different plants under a single Energy management system. Problems encountered by the company

The 21 chilling plants were about 150HP each! With increases in production of various APIs, the number of chilling plants and air compressors for cold water and instrument utilities kept on increasing. As each new chiller or compressor needed to be added, space was created and the needed power was arranged. Analogue energy meters were also installed to monitor the energy consumed in each chilling plant.

The chilled water was also served at various temperatures ranging from -40degs. C to 5 degs. C! Only the energy consumed by these chillers was being measured, with no accounting for the energy effectively utilised. It was also suspected that plants that were ageing or poorly serviced were drawing disproportionate electricity. Again shift personnel were assigned the task of keeping elaborate logs and preparing various reports. Time was wasted in preparing these reports to such an extent that it was impossible to analyse these reports and pinpoint the sources of inefficiency! Again, as the shift personnel had other tasks, these tasks or the quality of reporting would suffer! The purpose of regulating the energy usage remained un-attended and as a result the electricity bills were continuously increasing.

Proposed Solution
The existing energy meters were all be replaced by digital energy meters, which had an RS-485 Modbus port on each. A network of 6 small PLCs shared the data acquisition from the 21 energy meters. Each PLC also had enough I/Os for monitoring critical signals from the compressors & chillers. They also had to monitor the flow and temperature data in each chiller. Ethernet would then link all the PLCs to each other and also to the SCADA station.

The logic of the PLC was created to read in the flow-rate of brine at each chiller; the inlet and outlet pressures at each compressor and efficiency of the compressor and chiller would be calculated against what was theoretically possible at the energy being consumed! That is to say, from the flow-rate and temperature difference at the chiller, the produced refrigeration tonnage was calculated and the same was expressed in energy units. Likewise, the pressure data could enable calculation of mechanical work done by each compressor. Efficiency was estimated as a percentage of the theoretical, when compared with the electricity actually consumed.

SCADA with in-built data logging capabilities and synergistic interfaces with the PLCs. Mimics of each chilling plant were created using for on-line monitoring. Time stamped data logging and report generation was so extensive; the customer also needed the reporting in MS-Excel in the same format as existing. To this end Visual Basic was also needed.

The functioning of each plant was readily apparent at SCADA. Even at first glance, it became clear that many plants were being under-utilised. Those could be shut down with their small loads being transferred to other units with spare capacity. Above all the operators could finally concentrate on the basics of manufacturing and cost cutting rather than being burdened by the task of report generation. It became clear that the chilling plant’s efficiency was highest at a particular operating load. Load was managed such that any plant in operation had its load approximately near its optimal.

The relative differences in efficiency between plants of similar rating also became prominently displayed. It is expected that after servicing of these units, the energy usage will become even better. As lesser number of plants was now operational at any given time, more units became available for preventive maintenance. Customer’s engineers’ feedback is that the automation of the EMS would have been justified on the reliability aspect alone, to say nothing of the huge bonus that accrued in terms of reductions in the electricity bill

Let us look at another real-time application where how continuous process automation helped a pharma company (you may read it as Chemical company).
It was a Solvent Recovery Plant, with long columns. Plant owner was in a situation with following thinking.

The plant prior to automation was discrete instrumented for measurement of temperatures, pressures, levels etc.
All control decisions were fully manual.
Client felt that it was spending more on utility
Yields were much lower.
Technical and environmental challenges

The plant needed a reliable control algorithm that incorporated a good understanding of the distillation process

Technical description of the project
An indirect feed-split control strategy was taken up to form the basis of control

The combination of PLC + HMI (Human Machine Interface) + Process Instruments (Flow meters, Level transmitters ) & Valves became the part of Automation & Instrumentation system. Our Customer’s expectations bordered on the cynical based on past experience. Installation of the new instruments was done with least disturbance to production. Loop after loop of PID and cascades were tuned perfectly. Our studied approach and the excellent quality of the instruments showed up as magical control.

Their engineers had never seen such perfectly tuned loops. Level controls in reflux-drum and reboiler as dictated by the new algorithm was better than what anyone believed possible Fluctuations in column temperatures and intermittent flooding were finally solved Company achieved benefits of Purity improvement, Consistency and Reliability of operation and also energy savings.

Latest Trends in Process Automation
Though change in the technological aspect for Automation is a gradual process, a few trends are easily noticeable, especially in the global contest. Laborious cabling between the sensors, control instruments (read, Valves) and Control System is now widely being made digital, thereby saving on installation time and on maintenance.

With this, all sensors and control instruments are also come with digital interface. Motor Control Centres (MCCs) are also made digital for their monitoring and remote control. Today, it is not just important to log data of various process parameters on the computer, but it shall strive to give statistical analysis and action oriented messages or automated action commands. These are aimed at giving benefits as enumerated in the beginning of this paper.

Conclusion
Truly, Process automation is the order of the day to bring about changes in the environment that we work in, whether it is for safety of plant and personnel or bringing about consistency in the products shipped out.

Author
Mr. Rajeush Ballamwar,
Founder Director, Prolific Systems & Technologies Pvt. Ltd.
A Turnkey Contractor for Elect, Inst, Aut & IT, Global Testing Laboratory Provider and Trainer
Tel : +91 9820089094
Email : [email protected], Web: www.prolificindia.com, www.prolifictraining.com