Business Accent

Adding value through the process dashboard

Process control is an effective way to check and reduce inefficiencies in real-time, say H Krishnan and R Krishnaiah in the concluding part of a two-part series

Having captured and loaded production data into the SAP R/3 system for daily report processing, process engineers were interested in getting real-time information for better process control. Real-time data was available through workstations, but gave factual data. What was needed was real-time information (and not data) indicating the impact of operator actions on the bottomline.

In cement production, the focus is on controlling critical performance parameters—power and fuel consumption. Hence these are reviewed by managers closely. However at Rajashree Cements (Grasim Industries), fuel consumption (measured as Kcal/Kg of clinker production) is not directly measured in the PLC systems. A heat balance sheet is manually prepared wherein the total heat input is identified, and various losses estimated based on process operating parameters such as air flow, temperatures across kiln, ducts etc. From these, data fuel consumption (heat from coal burning) is calculated. A sample sheet is shown here (Heat balance of the kiln). Earlier, it was calculated manually, but now, it is generated by the PLC system on a real-time basis.

Due to the complex calculations involved, and the need to collect more than 20 process parameters, the heat balance is not calculated continuously. Once in two days, or during start ups or process upsets, data is taken from log sheets by process engineers and calculations made. Hence the control room operators are not able to monitor the impact of their actions upon these factors in real-time, except in an indirect way.

Since this could contribute directly to operational improvement through better monitoring, our team stepped in to provide a simple visual display for the control room operator. The steps involved were several.

• Identifying the heat input, heat loss factors.
• Identifying the underlying theoretical calculation formulae.
• Identifying the process parameters required
• Identifying the instrument tags for these parameters, if they are already measured by the PLC system
• Provide input screen for parameters not captured in PLC system, as well for the constants.
• Develop the stepwise calculation.
• Connect the tags with parameter values in a spreadsheet, for constant real time updation from PLC
• Make a visual display of critical performance parameters. (heat input, heat output, loss of heat, heat utilised from fuel (Kcal/kg of product) and false air in the system

Environment:

Data was picked up from ABB MP280/1 system through an intermediate real-time data analyser system named OSI-PI. Since a number of calculations were involved, Excel was used as the interface for input as well as for display of calculated output.

The final output sheet showing heat utilised, false air (%) in the system is shown below. These values change based on real-time values of tags.

Benefits:

• Control room operator can monitor critical parameters and can also see the effect of his action in meaningful terms for improved process control.
• Due to automation it is monitored continuously instead of once in two days.
• Since this is an application using TCP/IP over LAN, it can be installed in any PC even if it is away from the control room.
• Though the data can be monitored in real-time, to prevent network choking, data is refreshed.

Lesson: Visual display and continuous feedback leads to better operations.

H Krishnan, IT Head and R Krishnaiah, Senior Manager, Process of Rajashree Cements