Applied Control

Maximising return on investment is an important goal for all plant managers. Good regulatory control is the foundation of an effective control system in any Lean Manufacturing Environment. Although this seems obvious, its importance can not be overstated. Typically, 80% of potential savings from process control can be realised simply through better control of the process variables. 

In field testing of thousands of control loops in hundreds of plants, the following summarizes the opportunities that exist for improvement in the average control system:

-      More than 30% of all controllers are operating in manual

-      More than 40% of installed control loops produce less variance in manual than in automatic control! 

With the average process control engineer in charge of about 500 control loops, it is not surprising that badly tuned control loops are estimated to cost the industry about £30.000,000 per annum. Profits are being lost in most plants due to poor performance of the primary controllers. 

Plant managers often assume that a £multi-million automation project, i.e. installation of a Distributed Control System, DCS or Programmable Logic Controller, PLC systems will quickly translate into significant process improvements, savings and hence return on their investment. It is true that many automation projects do result in savings in variable costs through reduction in the workforce. However, savings in raw materials and energy through process control, can not be achieved by automation alone. Variance is not only caused by poorly tuned loops, but also by unidentified equipment and instrumentation problems and poorly understood dynamic interaction amongst various control loops.  

Although most of today's plant DCS/PLC Systems are capable of carrying out detailed analysis of control loop performance, such capability is not readily available on the control engineers' desktop. Access to plant data using Factory Information System, FIS in ‘near real-time’ is essential for performance analysis. Furthermore, historical plant data can be used for process diagnosis and trouble-shooting. There is a number of excellent commercially developed software as bolt-on for performance analysis of primary controllers and process optimisation.

It is time we made use of the available technology to run our plants more efficiently and profitably.