Root Cause Detection of Oscillation in Shell and Tube Heat Exchanger Process

Abstract

The key emphasis on Control Loop Performance Monitoring (CLPM) includes the detection of oscillations in control systems. Oscillations are the results of plant performance degradation and are a very common problem that occurs in the control loops of the process. This paper discusses the technique for detecting oscillations in process variables. The occurrence of oscillation in control loops, results in deviation from the setpoint, hence reducing the productivity and thus the profitability. Oscillations in control loops may be due to several causes such as aggressive tuning of the controller, external disturbances and sometimes may be due to stiction in control valve. Low maintenance of valves frequently produces large oscillations in a process which in turn affects the throughput. In time domain, detection of oscillations is tough when the signal includes disturbances. In frequency domain, Bispectrum analysis is a great tool for the detection and analysis of oscillations. To detect the oscillatory behaviors, the Modified Bispectrum tool was applied to a highly nonlinear Shell and Tube Heat Exchanger (STHX) process.