Detection and diagnosis of oscillation in shell and tube heat exchanger process

Abstract

Oscillations found in process control loops are the visible indications of process deterioration. The presence of oscillation in an industrial control loop may reduce quality of the product; increase the rejection rate and energy consumption which may result in reduced profitability. Many techniques stated in the literature for oscillation diagnosis has their own benefits and limitations. Performance assessment of a single control loop is a valued procedure to spot suddenly rising faults and slowly emerging degradation. In this paper, the oscillations present in the process variable of a Shell and Tube Heat eXchanger (STHX) process are diagnosed using the Higher Order Spectral Analysis (HOSA) in MATLAB. From HOSA, bispectrum, modified bispectrum and bicoherence analysis technique is applied to the laboratory STHX process to spot the probable root cause for oscillations.