Process variability reduction in flow control and wedge flowmeter performance evaluation

Abstract

In modern flow control settings, a slow controller sampling rate is often much slower than a flowmeter response, and flowmeters are often selected without consideration of the dynamic response characteristics. However, for fast loops which necessitate a high control sampling frequency, negligence in flowmeter selection might result in an undesirable control performance degradation. Such associated research is expected to be critical to design and evaluation of new flowmeters, i.e., wedge flowmeters in this study, but little work has been found in the public domain to address this issue. In this paper, a new way of calculating process variability is proposed to fast-track the evaluation of flow control performance and cost saving. In addition, based on frequency response analysis, a systematic study of how dynamic response characteristics of flowmeters impact flowmeter accuracy and process variability is presented. Moreover, the impact of controller sampling rate on process variability is researched. Last, the closed-loop stability of the flow control loop with new wedge flowmeters is evaluated for a wide range of its targeted applications. The results demonstrate that a flowmeter with a faster response will always lead to process variability reduction for a given controller sampling rate, and that with careful controller set up, a flow loop with wedge flowmeter is still stable despite relatively slow dynamics.