This article deals with the analysis of performances of electric actuators for control valves in industrial control loops. The objective of the recent collaboration between University of Pisa and CLUI AS is to assess potentials and benefits of control valve electric actuators, by testing and comparing devices of different typologies and manufacturers. As a premise, it should be noted that pneumatic actuators still represent the most commonly used actuation devices in the process industry, mainly because of high performance and fast response. In recent years, electric actuators, as a result of their enhanced features, are finding increasing applications in the area of process control. Anyway, some practical aspects, such as the degradation of the valve seat, an excessive tightening of the seal, and an expansion of metallic components due to high temperature operation, can cause malfunctions, and in particular, phenomena of wear and friction within a control valve regardless of the type of actuator. In fact, pneumatic and electric valves differ only in the actuation system; while the valve body, subject to most of the friction forces, is absolutely the same. In detail, the present work has been focused on the analysis of a recent electric actuator installed on an rotary control valve, and tested in the last biennium in an pilot plant, owned by ENEL in Livorno (Italy). Specific experimental tests were carried out, by collecting operating data in open-loop and closed-loop mode. The validity and effectiveness of the performance was verified in nominal and faulty conditions, in particular, by introducing a dead-band. Furthermore, performances of this electric actuator was compared with that of a conventional pneumatic actuator with positioner, coupled to the same valve, installed on the same plant line, and tested in equivalent experimental conditions. In general terms, it has been confirmed that the electric actuator for control valve is a promising technology, and its performance are fully comparable - if not superior - to those of the pneumatic actuator. In particular, some simple performance indices assume similar numerical values, and also the time trends of the positional error and the limit cycles registered on polar diagram between valve input and output signals are similar.
Comparative performance analysis of an electric actuator for control valves
Bacci di Capaci Riccardo
;Scali Claudio;
2017-01-01
Abstract
This article deals with the analysis of performances of electric actuators for control valves in industrial control loops. The objective of the recent collaboration between University of Pisa and CLUI AS is to assess potentials and benefits of control valve electric actuators, by testing and comparing devices of different typologies and manufacturers. As a premise, it should be noted that pneumatic actuators still represent the most commonly used actuation devices in the process industry, mainly because of high performance and fast response. In recent years, electric actuators, as a result of their enhanced features, are finding increasing applications in the area of process control. Anyway, some practical aspects, such as the degradation of the valve seat, an excessive tightening of the seal, and an expansion of metallic components due to high temperature operation, can cause malfunctions, and in particular, phenomena of wear and friction within a control valve regardless of the type of actuator. In fact, pneumatic and electric valves differ only in the actuation system; while the valve body, subject to most of the friction forces, is absolutely the same. In detail, the present work has been focused on the analysis of a recent electric actuator installed on an rotary control valve, and tested in the last biennium in an pilot plant, owned by ENEL in Livorno (Italy). Specific experimental tests were carried out, by collecting operating data in open-loop and closed-loop mode. The validity and effectiveness of the performance was verified in nominal and faulty conditions, in particular, by introducing a dead-band. Furthermore, performances of this electric actuator was compared with that of a conventional pneumatic actuator with positioner, coupled to the same valve, installed on the same plant line, and tested in equivalent experimental conditions. In general terms, it has been confirmed that the electric actuator for control valve is a promising technology, and its performance are fully comparable - if not superior - to those of the pneumatic actuator. In particular, some simple performance indices assume similar numerical values, and also the time trends of the positional error and the limit cycles registered on polar diagram between valve input and output signals are similar.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
