Performance Of Control Valve Research Articles

Effect of spool posture on control valve performance considering outlet shape and large fit clearance

The control valve serves as a crucial component of the downhole integrated water distributor in water injection oilfields, enabling waterflooding into oil reservoirs. However, the control valve opening cannot be adjusted in the practical environment, resulting in ineffective injection, which means that the spool is stuck. Furthermore, it is difficult to observe the details of the spool sticking and reproduce this phenomenon during testing. To reveal the mechanism of sticking, this paper establishes a CFD model, which considers the spool posture, large fit clearance and outlet shape, to study the spool performance. Additionally, the proposed model is demonstrated experimentally and theoretically. It is found that larger fit clearances result in significant distortion of the flow characteristic curve, with a flow regulation rate of only 90.87% observed when the fit clearance is 0.25 mm. Furthermore, the lateral outlet causes a reduction of 77.27% and 69.15% in radial forces for eccentricity or inclination angles changed from 0° to 180°, respectively. Sticking is strongly correlated with radial forces, the axial force is contingent upon the spool end face area. These findings provide crucial theoretical guidance for the design of control valves.

A method for improving flow control valve performance based on active differential pressure regulation

The existing flow control valves (FCV) generally have problems with low flow control accuracy, high-pressure loss, and difficult flow fine-tuning. Therefore, this paper proposes a method of active differential pressure regulation (ADPR) to improve FCV performance. An additional controllable force is added to the compensator spool to change the force balance state, so as to realize the differential pressure regulation. Next, the strategies of disturbance compensation and nonlinear flow correction are designed. And the feasibility of the ADPR method and strategies are experimentally verified. The experiment results show that by continuously controlling the force, the differential pressure and flow of the FCV can be changed in proportion, and the flow range can be actively adjusted; compensating the flow force, the flow control accuracy of the FCV is improved, and the flow control error under steady-state load is reduced from 27% to within 7%; adopting the nonlinear flow correction strategy, the flow can change with the expected target flow, which has a good consistency.

Hydraulic sensitivity analysis of discharge control valve: An experimental approach

Unexpected variations in spring characteristics could affect the performance of discharge control valves. In this study, a novel experimental procedure was used to quantify the effects of the spring's elasticity coefficient and unloaded spring length on water delivery by the discharge control valve. Based on an average sensitivity index reflecting the performance of a given structure, the hydraulic behavior of the discharge control valve was quantified. The results indicate that the valve was sensitive to the unloaded spring length, especially when it was slightly smaller than its nominal value. The discharge control valve performance was affected no more than about 16% by ± 4% variation in spring elasticity. In general, spring elasticity variations affect the valve of the smaller design discharge more than that designed for a higher discharge value. The outcome of this study should help design and fabricate discharge control valves to enhance their performance.

Generic framework for valve stiction detection and compensation with ANFIS-activated dual-mode MPC

Due to its continuous motion, control valve performance tends to deteriorate over time due to the presence of static-friction or also known as stiction. This, in turn, leads to high variability in product quality and an increased frequency of valve maintenance. Model Predictive Control (MPC) based stiction compensation methods can remove oscillations caused by stiction but it assumes that stiction is known a –priori to exist in the related loops. To overcome this limitation, an integrated framework is proposed to automate the detection of stiction using only process variable and controller output while compensating for stiction with MPC. The detection algorithm, which was validated using industrial data, uses an adaptive neuro-fuzzy inference system (ANFIS). Out of the 78 benchmark industrial loops tested, the proposed Intuitive ANFIS-based Method (IAM) has a detection accuracy of 65%, placing it on par with the best of the currently available methods reported in the literature for loops with stiction. Within the proposed framework, the detection component only activates the MPC-based compensation when needed. In a simulation of a multivariable process, it is demonstrated that the dual-mode MPC manages to eliminate oscillation caused by stiction with no chattering. This results in better overall performance when controlling a loop throughout the service life of the valve.

Design of Smart Positioner for a Control Valve to Optimise Backlash Problem

Control valves are an increasingly vital component of modern manufacturing around the world, since control valves are mechanical devices, their performance is less than ideal, and degrades over time. For a plant to perform optimally control valve performance must be tracked and maintained. Backlash is one of much invertible nonlinearity present in control valve, if a valve has some backlash, the loop will have a tendency to oscillate, which will get bigger and bigger as time goes by and will also make the loop slower to respond. At present, pneumatic valve Positioner is used which uses mechanical cam to correct the non-linear nature of control valves. Pneumatic valves Positioner typically are very simple and do not implement integral control. In this project a novel low cost Smart Positioner is designed and developed to improve the performance of control loops. A rotary potentiometer with a linear actuator is used to give feedback signals to the controller of the current position of the control valve. A specially designed control system which is cascade in nature increases the performance of the control system. The Position sensor control being a slave controller acts faster to position the valve and thereby avoiding backlash problem. The developed design is implemented in the Second Order Two Tank Level control system and the performance metrics such as Rise time, Settling time and Steady state errors evaluated found improved after implementing smart Positioner. The oscillation of control valve was found minimum compared to pneumatic Positioner which clearly an indication of reduced backlash in the system. The low cost smart Positioner is RVDT which fixed on a pinion rack and interfacing the proposed second order system using MATLAB for error analysis and LabVIEW software and NI DAQ6008 to run the proposed second order system.

Compressive and sealing characteristics of PTFE under cyclic loading-unloading

Compressive and sealing characteristics of PTFE under cyclic loading-unloading at room temperature are studied in order to evaluate the cyclic sealing performance of control valve comprehensively. The unloading characteristics are different from the loading ones, therefore there is hysteresis between the unloading and loading curves. Compressive hysteresis is the main factor that causes sealing hysteresis. The leakage rate of PTFE complies with the power law before it enters the relatively stable region. Lastly, the effect of working pressure on the compressive and sealing characteristics is discussed. The experimental results show that the working pressure has little effect on compressive deformation but has a great influence on leakage rate.

Improving the pneumatic control valve performance using a PID controller

Pneumatic control valves are still the most used in process industries due to their low cost and simplicity. This paper presents a design procedure of a PID controller for a pneumatic control valve. For comparison, P and PI controllers are also utilized for the control valve. The bond graph method is used to model the control valve, in order to compare the response characteristics of the valve. Simulation results are found for three controllers of the valve. The integral time absolute error criterion is used to calculate the controller parameters. The results show excellent closed-loop performance and the PID controller is more robust than the P and PI controller.

Three-Dimensional Modeling and Geometrical Influence on the Hydraulic Performance of a Control Valve

The ability to understand and manage the performance of hydraulic control valves is important in many automatic and manual industrial processes. The use of computational fluid dynamics (CFD) aids in the design of such valves by inexpensively providing insight into flow patterns, potential noise sources, and cavitation. Applications of CFD to study the performance of complex three-dimensional (3D) valves, such as poppet, spool, and butterfly valves, are becoming more common. Still, validation and accuracy remain an issue. The Reynolds-averaged Navier–Stokes equations were solved numerically using the commercial CFD package FLUENT V6.2 to assess the effect of geometry on the performance of a 3D control valve. The influence of the turbulence model and of a cavitation model was also investigated. Comparisons were made to experimental data when available. The 3D model of the valve was constructed by decomposing the valve into several subdomains. Agreement between the numerical predictions and measurements of flow pressure was less than 6% for all cases studied. Passive flow control, designed to minimize vortical structures at the piston exit and reduce potential cavitation, noise, and vibrations, was achieved by geometric smoothing. In addition, these changes helped to increase Cv and reduce the area affected by cavitation as it is related to the jet shape originated at the valve throat. The importance of accounting for full 3D geometry effects in modeling and optimizing control valve performance was demonstrated via CFD. This is particularly important in the vicinity of the piston. It is worth noting that the original geometry resulted in a lower Cv with higher velocity magnitude within the valve, whereas after smoothing Cv increased and served to delay cavitation inception.

Multi-Element Unstructured Analyses of Complex Valve Systems

The safe and reliable operation of high-pressure test stands for rocket engine and component testing places an increased emphasis on the performance of control valves and flow metering devices. In this paper, we will present a series of high-fidelity computational analyses of systems ranging from cryogenic control valves and pressure regulator systems to cavitating venturis that are used to support rocket engine and component testing at NASA Stennis Space Center. A generalized multi-element framework with submodels for grid adaption, grid movement, and multi-phase flow dynamics has been used to carry out the simulations. Such a framework provides the flexibility of resolving the structural and functional complexities that are typically associated with valve-based high-pressure feed systems and have been difficult to deal with using traditional computational fluid dynamics methods. Our simulations revealed a rich variety of flow phenomena such as secondary flow patterns, hydrodynamic instabilities, fluctuating vapor pockets, etc. In the paper, we will discuss performance losses related to cryogenic control valves and provide insight into the physics of the dominant multi-phase fluid transport phenomena that are responsible for the “choking-like” behavior in cryogenic control elements. Additionally, we will provide detailed analyses of the modal instability that is observed in the operation of a pressure regulator valve. Such instabilities are usually not localized and manifest themselves as a system-wide phenomena leading to an undesirable chatter at high flow conditions.

Numerical Analysis on the Performance of Control Valve in Variable Displacement Wobble Plate Compressor

The performance of control valve is analyzed in this paper in order to study characteristics of the variable displacement wobble plate compressor. The forces acting on the control valve are analyzed and the mathematical model to analyze its performance is developed. A test bench is set up to get the steady and dynamic performance of control valve. The steady-state performances predicted by the mathematical model agree well with the experimental data while the predicted dynamic performances agree with the experimental results qualitatively. With the mathematical model, the steady-state performances of the control valve with four different preset control points and three different effective areas of the evacuated bellows have been analyzed, and the dynamic behavior of one type control valve has been studied. It is shown that: (1) the suction pressure at preset control point is inversely proportional to the discharge pressure; (2) the larger the starting force of spring in control valve or the smaller the effective area of evacuated bellows, the larger the suction pressure at preset control point; and the larger the starting force of spring in control valve and the smaller the maximum opening of ball valve, the more quickly the crankcase pressure changes and the smaller mass flow rate of control valve; the slope ratio of crankcase pressure to suction pressure cannot be influenced by the starting force of spring in control valve but can be influenced by the effective area of evacuated bellows; (3) the transition time of the crankcase pressure is about 1 s and can be neglected when working condition changes.

Predicting Globe Control Valve Performance—Part I: CFD Modeling

Computational Fluid Dynamics (CFD) tools are evaluated for use in industrial design applications by predicting primary control valve performance characteristics. The performance parameter of primary interest to the manufacturer is the flow coefficient, Cv. Valves having relative valve capacity factors between 2.5 and 13 were modeled. The control valve Cv was experimentally measured and numerically predicted. Both equal percentage and linear characteristic valves were represented in the study. The numerical (simulation) study presented in Part 1 showed that the valve Cv and the inherent valve characteristic could be accurately predicted using axisymmetric flow models over most of the plug travel. In addition, the study demonstrates the usefulness of simplified CFD analysis for relatively complex 3-D flows.

Measuring the installed dead band of control valves

Specification of control valve performance is increasingly important in the process industries. In many process plants, dead band of significantly less than 1% is desired for certain control loops. Defining and measuring dead band approaching 0.1% presents new challenges for control valve vendors and users. This paper clarifies the existing terminology and illustrates (with laboratory data) phenomena that become significant at small amplitude, but can be missed by bench testing.

Using higher order CMAC to improve the performance of control valves

This paper presents a system based on a higher order Cerebellar Model Articulation Controller to improve the linearity and to compensate the hysteresis of a control valve. To highlight the benefits and drawbacks of the proposed approach, a Masoneilan Camflex II valve is used as a practical test bead. These results show that CMAC can effectively improve the valve performance. This improvement can be obtained by first collecting a set of data and then allowing CMAC to learn the necessary actions to compensate the non-linear effects.

80. Control valve performance demands accurate design data and correct pipe size: J R B Hinton,Instrum Practice, 19 (9), Sept 1965, 817–822

80. Control valve performance demands accurate design data and correct pipe size: J R B Hinton,Instrum Practice, 19 (9), Sept 1965, 817–822