Sensor-based performance monitoring of a control valve unit

Abstract

This is the second of a series of papers dedicated to the research and development work in the field of industrial control valve condition monitoring and fault diagnosis. This paper reports new results that were produced after conducting a series of tests to monitor the dynamic performance of a typical industrial control valve unit (which consisted of a control valve, an actuator and a digital valve controller) under various operating conditions. These included the gradual blockage of the actuator's vent hole, the build-up of deposits on the valve stem and the incorrectly replaced valve stem seals.These conditions were created by using a precision in-line flow regulator for the actuator's vent hole and a thin layer of a special type of adhesive film that crystallized and bonded to the valve stem and by replacing the polytetrafluorethylene valve stem seals with graphite-type seals under controlled conditions. The effects of these abnormalities on the pressure that was developed in the upper diaphragm casing of the actuator as well as the flowrate were carefully monitored using a range of sensors that were integrated into an intelligent data acquisition and processing system.It was evident that certain types of fault, including the fully blocked actuator's vent hole, could be identified with great accuracy using the responses of the flow transmitter and the pressure transducer. On the other hand, other types of fault, such as the simulated build-up of deposits on the valve stem, required a comparison of their statistical properties in addition to the transducers' responses to determine the condition reliably.The current-to-pressure converter is a vital element of any digital valve controller and its performance was, therefore, monitored under various conditions to establish the effects of the faults on its operation. The paper concludes by outlining the main results and the limitations of the diagnostic techniques utilized as well as the future work, which is to integrate the results into a user-friendly diagnostic system based on the Microsoft visual basic programming language.

Detection of Distributed Oscillations and Root-Cause Diagnosis

“…Once a candidate loop has been identified as the root cause then further analysis or manual testing may be applied to determine the nature of the problem. Thornhill and Hägglund (1997) and Horch (1999) have given procedures for on-line diagnosis of valve and other faults, while McMillan (1995) and Sharif and Grosvenor (1999) reported methods for physical testing of control valves. The benefit of root cause diagnosis is that the maintenance effort required for testing and diagnosis will be directed towards the equipment or control loop that needs it.…”

Fault Diagnosis of a Hydraulic Power System Using an Artificial Neural Network

“…Finally, the training input and output data matrices have the following forms, Eq. (11 & 12): 2 2 2 1 1 2 1 1 2 2 2 1 1 2 1 1 2 2 2 1 1 1 2 1 1 2 2 2 1 1 1 2 1 1 2 2 2 1 1 1 2 1 1 2 2 2 1 1 1 2 1 1 2 2 2 2 2 2 2 2 2 2 2 2 1 1 1 1 1 1 1 1 1 (12) where I and O are the input and output matrices respectively. w i , (i= 1 to m) is the i th data window, which covers 50 points length, m is the total number of windows covering the extending stroke of the actuator rod.…”

“…Extracting the training data for the ANN: To decide the training data of the ANN according to Eq. (10) to (12), nine healthy and faulty cases are used for training the ANN as outlined in Table 1. Each case covers eighteen windows of the piston extending stroke; l= 18 of 0.5 sec per window.…”

“…The ANN acted as a parameter estimator and its output was used as fault indicator. Sharif and Grosvenor [12] presented an approach for FD of a control valve unit. The approach is sensor-based in which sensors of pressure, temperature and position were used.…”

Artificial Neural Network Approach for Fault Detection in Pneumatic Valve in Cooler Water Spray System

“…So fault detection, fault identification and diagnosis of equipments, machineries and systems have become a vigorous area of work. Due to the broad scope of the process fault diagnosis problem and the difficulties in its real time solution, many methods have been developed for fault detection and diagnosis on valves [1]. One trend is to monitor faults using a special measuring device with additional sensors.…”