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Operability and performance analysis of various control valves

Herbert, Jasmine (2015) Operability and performance analysis of various control valves. Other thesis, Murdoch University.

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Abstract

In 2015 an assortment of control valves were implemented in the Murdoch University Instrumentation and Control Laboratory and in the Pilot Plant. This project is a result of this proposed implementation and is important to gain a proper understanding of the valves’ usage; behaviour; and to confirm the new valves are an improvement on any valves they may be replacing.

This project aimed to compare and analyse the operability and performance of the Baumann 24000S with Fisher 3660 Positioner and the existing Badger Meter Research Control Valves within the Instrumentation and Control Laboratory. The operability and performance was analysed by investigating the valves’ usage; functionality; hysteresis; valve type and sizing; dead band; and dead time.

The first test checked if one valve opening resulted in two flow rates for different directions of the stem movement (otherwise known as hysteresis). Eliminating hysteresis is important as it signifies that the valve is less susceptible to variations caused by friction and other forces, resulting in a single flow rate for each valve opening.

The valve type, sizing and usage was analysed with the flow coefficient and characteristic curves. The flow coefficient indicates a valve’s maximum flow capacity, whereas the characteristic curve shows the flow behaviour with change in valve opening; this should be as linear as possible. The type and size of a valve is important in order to optimise a process. A valve that is too small will not allow sufficient fluid to pass; whereas a valve that is too big will cause most of the process gain to come from the valve and not the controller [1].

Dead band is the range the valve opening can change in both directions without change in the flow being observed; this is a result of backlash and friction. The smaller the dead band the better the valve’s ability is to respond to minor changes.

Dead time allows the evaluation of the valve’s response time, in order to compare the speed of the valves.

In comparing the Research Valve results to the Baumann 24000S results, the Baumann 24000S had no visible hysteresis; it had the strongest linear relationship; it had a small dead band of 0.5% and a quicker dead time. Based on these findings it is determined that the Baumann 24000S surpasses the performance of the Research Valve; therefore it is advised that the Baumann 24000S with Fisher 3660 positioner is a suitable replacement for the Badger Meter Research Valve.

Publication Type: Thesis (Other)
Murdoch Affiliation: School of Engineering and Information Technology
Supervisor: Vu, Linh and Cole, Graeme
URI: http://researchrepository.murdoch.edu.au/id/eprint/28659
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