Author

Osei Prempeh

Date of Award

1-1-2020

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Energy Engineering

First Advisor

Edward Kolodka

Abstract

ABSTRACT

Ball valves with carbon steel bodies that help modulate flow rates are valuable parts in the process chemical industry. While corrosion monitoring is widely studied, there is not much information available regarding corrosion monitoring of control valves, as referenced in the literature review for this dissertation. This research investigated some foundational blocks for how corrosion can be monitored for a carbon steel body ball valve using ultrasonic technology. Topics that were addressed during this research include:

Monitoring corrosion in a carbon steel 1inch ball valve in a constant flow rate environment, in the presence of sodium chloride solution, mixtures of sodium chloride and acetic acid with pH ranging from 4 to 8.

Monitoring and analysis of the corrosion impact for the inlet and outlet of carbon steel ball valve using handheld ultrasonic thickness meter in constant flow conditions.

Embedded ultrasonic transducers on carbon steel control valve body for online corrosion monitoring.

Three experiments were conducted under various corrosive environment namely NaCl, acetic acid and NaCl mixtures for a total of 1,872 hours. Flow rates for these experiments were kept constant while process variables such as pressure, temperature, flow rates, total dissolved solids and power of hydrogen were measured. Microscopic images of the inlet and outlet of the valve were reviewed to validate corrosion characteristics of the valve body. Ultrasonic transducers were used to collect thickness data on the valve body in one experiment and embedded permanently for 648 hours while thickness measurements were monitored during the second and third experiments.

Statistical tools were used to analyze data from thickness measurements. The tools used are normal distribution, probability and regression. The inlet and outlet thickness measurements for the three experiments were not normally distributed as expected. The thickness loss for both inlet and outlet locations where thickness readings were taken on the valve for all three experiment, showed that the thickness losses were nonlinear in nature as expected, although for the 240 hours of run with the ultrasonic transducer embedded on the valve, the outlet readings were very close to linear.

Thickness measurements were tested against ambient conditions and valve positions which include, temperature, air pressure, noise, vibration and varying valve position. Apart from a high temperature at 300℉, which had an impact on the ultrasonic thickness readings, air pressure, noise exposure, vibration and changing valve position did not have adverse impacts on the measured thickness. These investigations have proven that, ultrasonic transducers can be embedded on ball valves with carbon steel bodies, to monitor both corrosion rates and total corrosion. These experiments will build the foundation for the next generation of carbon steel ball valves which have ultrasonic technology embedded to monitor corrosion online and in real time.

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