The post AutoQuiz: What Is the Cause of Cavitation in a Liquid Flow Stream? first appeared on the ISA Interchange blog site.
Today’s automation industry quiz question comes from the ISA Certified Automation Professional certification program. ISA CAP certification provides a non-biased, third-party, objective assessment and confirmation of an automation professional’s skills. The CAP exam is focused on direction, definition, design, development/application, deployment, documentation, and support of systems, software, and equipment used in control systems, manufacturing information systems, systems integration, and operational consulting. Click this link for more information about the CAP program.
As a liquid flows through the restriction of the control valve trim, the pressure drops and then recovers to a fraction (<1.0) of the upstream pressure. A common problem in the application of control valves is cavitation, which can cause surface damage to the wetted surfaces of the control valve or connecting pipe. Cavitation will occur in a liquid flow stream, like the one described above, when:
a) the fluid pressure remains constant across the trim of the control valve
b) the fluid pressure drops below the liquid’s vapor pressure and the vapor pressure is above the outlet pressure
c) the fluid pressure drops below the liquid’s vapor pressure and the vapor pressure is below the outlet pressured
d) the fluid viscosity decreases through the control valve trim to the point of cavitation
e) none of the above
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Source: ISA News