The post AutoQuiz: How to Determine Cause of the Apparent Discrepancy in Flow first appeared on the ISA Interchange blog site.
Today’s automation industry quiz question comes from the ISA Certified Automation Professional (CAP) 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.
The liquid flow control loop in the post image is installed at a plant where it is suspected that the amount of recycle flow is somewhat more than what is being displayed by FT-1, a digital flow transmitter. The flow transmitter was recently re-calibrated and does not display any signs of damage. The installation appears to be in conformance with good instrument installation practices. Given this information, you determine that one potential cause of the apparent discrepancy in flow may be:
a) The control valve positioner is outputting a signal that is higher than requested by the flow controller.
b) The flow control valve bypass valve is fully closed when it should be open.
c) The orifice plate that has been eroded, thereby increasing the effective size of the orifice.
d) Square root extraction is enabled at the transmitter, but should not be for this flow measurement loop.
e) none of the above
Source: ISA News