Process Flow and Instrumentation Flashcards

A magnetic flowmeter (magmeter) can only measure the flow of fluids that are:

Answer: Electrically conductive, like water

A magmeter relies on Faraday's law and requires an electrically conductive fluid to generate a measurable voltage.

In a feedforward control strategy, the controller acts based on:

Answer: A measured disturbance before it affects the controlled variable

Feedforward control measures a disturbance and corrects for it before it changes the process variable.

Two block valves with a vent valve between them, used to positively isolate a line, is called a:

Answer: Double block and bleed

A double block and bleed uses two isolation valves with a bleed/vent between them for positive isolation.

A pressure gauge reading 'gauge pressure' (psig) shows pressure relative to:

Answer: Atmospheric pressure

Gauge pressure is measured relative to local atmospheric pressure, reading zero at atmosphere.

On a P&ID, the letters 'LSH' identify a:

Answer: Level switch, high

In ISA tagging, L=Level, S=Switch, H=High, so LSH is a level switch that trips on high level.

An interlock (or shutdown system) in a process plant is designed primarily to:

Answer: Automatically take equipment to a safe state when limits are exceeded

Safety interlocks act independently of normal control to bring the process to a safe state during abnormal conditions.

A Coriolis flowmeter is valued because it can directly measure:

Answer: Mass flow rate (and often density)

A Coriolis meter measures true mass flow directly by sensing the deflection of vibrating tubes, and can also give density.