Process Flow and Instrumentation Flashcards

A PID controller's 'derivative' action responds to:

Answer: The rate at which the error is changing

Derivative action reacts to how fast the error is changing, helping to dampen rapid swings.

Which instrument would you use to measure the level in a sealed pressurized tank using differential pressure?

Answer: A DP level transmitter with high and low side taps

A DP level transmitter compares pressure at the bottom and top of a closed tank to infer liquid level.

In a cascade control loop, the output of the primary (master) controller becomes the:

Answer: Setpoint of the secondary (slave) controller

In cascade control the master controller's output sets the setpoint of the slave controller.

A thermocouple generates a measurable voltage based on the:

Answer: Temperature difference between two dissimilar metal junctions

A thermocouple uses the Seebeck effect, producing a voltage from the temperature difference at two dissimilar-metal junctions.

On a P&ID, the abbreviation 'PSV' attached to a vessel most likely identifies a:

Answer: Pressure safety (relief) valve

PSV stands for pressure safety valve, a relief device that protects equipment from overpressure.

If a flow controller is in 'manual' mode, the operator is directly setting the:

Answer: Controller output (valve position)

In manual mode the automatic logic is bypassed and the operator directly sets the controller output.

A variable-area flowmeter that uses a float rising inside a tapered tube is commonly called a:

Answer: Rotameter

A rotameter is a variable-area meter where a float rises in a tapered tube to a height proportional to flow.