Ramsay Test Process Flow and Instrumentation 3 — Questions and Answers
Question 1: A PID controller's 'derivative' action responds to:
- The size of the current error
- The accumulated error over time
- The rate at which the error is changing (Correct answer)
- The setpoint value only
Correct answer: The rate at which the error is changing
Derivative action reacts to how fast the error is changing, helping to dampen rapid swings.
Question 2: Which instrument would you use to measure the level in a sealed pressurized tank using differential pressure?
- A simple sight glass
- A DP level transmitter with high and low side taps (Correct answer)
- A thermocouple
- A pitot tube
Correct 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.
Question 3: In a cascade control loop, the output of the primary (master) controller becomes the:
- Final valve position directly
- Setpoint of the secondary (slave) controller (Correct answer)
- Alarm trip point
- Process variable of the master
Correct answer: Setpoint of the secondary (slave) controller
In cascade control the master controller's output sets the setpoint of the slave controller.
Question 4: A thermocouple generates a measurable voltage based on the:
- Resistance change of a metal wire
- Temperature difference between two dissimilar metal junctions (Correct answer)
- Expansion of a bimetallic strip
- Pressure of a sealed gas bulb
Correct 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.
Question 5: On a P&ID, the abbreviation 'PSV' attached to a vessel most likely identifies a:
- Process sampling valve
- Pressure safety (relief) valve (Correct answer)
- Pump suction valve
- Pneumatic shutoff valve
Correct answer: Pressure safety (relief) valve
PSV stands for pressure safety valve, a relief device that protects equipment from overpressure.
Question 6: If a flow controller is in 'manual' mode, the operator is directly setting the:
- Process setpoint
- Controller output (valve position) (Correct answer)
- Alarm limits
- Measurement range
Correct answer: Controller output (valve position)
In manual mode the automatic logic is bypassed and the operator directly sets the controller output.
Question 7: A variable-area flowmeter that uses a float rising inside a tapered tube is commonly called a:
- Rotameter (Correct answer)
- Venturi meter
- Magnetic flowmeter
- Coriolis meter
Correct answer: Rotameter
A rotameter is a variable-area meter where a float rises in a tapered tube to a height proportional to flow.
Ramsay Test Process Flow and Instrumentation 3
A PID controller's 'derivative' action responds to: