Ramsay Test Process Flow and Instrumentation 4

Question 1

A differential pressure transmitter connected to an orifice plate reads higher than expected even though the actual flow rate has not changed. Which condition is MOST likely responsible?

Accepted Answer

Partial blockage of the low-pressure impulse line

Answer

Blocking the low-pressure (downstream) impulse line traps a static head in that leg, artificially raising the differential pressure reading and causing the transmitter to report a higher-than-actual flow. A high-pressure line blockage would cause the reading to drop. Viscosity changes affect the discharge coefficient but not dramatically in turbulent flow, and pipe diameter is a fixed installation parameter.

Question 2

In a P&ID, a dashed line connecting an instrument bubble to a control valve represents:

Accepted Answer

An electrical signal

Answer

Per ISA 5.1 symbology, a dashed line between instruments denotes an electrical signal. A solid line represents pneumatic, a line with double dashes or hatching represents hydraulic, and a line with filled circles or filled squares denotes a capillary/filled-system connection. Misreading these line types is a common source of installation errors.

Question 3

A control loop is operating in cascade mode. The primary (outer) controller output is feeding the setpoint of the secondary (inner) controller. If the secondary controller is placed in manual mode, the PRIMARY controller will:

Accepted Answer

Continue adjusting its output, but the secondary controller will ignore the new setpoints

Answer

When the secondary controller is placed in manual, it stops responding to setpoint changes sent by the primary controller. The primary controller, still in auto, keeps calculating and adjusting its output (the secondary setpoint), but those setpoint changes have no effect on the final control element. This is why proper cascade implementation includes bumpless transfer logic — without it, the primary output may drift to an extreme value. The primary does NOT automatically go to manual; that would require external interlock logic.

Question 4

A vortex flowmeter is installed on a steam line and begins reporting erratic, low-frequency pulses well below the meter's stated minimum Reynolds number. The BEST corrective action is:

Accepted Answer

Reduce the pipe diameter at the meter location to increase velocity and Reynolds number

Answer

Vortex meters require a minimum Reynolds number (typically Re > 10,000–20,000) to shed stable vortices. Below that threshold, the Strouhal-based output is unreliable. Reducing the pipe bore at the meter (using a reducer/expander pair) increases local fluid velocity for the same mass flow, raising the Reynolds number into the meter's valid operating range. Switching to a PD meter is often impractical for steam. Increasing downstream pressure affects density but complicates the system. Using a larger bore lowers velocity and makes the Re problem worse.

Question 5

On a P&ID, an instrument tag reads 'FIC-204'. The letter 'I' in the middle of the tag designation indicates:

Accepted Answer

The instrument provides an indication (local or remote display) in addition to control

Answer

In ISA 5.1 instrument tag nomenclature, the first letter is the measured variable (F = Flow), subsequent letters are modifiers and functions (I = Indicate, C = Control), and the number is the loop identifier. 'FIC' means Flow Indicating Controller — the loop measures flow, displays it, and controls it. 'Inferred,' 'interlock,' and 'intrinsically safe' are not part of standard ISA tag letter coding.

Ramsay Test Practice Test

Ramsay Test Practice Test

Ramsay Test Process Flow and Instrumentation 4