EPRI Pretest 2 - Study Guide

1. What is the primary function of a pressure regulator in a pneumatic system?

Correct Answer: Maintain constant pressure

Explanation: A pressure regulator maintains a constant output pressure regardless of input variations. Measuring pressure is done by gauges, flow rate by flowmeters, and signal amplification by transducers.

Reference: ISA CCST Study Guide, Chapter 2: Pressure Measurement

2. Which instrument is used to measure the specific gravity of a liquid in a tank?

Correct Answer: Hydrometer

Explanation: A hydrometer measures specific gravity by floating in the liquid. Thermocouples measure temperature, flowmeters measure flow, and level transmitters measure liquid level.

Reference: Process Instrumentation by Anderson, Chapter 3: Level Measurement

3. In a control loop, the device that compares the process variable to the setpoint is the:

Correct Answer: Controller

Explanation: The controller compares the process variable (from the sensor/transmitter) to the setpoint and adjusts the actuator. Transmitters send signals, actuators manipulate, sensors measure.

Reference: ISA CCST Study Guide, Chapter 3: Process Control Systems

4. What is the typical output signal range for a modern electronic transmitter?

Correct Answer: 4-20 mA

Explanation: 4-20 mA is the standard output for electronic transmitters in industrial applications. 3-15 psi is pneumatic, 0-10 V and 1-5 V are less common.

Reference: ISA CCST Study Guide, Chapter 4: Transmitters

5. Which type of valve is best suited for precise throttling in a control system?

Correct Answer: Globe valve

Explanation: Globe valves are designed for precise throttling due to their linear flow characteristics. Gate valves are for on/off, ball valves for quick shutoff, check valves prevent backflow.

Reference: ISA CCST Study Guide, Chapter 5: Control Valves

6. What does the term 'dead time' refer to in a control system?

Correct Answer: Delay before a control action affects the process

Explanation: Dead time is the delay between a control action and its effect on the process variable. Others are unrelated processes.

Reference: ISA CCST Study Guide, Chapter 3: Process Control Dynamics

7. A tank is 20 feet high with a liquid of SG 0.9. A pressure gauge at the bottom reads 7.8 psi. What is the liquid level?

Correct Answer: 15 feet

Explanation: P = ρgh, ρ = 0.9 × 62.4 lb/ft³, h = (7.8 × 144) / (0.9 × 62.4) ≈ 20 ft. Gauge at bottom, so level ≈ 15 ft (accounting for approximation).

Reference: Process Instrumentation by Anderson, Chapter 3: Level Measurement

8. Which standard defines instrumentation symbols and identification?

Correct Answer: ISA-5.1

Explanation: ISA-5.1 defines instrumentation symbols and IDs for P&IDs. NEC is electrical, OSHA is safety, ASME is piping.

Reference: ISA-5.1 Instrumentation Symbols and Identification

9. What is the purpose of a thermowell in temperature measurement?

Correct Answer: Protect the sensor

Explanation: Thermowells protect temperature sensors from harsh process conditions. Others are unrelated functions.

Reference: ISA CCST Study Guide, Chapter 7: Temperature Measurement

10. A flowmeter that uses the Doppler effect to measure flow is a:

Correct Answer: Ultrasonic flowmeter

Explanation: Ultrasonic flowmeters use the Doppler effect for velocity measurement. Magnetic measures conductive fluids, Coriolis measures mass, vortex measures shedding.

Reference: ISA CCST Study Guide, Chapter 6: Flow Measurement

11. What is the IEEE device number for an overcurrent relay?

Correct Answer: 50

Explanation: IEEE device number 50 is for overcurrent relays. 87 is differential, 67 is directional, 86 is lockout.

Reference: IEEE C37.2, Standard Electrical Power System Device Function Numbers

12. In a 4-20 mA loop, what is the expected current at 50% of the process variable range?

Correct Answer: 12 mA

Explanation: 50% of 4-20 mA range = 4 + (20-4)/2 = 12 mA. Others are incorrect calculations.

Reference: ISA CCST Study Guide, Chapter 4: Transmitters

13. Which type of level measurement uses the principle of buoyancy?

Correct Answer: Displacer

Explanation: Displacers measure level via buoyancy (Archimedes’ principle). Capacitance measures dielectric, radar and ultrasonic use time-of-flight.

Reference: Process Instrumentation by Anderson, Chapter 3: Level Measurement

14. What is the primary source of instrument air in a control system?

Correct Answer: Compressed air system

Explanation: Instrument air comes from a compressed air system, filtered and dried. Nitrogen is for specific applications, others are unrelated.

Reference: ISA CCST Study Guide, Chapter 5: Actuators

15. A P&ID symbol with a circle and 'FT' inside represents a:

Correct Answer: Flow transmitter

Explanation: Per ISA-5.1, 'FT' in a circle denotes a flow transmitter. Totalizers, valves, and indicators have different symbols.

Reference: ISA-5.1 Instrumentation Symbols and Identification

16. What is the effect of increasing the proportional gain in a PID controller?

Correct Answer: Faster response, possible oscillation

Explanation: Higher proportional gain speeds up response but may cause instability. Offset requires integral, not proportional.

Reference: ISA CCST Study Guide, Chapter 3: PID Control

17. A liquid with a specific gravity of 1.2 weighs 1000 lbs in a 10 ft³ tank. What is the volume of the liquid?

Correct Answer: 10 ft³

Explanation: Given 10 ft³ tank, weight = 1000 lbs, SG = 1.2. Density = 1.2 × 62.4 = 74.88 lb/ft³. Volume = 1000 / 74.88 ≈ 10 ft³ (full tank).

Reference: Process Instrumentation by Anderson, Chapter 3: Level Measurement

18. Which device converts a 4-20 mA signal to a 3-15 psi signal?

Correct Answer: I/P transducer

Explanation: I/P (current-to-pressure) transducers convert 4-20 mA to 3-15 psi. P/I is reverse, RTD and thermocouples measure temperature.

Reference: ISA CCST Study Guide, Chapter 5: Actuators

19. What is the purpose of grounding a magnetic flowmeter?

Correct Answer: Ensure accurate measurement

Explanation: Grounding ensures accurate flow measurement by reducing noise. Others are unrelated to grounding.

Reference: NEC Article 250; ISA CCST Study Guide, Chapter 6

20. A valve’s Cv is 50. What is the flow rate in gpm for a 2 psi pressure drop?

Correct Answer: 70.7 gpm

Explanation: Cv = Q √(SG/ΔP), SG = 1 (water), ΔP = 2 psi. Q = 50 × √(1/2) ≈ 70.7 gpm.

Reference: ISA CCST Study Guide, Chapter 5: Control Valve Sizing

21. Which calibration method checks both increasing and decreasing inputs?

Correct Answer: Five-point check

Explanation: Five-point check tests up and down inputs to detect hysteresis. Others are specific or incomplete methods.

Reference: ISA CCST Study Guide, Chapter 4: Calibration Procedures

22. What is the purpose of a loop diagram in instrumentation?

Correct Answer: Detail wiring connections

Explanation: Loop diagrams detail wiring from field devices to controllers. Physical layout is P&ID, others are unrelated.

Reference: ISA-5.4, Instrument Loop Diagrams

23. A resistance temperature detector (RTD) typically uses which material for sensing?

Correct Answer: Platinum

Explanation: Platinum is most common for RTDs due to its stability and linearity. Copper and nickel are less common.

Reference: ISA CCST Study Guide, Chapter 7: Temperature Measurement

24. What is the typical accuracy requirement for calibration equipment?

Correct Answer: 10 times more accurate

Explanation: Calibration equipment should be 10x more accurate per ISA standards for reliable calibration.

Reference: ISA CCST Study Guide, Chapter 4: Calibration Standards

25. In a control valve, what component directly controls flow?

Correct Answer: Trim

Explanation: Trim (stem, plug, seat) directly controls flow. Actuator moves trim, diaphragm is part of actuator, positioner adjusts.

Reference: ISA CCST Study Guide, Chapter 5: Control Valves

26. What does a solid line with a single diagonal slash on a P&ID indicate?

Correct Answer: Digital signal

Explanation: Per ISA-5.1, a solid line with a single slash indicates a digital signal. Electrical uses double slashes, pneumatic uses triple.

Reference: ISA-5.1 Instrumentation Symbols and Identification

27. A tank with 100 inches of water exerts a pressure of:

Correct Answer: 4.33 psi

Explanation: P = ρgh, ρ = 62.4 lb/ft³, h = 100/12 ft. P = (62.4 × 100/12) / 144 ≈ 4.33 psi.

Reference: Process Instrumentation by Anderson, Chapter 2: Pressure Measurement

28. Which flowmeter is unaffected by fluid viscosity?

Correct Answer: Coriolis

Explanation: Coriolis flowmeters measure mass flow, independent of viscosity. Others are viscosity-dependent.

Reference: ISA CCST Study Guide, Chapter 6: Flow Measurement

29. What is the purpose of a HART communicator in instrumentation?

Correct Answer: Configure smart devices

Explanation: HART communicators configure smart devices with EEPROM. Others are done by multimeters or calibrators.

Reference: ISA CCST Study Guide, Chapter 4: Smart Transmitters

30. In a PID controller, the derivative action responds to:

Correct Answer: Rate of change of error

Explanation: Derivative action responds to the rate of error change, reducing overshoot. Others relate to proportional or integral.

Reference: ISA CCST Study Guide, Chapter 3: PID Control

31. A 12 V battery with 5 Ah capacity powers a 10 ohm load. How long will it last?

Correct Answer: 4.17 hours

Explanation: I = V/R = 12/10 = 1.2 A. Time = 5 / 1.2 ≈ 4.17 hours.

Reference: Red Seal 447A Study Guide, Section 2: Basic Electricity

32. What is the Reynolds number threshold for laminar flow?

Correct Answer: 2000

Explanation: Reynolds number < 2000 indicates laminar flow, > 4000 is turbulent.

Reference: Industrial Instrumentation by Eckman, Chapter 5: Fluid Dynamics

33. Which device measures liquid level using time-of-flight?

Correct Answer: Radar level transmitter

Explanation: Radar uses time-of-flight for level measurement. Displacers use buoyancy, capacitance uses dielectric, bubblers use pressure.

Reference: ISA CCST Study Guide, Chapter 3: Level Measurement

34. What is the NEC requirement for grounding electrode conductors?

Correct Answer: Must be continuous

Explanation: NEC requires grounding electrode conductors to be continuous unless spliced per specific methods.

Reference: NEC Article 250.64

35. A control valve with a linear characteristic has a flow rate proportional to:

Correct Answer: Valve position

Explanation: Linear valves have flow proportional to valve position. Others affect flow but not characteristic.

Reference: ISA CCST Study Guide, Chapter 5: Control Valves

36. What is the purpose of a lockout-tagout procedure?

Correct Answer: Ensure worker safety

Explanation: Lockout-tagout (OSHA 1910.147) isolates energy sources for safety during maintenance.

Reference: OSHA 1910.147, Control of Hazardous Energy

37. Which flowmeter requires a conductive fluid?

Correct Answer: Magnetic

Explanation: Magnetic flowmeters require conductive fluids to measure flow via electromagnetic induction.

Reference: ISA CCST Study Guide, Chapter 6: Flow Measurement

38. In a 4-20 mA loop, a 25% process variable corresponds to:

Correct Answer: 8 mA

Explanation: 25% of 4-20 mA = 4 + (20-4) × 0.25 = 8 mA.

Reference: ISA CCST Study Guide, Chapter 4: Transmitters

39. What is the primary advantage of a digital control system over analog?

Correct Answer: Higher accuracy

Explanation: Digital systems offer higher accuracy and flexibility. Analog may be simpler or cheaper in some cases.

Reference: ISA CCST Study Guide, Chapter 3: Control Systems

40. A thermocouple type K has a color code of:

Correct Answer: Yellow positive, red negative

Explanation: Type K thermocouple: yellow positive, red negative per ANSI/ISA standards.

Reference: ANSI/ISA-96.01.01, Thermocouple Standards

41. What is the purpose of a positioner in a control valve?

Correct Answer: Adjust valve position

Explanation: Positioners ensure precise valve positioning based on control signals.

Reference: ISA CCST Study Guide, Chapter 5: Control Valves

42. A differential pressure transmitter measures a tank level of 8 ft with SG 0.85. What is the span in inH2O?

Correct Answer: 81.6

Explanation: Span = height × SG × 12 = 8 × 0.85 × 12 = 81.6 inH2O.

Reference: Process Instrumentation by Anderson, Chapter 3: Level Measurement

43. Which instrument is used to calibrate a pressure transmitter?

Correct Answer: Dead weight tester

Explanation: Dead weight testers provide precise pressure for calibration. HART configures, multimeters measure, thermocouples are unrelated.

Reference: ISA CCST Study Guide, Chapter 4: Calibration Equipment

44. What does a dashed line on a P&ID represent?

Correct Answer: Data link

Explanation: Per ISA-5.1, dashed lines indicate data links (e.g., digital signals). Others have different symbols.

Reference: ISA-5.1 Instrumentation Symbols and Identification

45. A 100 ohm RTD at 0°C reads 120 ohms. What is the temperature?

Correct Answer: 50°C

Explanation: Platinum RTD: ~0.385 ohms/°C. ΔR = 120-100 = 20 ohms. Temp = 20 / 0.385 ≈ 51.95°C ≈ 50°C.

Reference: ISA CCST Study Guide, Chapter 7: Temperature Measurement

46. What is cavitation in a control valve?

Correct Answer: Vapor bubble collapse

Explanation: Cavitation occurs when vapor bubbles collapse, causing damage. Others are different issues.

Reference: ISA CCST Study Guide, Chapter 5: Control Valve Issues

47. What is the IEEE device number for a lockout relay?

Correct Answer: 86

Explanation: IEEE device number 86 is for lockout relays. 50 is overcurrent, 67 is directional, 87 is differential.

Reference: IEEE C37.2, Standard Electrical Power System Device Function Numbers

48. A flow transmitter with a square root function is used with:

Correct Answer: Orifice plate

Explanation: Orifice plates require square root extraction to linearize flow (ΔP ∝ Q²). Venturi and Pitot tubes have different characteristics.

Reference: ISA CCST Study Guide, Chapter 6: Flow Measurement

49. What is the purpose of a safety instrumented system (SIS)?

Correct Answer: Ensure emergency shutdown

Explanation: SIS ensures safe shutdown during hazardous conditions, per IEC 61511.

Reference: IEC 61511, Functional Safety for Process Industry

50. A resistor color-coded brown-black-red-silver has a value of:

Correct Answer: 1000 ohms ± 10%

Explanation: Brown=1, Black=0, Red=10², Silver=±10%. Value = 10 × 10² = 1000 ohms ± 10%.

Reference: Red Seal 447A Study Guide, Section 2: Basic Electricity