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NCCER Instrumentation practice questions

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Question 1Safety, Codes, and Standards

What is the primary purpose of a lockout/tagout procedure?

  1. To identify the spare parts required for a repair
  2. To record the calibration history of a transmitter
  3. To keep hazardous energy isolated during servicing Correct answer.
  4. To document the maintenance schedule for each instrument

Explanation

Lockout/tagout controls hazardous energy by isolating it and applying locks and tags before work begins. It protects personnel from unexpected energization, startup, or release of stored energy.

Question 2Safety, Codes, and Standards

A Class I hazardous location is one that contains or may contain:

  1. corrosive mists only
  2. combustible metal dusts
  3. ignitable flyings or fibers
  4. flammable gases or vapors Correct answer.

Explanation

NEC Class I locations are those where flammable gases or vapors may be present. Combustible dusts are Class II, and ignitable fibers or flyings are Class III.

Question 3Safety, Codes, and Standards

A Class I, Division 1 location is an area where ignitable concentrations of flammable gas:

  1. occur only during abnormal equipment failure
  2. are produced only by airborne dust
  3. exist under normal operating conditions Correct answer.
  4. are never expected to be present

Explanation

Division 1 covers locations where ignitable concentrations exist during normal operation or frequently during repair and maintenance. Division 2 covers concentrations that are normally confined or occur only under abnormal conditions.

Question 4Safety, Codes, and Standards

Which section of a safety data sheet gives exposure limits and personal protective equipment guidance?

  1. First-aid measures
  2. Physical and chemical properties
  3. Handling and storage
  4. Exposure controls and PPE Correct answer.

Explanation

The exposure controls and personal protection section lists occupational exposure limits and recommended PPE. It also describes engineering controls that may be needed.

Question 5Safety, Codes, and Standards

A combustible gas meter reads 25% LEL. What does this mean?

  1. The oxygen concentration is 25% by volume
  2. One-quarter of the LEL has been reached Correct answer.
  3. The atmosphere is safe for unlimited entry
  4. The gas concentration is above the upper explosive limit

Explanation

The lower explosive limit is the lowest concentration that can ignite, so 25% LEL means one-quarter of that threshold has been reached. This is an alarm condition, not a safe entry level.

Question 6Safety, Codes, and Standards

A confined space entry permit is required when the space:

  1. is entered for less than five minutes
  2. has limited entry and a possible hazardous atmosphere Correct answer.
  3. contains only inert equipment and verified clean breathing air
  4. is larger than 100 cubic feet in volume

Explanation

A permit-required confined space has limited entry or exit and may contain a hazardous atmosphere or other serious hazard. Short duration or clean equipment alone does not remove the permit requirement.

Question 7Safety, Codes, and Standards

A hot work permit is required before:

  1. reading a gauge during normal operation
  2. replacing a fuse in a de-energized panel
  3. welding or grinding near flammables Correct answer.
  4. calibrating a pressure transmitter

Explanation

Hot work permits control ignition sources such as welding, cutting, and grinding in areas where flammable materials may be present. The permit verifies fire watch, area preparation, and gas testing.

Question 8Safety, Codes, and Standards

Instrument cable shields are usually grounded at one end to:

  1. increase the signal voltage
  2. prevent ground loops Correct answer.
  3. provide power to the transmitter
  4. allow the shield to carry loop current

Explanation

Grounding a shield at one point drains interference without creating a closed path for circulating current. Multiple grounds can cause ground loops and add noise to the signal.

Question 9Safety, Codes, and Standards

An intrinsic safety barrier protects a hazardous-area circuit by:

  1. limiting energy delivered to the circuit Correct answer.
  2. increasing the loop supply voltage
  3. providing a purge air supply to the enclosure
  4. disconnecting the circuit during calibration

Explanation

Intrinsic safety limits voltage and current so that no spark or thermal effect can ignite the atmosphere. A barrier typically uses resistors and zener diodes to clamp the energy.

Question 10Safety, Codes, and Standards

A conduit seal is installed where a conduit enters an explosion-proof enclosure to:

  1. provide a grounding connection
  2. block gas passage through the conduit Correct answer.
  3. reduce electrical noise on signal wires
  4. drain condensation from the conduit

Explanation

Seals block the passage of flammable gases or vapors through the conduit system. This helps preserve the protection concept of the enclosure and prevents flame propagation through the conduit.

Question 11Safety, Codes, and Standards

In the Zone system, Zone 0 is an area where an explosive gas atmosphere is present:

  1. only during abnormal operation
  2. for less than one hour per year
  3. continuously or for long periods Correct answer.
  4. only in the presence of combustible dust

Explanation

Zone 0 is the most severe gas classification, covering continuous or long-duration presence of an explosive atmosphere. Zone 1 is likely during normal operation, and Zone 2 is unlikely or brief.

Question 12Safety, Codes, and Standards

Equipment marked with temperature class T4 has a maximum surface temperature of:

  1. 100°C
  2. 135°C Correct answer.
  3. 85°C
  4. 120°C

Explanation

Temperature class T4 corresponds to a maximum surface temperature of 135°C. The marked temperature must not exceed the ignition temperature of the gas present.

Question 13Safety, Codes, and Standards

Which measurement category applies to test instruments used at the utility service entrance?

  1. CAT I
  2. CAT II
  3. CAT III
  4. CAT IV Correct answer.

Explanation

CAT IV covers the origin of the installation, such as the utility service entrance. The CAT rating indicates the transient overvoltage the meter can withstand.

Question 14Safety, Codes, and Standards

The arc flash boundary is the distance at which:

  1. PPE is no longer required for any task
  2. the arc flash cannot occur
  3. the equipment becomes de-energized automatically
  4. incident energy equals 1.2 cal/cm² Correct answer.

Explanation

NFPA 70E defines the arc flash boundary at an incident energy of 1.2 cal/cm², the threshold for a second-degree burn. Inside the boundary, arc-rated PPE is required.

Question 15Safety, Codes, and Standards

On a P&ID, an instrument bubble with no line through it indicates a device that is:

  1. mounted in the field Correct answer.
  2. mounted in the control room
  3. mounted on the local panel
  4. not yet installed

Explanation

ISA 5.1 uses no line for field-mounted instruments, a single line for panel-mounted accessible instruments, and a double line for panel-mounted inaccessible instruments.

Question 16Safety, Codes, and Standards

A SIL 2 safety instrumented function generally has an average probability of failure on demand between:

  1. 0.01 and 0.001 Correct answer.
  2. 1 and 0.1
  3. 0.001 and 0.0001
  4. 0.1 and 0.01

Explanation

SIL 2 spans an average probability of failure on demand from 1×10⁻² to 1×10⁻³. A lower probability of failure on demand corresponds to higher safety integrity.

Question 17Safety, Codes, and Standards

Calibration traceability means that an instrument's calibration is:

  1. performed only by the original equipment manufacturer
  2. repeated every month without exception
  3. linked to a national standard by an unbroken chain Correct answer.
  4. recorded in the maintenance database

Explanation

Traceability links the calibration to a national or international standard through an unbroken chain of comparisons. Each step in the chain must have documented uncertainty.

Question 18Safety, Codes, and Standards

A high dew point in an instrument air supply can cause:

  1. increased air pressure at the pressure regulator
  2. condensation, freezing, and corrosion Correct answer.
  3. improved response of pneumatic valve actuators
  4. higher loop current

Explanation

Moisture in instrument air can condense, freeze, or corrode small passages and nozzles. ISA 7.0.01 sets air quality limits that include dew point.

Question 19Safety, Codes, and Standards

The OSHA permissible exposure limit for hydrogen sulfide is:

  1. 20 ppm ceiling Correct answer.
  2. 100 ppm ceiling
  3. 1 ppm time-weighted average
  4. 5 ppm ceiling

Explanation

OSHA sets a 20 ppm ceiling for hydrogen sulfide, with a 50 ppm peak allowed for up to 10 minutes once per shift. H2S can be deadly at high concentrations.

Question 20Safety, Codes, and Standards

Under OSHA general industry rules, fall protection is required when working at heights of:

  1. 3 feet or more
  2. 10 feet or more
  3. 4 feet or more Correct answer.
  4. 2 feet or more

Explanation

OSHA general industry requires fall protection at 4 feet or more above a lower level. Construction work uses a 6-foot threshold.

Question 21Safety, Codes, and Standards

For an intrinsically safe circuit, the barrier's open-circuit voltage (Voc) must not exceed the field device's:

  1. Ci
  2. Vmax Correct answer.
  3. Imax
  4. Li

Explanation

Entity evaluation compares barrier Voc to device Vmax and barrier Isc to device Imax. Capacitance and inductance limits are compared separately using Ci and Li.

Question 22Safety, Codes, and Standards

NFPA 496 Type X purging reduces the classification inside an enclosure in a Class I, Division 1 location to:

  1. Zone 0
  2. Division 1
  3. nonhazardous Correct answer.
  4. Division 2

Explanation

Type X purging reduces the internal classification to nonhazardous. Type Y reduces Division 1 to Division 2, and Type Z reduces Division 2 to nonhazardous.

Question 23Safety, Codes, and Standards

A source of release classified as Zone 2 is one that:

  1. is unlikely to produce a flammable atmosphere normally Correct answer.
  2. produces a flammable atmosphere continuously
  3. produces only combustible dust
  4. produces a flammable atmosphere during normal operation

Explanation

Zone 2 covers releases that are unlikely and, if they occur, are brief. Zone 0 is continuous, and Zone 1 is likely during normal operation.

Question 24Safety, Codes, and Standards

The main purpose of a proof test on a safety instrumented function is to:

  1. reveal undetected dangerous failures Correct answer.
  2. shorten the process shutdown time
  3. verify the transmitter's calibration accuracy only
  4. increase the loop's current output

Explanation

Proof tests detect dangerous failures that diagnostics cannot reveal, and the results support the probability-of-failure calculation. Test coverage and test interval affect the achieved SIL.

Question 25Safety, Codes, and Standards

The Zone system for hazardous (classified) locations is covered by NEC Article:

  1. 505 Correct answer.
  2. 500
  3. 501
  4. 502

Explanation

NEC Article 505 covers the Zone system for flammable gases and vapors. Article 500 covers the Class and Division system, Article 501 covers Class I, and Article 502 covers Class II.

Question 26Safety, Codes, and Standards

Under OSHA lockout/tagout rules, before an instrument technician repairs a motor-operated valve actuator, the technician must:

  1. attach a tag only, because locks are not required for instrument work
  2. rely on the machine operator to keep the start switch in the off position
  3. isolate, lock and tag, and verify zero energy Correct answer.
  4. verify zero energy, then isolate and apply a tag

Explanation

OSHA 1910.147 requires the equipment to be isolated from all energy sources, locked and tagged by each worker, and then tested to confirm that no hazardous energy remains. Verification comes after isolation and lockout, not before. A tag alone does not provide the physical protection of a lock.

Question 27Safety, Codes, and Standards

Safety data sheets for chemicals used at a facility must be:

  1. kept in the corporate office and provided within 24 hours of a request
  2. retained for one year after the chemical is purchased
  3. posted only in the maintenance supervisor's office
  4. readily accessible to employees in their work area during each shift Correct answer.

Explanation

The OSHA Hazard Communication Standard requires safety data sheets to be readily accessible to employees in their work areas during each work shift. Keeping them only in a remote office or with a supervisor does not meet the accessibility requirement. Retention rules apply to records, not to the day-to-day accessibility of SDSs.

Question 28Safety, Codes, and Standards

An atmosphere is considered oxygen-deficient when the oxygen content falls below:

  1. 21.0 percent by volume
  2. 12.5 percent by volume
  3. 19.5 percent by volume Correct answer.
  4. 23.5 percent by volume

Explanation

OSHA and confined-space practice define oxygen deficiency as an atmosphere containing less than 19.5 percent oxygen by volume. Normal outdoor air is about 20.9 percent. Testing for oxygen is part of the atmospheric monitoring done before and during confined-space entry.

Question 29Safety, Codes, and Standards

Which consensus standard specifies eye and face protection for occupational use?

  1. ANSI S1.4
  2. ANSI Z87.1 Correct answer.
  3. ANSI Z358.1
  4. NFPA 70E

Explanation

ANSI Z87.1 is the standard for eye and face protection and is referenced by OSHA's PPE rules. Safety glasses and goggles should be marked as meeting Z87.1. The other standards address emergency eyewash equipment, electrical safety, and sound-level measurement.

Question 30Safety, Codes, and Standards

A Class I, Division 1 location is one in which ignitable concentrations of flammable gases or vapors are:

  1. present only as combustible dust suspended in air
  2. present under normal operating conditions Correct answer.
  3. present only under abnormal conditions such as equipment failure
  4. never present because mechanical ventilation keeps the area clear

Explanation

Class I, Division 1 covers locations where ignitable gas or vapor concentrations exist under normal operating conditions or may exist frequently during repair and maintenance. Division 2 covers concentrations that occur only under abnormal conditions. Combustible dust falls under Class II rather than Class I.

Question 31Safety, Codes, and Standards

On a construction site, OSHA requires ground-fault circuit interrupter protection for:

  1. all 125-volt, 15- and 20-ampere receptacles Correct answer.
  2. only receptacles installed in wet or damp outdoor locations
  3. only receptacles feeding permanently installed equipment
  4. only 480-volt three-phase receptacles feeding portable welders

Explanation

OSHA's construction standards require GFCI protection for 125-volt, single-phase, 15- and 20-ampere receptacles that are not part of the permanent wiring of the building. The requirement is not limited to wet locations or to specific equipment. Higher-voltage and permanently installed circuits are addressed by other rules.

Question 32Safety, Codes, and Standards

Combustible metal dusts such as aluminum or magnesium are classified in which hazardous location group?

  1. Class I, Group D
  2. Class II, Group G
  3. Class III, Group F
  4. Class II, Group E Correct answer.

Explanation

In the Class II dust classification, Group E covers combustible metal dusts, including aluminum and magnesium. Group F covers carbonaceous dusts such as coal, and Group G covers agricultural and other nonconductive dusts. Class III covers fibers and flyings.

Question 33Safety, Codes, and Standards

For an intrinsically safe installation, the total capacitance of the field device plus its connected cable must not exceed:

  1. the field device's maximum input power (Pi)
  2. the barrier's maximum output voltage (Voc)
  3. the barrier's maximum output current (Isc)
  4. the barrier's allowable capacitance (Ca) Correct answer.

Explanation

Intrinsic safety entity evaluation compares the field device and cable capacitance with the barrier's allowable capacitance, Ca. The total of Ci plus cable capacitance must be less than or equal to Ca. Voltage, current, and power parameters are compared separately with Voc, Isc, and Po.

Question 34Safety, Codes, and Standards

In a Class I, Division 2 location, a Type Z pressurized enclosure reduces the interior classification to:

  1. Division 1 at all times
  2. nonhazardous during normal operation Correct answer.
  3. Zone 0 during normal operation
  4. Class II, Division 1 during normal operation

Explanation

NFPA 496 Type Z pressurization is used to reduce the interior of an enclosure in a Division 2 location to nonhazardous during normal operation. Type Y reduces Division 1 to Division 2 inside the enclosure, and Type X reduces Division 1 to nonhazardous. The type designation reflects the starting classification and the required reduction.

Question 35Safety, Codes, and Standards

After welding or cutting hot work is completed, a fire watch must normally remain in the area for at least:

  1. 5 minutes
  2. 2 hours
  3. 30 minutes Correct answer.
  4. until the next shift begins

Explanation

NFPA 51B requires the fire watch to remain in the area for at least 30 minutes after hot work is finished to detect and extinguish smoldering fires. The watch is maintained beyond the completion of the work, not just during it. Longer periods may be required by site-specific procedures.

Question 36Safety, Codes, and Standards

A GHS hazard pictogram showing a flame over a circle indicates:

  1. oxidizing material Correct answer.
  2. acute toxicity
  3. corrosive material
  4. compressed gas

Explanation

The GHS pictogram with a flame over a circle identifies oxidizing materials, which can intensify fire. A plain flame pictogram indicates flammable material. Corrosives are shown by corrosion symbols on a surface and hand, while compressed gas uses a cylinder symbol.

Question 37Safety, Codes, and Standards

The limited approach boundary around exposed energized electrical conductors is the distance at which:

  1. arc-rated PPE must always be worn by anyone crossing
  2. an unqualified person needs an escort to cross Correct answer.
  3. the circuit is considered de-energized for maintenance
  4. only qualified persons may cross under any circumstance

Explanation

The limited approach boundary is the shock-protection boundary at which unqualified persons must not cross unless accompanied by a qualified person. Qualified persons may cross when following the applicable work rules. Arc-rated PPE requirements are governed separately by the arc flash boundary and incident energy analysis.

Question 38Safety, Codes, and Standards

Before changing the trip setpoint of a safety instrumented function, the facility should complete:

  1. a verbal approval from the shift operator
  2. a management-of-change review of the safety impact Correct answer.
  3. an update to the P&ID drawing only
  4. a fresh calibration certificate for the transmitter only

Explanation

A setpoint change alters the performance of a safety instrumented function, so it falls under management of change. The review evaluates the safety impact, updates documentation, and confirms that the function still meets its SIL requirement. Calibration records or drawing updates alone do not authorize the change.

Question 39Safety, Codes, and Standards

Under intrinsic safety rules, a simple apparatus is a device that:

  1. requires a continuous purge system to operate
  2. contains energy-storing components rated above 1.2 V
  3. stores no more than 1.2 V, 100 mA, or 25 mW Correct answer.
  4. is always listed as explosion-proof for the area

Explanation

A simple apparatus neither generates nor stores more than 1.2 V, 100 mA, 25 mW, or 20 microjoules. Examples include passive switches, thermocouples, and resistive elements. Because its energy is inherently limited, it can be used in an intrinsically safe circuit without individual entity evaluation.

Question 40Safety, Codes, and Standards

Compared with a 1oo1 architecture, a 1oo2 redundant sensor architecture in a safety instrumented function generally:

  1. raises PFD while also lowering the spurious trip rate
  2. lowers PFD but raises the spurious trip rate Correct answer.
  3. has no measurable effect on either PFD or spurious trips
  4. increases the spurious trip rate and lowers safety availability

Explanation

A 1oo2 arrangement trips when either channel detects a hazardous condition, so it reduces the probability of failure on demand and improves safety availability. The tradeoff is that a fault in either channel can cause a trip, so the spurious trip rate increases. Voting architecture selection balances safety integrity against nuisance trips.

Question 41Instrument Installation and Mounting

For a thermowell installed in a liquid-filled pipe, the well tip should extend to which position?

  1. Flush with the inside wall of the pipe
  2. One-quarter of the way across the bore
  3. Just touching the far inside wall
  4. Slightly past the centerline of the pipe Correct answer.

Explanation

In liquid service the well is inserted so the sensing element sits slightly past the pipe centerline, in the flowing core of the stream. That position gives a fast, accurate response without blocking an excessive amount of the bore.

Question 42Instrument Installation and Mounting

Impulse lines for a liquid-service differential pressure transmitter should be sloped in which direction?

  1. Level, with no slope in either direction
  2. Steeply upward, then looped above the tap
  3. Downward from the tap toward the transmitter Correct answer.
  4. Upward from the tap to the transmitter

Explanation

Liquid-service impulse lines are run with a continuous downward slope of at least 1 in/ft from the process tap to the transmitter. Any gas or vapor that forms then rises back into the process instead of collecting in the line.

Question 43Instrument Installation and Mounting

How is a pneumatic control valve normally oriented when installed in a horizontal line?

  1. Actuator below the body, stem vertical
  2. Any angle, provided the handwheel is reachable
  3. Body horizontal and actuator sideways
  4. Actuator above the body, stem vertical Correct answer.

Explanation

The standard mounting is with the actuator on top and the stem vertical. This keeps the packing evenly loaded, keeps debris off the packing, and lets the actuator stroke freely under normal support.

Question 44Instrument Installation and Mounting

What is the correct method for cutting 1/2 in. stainless steel instrument tubing to length?

  1. A tubing cutter with no further preparation
  2. Side-cutting pliers, then file the end square
  3. A roller-type tube cutter, then ream the burr Correct answer.
  4. A hacksaw, then wipe the end dry

Explanation

Instrument tubing is cut with a roller-type tube cutter so the end stays round and square to the axis. The raised burr must then be reamed out so it cannot shed chips into the fitting or restrict flow.

Question 45Instrument Installation and Mounting

In a classified location, a conduit seal fitting must be installed within what distance of an explosionproof enclosure?

  1. Within 6 inches of the enclosure
  2. Within 18 inches of the enclosure Correct answer.
  3. Within 36 inches of the enclosure
  4. Anywhere along the conduit run

Explanation

A seal fitting is required in the conduit within 18 in. of the enclosure in a hazardous location. The seal confines an internal explosion to the enclosure and blocks process gas from migrating through the conduit system.

Question 46Instrument Installation and Mounting

In what sequence should the bolts of a flanged instrument connection be tightened?

  1. All bolts on one side, then the other side
  2. Random order in a single final pass
  3. A crossing pattern in several increments Correct answer.
  4. One bolt at a time, clockwise, to full torque

Explanation

Flange bolts are brought up in a crossing or star pattern in several increments, near 30 percent steps, so the gasket compresses evenly. One-pass or sequential tightening cocks the flanges and causes leaks.

Question 47Instrument Installation and Mounting

Where should the root (block) valve of an instrument impulse line be located?

  1. At the low point of the impulse line
  2. Directly at the transmitter inlet
  3. At least 10 ft along the line from the tap
  4. Close to the process tap Correct answer.

Explanation

The root valve belongs as close to the process connection as practical so the impulse line can be isolated for maintenance. Keeping the valved section short minimizes plugged or trapped lengths that stay pressurized.

Question 48Instrument Installation and Mounting

A variable-area (rotameter) flowmeter must be mounted in which position?

  1. Any position, as long as the scale is readable
  2. Horizontal, with flow left to right
  3. Vertical, with flow upward through the tube Correct answer.
  4. Vertical, with flow downward through the tube

Explanation

A rotameter relies on gravity to position the float, so the tube must be vertical with flow entering from the bottom. Any tilt or reverse flow changes the float position and invalidates the scale.

Question 49Instrument Installation and Mounting

An impulse line serving a gas-service differential pressure transmitter should slope in which direction?

  1. Upward from the transmitter toward the tap Correct answer.
  2. Level, with a drip leg at the transmitter
  3. Downward, with a low-point drain at the transmitter
  4. Downward from the tap to the transmitter

Explanation

Gas-service lines slope at least 1 in/ft upward from the transmitter toward the process tap. Any condensate that forms then drains back into the process rather than accumulating at the cell.

Question 50Instrument Installation and Mounting

How is an orifice plate oriented in a pipeline?

  1. Sharp edge downstream, but only in gas service
  2. Either orientation, since the plate is symmetrical
  3. Sharp edge upstream, bevel downstream Correct answer.
  4. Bevel upstream, sharp edge downstream

Explanation

The square-edged bore faces upstream so the flow contracts across the sharp edge, which is what the discharge coefficient assumes. The bevel faces downstream so the expanding jet does not strike the plate face.