Instrument Technician Practice Exam Flashcards

A collection of practice questions and answers for Instrument Technician certification, covering loop checks, electrical troubleshooting, valve mechanics, and piping standards, and safety procedures.

When is the BEST time to document each loop check for commissioning?

At the time each test is completed

Teflon paste must not be used on:

Nitrogen service

If a 120VAC input measures 120V between hot and ground but 72V between hot and neutral, what is the most likely cause of the 24VDC power supply failure?

Lost the neutral

Gain increase when tube:

Back bends are made

A temperature measuring device that produces a voltage as the temperature changes is a/an:

Thermocouple

A pressure piping code is found in:

ANSI B 31.1

When marking tubing for cutting, the preferred method is to:

Mark the tube with a grease pencil

An example of direct measurement indicator is a:

Pressure gauge

In loop checks, all of the following are performed EXCEPT:

Tuning

If 75 volt DC potential is applied to a 25 ohm load, the circuit current is:

$$3.0\text{ amps}$$

A valve has linear-flow characteristics when the:

Differential pressure corresponds directly to the valve stem position

What is a circuit current if 45 VDC is applied to a 250 ohm load?

$$0.18\text{ amp}$$

All of the following valves are used to regulate flow EXCEPT:

Gate

The value of the dynamic variable desired in a process is the:

Set point

An acceptable tool for marking 360 degrees around the outside of tubing is a:

Ferrule

What process variable is defined as the amount of force exerted by a substance over a given unit of measure?

Pressure

Storage of steel wool can be considered a fire hazard when stored around _____.

Batteries

The MINIMUM value of the measured process range is considered to be:

3psi and 4ma

A bubbler system is used to measure:

Specific Gravity

To prevent travel damage to a limit switch, use a(n) _______.

Mechanical stop

In a controller, automatic control describes:

The final element as controlled by the setpoint of the controller locally

When using soft rolled tubing, it must be unrolled and straightened:

By hand

Where would an instrument fitter find the PROPER method to connect an instrument to a process tap?

On an installation detail

The part of a control valve that controls the plug proportionally to the output of the controller is the:

Valve positioner

Workers should always assume that all electrical equipment and lines are _____.

energized until proven

the main function of a transducer is to

Convert once signal form into another signal form

What type of liquid is used for degreasing electronic equipment?

Isopropyl alcohol

The high pressure gas line has a large self-operated regulator. Inlet pressure is 300psi; Outlet pressure is 100psi. The regulator is sluggish during load changes. What is the first step to improve the operation of the regulator?

Lower the inlet pressure

During acid cleaning a tubing run after installation it is very important to ______.

Drain low points

On a field mounted controller, the setpoint is changed:

By the control room operator

When using a multimeter to drive loop current, the meter should be set to _____.

Output mA

When the leads and selector switch are in the correct position why would a multimeter read voltage correctly but be unable to read milliamp current?

The meter's current fuse is blown

When installing packing rings, how much should the cute ends be staggered?

90 Degrees

As a rule of thumb, how much will $1/2\text{ inch}$ tubing gain for every 90-degree bend?

$$3/8\text{ inch}$$

When removing an instrument from receiving, what does NOT need to be checked?

Check the shipping date from the manufacturer

Where are rubber gaskets typically used?

In low pressure/low temperature systems

The purpose of an instrument index is to:

list every instrument used on a project

What are the two types of material used for shielding?

Foil and braided

What type of control does an employee have over energy potential if they hold the power plug after removing it from the outlet?

Exclusive control

What does the term "fail open" mean in relation to valve actuators?

When the actuator power is lost, the valve will open

An instrument fitter needs to withdraw two sticks of ½-inch Hastelloy B tubing from stores. It is not labeled and is mixed in with ½-inch 316 stainless steel tubing that is also not labeled. What should be done?

Report the problem to the supervisor and have the tubing PMI'd

What two factors determine the static head pressure close to the bottom of a tank?

The height of the level and the specific gravity

A transmitter with an RTD is not working. Using the multimeter, which two parameters will help the best with troubleshooting?

DC voltage and resistance

What part of an instrumentation installation drawing lists the REQUIRED fittings?

Materials list

Solve using the equation: Absolute vacuum pressure = barometric pressure − vacuum gauge reading. Given that a vacuum gauge reads 22.2 inHg, and the barometric pressure reads 27.68 inHg, find the absolute pressure.

$$5.48\text{ inHg}$$

A severe shock is affected by:

Amount of current in the body

If a sump pump motor continues to run after the tank is empty, what is the likely cause in the float switch?

Contacts are welded closed

The types of gaskets and gasket materials to be used on a project are listed in:

A section of the specifications

The preferred medium to remove debris from a new instrument air line prior to service is:

Air

A strain gauge measures the external force applied to a fine wire by causing a change in _____.

Resistance

Which of the following purging gases should be avoided for use with hydrocarbons?

Air

A differential pressure transmitter mounted on a non-vented vessel is used to measure the:

Density of the product in the vessel

Convert the length 2’ 10-3/4” to its decimal equivalent (in feet).

2.896’

Using the image, the valve shown is NOT:

Air-to-open

Flow can be described in units of all of the following EXCEPT:

Density

When an 8mA signal is connected across a 250 ohm resistor, the voltage drop across the resistor would be:

2 Volts

PTFE tape used as a sealant should be wrapped:

In the same direction as the threads

What is a common material used to minimize moisture in instrumentation?

Desiccant

The pneumatic output of a 3–15 psi instrument is at 50%. The actual output pressure is:

9 psi

The standards of which organization identify the characteristics of metals used for piping?

ASTM

The output of a thermocouple is expressed in:

Millivolts

MOST pneumatic receivers operate in the range of:

3-15 psi

The five-point method of calibration checks the device output at:

4 mA, 8 mA, 12 mA, and 20 mA and back at 4 mA

When pressure testing, the required documentation includes:

Specification sheets

An air-to-open valve uses a:

Fail-in-position actuator

The MOST common method used to measure the flow of liquid in a pipe is to introduce a restriction in the pipe and measure the:

Velocity

What is the resistance in the circuit?

200 ohms

After a bend is completed, all tubing will exhibit:

Spring back

What valve REQUIRES a 90-degree turn to operate the valve 100% open or closed?

Ball Valve

Where is the drain wire terminated in an instrument system?

At the control cabinet

On the image, how many hand valves are installed on Tank 1201C?

3

On the image, how many hand valves are installed on Tank 1201C?

3

What is the first step in troubleshooting a problem in a system?

Verify that there is a problem

Where can the appropriate elevation of an instrument be found?

P&ID

Chemical cleaning of tubing attached to instruments may cause damage to sensor _____.

elements

When making a 90-degree tubing bend, allowance for springback should be:

1 to 3 degrees

Cable shields should be connected to the:

Ground at each accessible location

Polarity of a diode is checked by selecting which of the following on the multimeter?

OHMS

To accurately measure liquid level in a closed tank under pressure, use a:

DP transmitter

OSHA requires that existing conditions be tested or inspected before beginning work on electrical equipment by using a(n) ________.

Multimeter

Weight is defined as:

The force exerted by a mass due to gravity

Deadband in a switch refers to the:

A range of process change before switch actuation

The adjustment that allows pressure contacts to reset is called the _______.

Reset point

The value of the dynamic variable desired in a process is the:

Set point

A nuclear measuring device is typically used to measure:

Level

What does a solenoid valve do?

Serves as an actuator to open and close pneumatic and hydraulic valves

What is the psi reading on MOST gauge pressure indicators at atmospheric pressure?

Zero

Proportional control is also known as:

Derivative control

The documentation required to loop check and commission are:

P&ID, loop diagrams, and instrument specification sheets

In an instrument loop, where would wet instrument air show up first?

At the dryer

What is the total current of the circuit?

0.12 amps

Bills of materials are found in:

General arrangement drawings

Signal cable shields should be connected to ground at:

1 point in the signal path

Where would an instrument fitter find a P&ID number for a particular instrument?

In an instrument index

To measure level, which variable is critical for accurate measurement?

Specific gravity

The ASTM factors affecting required wall thickness of tubing include all of the following EXCEPT:

Support type

What instrument drawing shows an actual representation of a process operating sequence?

P&ID

What is the total circuit current?

0.096 amps

The three basic types of fluid flow are laminar flow, turbulent flow, and:

Transitional flow

When calibrating a loop pressure instrument during loop checks, the source of pressure is the:

Pressure calibrator