Deck 20: Hazardous Locations

Question 1

As a general rule, equipment installed in a Class II location must be .

A) dustproof
B) explosionproof
C) waterproof
D) dust-ignitionproof

Answer 1

D

Question 2

Describe the mating surfaces of explosionproof equipment.

Answer 2

Great care must be exercised when installing or maintaining explosionproof equipment. The improper installation or maintenance of this equipment can completely negate the system's integrity. The mating surfaces of explosionproof boxes are ground flat to provide a very close fit. A screwdriver gouge or deep scratch can provide the exit point for hot gases to escape and ignite the surrounding atmosphere. The ground surfaces of explosionproof enclosures should be cleaned with solvent to remove dirt particles before the parts are bolted together. If it is necessary to remove a substance that cannot be cleaned with solvent, use a fine steel wool; never use sandpaper or a sharp scraping instrument such as a putty knife. All bolts must be in place and tight. If one bolt is missing, the enclosure may not be able to prevent ignition of the surrounding atmosphere in the event of an internal explosion.

Question 3

When horizontal seals are installed, fiber dams must be used.

A) two
B) three
C) four
D) five

Answer 3

A

Question 4

What conditions are required for flexible cords and attachment plugs to be used in hazardous areas?

Question 5

In general, the floor area of a garage, up to a level of 18 in. (450 mm) above the floor, is considered to be a location.

A) Class I, Division 1
B) Class I, Division 2
C) Class II, Division 1
D) Class II, Division 2

Question 6

Class III locations are areas that contain combustible .

A) dusts
B) gases
C) fibers
D) vapors

Question 7

are used to minimize the passage of gas and to prevent the passage of flame through the conduit.

A) Outlet boxes
B) Seals
C) Fibers
D) Vacuums

Question 8

The rating indicates the maximum operating temperature of a luminaire.

A) T
B) MOT
C) MT
D) TEMP

Question 9

To help prevent condensation, some vertical seals are designed with .

A) fiber dams
B) conductors
C) drain plugs
D) horizontal seals

Question 10

locations are considered to be the most hazardous.

A) Class I, Division 1
B) Class I, Division 2
C) Class II, Division 1
D) Class II, Division 2

Question 11

What do Group C and D atmospheres encompass?

Question 12

If a stem is longer than in., lateral braces must be placed within 12 in. (300 mm) of the luminaire, or an explosionproof flexible coupling must be used within 12 in. (300 mm) of the junction box.

A) 6
B) 10
C) 12
D) 14

Question 13

When circuit breakers are installed in Class I locations, they must be .

A) dustproof
B) dust-ignitionproof
C) explosionproof
D) waterproof

Question 14

A Group A atmosphere contains .

A) hydrogen
B) 2-butanol
C) butadiene
D) acetylene

Question 15

What is the hazard level of an aircraft hangar?

Question 16

Some types of explosionproof enclosures are designed to be drilled and tapped in the field. When this is done, at least full threads should be engaged between the conduit and the enclosure.

A) three
B) five
C) seven
D) 11

Question 17

Intrinsically safe equipment and circuits operate .

A) without electricity
B) at low power levels
C) at high voltage
D) at high current

Question 18

If it is necessary to remove a substance from the surface of an explosionproof enclosure that cannot be cleaned with solvent, use .

A) a chisel
B) a putty knife
C) sandpaper
D) a fine steel wool

Question 19

A Group E atmosphere contains .

A) combustible metal dusts
B) carbonaceous dusts
C) acetaldehyde
D) propylene oxide

Question 20

What is the difference between Division 1 and Division 2 hazardous locations?