Class I
Class II
General
Seals and Drains
Definitions Category
100
Butane, which is included in Class I, Group B, has a lower flammable limit of __ ___ by volume and an upper flammable limit of ____ by volume.
1.6% / 8.4%
100
Pittsburgh experimental coal, included in Class II, Group F (Carbonaceous Dusts), has a minimum cloud or layer ignition temperature of ? .
338°F
100
What type of Hazard will be present in a Class I location?
Gases or flammable Vapors
100
EYD drain seals provide continuous draining which prevents water accumulation, and range in size from ? inclusive.
1/2" to 4"
100
The ? of a liquid is the minimum temperature at which it gives off sufficient vapor to form an ignitible mixture with the air near the surface of the liquid or within the vessel used.
flash point
200
The autoignition temperature of gasoline, which is included in Class I, Group D, ranges from ? to ? .
536°F / 880°F
200
Chlorinated polyether alcohol, a Class II, Group G material, has a minimum cloud or layer ignition temperature of ? .
460°
200
What type of Hazards are present at a Class II location?
Combustible dust
200
Improperly packed or weak dams permit a loss of compound into conduit systems, which both wastes compound and makes ? seal.
an unsafe seal
200
The ignition temperature of a combustible solid is influenced by the rate of air flow, rate of heating, and ? of the solid.
size
300
Name 3 wiring methods allowed in a Class I division I location
NEC article 501.10(A)(1)
300
Will the following statement be True or False?
It is very unlikely that a device suitable for Class I locations would, when blanketed by dust, overheat in a Class II location, or that the presence of dust might interfere with safe operation in some other way.
False
300
What type of Hazard will be present at a Class III location?
Fibers and Flyings
300
What is this called?
EYD drain seal
300
Vapor density is the weight of a volume of ? vapor or gas (with no air present) compared to the weight of an equal volume of dry air at the same temperature and pressure.
pure
400
Will this statement be True or False?
Boundary-line mixtures of vapor or gas with air, which if ignited will just propagate flame, are known as the “lower and upper flammable limits” and are usually expressed in terms of percentage by density of gas or vapor in air.
False
400
In the Zone Classification system, an area where combustible dust or ignitible fibers/flyings are likely to exist occasionally under normal operation in quantities sufficient to be hazardous is classified as ? .
Zone 21
400
Will the following statement be True or False?
In selecting a device for installation in a hazardous (classified) location, care should be used to make sure that it is suitable for the group or groups involved in the hazardous location.
True
400
While not an NEC requirement, many engineers consider it good practice to sectionalize long conduit runs by inserting seals not more than ? apart, depending on the conduit size, to minimize the effects of “pressure piling.”
50' to 100'
400
Alternate increases and decreases in temperature and/or barometric pressure due to weather changes or due to the nature of the process carried on in the location where the conduit is installed will cause ? .
breathing or condensation
500
Group IIC gases which are in a(n) Zone 1, Zone 2, and Zone 3 area, are equivialent to a combination of Class I, Group ______ and Class I, Group ______ gases.
NEC article 505.6(A) informational note. Group A and Group B
500
A vertical raceway not less than ? long that extends downward from a dust-ignitionproof enclosure is a permitted method of raceway sealing in Class II locations.
5'
Article 502.15(3)
500
Ventilating pipes for motors, generators, or other rotating electrical machinery, or for enclosures for electric equipment, installed in Class III locations, shall be of metal not less than 0.53 millimeters (0.021 inches) in thickness, or ? .
of equally substantial noncombustible material
NEC Article 503.128
500
Sealing fittings are required where cables leave Class I, Division 1 locations and where they leave a Class I, Division 2 location if they are attached to process equipment that may cause a pressure of over ? to be exerted on a cable end.
6" of water
500
Will the statement be True or False?
It is very unlikely that a device suitable for Class I locations would, when blanketed by dust, overheat in a Class II location, or that the presence of dust might interfere with safe operation in some other way.
True