Lesson 7: Article 506 - Zone 20, 21, And 22 Locations Flashcards
Associated nonincendive field wiring apparatus is apparatus in which the circuits are not necessarily nonincendive themselves but that affects the energy in nonincendive field wiring circuits and is relied on to maintain nonincendive energy levels.
a. True
b. False
NEC REF:
a. True
100
A combustible dust has solid particles that are _____ or smaller (i.e., material passing a U.S. No. 35 Standard Sieve as defined in ASTM E11-17, Standard Specification for Woven Wire Test Sieve Cloth and Test Sieves) that can form an explosible mixture when suspended in air at atmospheric pressure and temperature. [499:3.3]
a. 420 µm
b. 500 µm
c. 520 µm
d. none of the above
NEC REF:
b. 500 µm
100
Dusttight equipment is enclosed in a manner that excludes dusts and does not permit arcs, sparks, or heat otherwise generated or liberated inside of the enclosure to cause ignition of exterior accumulations or atmospheric suspensions of a specified dust on or in the vicinity of the enclosure.
a. True
b. False
NEC REF:
b. False
100
Note: The question is false because it defines dust-ignitionproof, not dusttight equipment. The question can be answered by referencing the definition of Dusttight or Dust-Ignitionproof.
A nonincendive circuit is a circuit, other than field wiring, in which any ______ or thermal effect produced under intended operating conditions of the equipment is not capable, under specified test conditions, of igniting the flammable gas–air, vapor–air, or dust–air mixture.
a. arc
b. ground fault
c. short circuit
d. spark
NEC REF:
a. arc
100
Nonincendive equipment has electrical/electronic circuitry that may, under normal operating conditions, cause ignition of a specified flammable gas–air, vapor–air, or dust–air mixture due to arcing or thermal means.
a. True
b. False
NEC REF:
b. False
100
Nonincendive field wiring enters or leaves an equipment enclosure and, under normal operating conditions of the equipment, is not capable, due to arcing or thermal effects, of igniting the flammable gas–air, vapor–air, or dust–air mixture.
a. True
b. False
NEC REF:
a. True
100
Match each of the following definitions to its correct term.
- Type of protection where electrical parts that could cause ignition of a mixture of combustible dust or fibers/flyings in air are protected by enclosing them in a compound in such a way that the explosive atmosphere cannot be ignited.
-Type of protection for explosive dust atmospheres where electrical equipment is provided with an enclosure providing dust ingress protection and a means to limit surface temperatures.
-Type of protection where any spark or thermal effect is incapable of causing ignition of a mixture of flammable or combustible material in air under prescribed test conditions.
-Type of protection for electrical equipment that uses the technique of guarding against the ingress of the external atmosphere, which might be explosive, into an enclosure by maintaining a protective gas therein at a pressure above that of the external atmosphere.
Choices:
- Encapsulated “m”
- Pressurized Enclosure “p”
- Flameproof “d”
- Intrinsic Safety “i”
- Protection by Enclosure “t”
- Encapsulated “m” - Type of protection where electrical parts that could cause ignition of a mixture of combustible dust or fibers/flyings in air are protected by enclosing them in a compound in such a way that the explosive atmosphere cannot be ignited.
- Protection by Enclosure “t” - Type of protection for explosive dust atmospheres where electrical equipment is provided with an enclosure providing dust ingress protection and a means to limit surface temperatures.
- Intrinsic Safety “i” - Type of protection where any spark or thermal effect is incapable of causing ignition of a mixture of flammable or combustible material in air under prescribed test conditions.
- Pressurized Enclosure “p” - Type of protection for electrical equipment that uses the technique of guarding against the ingress of the external atmosphere, which might be explosive, into an enclosure by maintaining a protective gas therein at a pressure above that of the external atmosphere.
An area where combustible dust, combustible fibers/flyings, or ignitible fibers/flyings are likely to exist occasionally under normal operation is classified as ______.
a. Zone 20
b. Zone 21
c. Zone 22
d. None of the above
NEC REF:
b. Zone 21
506.5(B)(2)(1)
Locations shall be classified as Zone 20, 21, or 22, on the basis of the ______ of the combustible dust, combustible fibers/flyings, or ignitible fibers/flyings that may be present and the likelihood that a combustible or ignitible concentration or quantity is present.
a. autoignition temperature
b. ignition temperature
c. particle size
d. properties
NEC REF:
d. properties
506.5(A)
An area where ignitible concentrations of combustible dust, combustible fibers/flyings, or ignitible fibers/flyings are present continuously or for long periods of time would be classified as ______, when using the zone classification system.
a. Zone 2
b. Zone 20
c. Zone 21
d. Zone 22
NEC REF:
b. Zone 20
506.5(B)(1)(1)
An area adjacent to a Zone 20 location, from which ignitible concentrations of combustible dust, combustible fibers/flyings, or ignitible fibers/flyings could be communicated, is classified as ______, unless communication is prevented by adequate positive pressure ventilation from a source of clean air and effective safeguards against ventilation failure are provided.
a. Zone 2
b. Zone 20
c. Zone 21
d. Zone 22
NEC REF:
c. Zone 21
506.5(B)(2)
An area in which combustible dust, combustible fibers/flyings, or ignitible fibers/flyings are handled, processed, or used but in which the dust or fibers/flyings are normally confined within closed containers of closed systems, from which they can escape only as a result of the normal operation of the equipment with which the dust or fibers/flyings are handled, processed, or used would be classified as Zone 21.
a. True
b. False
NEC REF:
b. False
506.5(B)(3)(2)
Note: The question is false because of the phrase “as a result of the normal operation.” The word “normal” is “abnormal” in the subdivision.
Classification of areas, engineering and design, selection of equipment and wiring methods, installation, and inspection shall be performed by ______.
a. architects
b. engineers
c. qualified persons
d. none of the above
NEC REF:
c. qualified persons
506.7(A)
In instances of areas within the same facility being classified separately, Zone 22 locations shall not be permitted to abut or overlap Class II or Class III, Division 2 locations.
a. True
b. False
NEC REF:
b. False
506.7(B)
The dust ignitionproof protection technique is permitted for equipment installed in the Zone 20, Zone 21, and Zone 22 locations for which it is ______.
a. identified
b. labeled
c. listed
d. none of the above
NEC REF:
a. identified
506.8(A)
Match the zone(s) to the protection method that is permitted to be installed.
- Pressurized
- Intrinsic Safety
- Protection by Encapsulation “m”
- Protection by Enclosure “t”
Choices:
- Zone 21 and Zone 22 (where identified)
- Zone 20, Zone 21, and Zone 22 (where identified)
- Zone 20 and Zone 22 (where identified)
- Pressurized
- Zone 21 and Zone 22 (where identified - Intrinsic Safety
- Zone 20, Zone 21, and Zone 22 (where identified) - Protection by Encapsulation “m”
- Zone 20, Zone 21, and Zone 22 (where identified) - Protection by Enclosure “t”
- Zone 20, Zone 21, and Zone 22 (where identified)
Encapsulation “m” is a type of protection where electrical parts that could ignite an explosive atmosphere by either sparking or ______ are enclosed in a compound in such a way that this explosive atmosphere cannot be ignited.
a. arcing
b. heating
c. overloading
d. shorting
NEC REF:
b. heating
100
Protected Optical Radiation “op pr” minimizes the risk of ignition in explosive atmospheres from optical radiation where visible or infrared radiation is confined inside optical fiber or other transmission medium under normal constructions or constructions with additional mechanical protection based on the assumption that there is ______ radiation from the confinement.
a. a reduction in the
b. insignificant
c. limited
d. no escape of
NEC REF:
d. no escape of
100
Electrical Resistance Trace Heating “60079-30-1” uses the production of heat on the principle of electrical resistance and is typically composed of one or more ______ conductors and/or an electrically conductive material, suitably electrically insulated and protected.
a. aluminum
b. copper
c. metallic
d. none of the above
NEC REF:
c. metallic
100
Special Protection “s” is a type of protection that permits design, assessment, and testing of equipment that cannot be fully listed for a recognized type of protection or combination of recognized types of protection because of functional or operational limitations, but that can be demonstrated to provide the necessary equipment protection level (EPL).
a. True
b. False
NEC REF:
b. False
100
Evidence of equipment evaluation from a qualified testing laboratory or inspection agency concerned with product evaluation is a method of determining the ______ of identified equipment for use in Zone 20, 21, and 22 locations.
a. approval
b. labeling requirements
c. listing requirements
d. suitability
NEC REF:
d. suitability
506.9(A)(2)
Equipment that is ______ for Zone 20 shall be permitted in a Zone 21 or Zone 22 location of the same dust or ignitible fiber/flying.
a. identified
b. labeled
c. listed
d. suitable
NEC REF:
c. listed
506.9(B)
Equipment shall be marked to show the maximum surface temperature referenced to a 40°C ambient or at the higher marked ambient temperature if the equipment is rated and ______ for an ambient temperature greater than 40°C.
a. labeled
b. listed
c. marked
d. a. and b.
NEC REF:
c. marked
506.9(D)
Conduit and fittings installed in Zone 20, Zone 21, and Zone 22 locations must be made wrenchtight to prevent sparking when the fault current flows through the conduit system and to ______.
a. ensure the integrity of the conduit system
b. prevent entry of hazardous materials
c. provide an effective ground fault path
d. none of the above
NEC REF:
a. ensure the integrity of the conduit system
506.9(E)
