hazardous locations lesson 1
Explosionproof or dust-ignitionproof equipment is not permitted for use at temperatures lower than ? unless they are identified for low-temperature service.
-13 degrees farenheight
The special bonding requirements of the "dot" 30(B)(2)(a) subdivisions of Articles 501, 502, 503, 505, and 506 require an equipment bonding jumper of the wire type complying with 250.102 to be installed in ? .
1 and 3
Which of the following methods is/are used to make plug-receptacle combinations safe for use in hazardous (classified) locations?
1 and 3
A Zone 0 location is a location in which ignitible concentrations of flammable gases or vapors are present ? .
1&2 ref: 505.5(B)(1)
Protection technique concepts include ? .
1&2 and 3
A Class I, Division 2 location is one in which flammable gases, flammable liquid-produced vapors, or combustible liquid-produced vapors ? .
1, 2 and 3 500.5(B)(2)
The point where a flammable or combustible substance is capable of ignition depends on the substance type and which of the following?
1,2, 3 and 4
The bonding requirement in "dot" 30(B)(2)(a) is not required for listed liquidtight flexible metal conduit 6 feet or less in length, installed with fitting listed for grounding, with the overcurrent protection rated ? amperes or less, and the load is part of a meter, instrument, or relay circuit.
10 amps
A Class II liquid has a flash point at or above ? but below 140°F.
100 degrees farenheight
Article 505 of the NEC has ? revisions in the 2023 edition.
135
Refrigerant machinery rooms containing ammonia refrigeration systems are permitted to be classified as unclassified locations where they have adequate mechanical ventilation that operates continuously, or where a detection system initiates the ventilation where the ammonia concentration reaches ? .
150 ppm
The first mention of hazardous locations appeared in the ? edition of the NEC.
1920
In the ? NEC revision, the requirements for hazardous locations were reformatted into four articles: 500, 501, 502, and 503.
1959
The ? revision of the NEC added the word classified to Hazardous (Classified) Locations.
1975
The use of ? in hazardous locations is prohibited by the special bonding requirements for hazardous locations.
2&3
Article 506 which covers the Zone System requirements for the Class/Division hazards in Article 502 and Article 503 was added to the NEC in ? .
2005
Article 510, created in 1953 for six special occupancies and revised in 1959 by moving the six special occupancies to separate new articles, was finally deleted in ? .
2023
Fires or explosions may only occur when ? basic condition(s) exist(s).
3
Explosionproof equipment must withstand hydrostatic pressure tests in a range of ? the maximum pressure from an explosion within the enclosure.
3 to 6 1/2
Materials in Class I, Division 1 and Division 2 hazardous (classification) locations are assigned to one of ? groups.
4 500.6(A)
An alternate "zone classification" system found in Article ? was added to the NEC in 1996.
505
Which of the following materials would be found in one of the three location classes of the class/division system?
all of the above ref: 500.1
Equipment with contacts such as switches, circuit breakers, motor starters, pushbutton stations, and other similar equipment can produce arcs or sparks in normal operation when ? and become a potential ignition source.
both A and B
Metal combustible fibers/flyings are classified as ? .
class 2 division 1, group E ref: 500.5(D)(1)(a)
The possibility that a gas mixture may be above the upper flammable limit does not ensure that the gas is safe. The gas must first pass through the flammable range as its ? increases from being below the lower flammable limit to a concentration above the upper flammable limit.
concentration
Combustible liquids will only form an ignitible mixture when they are heated above their ? .
flash point
The purged and pressurized protection technique is permitted in any hazardous (classified) location for which it is ? .
identified ref: 500.7(D)
The upper flammable limit is the highest ? (or volume) concentration of a combustible substance in an oxidizing medium that will propagate a flame.
molar
Grounding in hazardous locations must comply with the requirements of ? of Article 250.
parts 1 and 6
When explosions run through a conduit system, the gas in front creates a ? that may result in extreme explosive and mechanical pressures.
pressure piling effect
Explosionproof equipment is defined as equipment enclosed in a case that is capable of withstanding an explosion of a ? gas or vapor that may occur within it and of preventing the ignition of a specified gas or vapor surrounding the enclosure by sparks, flashes, or explosion of the gas or vapor within, and that operates at such an external temperature that a surrounding flammable atmosphere will not be ignited.
specified ref: 100
The flash point of a liquid is the minimum temperature at which it gives off vapor in ? concentration to form an ignitible mixture with the air near the surface of the liquid, as specified by test.
suffcient
A source of ignition is all that is needed to create a fire or an explosion when an ignitible or explosible mixture of a flammable gas or a combustible dust is mixed with air or oxygen in proportions that create an ignitible or explosible mixture.
true
An area where nonmetal combustible fibers/flyings are in the air under normal operating conditions in quantities sufficient to produce explosible mixtures would be classified as Class III, Division 1.
true ref: 500.5(D)(1)(a)
