Questions and Answers
An area adjacent to a Division 1 location into which volatile gases might occasionally flow should be designated ___.
Division 2
A grinding area would most likely be designated as ___.
Class II, Division 1
A cotton textile mill would most likely be designated as ___.
Class III
A Class II atmosphere containing charcoal or coal dust would most likely be designated as ___.
Signup and view all the answers
Which of the following is true with regard to ignition?
Signup and view all the answers
Explosion-proof equipment is rated by both classification and ___.
Signup and view all the answers
How many classification(s) of hazardous atmospheres are listed in the NEC?
Signup and view all the answers
How many division(s) are there for each hazardous atmosphere classification?
Signup and view all the answers
How many group(s) are listed under Class I, Division I?
Signup and view all the answers
Which of the following are the groups listed under Class II, Division 1?
Signup and view all the answers
When installing circuit breakers in Class II, Division 1 hazardous locations, a ___.
Signup and view all the answers
When rigid metal conduit is required in hazardous locations, the threads must be cut at taper per foot?
Signup and view all the answers
The main purpose of a union in conduit runs is to ___.
Signup and view all the answers
When installing switches or other arc producing apparatus in Class I, Division 1 locations, sealing fittings shall be installed within ___.
Signup and view all the answers
The purpose of packing fiber in a sealing fitting is to ___.
Signup and view all the answers
Which of the following best describes the time to pour in the sealing compound in a sealing fitting?
Signup and view all the answers
What location is considered a hazardous location?
Signup and view all the answers
Describe a Class I hazardous location.
Signup and view all the answers
Describe a Class II hazardous location.
Signup and view all the answers
Describe a Class III hazardous location.
Signup and view all the answers
One way to reduce the hazards in a Class II area is by installing dust-collecting systems.
Signup and view all the answers
The NEC article that covers motor fuel dispensing stations is ___.
Signup and view all the answers
The classification and division of an unvented service station pit in a commercial garage is ___.
Signup and view all the answers
The entire area of an airport hangar, including any adjacent area not suitably cut off from the hangar, is considered to be a Class I, Division 2 location up to a level of ___ above the floor.
Signup and view all the answers
The NEC article that covers the general wiring of healthcare facilities is ___.
Signup and view all the answers
The use of intrinsically safe equipment is primarily limited to ___.
Signup and view all the answers
In addition to preventing the passage of gases, vapor, and flames, what other purpose are served by seal-off fittings?
Signup and view all the answers
Where sealing fittings are used, they must be accessible.
Signup and view all the answers
In humid atmospheres where it is not possible to incline the raceway for the purpose of draining, special ___ fittings should be used.
Signup and view all the answers
Conductor splices or taps must NOT be made in enclosures where sealing compound is to be used.
Signup and view all the answers
Sealing compound must NOT have a melting point of less than ___.
Signup and view all the answers
In hazardous locations where threaded metal conduit is required, joints must be made up with at least ________ threads fully engaged.
Signup and view all the answers
Which of the following best describes the devices that will help prevent moisture from collecting in raceway systems?
Signup and view all the answers
Which of the following covers intrinsically safe equipment?
Signup and view all the answers
A permanent and effective seal is one method of preventing the entrance of dust into enclosures through a raceway system In a Class II, Division 2 location.Another way is a _____.
Signup and view all the answers
The main purpose of an explosion-proof flexible coupling is to connect ___.
Signup and view all the answers
________ is approved for use in most Class I, Division 1 locations.
Signup and view all the answers
A Class I, Division 1 location is best described as an atmosphere that ________ hazardous.
Signup and view all the answers
Which of the following groups represents the most hazardous location?
Signup and view all the answers
Where in the NEC would you find definitions related to hazardous locations?
Signup and view all the answers
Study Notes
Hazardous Locations – Key Definitions
- Division 2 designates areas adjacent to Division 1 locations where volatile gases may flow occasionally.
- Class II, Division 1 applies to areas with combustible dust, such as grinding operations.
- Class III designates locations like cotton textile mills due to fibers’ presence.
- Group F represents Class II atmospheres that contain charcoal or coal dust.
Ignition and Equipment Ratings
- Volatile vapors causing ignition require dilution below the lower explosion limit to prevent risks.
- Explosion-proof equipment must be rated by both classification and temperature.
- The NEC recognizes three classifications of hazardous atmospheres, each with two divisions.
Groups and Installations
- Class I, Division I includes four defined groups.
- Class II, Division 1 delineates groups E, F, and G, significant for installations in such areas.
- Circuit breakers in Class II, Division 1 require a dust-proof enclosure for safety.
Conduit and Fittings Guidelines
- Rigid metal conduit threads should taper at ¾ inch per foot for hazardous locations.
- Unions in conduit runs facilitate the installation and removal of equipment.
- Sealing fittings must be installed within 18 inches of arc-producing switches in Class I, Division 1 locations.
Sealing Fitting Purpose and Installation
- Packing fiber in sealing fittings contains the sealing compound until it hardens.
- Filling seal fittings with sealing compound should occur after system installation.
- A hazardous location is any area with potential for ignitable vapors, dust, or fibers.
Classifications of Hazardous Locations
- Class I locations have flammable gases or vapors in quantities that can form explosive mixtures.
- Class II locations are hazardous due to combustible dust presence.
- Class III locations are defined as hazardous because of ignitable fibers.
Reducing Hazards and NEC Articles
- Installing dust-collecting systems can reduce hazards in Class II areas.
- NEC Article 514 covers motor fuel dispensing stations, while Article 517 part II focuses on general wiring in healthcare facilities.
- Class I, Division 2 applies to unvented service station pits in commercial garages.
Special Considerations and Sealoff Fittings
- Class I, Division 2 locations relate closely to common areas like airport hangars at up to 18 inches above the floor.
- Intrinsically safe equipment primarily serves process control instrumentation given low energy requirements.
- Sealoff fittings not only prevent gas passage but also limit explosions and precompression of pressure.
Accessibility and Splicing Regulations
- Sealing fittings must remain accessible for maintenance and operation.
- Conductor splices or taps shouldn't occur in areas where sealing compound is used, as dictated by NEC guidelines.
- Sealing compound used must have a melting point of no less than 93 degrees Celsius (200 degrees Fahrenheit).
Mechanical Connections and Raceway Systems
- In threaded metal conduit, joints must have at least five threads fully engaged for secure connections.
- Integral drains in raceway systems help avert moisture accumulation.
- NEC Article 504 details the requirements for intrinsically safe equipment use.
Maintaining Enclosure Integrity
- A permanent seal is pivotal to keep dust out of enclosures within Class II, Division 2 locations.
- A horizontal raceway of at least 10 feet serves as another method for maintaining integrity.
- Explosion-proof flexible couplings connect motors to raceway systems while ensuring safety.
General Guidelines
- Rigid metal conduit (RMC) is suitable for most Class I, Division 1 environments.
- Class I, Division 1 areas are characterized by atmospheres that are typically hazardous.
- Group A is identified as the most hazardous location among classifications.
- Definitions related to hazardous locations can be referenced in NEC Article 500.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Description
Test your knowledge on key definitions and safety classifications related to hazardous locations. This quiz covers various classes, divisions, and equipment ratings necessary to ensure safety in environments with volatile gases and combustible dust. Understand the implications of working in these specialized areas and the necessary precautions.
