There are a number of technical terms that should be understood, when discussing Hazardous Areas, such as compartments containing flammable/explosive gas & air mixtures (propane gas in bilges).
A Few Hazardous Area Approval Explanations:
CFR 183.410 - Ignition Protection
(a) Each electrical
component must not ignite a propane gas and air mixture that is 4.25 to 5.25 percent propane gas by volume surrounding the electrical component when it is operated at each of its manufacturer rated voltages and current
loadings, unless it is isolated from gasoline fuel
sources, such as engines, and valves, connections, or other fittings in vent lines, fill lines, distribution lines or on fuel tanks
, in accordance with paragraph (b) of this section.
It is not the intention to require Ignition Protected devices to be “Explosion Proof”, as that term is defined in the National Electrical Code of the National Fire Protection Association pertaining to shore systems, or within the meaning of 46 CFR 110.15-65.(e), Subchapter J, “Electrical Engineering”. It is intended that the protection provided be generally equivalent to that of wiring
permitted by this standard wherein a definite short or break would be necessary to produce an open spark.
CFR Title 46: Shipping
, PART 183 - ELECTRICAL INSTALLATION
SAE J1171 “External Ignition Protection of Marine Electrical Devices”
UL 1500 “Standard Test Procedure for Ignition Protection”
USCG “USCG Compliance Test Procedure — Electrical System Standard”
Published January, 1973.
This method of protection limits the energy passing into the hazardous area. The energy limitation is provided by the use of safety
barriers which are mounted in the safe area. Because of the energy limitation, regardless of the fault in the hazardous area, sufficient energy cannot be released to ignite the explosive atmosphere.
: There are approval methods used by approval authority to assure an intrinsically safe system.
The system approval method is one in which specific field devices are examined in combination with specific barriers. No other field device or barriers may be substituted unless specifically examined by the approval authority.
The entity approval method is one in which each piece of equipment
is evaluated separately and assigned a set of safety
: A device may be installed in division 2 locations if it has been approved as nonincendive. Nonincendive equipment
is incapable of releasing sufficient electrical or thermal energy to ignite flammable gases or vapors under NORMAL operation and environmental conditions. Nonincendive devices need no special enclosure or other physical safeguard.
This is the most popular method of protection. When an explosive gas enters an enclosure containing electrical equipment an explosion could occur. With the enclosure properly installed, and the tight tolerance between the enclosure and the cover, the flame will cool sufficiently by the time it reaches the outside atmosphere. Hence, Explosion-proof products are capable of containing an internal explosion. The term "explosion-proof" does not indicate that the product is capable of withstanding an external explosion, but only of withstanding an internal explosion without allowing flames or hot gases to escape from the equipment housing to trigger an explosion in the surrounding atmosphere.