Electrical Systems

Manufacturer Requirements

An electrical component that is “ignition protected” is capable of operating in an explosive environment without igniting that environment. “Ignition protection” of electrical devices is accomplished by the use of seals, flame arrestors and potting (sealing), or a combination of such means.

An “ignition protected” component:

• will not ignite a flammable hydrocarbon mixture surrounding the device when an ignition source causes an internal explosion, or;
• is incapable of releasing sufficient electrical or thermal energy to ignite a hydrocarbon mixture; or
• has the source of ignition hermetically sealed.

A flammable hydrocarbon mixture is a mixture of gasoline and air, or propane and air, between the lower explosive limit (LEL) and the upper explosive limit (UEL).

In general, the tests are conducted in an explosion chamber containing an explosive atmosphere, defined by this regulation as a 4.25 (LEL) to 5.25 (UEL) percent mixture by volume of propane gas and air. The mixture is introduced into the component where internal sparking occurs, or is induced, so that an explosion is evident within the component. An internal explosion must not ignite the explosive atmosphere surrounding the device in order for the component to pass the test. To assure compliance of a component, this sequence is repeated 50 times. Propane, not gasoline, is used for ignition protection tests because it is much easier to get repeatable results using this mixture rather than gasoline vapor.

NOTES:

1. It is not the intention to require such 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.
2. Devices that are “explosion proof “ are considered to be “ignition protected” when installed with the appropriate fittings to maintain their “explosion proof’ integrity.

To determine if a component is “ignition protected”, there are a number of test procedures available that are acceptable to the U.S. Coast Guard. For details of these test procedures, refer to the following:

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