What are Flameproof Motors?

In a flame proof motor any spark developed inside the enclosure will not propagate outside the enclosure. In a normal motor that chance is there.

The main difference between normal motor and flameproof motor is the construction of the frame of the motor. Electrically the 2 motors are identical (depending on the manufacturer and money)

The flameproof motor's frame is more robust with larger spigots and end caps on the bearing housing. This more robust frame is needed if a gas explosion (not electrical explosion) occurs inside the frame of the motor, the explosion needs to be contained inside the frame and the flame need to be cooled down by the time it reaches the outside.The larger spigots on the frame is acting same as a cooler for the flames (this is called the flame path).

The sizes of the spigots are determined by the volumetric capacity of the frame, in other words the larger the frame size the larger the spigots. This effectively is needed because the more gas that will be able to gather in the frame of the motor, the bigger the explosion will be, the bigger the spigots needs to be to create a longer flame-path to cool the flame down.

Additional help can be obtained from:

http://www.brookcrompton.com/pdf-files/2203e_hazcat_v1.pdf

http://cr4.globalspec.com/thread/44009

- MS

The selection and installation of electrical equipment for use in hazardous areas requires a certain amount of training. As well as the motor, the cable glands leading to it have to be selected to suit.

If in doubt, consult an experienced designer and delegate the task to that individual.

http://en.wikipedia.org/wiki/Electrical_Equipment_in_Hazardous_Areas

Flame proof motors are used where chances of explosive vapours to be present in a plant.So even if explosion takes place due to flammable gases /vapours enetering the machine it can withstand and contain it.The design needs certification by certain accredited labs.The mating surfaces are designed keeping the flame paths in mind.You need to have a good knowledge of hazardous areas ,gas Group classification for selection and application of flame proof motors.Though electrical design is same mechanical designs are totally different.

In flameproof motors even if sparks are generated inside the motors are not able to ignite the hydrocarbon which may present outside..because it's constructed in such a way that the gaps in the joints of the equipment is very very small,of the order of 0.1mm.....& the flame path is also moreby which time it comes outside it carries insuffienet energy which can ignite the hydrocarbon...different types of flameproof motors are present depending upon the types,probability of the hydrocarbons....

One can mount a type-tested and certified <...Flameproof Motor...> in a Zone 2 or a Zone 1 hazardous area subject to its gas group being correct for the application; one cannot do this with a <...normal motor...>.