Flameproof Motor

The flameproof motors are those motors that are approved to be used in Class I locations. The Class I location refers to the locations where it is filled with ignitable vapors, explosives, and gasses. The Class I locations are the foreseeable parts of the manufacturing process and thus, the flameproof motors we offer for Class I locations are capable of containing the explosion within its unit without rupturing.

The locations where the considered materials wreck chaos due to the ruptured container, then this is distinguished as Class II locations. In these types of locations, the environment is composed of dust which may form explosive mixtures. In Class II locations, the flameproof motor used is dustproof. For example, in the case of the flour industry; wheat flour is considered a hazardous mixture or dust due to its capability to catch fire.

If the reaction gets serious, it may lead to a heavy explosion and the wheat flour industry can turn into dust. Thus, it is necessary to classify your location before availing of a flameproof motor because there are explosive gases, liquids, and vapors nearby which can cause some serious destruction.

Class III locations are those locations where the whole environment is exposed to combustible components like ignitable fibers. Thus, using a flameproof motor according to the area specification is very necessary. Choosing a flameproof motor for Class III locations can be a bit tricky because the materials of the Class III locations are not airborne. They tend to settle down at a rapid speed because they heft.

However, not being airborne makes them heavier materials and doesn't impact they're being highly flammable. Thus, in this case; if even a small ignitable component is brought closer to electrical equipment, it will surely create a hazardous situation. The Class III locations include industries engaged with cocoa fiber, rayon, Spanish moss, sawdust, jute, hemp, and more.

Given that an explosive atmosphere is allowed to enter the enclosure, the enclosure must be strong enough to contain an explosion. Both the metallic and non-metallic materials that are part of the flamepath or constitute the enclosure walls must be strong enough to withstand the explosion pressure and impact. Similarly, the materials must be able to survive any naturally occurring physical damage to the exterior of the enclosure that could invalidate the integrity of the flamepath (if the enclosure is bumped, for example).

if any portion of the flamepath or walls of the enclosure is made of non-metallic material, these materials must be just as strong as metallic materials and similarly need to withstand the explosion pressure and impact.

There are normally gaps in flameproof enclosures. Generally, there are two essential properties of a flamepath: the clearance (the size of the gap) and the length of the path. By design, gaps in the flamepath must be narrow enough to cool the hot , pressurized, burning gases before they can come into contact with the external atmosphere. The flamepath must quench any flame before it reaches the outside atmosphere. It is not possible or desirable to design an enclosure with no gaps between the various parts. An allowable gap between different parts is accepted, but strictly defined in the Standards. Gaps help to relieve the pressure inside the enclosure caused by an explosion.

The design of the enclosure must also ensure that the gaps are not damaged mechanically if an explosion does take place.

Because cables enter enclosures through a cable entry hole (which is a flamepath) normally provided during the manufacturing, cable entries in Ex d enclosures must satisfy the requirements in the Standards for flameproof enclosures. Cable connections in a flameproof enclosure may be either "direct entry" or "indirect entry".

Direct entry

Direct entry connection means that the connection facilities (the terminal block) are inside the enclosure for connection outside. For direct entry, cables enter flameproof enclosures via a cable gland (made of metallic or non-metallic materials) or conduit. Cable glands of a given pressure rating are basically mechanical cable entry devices. They are sealed onto the cable. Flames and sparks are prevented from travelling from the electrical equipment to the environment outside the enclosure. Cable glands allow cables to be safely passed into the enclosure.

The threaded hole must satisfy the requirements for threaded joints that are in the Standards. The word "direct" is used to describe them because the external circuit (power supply) is directly connected to the terminal block of the enclosure to energize the circuit within the enclosure. Cable glands offer a safe and secure connection between the electrical device and the cable to which it's connected.

Cable glands must not be opened when a circuit is energized.

Indirect entry

An indirect entry cable connection has a separate terminal box, which may be connected to the main enclosure by bushing or a sealed flying lead. The advantage of an indirect entry is that wiring does not directly enter the flameproof enclosure. The cable bushings are installed by the manufacturer of the enclosure, which can therefore be tested at the factory. The installer needs only to have access to the bushing or a sealed flying lead for wiring termination externally, but not the flameproof enclosure itself, in order to connect the wires.

The internal geometry, dimensions and volume of the enclosure are all critical to its effectiveness. The amount of heat and pressure produced by an explosion are directly proportional to the free internal volume of the enclosure. The enclosure's volume must therefore be taken into account when designing the flamepath. The larger the volume, the longer the flamepath needs to be and the smaller the gap needs to be.

Pressure piling involves, as the name implies, the build-up of pressure that is higher than the expected peak pressure. Pressure piling can happen when explosion proof enclosures are not designed and installed properly for use in a hazardous area. The result of pressure piling can lead to a catastrophic event. (See our article "Pressure Piling")