Explosion Proof and Intrinsically Safe: Different Methods, Same Goals|
Deciding on the proper lighting for a particular work location can result in some unexpected confusion. Although many people understand that the presence of flammable or volatile materials and gases present a hazard, they do not understand the nature of equipment that must be used in such locations. Considering that any location that presents the possibility for fire or explosion due to the presence of volatile materials may constitute what is known as a hazardous environment, it is critical that anyone who is going to be working under such conditions understand the nature of equipment these environments require.
In general, any environment that presents a fire or explosion hazard due to the presence of volatile gases, vapors, chemicals, or materials such as dust or suspended particles represents a hazardous location. Examples of this include but are not limited to, storage tanks used to store petrochemicals, grain silos, buildings that house operations where chemicals are routinely used or operations produce fine particulates, tank farms, power plants, ship based storage containers or fuel tanks, automotive spray booths, and many more.
In order to work in these areas, it is necessary that adequate lighting be provided in order to perform work safely and ensure that productivity and quality remain high. The problem however is that electricity and volatile vapors or materials do not mix well together. Most electrical equipment either produces some sort of spark during the normal course of its operation, or has the potential to produce unexpected sparks or flame. In reducing the chances for inadvertent ignition in hazardous locations the main emphasis is on removing any potential sources of ignition. Thus, any electrically powered equipment to be used in a hazardous location needs to have some sort of provisions to prevent it from creating an ignition source. It is here that explosion proof and intrinsically safe lighting comes into play.
The first thing to consider is the fact that the terms explosion proof and intrinsically safe do not represent the same thing. Explosion proof lighting is designed for use in hazardous locations and must be certified for such use by accredited institutions such as Underwriters Laboratories for use in these environments. Additionally, not only must equipment be certified as explosion proof, but it must also be properly rated according to the type of environment it is to be used in. Explosion proof lighting like Larson Electronics’s Explosion Proof Light - Tripod Mount - 70 Watt Metal Halide Light reduces the chances of ignition by being capable of containing an explosion or ignition of materials within its housing, preventing them from escaping at temperatures that could ignite the surrounding atmosphere. Keep in mind that these are broad explanations of how explosion proof lighting works and that for a full explanation of hazardous location lighting and the various ratings assigned to it you need to refer to OSHA or a similar regulatory agency for a detailed descriptions. It also needs to be noted that regulations vary by country and that the relevant country’s regulating bodies have the definitive jurisdiction over the regulations regarding hazardous location equipment.
Intrinsically safe lighting on the other hand achieves the same goal as explosion proof lighting; the prevention of ignition, but through a different methodology. Rather than being designed primarily to contain explosions or ignitions, intrinsically safe lighting relies on very low voltages and rugged designs made of materials that resist creating sparks when coming into contact with other surfaces. Intrinsically safe lighting is usually battery powered and uses so little current that it is incapable of either producing sparks or producing enough heat to ignite gases or materials. In either case, the end goal is the same although achieved through different means. It is also important to note that intrinsically safe equipment and explosion proof rated equipment is not interchangeable. As noted above, the proper equipment rated for the particular environment it will be used in must be utilized.
All lighting equipment to be used in hazardous locations is rated by Class, Division and Group/Zone. Each rating pertains to the different hazards presented by the conditions in a given location and because of this lighting must carry the corresponding ratings to be allowable for use in that location. For example, a light rated for use in a Class I, Division II area is not suitable for use in an area rated as Class I, Division II. So if you have a light that is certified Class I Division II and is rated for use in areas where chemicals or vapors may be present intermittently or at moderate levels, but the area you need to work in is rated Class I, Division I because there is a constant presence of volatile materials and at high levels, then you cannot use the Division II rated light in this area and must obtain a light that is rated Class I Division I.
Another thing to consider about explosion proof rated lights is that just because they are rated explosion proof does not mean they are air or water tight. The explosion proof rating simply means that they will prevent internal ignitions from escaping and igniting the surrounding and so are not airtight or waterproof. This means that explosion proof lighting should not be submerged or subjected to heavy liquid contamination unless it is specifically rated as water and air tight and capable of withstanding such treatment.
One other important issue to keep in mind that although there is a lot of equipment available that is rated as vapor proof, this does not mean it is safe for use in hazardous locations. Although such equipment may in fact be vapor proof, this does not mean that it cannot get hot enough to cause ignitions, or contain the effects of an exploding bulb within its housing. By the same token, just because equipment is rated as explosion proof, does not automatically infer that it is vapor proof. Equipment must be certified explosion proof and if it does not carry the proper identification then it is likely not suitable for use in dangerous environments.
Before entering into a hazardous location to perform work it is necessary and in fact required by law that any equipment you use be properly rated. To ensure your safety and that of those around you be certain to educate yourself about how explosion proof equipment is rated and what those ratings mean for your workplace. Although it may seem confusing at first, explosion proof equipment really isn’t very difficult to understand. The safety and feeling of security that comes from knowing you are using the right equipment for the job is worth the effort it takes.