Basics of Hazardous Location Confined Space Lighting|
Article- Sept, 2013 By Larson Electronics.com
Larson Electronics Hazardous Area LED Work light
Entering confined spaces represents one of the greatest hazards a worker can face. Confined spaces are so dangerous because of the reduced maneuvering room, their tendency to be very poorly ventilated, potential low levels of oxygen, the potential for the presence of dangerous fumes, gases, and vapors that can present either a toxicity or fire and explosion risk. Aside from the obvious risks such as the problems presented with performing rescue operations of trapped or injured workers, some of the greatest hazards are posed by the flammability of gases and vapors.
Confined spaces represent such a serious fire hazard due to the tendency of gases and vapors to accumulate in poorly ventilated areas, and the explosive potential created when these gases and vapors become trapped within an enclosed area. For an example, if you have ever grilled outside, you are likely familiar with wetting down the charcoal with charcoal fluid and then lighting it. You have also likely noticed what happens when you use a bit too much fluid and it has time to set before lighting. When you touched the match to that fluid soaked charcoal, a large *whoof!* of flame likely occurred, and you were lucky to get away with just singed eyebrows.
This was because the charcoal fluid soaked briquettes had time to release flammable vapors, which then settled into the area within the grill and around it. When you lit the charcoal, those vapors also ignited, creating a mini-fireball. Now imagine what would happen if you were to fill a room with those vapors, close all the doors and windows, then expose the room to an open flame. The result would be an explosion of extreme force and power, capable of causing serious injury and death.
Obviously, for the worker who must enter into and perform work within a confined space, protecting against these sorts of accidental ignitions is a critical aspect of the job. Although to enter a confined space deemed hazardous due to atmospheric issues requires the use of atmosphere monitoring equipment and gear to determine safe oxygen levels and the presence of dangerous fumes, the atmosphere can change significantly over a fairly short period of time, making monitoring only part of the solution. Since confined spaces are rarely intended for occupation, they usually have no accommodations such as lighting, and any illumination must be provided by the worker. Since lighting equipment operates electrically, it represents a potential ignition source, which in turn means you must protect against this potential ignition.
In order to prevent lighting from becoming a potential source of ignition in enclosed spaces, only equipment properly rated for a given hazardous space may be used. In most cases, equipment certified as explosion proof or intrinsically safe may be used within a confined space, and in many cases only intrinsically safe low voltage equipment may be used. The most important aspect is that this equipment be matched to the types of hazards to be encountered. Classing these hazards is done by a ratings system known as Classes, Divisions, Groups, and Temperature ratings, and each touches on a specific part of the hazards to be addressed. For an area considered a Class 1 Division 2 Groups A, B and C location, equipment with this same rating or better must be used.
The terms explosion proof and intrinsically safe refer to different types of electrical equipment which have been designed specifically to be used in locations where potential flammable or explosive atmospheres are present. Explosion proof equipment is generally higher powered and designed to prevent any ignitions within the lamp from igniting the atmosphere outside the lamp. Foe example, if gases enter into the lamp housing and are ignited by a spark, the lamp contains the ignited gases long enough to allow them to cool before they can exit the lamp.
Intrinsically safe lighting on the other hand is generally lower powered and considered unable to actually cause ignition. These units generally cannot create sparks or enough heat to ignite gases, and use such low voltages that a short or fault will not create enough heat to cause ignition as well. Because of the severe danger posed by enclosed spaces and the types of flammable atmospheres that may be encountered, the maximum protection possible in the form of intrinsically safe low voltage lighting systems is required. These fixtures usually run on 12 or 24 volt current in addition to being intrinsically safe, making them less prone to producing a heat source capable of producing ignition.
Determining whether a location is considered an enclosed space or not is really pretty straightforward.
Confined spaces loosely defined by a few general characteristics.
- The area is large enough to permit entry and the performance or work;
- Has limited openings for entry and exit; and
- Is not intended for continuous worker presence within the space.
A few examples of a confined space would be the tanker rail cars, storage tanks used at petrochemical plants, silos, utilities service orifices, ship cargo tanks, and many similar types of enclosed containers with limited entrance and ventilation. The classification of hazard in these areas will be determined by the types of materials present, at what temperature they can be ignited, and the likelihood of their presence. Since enclosed spaces really leave little room for error, in most cases, as mentioned earlier, maximum protection in the form of intrinsically safe equipment is preferred or required by regulations. However, as long as equipment meets the minimum requirements assigned to a location, safety should be assured to the best degree possible.
There are a wide array of factors that determine how hazardous confined spaces may be. Atmospheric conditions represent one of the most important issues to address due to the dangers flammable and explosive gases, vapors, and fluids present. In all cases of entering an enclosed space not normally intended for human occupation, it is necessary to properly evaluate and test the location prior to entry in order to formulate a safe entry plan. This and the inclusion of properly rated lighting equipment will go a long ways towards reducing the danger the enclosed space presents.