My line of work brings me into contact with a lot of hazardous locations. Some weeks I feel I should just sleep in my FR coveralls! But each month we find errors in hazardous location classifications that could have disastrous results. This article is an attempt to bring to light some of the common errors we have come across:
1) Be able to state what Recognized and Generally Accepted Good Engineering Practice (RAGAGEP) that was used to establish the hazardous locations. I am partial to NFPA 497 for the Class I locations and 499 for the Class II locations. But there are other codes/RAGAGEPs that are popular and can be used across many different industries. The reason why I like NFPA 497 is that it has pictures! Seriously, it has diagrams of all the different situations that a plant could have and they clearly show how to rate the different areas.
2) For those of us in the USA, OSHA now (since 8/2007) requires that any new hazardous locations be documented and that this documentation be available to those authorized to design, install, inspect, maintain, or operate electric equipment at the location. This can be interpreted in different ways, but we take it for face value and feel that any area established as a HAZLOC after 8/13/2007, have a plot plan with a written explanation of the designation.
3) Don’t forget roof tops! This is by far the most common error we come across. Rooftops are often the location where process vents end up venting to and this same area is often the location for HVAC units. I do not know of any code or RAGAGEP that does not classify the area around a flammable liquid vessel vent discharge (5′ bubble) as a Class I Division 1 location and Div 2 for 10-25′ beyond that (depending on code used). Plants also tend to put ventilation duct work that carries flammable vapors or dusts on roof tops and these items could also require parts of the rooftop be a hazardous location, usually a Division 2 location.
4) Mark your boundaries. Although not specifically required by OSHA, it certainly makes sense so that workers, especially contractors, will know when they are in a Hazardous Location. I do not differentiate my markings between Div 1 and Div 2 areas, but posting the entry ways into the area is a good idea.
5) Division 1 areas mean that we expect flammable vapor to be there in ignitable mixtures under normal conditions. There are locations where Div 1 areas are a reality, but they are rare in working areas where workers are positioned. Vessel openings inside the process area would be considered a Div 1, the same as vent discharges with a 5′ bubble around the opening. This is REGARDLESS of your mechanical ventilation in the area. Any facility claiming a Div 1 location in the working area (other than around vessel openings) will raise red flags for any inspector or auditor. Not only is this very serious from a flammability perspective, it also raises questions about chemical exposures as most of the flammable vapors have PEL’s well less than their LEL, so if we are saying we have a Div 1 location we should be doing some air monitoring to determine chemical exposures to these vapors.
6) If your facility has a true Class I Division 1 location, these areas require an aggressive effort to control ignition sources. A thorough hazards analysis needs to take place to identify tasks that are done within the Div 1 location. MANY TIMES we are the ignition source or we create the ignition source (see my articles about static electricity hazards) in these Div 1 locations. For example a worker standing over a man-way doing manual additions to a vessel containing a flammable liquid is working in a Div 1 location and the manner in which he/she is making their manual additions is ABSOLUTELY CRITICAL, even if they are doing these additions into a vessel inerted with nitrogen!
7) Tools for the trade in Hazardous Locations! This one is about as clear as mud. We feel non-sparking tools are needed when working in hazardous locations. I will agree that Div 2 locations are less necessary than Div 1 locations, which are without a doubt ABSOLUTELY NECESSARY. My position on allowing different tools into the areas is that we will eventually find regular tools in the Div 1 location and this can not be accepted at any level; therefore, I have always required ONLY non-sparking tools in a hazardous location, regardless of division rating.
8) Height of the hazardous location. There is a little rule for flammable vapors that allow a facility to limit their hazardous locations from the ground up to a height of only 3′. This is of course based on the fact that your flammable vapors are HEAVIER than air and they will settle along the floor/ground. Using this “rule” allows a facility to install ordinary ceiling lighting in the area and some even install all of their electrical panels so that the bottom of the panel is at least 3′ high. We have even seen facilities install ordinary outlets at the 3′ high mark to get around installing rated outlets. Then they would plug in equipment that is not intrinsically safe and use it in a hazardous location!!!! But here is the catch to using the 3′ rule: if the building has two floors and there are flammable liquids used on the second floor, it is very RISKY to use the 3′ rule. The concern is the floor openings for pipes, vessels, etc. will allow spills/vapors on the second floor to migrate down to the first floor, passing by this ordinary lighting and sometimes even spilling/dripping down onto the ordinary equipment. Facilities can certainly use the 3′ rule, but this should be done after serious consideration and plant operating history and experiences.
Classifying hazardous locations is a SERIOUS matter and should be done by well qualified individuals. These individuals should be able to clearly demonstrate why an area was classified in a particular way using the code of their choice as their RAGAGEP. After all of this, just remember… establishing the hazardous locations is actually the easy part!