An arc flash hazard study is a complicated engineering survey and analysis that typically is performed by an engineering consultant. Preparing for the study in advance can make the process much easier and more accurate. Although an arc flash hazard study can be time consuming, a correctly executed study can help improve plant safety by identifying where the most dangerous hazards are located and whether or not safety can be improved.
The arc flash hazard study involves four phases:
Engineering analysis of the data,
Report presentation, PPE procurement, and labeling, and
Of these four phases, only the engineering analysis and report preparation are typically done off site. The remainder of the study occurs within your plant, which brings us to the point of what you can do to best facilitate the process.
When planning for an arc flash hazard study, it's important to consider who at your facility will need to be present for each phase of the process. During phase one, the data collection phase, an experienced plant electrician or someone with similar knowledge will need to escort the outside field technician or engineer around the plant and help him with equipment identification tasks.
If the location of any panels or equipment is going to require an individual to have special access clearance, make arrangements for field technicians prior to their visit. For example, during the course of an arc flash hazard study at a defense contractor, the field technician realized there was a panel located in a clean room that he did not have the proper clearance to enter. Another instance occurred at a medical equipment manufacturer — where a rooftop panel serving air handlers for a clean room could not be opened without being shut down. The facility was unable to shut it down during the field technician's visit. In both cases, plant personnel collected the data at a later date and forwarded it on to the field technician. Plan for these events before the study to prevent delays.
After engineering analysis of the data is complete, phase three of the study will require plant management, safety personnel, engineers, and select other personnel to be present. This should only take a few hours. Phase four of the study will involve the training of many people. Qualified and unqualified personnel must be trained.
Remember that procedures developed as a result of the study are not only a big change for your electrical staff, but also for other plant personnel working in the vicinity of energized equipment.
In addition to preparing the plant for the study, facilities management personnel also need to prepare themselves for the process. If you're a facilities manager, it's important to remember that you are not just conducting an arc flash hazard study to identify places where your electrical personnel will have to wear special personal protective equipment (PPE). The wearing of PPE should be viewed as a last resort. Whenever possible, circuits should be put in an electrically safe condition before work begins; however, circuits can't always be de-energized. For this reason, an arc flash hazard study is necessary.
The study will identify hazards so that you can remove as many of them as possible. When hazards cannot be removed — and where circuits cannot be shut down — your personnel will have to wear special PPE while working on exposed live parts or when verifying that a circuit is safe during lockout/tagout procedures.
Prepare your personnel
As the outside field technicians or engineers arrive at your facility, your personnel are going to have some questions. It's best to prepare yourself for these questions in advance, as the field technicians likely will be wearing PPE when they open panels — and some of this PPE might be foreign to your staff.
One of the common questions from maintenance staff is, “Am I going to have to wear that gear?” Your answer should be that they are wearing the PPE to protect themselves as they identify potential hazards. You should also tell them the study is being conducted in hopes of making adjustments to the system to eliminate or avoid these hazards in the future. This might result in them not having to wear PPE when performing these same tasks.
Use your personnel
The demands on plant personnel are greatest in phase one of the project. In this phase, the outside field technician or engineer will arrive at your facility and collect data on your electrical distribution system. It's crucial that you and your personnel assist them in their efforts.
Field technicians will begin at the connection point(s) to your electric utility, recording transformer kVA, wire size, wire length, etc. From there, they will review your main switchgear, where they will collect fuse and/or circuit breaker information and wire size and length, recording the information on the panels and equipment fed from the switchgear. They will then move to those loads and panels, repeating the process until they have gathered data on your entire system.
If your plant has a complete set of accurate one-line drawings of your electrical distribution system, phase one could be eliminated. However, few plants retain accurate and updated drawings. Some facilities choose to do the data collection process themselves, but be aware that allowing personnel who have not been trained in recognizing the hazards of exposed conductors presents significant safety risks. Allowing only trained professionals to collect data ensures that appropriate safety procedures are followed.
Depending on the size of your facility, the data collection phase could take anywhere from half day to several months, and someone from your plant should be available to assist the field technicians when needed. Consider the following example of how your personnel could provide the field technicians with valuable and time-saving information.
A circuit breaker in a panel is labeled “Press #16.” The field technician needs to know the location of Press #16 so he can record conductor lengths and evaluate the piece of equipment. Generally, the field technician will not be familiar with your plant and will have no idea where that machine is or how to find it. On the other hand, your personnel will know exactly where the machine is located, and whether you even still own it. Oftentimes, your employee will remember that the machine was removed two years ago, and that now Furnace #5 is sitting in this place. At that point, it must be determined what, if anything, this breaker is actually feeding and its location in the facility; otherwise, the study will be plagued with inaccuracies.
The importance of confirming proper labeling prior to the start of the project cannot be emphasized enough. If panel labels are updated and confirmed prior to the arrival of the field technician, the study will be much more accurate, and less rework will be required.
Once the engineering analysis is complete, the consultant will write a report and pass it on to you. The report will include information on labeling requirements and appropriate levels of PPE needed to be worn by maintenance and operation personnel at various points in the system.
The removal and/or minimization of hazards are the final steps in the process. Although not part of the study, this step is the most important in protecting your personnel from the dangers of an arc flash. Money and time will have to be budgeted for these changes, which might involve changing fuses or adjusting trip settings on breakers or relays. After the hazard removal recommendations have been carried out, new labels may need to be made, and your study updated to reflect these changes.
More importantly, issue a policy requiring anyone making modifications to the plant electrical distribution system to properly record these changes. Implementing the policy and making it common practice can help prevent undocumented changes from rendering your study inaccurate. Most companies are making annual updates a part of their safety program. Your safety program should include information on how future modifications will be handled between the time they are made and recorded, as well as when the arc flash study needs to be updated.
Lewellyn is the president and founder of Lewellyn Technology, Linton, Ind.
Editor's Note: An original version of this article first appeared in Compliance magazine, Copyright 2007, Douglas Publications. However, the editors of EC&M have modified the text to meet the needs of its readers.