June-July 2018 Q&A
Q: Whenever we see graphics for single-point grounding, it’s always a cluster, a connection to the neutral, a connection to a phase and a chain connecting to the other two phases. But when we check with other utilities or consultants, we see all kinds of arrangements, such as bracket grounds with a single point or two sets of single-point grounds bracketing the workspace. Where do we find the definitive arrangement, and why are there so many variations?
A: Under OSHA, the employer is solely responsible for determining how they will meet the requirements of 29 CFR 1910.269(n)(3), “Equipotential zone,” which requires that grounding of de-energized phases be installed in an arrangement that prevents employees from being exposed to differences in electrical potential. In addition to 1910.269(n)(3), there also is Appendix C to 1910.269, “Protection From Hazardous Differences in Electric Potential,” as well as IEEE 1048-2016, “IEEE Guide for Protective Grounding of Power Lines,” a consensus standard that may be considered the authoritative best practice. IEEE 1048 is filled with detailed electrical data – from modeling to application – to explain how to create equipotential protection and effective tripping of grounded circuits that may inadvertently be energized.
Still, a lot of utility practices are based on old habits that don’t necessarily improve protection. We ground to trip circuits. We bond to protect workers. That means that grounding phases to earth is for one purpose, and that how we arrange the grounds to create an equipotential arrangement is for a different purpose. It also is important that the grounding cables themselves are capable of carrying the necessary load for the time required to trip the circuit. If the grounds keep the voltage across the worker low enough that a hazardous current cannot flow across the worker, we have accomplished the goal. But no matter how many ground sets you put up, grounds are still there to cause immediate operation of a protective device. Grounding to the neutral or static does not ensure protection of the worker. That is why the new OSHA standard clearly states that grounds shall be arranged to ensure that employees are not exposed from differences in potential should the circuit become inadvertently energized.
As to the number of ground sets, in some cases, one set of grounds may not provide enough capacity to meet the calculated demand of the maximum available fault current. In that case, an employer may require two sets. Redundant sets provide more current-carrying capacity. If those ground sets are the limiting factor for the total current flowing in the fault, that would mean more current across the worker if the worker is not at equal potential. If the worker is bonded in, it does not matter where the grounds are installed in reference to the worker because it is the equipotential installation that provides worker protection.
Even how we connect to phases is not settled. We have always advocated phase-to-phase chains with a connection to neutral, yet the latest IEEE modeling shows some decrease in voltage across a protected worker when brackets are installed phase to neutral for each phase. And, depending on relaying, there may be merit to using sets in the three-phase-to-ground connections, or two chains with one connection to earth and one connection made in an equipotential arrangement. But no matter how you decide to connect, what you do ultimately depends on the employer’s analysis of the conditions on the circuit.
Adding unnecessary sets in a bracket configuration could create circulating current, either from induction or in the case of a fault. While circulating current in a grounding arrangement is not necessarily bad, circulating current can bring other issues under some conditions. Ultimately, no matter how you decide to hang your tripping grounds, it is bonding that provides the most protection for the worker. With that in mind, it seems that adding grounding sets without a compelling electrical fault management purpose makes little sense if it does not add protection for the worker.
Q: I am new to the safety management role at our power plant, but I do recognize we need to put a better training program in place for our forklift operators. I’ve been asking vendors how to become certified to train the operators and they have been kind of vague about it. Am I asking the wrong question?
A: You’re not asking the wrong question, but you may be asking the wrong people. It’s possible vendors would rather sell you the training than teach you how to do it. The fact is that there is no published criteria for certification of a forklift trainer. There also is no requirement that an employer use a certified trainer since there is no certification required for operators, only the employer’s assurance of competency. You may call the employer’s assurance of competency a certification of operators. Certification simply means that an authority – in this case the employer – certifies that the operator meets the criteria to be a qualified operator. The criteria for the qualified operator is in the OSHA standard that covers forklifts, or, as OSHA refers to them, powered industrial trucks. Those rules are found in 1910.178(l). The OSHA standard requires the employer to ensure operators meet the requirements for a qualified operator. The requirements for a trainer are found in 1910.178(l)(2)(iii). To be a trainer, you must be an expert on the OSHA requirements for employer’s training and certification of powered industrial truck operators, and you must be competent to observe and evaluate the operator’s demonstration of lift inspection and operation. It’s up to the employer to decide who to use to train and certify their operators.
Q: I am currently on a job with a few man baskets. I have used many in the past and am quite aware of all of the regulations about testing and so forth. I am accustomed to storing the basket in the deck of the crane after each use. The new company I am working with thinks it’s OK to travel with the basket mounted, but to me that seems to cause unnecessary wear on the basket mounts. Are there any regulations prohibiting this?
A: OSHA treats both a suspended man basket and a boom-mounted basket the same way. The only time it is prohibited to travel with a mounted basket is when there are personnel in the basket or if the crane manufacturer prohibits it. Otherwise, there is no prohibition in OSHA or the consensus standards. OSHA does require the operator’s manual to be on the crane, so begin there. You are correct, though, that basket weight on rough terrain has damaged some mounting fittings. For that reason, the requirement to perform a trial lift after every setup and a proof test after every removal and reinstallation is important. There also is another emerging issue with crane-mounted baskets that the industry should recognize. OSHA prohibits the use of cranes to hoist personnel in rule 1926.1431(a), which states, “The use of equipment to hoist employees is prohibited except where the employer demonstrates that the erection, use, and dismantling of conventional means of reaching the work area, such as a personnel hoist, ladder, stairway, aerial lift, elevating work platform, or scaffold, would be more hazardous, or is not possible because of the project’s structural design or worksite conditions.”
As an industry, we have been able to claim the exemption and use crane-mounted baskets with relative impunity from OSHA. Usually it was because of space and minimum approach distance for cranes, particularly in corridors where other lines run parallel to the work area. A bucket truck with folding booms would not fit in the area without boom elbows coming too close to those parallel lines. However, thanks to very recent innovations of aerial lift manufacturers, we now have sectional extending booms, just like the hydraulic cranes we’ve been mounting baskets on. These lifts reach the highest structures and are designed as lifts for personnel. They also will perform the reach without the risk posed by folding booms. It’s a matter of standards for the design of material lifts compared to the design of personnel lifts. OSHA’s position is that cranes are designed as material lifts and converting them to lift personnel is not as safe as using lifts designed as personnel lifts. Utilities and contractors should familiarize themselves with the requirements and prepare to change from cranes used with man baskets to personnel lifts where the new lifts will serve the requirements. It’s somewhat more expensive to use the man lifts as opposed to cranes, but OSHA will not permit that excuse to be the reason for using cranes.
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