2The Limited Approach Boundary (LAB) is the distance from an exposed energized electrical conductor or circuitpart within which a shock hazard exists.For this presentation the LAB will be shown as a box instead of a circle as is customary.NFPA 70E 100 Definitions
3In this situation there is not a Limited Approach Boundary since the doors are closed and there are no exposed energized electrical conductors or circuit parts.
4With the door open there could be exposed energized electrical conductors and circuit parts. Hazardous energy control would be required before entering the Limited Approach Boundary or Flash Protection Boundary (FPB).
5The distances for a Limited Approach Boundary change based on the voltage and the type of conductor or circuit part. This can be seen on this table from NFPA 70E.NFPA 70E Table 130.2(C)
6If this motor starter were operating at 120 Volts, the Limited Approach Boundary would be 3 ft. 6 in. from the energized conductor or circuit part.7Ft7Ft3 ft. 6 in.3 ft. 6 in.7FtNFPA 70E Table 130.2(C)
7Assuming there is not a lock out and the exposed fixed conductor and circuit part voltages are less than 750 Volts, the worker could not work within 3.5 ft of those parts without having justification.
8Justifications for Energized Work within the Limited Approach Boundary Greater HazardInfeasibleLess than 50 volts.NFPA 70E (A)(1),(2),(3)
9Greater Hazard – De-energizing the cabinet would cause a greater hazard, such as loss of life support systems.NFPA 70E (A)(1),(2),(3)
10If it is infeasible to de-energize the cabinet such as for design limits, operational limits, testing or troubleshooting that cannot be performed de-energized.NFPA 70E (A)(1),(2),(3)
11The voltage level is less than 50 volts. <50 volts – no justification required>50 volts – need justification to work energizedMust still take into account hazards from heat generation and electrical arcs in an explosive environment.NFPA 70E (A)(1),(2),(3)
12A “Work Boundary” is the immediate area within which the defined work scope is to be performed. Includes physical space beyond the defined work scope where the workers may move and use tools.
13THE FIRST CHOICE IS TO LOCK OUT ALL SOURCES OF HAZARDOUS ENERGY WITHIN THE WORK BOUNDARY PRIOR TO WORKING ON ELECTRICAL COMPONENTS.NFPA 70E (A)
14THIS IS A WORK BOUNDARY THAT REQUIRES ADDITIONAL PROTECTIVE MEASURES THE SECOND CHOICE IS - LOCK OUT TO THE MAXIMUM EXTENT POSSIBLE. THE QUALIFIED WORKER WOULD THEN NEED TO BE INSULATED OR GUARDED FROM THE REMAINING SOURCES OF HAZARDOUS ENERGY THAT CANNOT BE LOCKED OUT.THIS IS A WORK BOUNDARY THAT REQUIRES ADDITIONAL PROTECTIVE MEASURESNFPA 70E (A)(1),(2),(3)
15Working within the LAB of energized conductors or circuit parts may require an Energized Electrical Work Permit (EEWP) depending on the scope of work.NFPA 70E (B)(1)
16When planning a work package all sources of hazardous energy within the Work Boundary need to be considered and controlled.DOE 0336
17The controlling organization cannot limit their focus to the hazard presented by the component to be worked on.
18There may be additional electrical energy sources, each of which have their own limited approach boundary.
19An “Electrically Safe Work Boundary,” once established, does not have a Limited approach Boundary or Flash Protection boundary within it.
20A detailed Shock Hazard Analysis and an Arc Flash Hazard Analysis must be performed for all electrical work. This includes lock out activities for safe condition checks.NFPA 70E
21The Shock Hazard Analysis helps to protect the qualified worker from electric shock by defining the boundaries, voltages and the PPE required.NFPA 70E (A)
22The Arc Flash Hazard Analysis helps to protect the qualified worker from an Arc Flash by defining the Flash Protection Boundary and the PPE required for a given work scope.NFPA 70E 130.3
23This Arc Flash Event injured 3 workers who were not wearing PPE and decided to perform work on energized components without removing the hazardous energy.
24More thoughts on electrical work… If you are working in tight places, consider inadvertent contact caused by tripping, elbows, hand slipping off a tool, etc., that might lead you to expand the area to be either de-energized or guarded.
25More thoughts on electrical work… Look-Alike EquipmentWhere work performed on equipment that is de-energized and placed in an electrically safe condition exists in a work area with other energized equipment that is similar in SIZE, SHAPE and construction; Safety Signs and Tags, Barricades Attendants shall be employed to prevent the employee from entering the Look-Alike equipment.orNFPA 70E (E)(4)
26Additional potential hazards outlined in your company’s hazardous energy control procedure must be identified and addressed as well.
27EFCOG Electrical Safety Subgroup Please maintain a questioning attitude and look at all of the potential hazards while preparing for a job using your work control process.EFCOG Electrical Safety Subgroup