limited approach boundary. the limited approach boundary (lab) is the distance from an exposed...

LIMITED APPROACH BOUNDARY

The Limited Approach Boundary (LAB) is the distance from an exposed energized electrical conductor or circuit

part within which a shock hazard exists.

NFPA 70E 100 Definitions

For this presentation the

LAB will be shown as a box instead of

a circle as is customary.

In 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.

With 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).

The 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)

If 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.7Ft

7Ft

7Ft

3 ft. 6 in.

3 ft. 6 in.

NFPA 70E Table 130.2(C)

Assuming 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.

Justifications for Energized Work within the Limited Approach Boundary

•Greater Hazard•Infeasible•Less than 50 volts.

NFPA 70E 130.1 (A)(1),(2),(3)

Greater Hazard – De-energizing the cabinet would cause a greater hazard, such as loss

of life support systems.

NFPA 70E 130.1 (A)(1),(2),(3)

If 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 130.1 (A)(1),(2),(3)

The voltage level is less than 50 volts.

<50 volts – no justification required

>50 volts – need justification to work energized

Must still take into account hazards from heat generation and electrical arcs in an explosive environment.

NFPA 70E 130.1 (A)(1),(2),(3)

A “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.

THE FIRST CHOICE IS TO LOCK OUT ALL SOURCES OF HAZARDOUS ENERGY WITHIN THE

WORK BOUNDARY PRIOR TO WORKING ON ELECTRICAL COMPONENTS.

NFPA 70E 130.1 (A)

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 130.1 (A)(1),(2),(3)

Working 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 130.1 (B)(1)

When planning a work package all sources of hazardous energy within the Work Boundary need to

be considered and controlled.

DOE 0336

The controlling organization cannot limit their focus to the hazard presented by the component to be

worked on.

There may be additional electrical energy sources, each of which have their own limited approach

boundary.

An “Electrically Safe Work Boundary,” once established, does not have a Limited approach

Boundary or Flash Protection boundary within it.

A 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 130.2 130.3

The Shock Hazard Analysis helps to protect the qualified worker from electric shock by defining the

boundaries, voltages and the PPE required.

NFPA 70E 130.2 (A)

The 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

This Arc Flash Event injured 3 workers who were not wearing PPE

and decided to perform work on

energized components without

removing the hazardous energy.

More 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.

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.

NFPA 70E 130.7 (E)(4)

or

More thoughts on electrical work…

Additional potential hazards outlined in your company’s hazardous energy control procedure must be identified

and addressed as well.

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 Subgrouphttp://www.efcog.org/wg/esh_es/index.htm