Transcript Work Area Boundaries-Limited Approach Boundary

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.
For this
presentation the
LAB will be shown
as a box instead of
a circle as is
customary.
NFPA 70E 100 Definitions
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
3 ft. 6 in.
3 ft. 6 in.
7Ft
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 deenergized.
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 MEASURES
NFPA 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.
More thoughts on electrical work…
Look-Alike Equipment
Where 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 or Attendants shall be
employed to prevent the employee from
entering the Look-Alike equipment.
NFPA 70E 130.7 (E)(4)
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 Subgroup
http://www.efcog.org/wg/esh_es/index.htm