Document ID: OSHA-2010-0001-0066
Agency: osha
Document Type: Supporting & Related Material
Title: 
Posted Date: 2010-11-12T05:00Z

Process:  Electrical Safety

Matrix:   Hazard - shock  

Threshold of Perception,  

Startle Reaction

No-Let Go Current

Ventricular Fibrillation

Asystole

Respiratory Arrest

		-Electric Arc Flash

Burns from incident energy

Pressure Wave

Fire

Shipyard Electrical Work

1.  Shipboard:  Installation, Removal Upgrade, Repair & Grooming, 
Troubleshooting, Testing.

	2.  Shop Test Bench 

	3.  Industrial Equipment and Tools

	4.  Sources:

Shipboard Generated Power

Temporary Power

Storage systems (e.g. batteries)

Facility Power

Parallel Sources

	3.  Facility Powered Systems

	4.  Temporary Electrical Power

	

Hazard:  Electric Arc Flash

1.   May occur during an electrical fault.   Enclosures such electrical
panels and junction boxes typically designed to contain the energy
associated with an arc flash.  During repair and maintenance, electrical
panels and systems are opened supporting the work by shipyard
electricians.  If an arc flash occurs when an electrical panel is open,
shipyard workers in the area will be exposure to the energies associated
with the arc flash.    During an arc flash electrical current due to a
fault can rapidly exceed conductors and electrical components current
carrying capacity.  Before protective devices such as circuit breakers
or fuses activate, the excessive current may cause conductors and
components to melt or vaporize.   Employees working on or near open
enclosure during an arc flash will be exposed to an explosively
expanding high temperature plasma molten metal and vapor that
immediately ignites or melts clothing and all but specialized PPE.

2.  The amount of energy release during an arc flash event depends upon
multiple factors, most of which cannot be determined except by design
calculations.  Factors such as the trip settings of over current devices
(circuit breakers and fuses), the tripping time of these devices, and
the available fault current available from upstream electrical sources
directly affect the energy an electric arc flash and even prevent such
events from occurring.   Arc flashes have been observed associated with
all nominal AC voltage ranges that typically are found at shipyards,
including shipboard systems such as 480 V. 

3.   The most effective way to protect from the hazards of electric arc
flash is to de-energize electrical systems utilizing compliant
(1910.147, 1910.333, 1915.89) lockout/tagout procedure and verifying the
de-energized condition with approved test instruments.   Until the
de-energized condition is verified or when work must be performed
energized, the appropriate PPE must be utilized.  

4.  Selecting PPE for electric arc flash protection while simple in
concept is a complex process.  NFPA 70E, Electrical Safety in the
Workplaces should be consulted to assist in the calculations to
determine if an arc flash hazard is present for a given electrical
circuit  and the selection of PPE necessary to protect against the
hazard.

	(Note: Should IEEE Std 1584 be mentioned or referenced)

5.  Shipyard Employers are required by 1915.152 to assess work activity
and determine whether there are hazards present, or likely to be
present.    When electrical work is performed, arc flash hazard
assessments are necessary to determine if the hazard is present and the
suitable PPE necessary to protect the shipyard workers involved.



 

Case History: #TBD

Possible abatement strategies to prevent this accident:

Perform an arc flash PPE assessment.   

Determine suitable PPE to protect against arc flash hazards.  

Train employees on the use, care, and selection of available PPE based
upon the hazard assessment.

  

    

Draft

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