Electrical Safety Principles

[Paul W. Abernathy]

Electrical Safety Principles

When planning and performing work on electrical systems and equipment, keep these principles in mind:

• Plan every job
• Think about what could go wrong
• Use the right tools for the job
• Use procedures, drawings and other documents as tools to do the job
• Isolate the equipment from energy sources
• Identify the electric shock and arc flash, as well as other hazards that may be present
• Minimize the hazard by guarding or approach limitations
• Test every circuit, every conductor, every time before you touch
• Use personal protective equipment as a last line of defense in case something goes wrong
• Ask yourself, "Do I have the skills, knowledge, tools and experience to do this work safely?"

Electrical Shock Dynamics (3 important considerations)

• Path - entering the body and exiting the body
• Amount of current or energy flowing in the body
  • 
    60 Hz AC CurrentResponse0.5 - 3 mAstart to feel the energy, tingling sensation3 - 10 mAexperience pain, muscle contraction10 - 40 mAgrip paralysis threshold (brain says let go; but physically cannot do so)30 - 75 mArespiratory systems shuts down100 - 200 mAexperience heart fibrillation200 - 500mAheart clamps tightOver 1,500 mAtissue and organs burn
• Duration of exposure - degree of injury also depends on the duration and frequency of the current. Note: "Shock" injuries can resemble an "Iceberg" where most of the injuries are internal, with only an entry and exit wound visible. Prompt attention is required by individuals specifically trained to treat electrical injuries.

Accident victims can also incur the following injuries from electrical shock:

• Low-voltage contact wounds
• High-voltage contact wounds frrom entry and exit of electrical current
• Burns
• Respiratory difficulties (the tongue may swell and obstruct the airway; or vaporized metal or heated air may have been inhaled)
• Infectious complications
• Injury to bone through falls, heat necrosis (death of tissue) and muscle contraction (shoulder joint injuries and fracture of bones in the neck are common injuries caused by muscle contraction).
• Injury to the heart such as ventricular fibrillation, cardiac arrest or stoppage
• Internal and organ injuries
• Neurological (nerve) injury
• Injury to the eyes (cataracts from electrical injury have occurred up to three years after the accident)

Hazard Identification and Analysis
Every electrical safety program should include a procedure for analyzing the risks and hazards associated with each job. Employees should always consider the following:

• Environment
  • wet or dry
  • indoors or outdoors
  • open or cramped
  • well lit or dim
  • metal ladders in area where overhead wires or exposed conductors are present
  • electrical cords over a heat source
  • overloaded electrical outlets
• Condition of Equipment
  • age of equipment
  • integrity of grounding system
  • internal safety mechanisms
  • operating voltage
  • electrical wiring and loads incurred
  • fault current available to produce arc flash
• Electrical Safety Work Practices
  • ensure that operating procedures are up to date and appropriate for conditions
  • evaluate circuit information drawings
  • determine degree and extent of hazards
    • comply with minimum clearances when working around electrical power lines or other exposed conductors
    • determine approach boundaries:
    • flash protection boundary - linear distance to prevent injury from a potential arc-flash
    • limited approach boundary - restricted distance for "unqualified" persons
    • restricted approach boundary - restricted distance for "qualified" persons
    • prohibited approach boundary - PPE for direct contact with live parts - flashover distance
  • determine "flash protection boundary" requirements from approach boundaries table (NFPA 70E)
  • determine appropriate personal protective equipment (PPE) based on potential hazards present
    • always wear safety glasses and a hard hat when working on live circuits
    • use electrically insulated tools
    • use electrically insulated gloves
    • test dates for integrity of equipment and protective clothing - independent safety lab
    • wear required personal protective clothing (i.e., long sleeve shirt and long pants)- flame resistant materials for clothing (different weights for protection dependent on fault levels and clearing times)
  • your hands are your most valuable tools. Protect them by wearing appropriate safety gloves. Before using, inspect the gloves for signs of wear and tear and other damage.
  • evaluate personnel qualifications
  • use ladders with nonconductive siderails if there is any possibility the ladder could contact exposed energized parts
  • follow lock-out/tag-out procedures
  • use power tools that are double-insulated or that have ground-fault circuit interrupters protecting the circuit
  • inspect all extension cords for wear and tear and make sure they are listed by a third-party testing laboratory
  • never drape electrical cords over heat sources
  • never store flammable liquids near electrical equipment, even temporarily
  • be aware of special training requirements
  • motors with thermal protection can restart without warning, always lockout the motor before working on it.
  • only qualified personnel should perform maintenance, inspection and repairs on any electrical equipment.
  • do not use tin stranded wire with solder - this promotes corrosion and limits contact area.
  • if measuring voltage with respect to ground, make the ground connection first and remove it last.
  • plugs and connectors should be wired with additional slack. In the event of undue strain on the cord, the grounding will be the last broken.
  • grounding continuity should be checked on new tools and equipment before being put into service.
  • remove paint from mating surfaces or use a locknut or set screw to penetrate the paint and make a metal-to-metal contact.
  • don't overbend cables when pulling them through a bend in a raceway, often a pressure or squeezing develops causing insulation damage.

Reprint Courtesy of : ESFI Safety Foundation

[Paul W. Abernathy]

Bump.....be Safe !

[Paul W. Abernathy]

Bump Again...Think Safety

[mbledsoe]

Great Post !! Should we have a safety category on the board?

[Paul W. Abernathy]

naw........we just like to BUMP up old posts that may make ya be just a little safer......

[Paul W. Abernathy]

Bumpin Again.....

[Michael Larson]

Thanks Paul for the reminder, reminder, reminder, reminder. None of of us can hear or see to often. I have been doing safety for over 30 years and I still need reminders. Its just too darn easy sometimes to get stupid and not put on the PPE and think. Keep reminding us Paul. I have stories I will share in the future where the safety "rules" were not followed and a price was paid.

[Robert J. OConnor]

Originally Posted by mlarson

Thanks Paul for the reminder, reminder, reminder, reminder.

I second that notion ...

[Paul W. Abernathy]

New Years Reminders....