S A F E T Y M O D E L S TAG E 1 — r E C O G N I Z I N G H A Z A r D S
Operating a crane near overhead wires is very hazardous.
Shocks and electrocutions occur where phys- ical barriers are not in place to prevent con- tact with the wires. When dump trucks, cranes, work platforms, or other conductive materials (such as pipes and ladders) contact overhead wires, the equipment operator or other workers can be killed. If you do not maintain required clearance distances from powerlines, you can be shocked and killed. (The minimum distance for voltages up to 50kV is 10 feet. For voltages over 50kV, the minimum distance is 10 feet plus 4 inches for every 10 kV over 50kV.) Never store materials and equipment under or near over- head powerlines. You need to recognize that overhead powerlines are a hazard.
F ive workers were constructing a chain-link fence in front of a house, directly below a 7,200-volt energized powerline. As they p r e p a r e d t o i n s t a l l 2 1 - f o o t s e c t i o n s o f m e t a l t o p r a i l o n t h e fence, one of the workers picked up a section of rail and held it up vertically. The rail contacted the 7,200-volt line, and the worker was electrocuted. Following inspection, OSHA determined that the employee who was killed had never received any safety training from his employer and no specific instruction on how to avoid the hazards associated with overhead powerlines.
In this case, the company failed to obey these regulations:
Employers must train their workers to recognize and avoid unsafe conditions on the job.
Employers must not allow their workers to work near any part of an electrical circuit UNLESS the circuit is de-energized (shut off) and grounded, or guarded in such a way that it cannot be contacted.
Ground-fault protection must be provided at construction sites to guard against electrical shock.
Defective insulation hazards
❚ insulation—material that does not conduct electricity easily
Insulation that is defective or inadequate is an electrical hazard. Usually, a plastic or rubber covering insulates wires. Insulation pre- vents conductors from coming in contact with each other. Insulation also prevents conductors from coming in contact with people.