A typical electrical plant of a vessel involves diesel generator for electric power production, main switch board for distribution and emergency generator with emergency switch board for emergency electrical power production. Usually a 3phase, 60Hz, 440 Volts supply is being generated and distributed on board; the power through cables and ducts run across the vessel to all compartments.
Namely, electrical current may cause injury in three ways: by converting energy into heat within the body, resulting in burns; by direct effects on the heart; and by causing falls, which can result in injury.
Effects on human body depending on current level
|Current Level (Milliamperes)||Probable effect|
|1 mA||Perception level. Slight tingling sensation. Still dangerous under certain conditions.|
|5 mA||Slight shock felt; not painful but disturbing. Average individual can let go, however strong involuntary reactions to shocks in this range may lead to injuries|
|6-16 mA||Painful shock, begin to lose muscular control. Commonly referred to as the freezing current or ‘let-go’ range|
|17-99 mA||Extreme pain, respiratory arrest, severe muscular contractions. Individuals cannot let go. Death is possible|
|100 -2000 mA||Ventricular fibrillation (uneven, uncoordinated pumping of the heart) Muscular contraction and nerve damage begins to occur. Death is likely.|
Electrical shock hazards
OHSA defines the electric shock as the physical stimulation or trauma caused by the flow of electricity through the human body. It can occur during contact with or by being near live (energized) electrical parts. An electric shock can occur without direct contact with electricity. Electrocution results when death occurs from an electric shock. The most common shock-related injury is a burn. Electrical shock hazards can be created by:
- Defective electrical tools: Untrained or unqualified personnel attempting electrical power connections
- Improper electrical phasing: Damaged wire insulation as a result of hot work processes
- Inaccurate schematic drawings: Corroded connectors due to saltwater intrusion or contact
- Worn or frayed electric cables: Inadequate electrical isolation, failure to test for de-energization, and improper lockout/tags-plus application
- Electric cables pinched in hatches/doors: Tools and equipment not properly grounded
- Electric cables struck by grinders/saws: Blind-side drilling into electrical conductors
How to respond to electrical burns
- When approaching a person in contact with electricity, it has to be ensured that the victim is not under current contact any more. The power of electrical power should be switched off If possible.
- If the current cannot be switched off, put on rubber gloves and rubber boots, or stand on an insulating rubber mat before approaching and touching the casualty. If the victim is entangled in electrical lines, try to remove the lines with a wooden pole, a wooden chair, an insulated cord, or any other suitable non-metal object.
- Check immediately for breathing and heartbeat.
- If the casualty is not breathing, give artificial respiration.
- If there is no heartbeat, apply chest compressions.
- When breathing is restored, cool any burned areas with cold water and cover with a clean, dry, non-fluffy dressing.
- Treat as for heat burns (i.e. relieve pain, prevent or treat shock, and prevent or treat infection).
Electrocution can stop the heart suddenly or cause it go into an abnormal rhythm, which can cause immediate death. If it does not cause immediate death, an abnormal rhythm can last for several hours, in which case it is usually not dangerous. Electrocution causes sudden widespread muscle contraction powerful enough to cause fractures of the vertebrae or falls: always check an electrocuted patient carefully for injuries.
Serious problems are unlikely if ALL the following conditions are present:
- electrocution has occurred with voltages less than 1000 volts;
- the crew member feels well;
- pulse rate and blood pressure are normal;
- pupil size and mental function are normal;
- speech and walking are normal;
- there are no skin burns.
If ALL of the above conditions are NOT PRESENT, operators need to arrange for evacuation the crew member(s) affected to an onshore hospital; insert an intravenous cannula and administer normal saline (0.9% sodium chloride) at a rate sufficient to produce copious pale urine (start with 150 to 200 ml per hour); and treat skin burns in the same way as other burns.
Electrical shocks can be very serious and can cause real physical injury, permanent damage and even death Therefore, seafarers should be well informed and trained in order to be familiar with the use of electrical power on board and use protective clothing or other personal protective equipment before an electrical work is performed.
The following OSHA standards specify safety measures that must be followed to protect workers from electrical hazards in ship repairing, shipbuilding, or shipbreaking activities:
- 29 CFR 1915.181 - Electrical Circuit and Distribution Boards, applies to the vessel's permanently installed electrical circuits and distribution systems;
- 29 CFR 1915.132 - Tools and Related Equipment, applies to temporarily installed electrical systems (such as extension cords, portable service panel, "spider box"); and
- 29 CFR 1915.89 - Control of Hazardous Energy (Lockout/Tags-plus) applies to all machinery, equipment, or systems on vessels, vessel sections, and at landside facilities where their servicing, maintenance, and repair presents the potential for the uncontrolled release of electrical energy.