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Questions and Answers
What unit is the measure of electric shock intensity?
What unit is the measure of electric shock intensity?
Current (Amperes)
What level of current will a person be unable to let go?
What level of current will a person be unable to let go?
10 Milliamps
What level of current can be fatal if felt for more than 1 second?
What level of current can be fatal if felt for more than 1 second?
100 Milliamps
PPE is required when working with what voltage?
PPE is required when working with what voltage?
What are the symptoms of electric shock?
What are the symptoms of electric shock?
If someone experiences electric shock, what action should be taken for loss of breathing?
If someone experiences electric shock, what action should be taken for loss of breathing?
What are the first two steps when someone is being electrocuted?
What are the first two steps when someone is being electrocuted?
What is a flash protection boundary?
What is a flash protection boundary?
What is the purpose of equipment grounding?
What is the purpose of equipment grounding?
What is an EMI Filter used for?
What is an EMI Filter used for?
What are TVSS systems?
What are TVSS systems?
What are Arc Fault Detection Systems?
What are Arc Fault Detection Systems?
Work on energized systems above this voltage is prohibited unless approved by NAVSEA.
Work on energized systems above this voltage is prohibited unless approved by NAVSEA.
When may interlocks be 'cheated'?
When may interlocks be 'cheated'?
Whose approval is required for work on energized electrical equipment over 30 volts?
Whose approval is required for work on energized electrical equipment over 30 volts?
What are some safety precautions when working on energized equipment?
What are some safety precautions when working on energized equipment?
What are STW Checks?
What are STW Checks?
What safety checks must be completed during STW checks?
What safety checks must be completed during STW checks?
When do STW checks not need to be completed?
When do STW checks not need to be completed?
What is 'deranged equipment' now called?
What is 'deranged equipment' now called?
For repair activity work conducted shipboard not IAW NSTM Chapter 300, a ___ between shipyards/repair activities and Ship's Force must be documented.
For repair activity work conducted shipboard not IAW NSTM Chapter 300, a ___ between shipyards/repair activities and Ship's Force must be documented.
For naval applications, voltages greater than or equal to ___ are considered high voltage.
For naval applications, voltages greater than or equal to ___ are considered high voltage.
The resistance of a human body is about ___
The resistance of a human body is about ___
When the skin is damp, the resistance of a human body is about ___
When the skin is damp, the resistance of a human body is about ___
A situation where electrical current passes through air gaps between ungrounded conductors or between conductors and grounded components is called?
A situation where electrical current passes through air gaps between ungrounded conductors or between conductors and grounded components is called?
Another product of an arc flash is the incident energy, which is ___
Another product of an arc flash is the incident energy, which is ___
Occurs when the severity of an arc or short circuit current causes destructive heating and explosive vaporization of both the surrounding air and the metal in the current path?
Occurs when the severity of an arc or short circuit current causes destructive heating and explosive vaporization of both the surrounding air and the metal in the current path?
The unobstructed distance from exposed energized circuits within which unprotected skin could receive a second degree burn if an arc flash were to occur is known as?
The unobstructed distance from exposed energized circuits within which unprotected skin could receive a second degree burn if an arc flash were to occur is known as?
Flash Protection Boundaries is abbreviated as?
Flash Protection Boundaries is abbreviated as?
The FPB distance aboard a ship for 450-volt circuits is ___
The FPB distance aboard a ship for 450-volt circuits is ___
The FPB distance aboard a ship for 4160-volt circuits is ___
The FPB distance aboard a ship for 4160-volt circuits is ___
The FPB distance aboard a ship for 13.8K volt circuits is ___
The FPB distance aboard a ship for 13.8K volt circuits is ___
An FPB of 4 feet is applicable to circuits with rated voltages between ___
An FPB of 4 feet is applicable to circuits with rated voltages between ___
An FPB of 11 feet is applicable to circuits with rated voltages between ___
An FPB of 11 feet is applicable to circuits with rated voltages between ___
An FPB of 13 feet is applicable for voltages ___
An FPB of 13 feet is applicable for voltages ___
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Study Notes
Electric Shock and Current
- Electric shock intensity is measured in Amperes (current).
- 10 milliamps is the current level at which a person cannot release their grip.
- A current of 100 milliamps can be fatal if sustained for more than one second.
Personal Protective Equipment (PPE)
- PPE is mandatory when working with voltages of 30 volts and above.
Symptoms and Emergency Actions
- Symptoms of electric shock include pale or bluish skin, weak pulse or breathing, and body stiffness.
- Perform CPR if a person loses breathing due to electric shock.
- First two steps during an electrocution incident: shut off power (or remove the victim using dry, non-conductive materials) and administer first aid.
Safety and Protection Measures
- Flash protection boundary (FPB) is defined as the distance from an energized circuit that could cause a second-degree burn from an arc flash.
- Equipment grounding ensures a low-resistance path to reduce dangers from electrical failures.
Electrical Systems and Protection Devices
- EMI Filters minimize interference in shipboard electrical and electronic systems.
- Transient Voltage Surge Suppression (TVSS) systems absorb and clamp voltage spikes on the main AC bus.
- Arc Fault Detection Systems are installed on switchboards to detect arc flashes and minimize damage.
Voltage Regulations and Approvals
- Work on energized systems is prohibited above 1000 volts unless approved by NAVSEA.
- Commands for work on energized electrical equipment over 30 volts require Commanding Officer approval.
Safe Practices in Energized Conditions
- Safety precautions include removing all metal, wearing rubber gloves, using one hand while working, and ensuring someone CPR qualified is present.
- Safe-to-Work (STW) checks are necessary after prolonged inactivity or changes in boundaries, including verifying danger tags, work authorization forms (WAFs), and voltage levels.
- STW checks are unnecessary when working on systems under 30 volts.
Equipment and Voltage Classifications
- "Deranged equipment" is now referred to as damaged equipment.
- For naval applications, voltages equal to or greater than 1000 volts are categorized as high voltage.
Human Body Resistance
- The average resistance of a human body is around 500 ohms, which decreases to 300 ohms when the skin is damp.
Arc Phenomena
- An arc flash occurs when current passes through air gaps between ungrounded conductors or between conductors and ground.
- Incident energy from an arc flash is classified as radiant energy.
- An arc blast results from severe heating due to high current, leading to explosive vaporization of air and surrounding metal.
Flash Protection Boundary (FPB) Details
- FPB defines the distance where unprotected skin could suffer burns from an arc flash.
- FPB ranges for energized circuits aboard ships:
- 4 feet for circuits rated between 30-1000 volts.
- 11 feet for circuits rated between 1000-5000 volts.
- 13 feet for voltages exceeding 5000 volts.
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