Electrical Safety Electric Hazard Electric Shock Electric shock

Electrical Safety

Electric Hazard • Electric Shock – Electric shock is a term that relates to the consequences of current flowing through nerves, muscles and organs of a body. • Effects of Electric Shock – Heating effect of current damages body tissues by burn. – Death could occur when the rhythm of the heart is disturbed such as to effect blood flow. This is known as VENTICULAR FABRILATION.

Electric Hazard Ø Factors Governing Shocks Ø Amplitude of current. Ø Duration of current. Ø Condition of the body. Ø Sex & age of the person. Ø Ambient temperature and humidity. Ø O 2 and CO 2 content in surrounding air. Ø Material / Flooring. Ø Positions of hands and legs. Ø Condition of Earthing.

Electric Hazard Amplitude of Current (m. A) Effect on the body Up to 1 No sensation 1 to 8 Sensation there , but no pain 8 to 15 Painful shock but muscular control still there 15 to 20 Muscular control lost , resulting in sticking 20 to 50 Severe muscular contraction 50 to 200 Ventricular fibrillation or death 200 & above Severe burn and death due to heart attack.

Electric Hazard Causes of Electrical Accidents Ø Poor knowledge of equipments / system. Ø Over confidence. Ø Taking a chance or risk. Ø Hurry to complete the job or charge the equipment. Ø Monkey tricks. Ø Working without concentration.

Electric Hazard Causes of Electrical Accidents Ø Poor maintenance of equipments. Ø Poor quality of tools. Ø Not using PPE’s. Ø Miscommunication. Ø Not following safety procedure. Ø Temporary repairs. Ø Poor earthing.

Hazards of Static Electricity & Its Control

Static Electricity • When dissimilar materials come in contact and separate, (i. e. they are in motion & maintain contact with each other) there is a transfer of electrons from one material to the other material. • The excess of electrons is called negative charge and deficiency of electrons is called positive charge. • When heavy cloud of charge tries to break the air insulation and finds it way to earth , it results into static electricity. When one of the material is non conductor, static charge can accumulate. • Attraction can be measured as potential difference or voltage. • Larger Voltage results in larger spark. • Flow of static electricity causes spark / Explosion in hazardous area.

Static Electricity Source of Generation • Rubbing wool or plastic. • Pouring bulk material out of bag / container. • Unrolling of plastic or PVC film. • Flow of liquid through pipe line. • Spraying of paint on a wall. • Impact of dust particles on a wall. Measurable charge will be created only if one of the materials involved is a non conductor of electricity

Static Electricity Conditions for Accident • Rate of generation is higher than the rate of discharge. • The gas mixture around the spark is flammable. • Accumulated charge is sufficient to cause a spark. • Spark is sufficient to ignite the mixture. • The proportion of flammable mixture is within the explosive limit. (LEL & UEL)

Static Electricity Steps for Controlling • Draining the accumulated charge by bonding and earthing. • Avoid splash filling. • While designing pipe line ‘ Relaxation time’ should be kept in view. • Control Flow / Velocity. (Up to 200 mm diameter pipe, less than 7 meter/second & for higher sizes velocity less than 1. 5 meter / second. ) • Maintain high relative humidity in the atmosphere near material. • Provide nitrogen blanketing. • Provide ionized atmosphere.

Cautions During Work

Static Electricity Control Measures • While Filling Drums and Containers – Do proper earthing. – Avoid splash filling. – Avoid use of non – metallic pipes & drums. – Weighing scale platform should be earthed. – During filling a drum , a small vent should be open to release pressure.

Static Electricity Control Measures • Filling of Storage Tanks – Earthing of tanks , pipeline & pumps should be proper. – Sampling should be carried only after surface turbulence is subsided. – Floating roof tank & inert gas blanketing should be used.

Static Electricity Control Measures • Loading / Unloading Tanker. – Tanker should be earthed first , before opening the dome. – Earth point should be thoroughly cleaned of paints. – Avoid splash filling. – Once tanker is loaded wait for 5 to 10 minutes before removing earthing clamp. – Start unloading after 5 to 10 minutes of connecting earthing. – Lower dip rod after 5 to 10 minutes of connecting earthing.

Electric Hazard Condition of Earthing Ø If earthing is good, protection system will immediately disconnect the faulty equipment. Ø If earthing is not proper , the system will not give any protection against accident.

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