Electrical Safety in Die Casting

Transcription

1 Electrical Safety in Die Casting April 2016 Beau Glim NADCA Project Manager

2 NADCA Safety Series 4 parts Basic Safety Machine Maintenance Safety Electrical Safety Managing Safety General safety information Visitors, new employees, refresher Can supplement, but does not replace plant safety training

3 Outline Electricity 101 Shocks Arc Flash Personal Protective Equipment

4 Reporting Incidents If an accident or near miss occurs, report it immediately to a supervisor, manager or safety director

5 What is Electricity? A flow of electrical charges, such as electrons, through a conductor American Heritage New Dictionary of Cultural Literacy Electricity is a form of energy that can easily be transported over long distances to power: Lights Motors Furnaces Computers

6 Electricity Terms Voltage Force that transmits electricity through a wire. The more volts the more electricity tries to move through the wire. (Volts) Current Amount of electricity that is flowing through a wire. (Amps) Resistance Amount of energy blocked, while traveling through a circuit. (Ohms) Power Amount of energy being consumed by a source. (Watts)

7 Ohm s Law VI VI R V = Voltage Voltage = Current I = Current Resistance = Current R = Resistance

8 Power P I V P = Power I = Current V = Voltage

9 Conductor vs. Insulator Conductor Provides little resistance for electricity to pass through Metals (Copper, Aluminum, Iron, etc.) Dirty Water Concrete Insulator Provides high resistance causing difficulty for electrical current to pass through Rubber Plastic Ceramic Pure Water (deionized) Dry Wood

10 Resistance Condition Resistance (ohms) Dry Wet Finger Touch 40,000 1,000,000 4,000 15,000 Hand Holding Wire 15,000 50,000 3,000 6,000 Finger Thumb Grasp 10,000 30,000 2,000 5,000 Hand Holding Pliers 5,000 10,000 1,000 3,000 Palm Touch 3,000 8,000 1,000 2,000 Hand Around 1.5 Pipe 1,000 3, ,000 Hand Immersed Foot Immersed *Owensboro Community and Technical College - Electric Safety Manual

11 Example 830 ma 120 Volt 1.2 ma 100,000 Ohms 100 Watts 145 Ohms

12 Shock The body completes an electric circuit, allowing electricity to flow through the body Damage to the body can range from a tingling sensation to cardiac arrest and death Severity of the shock depends on: Path of current through the body Amount of current flowing through the body Duration of shock A shock that is fatal is called electrocution Electricity accounted for 3% of all work place fatalities in 2013

13 Shock Injuries External Injuries Entrance and Exit Wounds Skin Burns Internal Injuries Internal Burns Swelling Involuntary Muscle Contraction

14 Muscle Contractions Muscle contractions from shock can lead to more serious injuries such as: Falling From height From ground level Unintentional movement into hazardous areas Freezing

15 Freezing Muscles contract, preventing person from pulling free of the electric circuit Increases exposure time If you see someone frozen : Turn off current (if possible) Use non-conducting or insulated boards, poles or sticks to safely push or pull the person away Act quickly and protect yourself from shock and electrocution

16 Shock Severity Electric Current (1 second contact) Physiological Effect Voltage required to produce the current with assumed body resistance 1 ma Threshold of feeling, tingling sensation 3 ma Painful shock which may cause indirect accidents 5 ma Accepted as maximum harmless current ma Beginning of sustained muscular contraction ( Freezing ) 30 ma Lung paralysis- usually temporary 50 ma Possible ventricular fibrillation (heart dysfunction, usually fatal) ma Certain ventricular fibrillation, fatal 100,000 ohms (dry) 100 V 1 V 300 V 3 V 500 V 5 V 1,000 V 10 V 3,000 V 30 V 5,000 V 50 V 1,000 ohms (sweaty) 10,000 V 100 V 4 Amps Heart paralysis, severe burns 400,000 V 400 V 5 Amps Flesh burns, defibrillation, temporary respiratory paralysis 500,000 V 500 V *Owensboro Community and Technical College - Electric Safety Manual

17 Example 120 Volt Dry 100,000 Ohms 1.2 ma Wet 5,000 Ohms 24 ma

18 Avoiding Shock Hazards Keep work area clean and free of clutter Clean up spills and fix fluid leaks Repair or replace damaged tools, cords or outlets before using Do not overload outlets Wear proper PPE for the hazards De-energize equipment before starting any electrical work Use Left-Hand Rule when opening electrical panels

19 Arc Fault Short circuit through the air caused by an open circuit accidentally closing Resistance in circuit drops to nearly zero 480 V is enough to produce arc flashing Causes arc flash and arc blast

20 Arc Flash Bright light and intense heat Temperatures can reach 35,000 F (19,400 C) Burn non-fire resistant clothing and skin Cause internal burns

21 Arc Blast Physical hazard caused by arc flash Intense physical pressure of the explosion Can knock a person back or collapse lungs Can damage hearing *Owensboro Community and Technical College - Electric Safety Manual

22 Causes Incidental contact (tooling or part of the body) Parts falling into the electrical panel Loose wire connections Water, debris or corrosion Bugs or small animals

23 Left-Hand Rule To prevent serious injury due to arc-flash and arc-blast the Left-Hand Rule should be used when opening electrical panels where the disconnect is located on the right side. Stand to the right side of the switch Grab the disconnect with your left hand Turn your body and face away from the switch Close your eyes Take a deep breathe and hold Throw the disconnect lever

24 Approach Boundries Flash Protection Boundary 2 nd degree burns possible Limited Approach Boundary Unqualified person must be accompanied by qualified person Restricted Approach Boundary Qualified person only Prohibited Approach Boundary Qualified person only, PPE if direct contact with live part

25 Boundary Table

26 Calculating Boundaries NFPA 70E Table 130.7(C) NFPA 70E and IEEE Standard 1584 formulas IEEE spreadsheet based calculator Commercial software

27 Personal Protective Equipment High voltage = high current High resistance = low current The higher the voltage being worked on the more resistance (insulation) is required The type of work and environment will determine minimum PPE requirements

28 Arc Flash PPE Categories 4 Levels of Arc Flash PPE NFPA 70E Table 130.7(C)(15)(A)(b) provides Arc Flash PPE Category

29 Arc Rated Clothing Categories Typical Protective Clothing Systems Hazard Risk Category Clothing Description (number of layers in parenthesis) Minimum Arc Rating 0 Non Melting Flammable Materials (1) N/A 1 FR Shirt and FR Pant or FR Coverall (1) 4 2 Cotton Underwear PLUS FR Shirt and FR Pant or FR Coverall (1-2) 8 3 Cotton Underwear PLUS FR Shirt and FR Pant or FR Coverall (2-3) 25 4 Cotton Underwear PLUS FR Shirt and FR Pant PLUS Double Layer Switching Coat and Pants (3 or more) 40 Example only - See NFPA 70E Table 130.7(C)(16) for specific PPE requirements

30 Gloves Type I Greater dexterity, but not ozone resistant Type II Less dexterity, but won t deteriorate when exposed to ozone and UV over time

31 Eye Protection Required where eyes are exposed to potential hazards, such as arc flashing Eye and face protection shall comply with ANSI Z87.1

32 Head Protection Type I Offer protection for top of the head Type II Offer protection for both top and sides of the head Class G (General) Helmets Proof tested at 2,200 volts Class E (Electrical) Helmets Proof tested at 20,000 volts Class C (Conductive) Helmets Provides no electrical insulation

33 Foot Protection Electrical shock resistant (EH) footwear: No current flow or leakage current in excess of 3.0 ma under the following conditions: Dry 14,000 volts 60 hertz 1 minute

34 Insulating Equipment Blankets, matting, covers, line hose, gloves and sleeves made of rubber Type 1 Non-ozone resistant Type 2 Ozone resistant Blankets, gloves and sleeves must be seamless and marked with arc flash PPE category

35 Insulated Tools Insulated tools shall be used when working near exposed, energized conductors or circuit parts.

36 Electrical Panels Segregate electrical panels based on voltage 120 V 480 V

37 Summary While voltage stays constant the current can change based on resistance Even low voltages can cause serious injury Muscle contractions can lead to falling or entering hazardous areas Arc flash can blind and burn, while arc blast can cause physical damage Proper limits and PPE should be observed around open electrical panels Insulating PPE should be worn when working with electricity

38 Questions Name: Beau Glim Phone: