Focus Four Hazard Training For Masonry Construction Module 1 - Electrical Safety Susan Harwood Grant Training Program
Disclaimer/Usage Notes This material was produced under grant number SH-17793-SH8 from the Occupational Safety and Health Administration, U.S. Department of Labor. It does not necessarily reflect the views or policies of the U.S. Department of Labor, nor does mention of trade names, commercial products, or organizations imply endorsement by the U.S. Government. Images shown may depict situations that are not in compliance with applicable OSHA requirements. These photos are clearly marked as non-compliant. It is not the intent of RMMI to provide compliance-based training in this presentation, the intent is more to address Focus Four hazard awareness in the masonry construction industry, and to recognize overlapping hazards present in many construction workplaces. It is the responsibility of the employer, its subcontractors, and its employees to comply with all pertinent rules and regulations in the jurisdiction in which they work. Copies of all OSHA regulations are available from www.osha.gov. This presentation is intended to discuss Federal regulations only. If this training is held in a state that is operating under an OSHA-approved State Plan, State OSHA requirements for that state must be included in the training. It is assumed that individuals using this presentation or content to augment their training programs will be "qualified" to do so. Developed under an OSHA Susan Harwood Grant, #SH-17793-SH8, by the Rocky Mountain Masonry Institute, Denver, Colorado
SUBPART Masonry Electrical Safety K 1 Training Objectives • After completing this unit, you will: • Be familiar with the basic concepts of electricity. • Understand the potential effects of electricity on the human body. • Be able to recognize common electrical hazards associated with masonry work. • Be familiar with electrical protective devices. • Be knowledgeable of safe work practices.
SUBPART Masonry Electrical Safety K 2 References • 29 CFR 1926.400; Subpart K • National Electric Code (NEC)
SUBPART Masonry Electrical Safety K 3 Take Electricity Seriously • Electricity is the second leading cause of death in construction. • Electrocutions make up 12% of construction fatalities annually. • Over 30,000 non-fatal shocks occur each year. • Over 600 deaths occur annually due to electrocution. Source: Bureau of Labor Statistics
SUBPART Masonry Electrical Safety K 4 Electrical Accidents • Leading Causes of Electrical Accidents: • Drilling and cutting through cables • Using defective tools, cables and equipment • Failure to maintain clearance distance of 10 feet • Failure to de-energize circuits and follow Lockout/Tagout procedures • Failure to guard live parts from accidental worker contact • Unqualified employees working with electricity • Improper installation/use of temporary electrical systems and equipment • By-passing electrical protective devices • Not using GFCI (ground fault circuit interrupters) devices • Missing ground prongs on extension cords
SUBPART Masonry Electrical Safety K 5 Hazards of Electricity • Shock – Most common and can cause electrocution or muscle contraction leading to secondary injury which includes falls • Fires – Enough heat or sparks can ignite combustible materials • Explosions – Electrical spark can ignite vapors in the air • Arc Flash - can cause burns ranging from 14,000 degrees f. to 35,000 degrees f • Arc Blast – In a short circuit event copper can expand 67,000 times. The expansion causes a pressure wave. Air also expands adding to the pressure wave
SUBPART Masonry Electrical Safety K 6 Fundamentals of ElectricityLike Water In A Garden Hose Resistance = Diameter of Hose Example – Larger hose (less resistance), more water flows Flow of Water Current = Flow Rate Example – 15 gallons per minute Voltage = Water Pressure Example – 45 PSI
SUBPART Masonry Electrical Safety K 7 Fundamentals of Electricity • Electrical current is the flow of electrons through a conductor. • A conductor is a material that allows electrons to flow through it. • An insulatorresists the flow of electrons. • Resistance opposes electron flow.
SUBPART Masonry Electrical Safety K 8 Current Flows in a Loop or Circuit • Circuits are AC (alternating current) or DC (direct current). • Current is usually AC. • AC current has five parts: (1) Electrical source (2) HOT wire to the tool. (3) The tool itself (4) NEUTRAL wire returns electricity from the tool (5) GROUND
SUBPART Masonry Electrical Safety K 9 How Shocks Occur • Current travels in closed circuits through conductors (water, metal, the human body). • Shock occurs when the body becomes a part of the circuit. • Current enters at one point & leaves at another.
SUBPART Masonry Electrical Safety K 10 Shocks Occur in Three Ways • Contact with both conductors • Contact with one conductor and ground • With a tool: contact with “hot” metal part and ground (1), (2) & (3)
SUBPART Masonry Electrical Safety K 11 Severity of the Shock • Severity of the Shock depends on: • Amount of current • Determined by voltage and resistance to flow • Path through the body • Duration of flow through the body • Other factors such as general health and individual differences.
SUBPART Masonry Electrical Safety K 12 He sweats - and he dies... Luling, La. - A man was electrocuted when his sweat dripped into the electric drill he was using to build a swing set in his backyard, the coroner said. Richard Miller was pronounced dead Sunday at St. Charles Hospital, said David Vial, St. Charles Parish coroner. Miller, 54, had been using an electric drill in 90 degree heat, Vial said Monday. “Apparently the man was sweating profusely,” Vial said. “He probably was pushing against the drill with his chest and his perspiration went into the drill itself and made a contact.” The Associated Press
SUBPART Masonry Electrical Safety K 13 Effects of Current Flow • More than 3 milliamps (ma): painful shock • More than 10 ma: muscle contraction • More than 20 ma: considered severe shock • More than 30 ma: lung paralysis - usually temporary • More than 50 ma: possible ventricular fibrillation (usually fatal) • 100 ma to 4 amps: certain ventricular fibrillation (fatal) • Over 4 amps: heart paralysis; severe burns
SUBPART Masonry Electrical Safety K 14 Using a 120 volt circuit and resistance for wet & dry skin: E=IR: Voltage=Current x Resistance (Volts) (Amps) (Ohms) So: I=E/R Dry Skin =120/100,000=.0012 amps =1.2ma flowing through body to ground Wet skin =120/1000=.120 amps =120ma flowing through body to ground Remember: 1 Amp = 1000 milliamps
SUBPART Masonry Electrical Safety K 15 Effects of Current Flow
SUBPART Masonry Electrical Safety K 16 Controlling Electrical Hazards • Employers must follow the OSHA Electrical Standards (Subpart K) • Electrical installation • Subpart K includes four proactive methods: • Electrical Isolation • Equipment Grounding • Circuit Interruption • Safe Work Practices
SUBPART Masonry Electrical Safety K 17 Electrical Isolation • We can be safe by keeping electricity away from us. We can: • Insulatethe conductors. • Example: The insulation on extension cords. • Elevatethe conductors. • Example: Overhead powerlines. • Guard the conductors by enclosing them. • Example: Receptacle covers, boxes, & conduit.
SUBPART Masonry Electrical Safety K 18 Insulating the Conductors • The first way to safeguard workers from electrically energized wires is through insulation. • Rubber and plastic is put on wires to prevent shock, fires, short circuits and for strain relief. • It is always necessary to check the insulation on equipment and cords before plugging them in. • Remember, even the smallest defect will allow leakage!
SUBPART Masonry Electrical Safety K 20 19 Defective Extension Cords Photos depict hazardous condition
SUBPART Masonry Electrical Safety K 20 Defective Cord Incident • Worker attempted to climb scaffold with electric drill. • Drill’s cord was damaged with bare wires showing. • The bare wire contacted the scaffolding. • The worker died! Depicts hazardous condition
SUBPART Masonry Electrical Safety K 21 Elevating the Conductors • The second way to safeguard workers from electrically energized wires is by elevatingthem. • Wires are often elevated by the power company. • It is always necessary to check the location of overhead lines before you begin work each day. • Remember, never allow yourself, your tools, or the materials you are working with to be within 10 feetof energized lines! Photo depicts hazardous condition
SUBPART Masonry Electrical Safety K 22 Working Near Overhead Lines • Clearance of worker and any equipment, tools, materials, or scaffold near uninsulated lines is 10 feet! Photo depicts hazardous condition
SUBPART Masonry Electrical Safety K 23 Overhead Line Incident • A worker was attempting to move mobile scaffold. • Scaffold made contact with 7200 volt line. • The worker died. Photo depicts hazardous condition
SUBPART Masonry Electrical Safety K 24 Guarding the Conductors • The third way to safeguard workers from electrically energized wires is by guardingthem. • Covers, boxes, and enclosures are often put around conductors to prevent worker contact. • It is always necessary to check that electrical boxes and panels are covered and free from missing “knock-outs”. • Remember, electric equipment operating at 50 volts or more must be guarded! Photo depicts hazardous condition
SUBPART Masonry Electrical Safety K 25 Guarding the Conductors Photos depict hazardous condition
SUBPART Masonry Electrical Safety K 26 Guarding the Conductors Photos depict hazardous condition
SUBPART Masonry Electrical Safety K 27 Equipment Grounding • We can be safe by providing a separate, low resistance pathway for electricity when it does not follow normal flow (ground prong). • Grounding gives the stray current somewhere to go and keeps you from becoming part of the circuit.
SUBPART Masonry Electrical Safety K 28 Can You Rely on Grounding? • Grounding will not workif the electricity can flow through you more easily than the ground. This can happen when: • Your tool doesn’t have a ground pin. • You’re working in wet locations. • You’re touching a metal object.
SUBPART Masonry Electrical Safety K 29 What Must be Grounded? • All circuits and extension cords. • All noncurrent carrying metal parts. • Portable & semi-portable tools and equipment unless double insulated.
SUBPART Masonry Electrical Safety K 30 Do Not Eliminate the Ground! You become the next-best path for current! Photos depict hazardous condition
SUBPART Masonry Electrical Safety K 31 Do Not Reverse Polarity The prongs are different sized so you can’t turn the plug around. If you do, the electrical fields within the motor are always energized. If there is moisture present, the case is likely to be “hot”. Even with double-insulated tools, you still could get a shock. Photo depicts hazardous condition
SUBPART Masonry Electrical Safety K 32 Circuit Interruption • We can be safer by automatically shutting off the flow of electricity in the event of leakage, overload, or short circuit. • Ground Fault Circuit Interrupters (GFCI) are circuit protection (or “overcurrent”) devices that protect you, the worker. • Circuit breakers & fuses protect equipment, not you, because they take too much current & too much time to trip.
SUBPART Masonry Electrical Safety K 33 Circuit Protective Devices • Circuit Breakers and Fuses • Onlyprotect the building, equipment, and toolsfrom heat build-up! • Never depend on circuit breakers or fuses to prevent shocks! • Ground Fault Circuit Interrupter (GFCI) • Is the only device which willprotect the worker from shock and electrocution!
SUBPART Masonry Electrical Safety K 34 GFCI Protection • All temporary circuits are required to have GFCI protection or: • Equipment & cords must be included in anAssured Equipment Grounding Conductor Program • An extension cord is a temporary circuit. • Types of GFCIs: receptacle, circuit breaker and portable • Must be wired correctly and tested.
SUBPART Masonry Electrical Safety K 35 How a GFCI Works The GFCI detects ‘leakage’ of 4-6 milliamps & opens the circuit in 1/40th of a second. It will work without the ground plug but not fast enough if you are the ground .
SUBPART Masonry Electrical Safety K 36 Types of GFCI Protection
SUBPART Masonry Electrical Safety K 37 Types of GFCI Protection A GFCI breaker must be installed to protect workers using 220V masonry saws.
SUBPART Masonry Electrical Safety K 38 GFCI Testers
SUBPART Masonry Electrical Safety K 39 Assured Equipment Grounding Conductor Program Requires the following: -Written programand specific procedures -Program implemented by a Competent Person (one who is capable of identifying existing and predictable hazards in the surroundings or working conditions which are unsanitary, hazardous, or dangerous to employees, and who has authorization to take prompt corrective measures to eliminate them. -Equipment grounding conductors must be tested(tools, extension cords, and circuits): At least every three months for cords & tools At least every six months for receptacles Results recorded - equipment coded (colored tape)
SUBPART Masonry Electrical Safety K 40 Checking for Ground Continuity What else we should we notice here? Photo depicts hazardous condition
SUBPART Masonry Electrical Safety K 41 Temporary Wiring • There must be separate circuits for electric tools and lighting, each labeled as such. • Light circuits do not require a GFCI. • Unless used in a wet location. • Test branch circuits before use. • Maintain vertical clearances. • Insulate wires from their supports.
SUBPART Masonry Electrical Safety K 42 Permanent Equipment in Temporary Use What is wrong with using this as a ‘splitter’? Photo depicts hazardous condition
SUBPART Masonry Electrical Safety K 43 Extension Cords and Cables • Must be in good shape without splices. • Cannot be secured with staples, nails or bare wire. • Must be protected from damage. • Must have a ground pin. • Should be inspected regularly and pulled from service if defective. • Cannot be repaired with electrical or duct tape. Must repair with heat-shrink sleeve or bonding/vulcanizing tape to retain original insulation properties. Photos depict hazardous condition
SUBPART Masonry Electrical Safety K 44 Acceptable Cord Types • All cords must meet the National Electric Code’s (NEC) requirement for Hard/Extra Hard type. • Look for markings stamped on cords. • Acceptable Cord Types • Extra Hard Use Markings: S, ST, SO, STO • Hard Usage Markings: SJ, SJO, SJT, SJTO
SUBPART Masonry Electrical Safety K 45 Photo depicts hazardous condition
SUBPART Masonry Electrical Safety K 46 Extension Cords-What’s the Difference? No flat cords allowed on construction sites!
SUBPART Masonry Electrical Safety K 47 Clever Or Foolish? Photos depict hazardous condition
SUBPART Masonry Electrical Safety K 48 Temporary Lighting • All bulbs must be guarded • No broken bulbs or empty sockets • Not suspended by wiring • Low voltage for wet locations Photos depict hazardous condition