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Transcript
Office of Safety & Health Consultation presents Electrical in Construction Objectives In this course, we will discuss the following: • Common electrical hazards • Standards relating to those hazards • Electrical equipment defects/hazards • Tools/techniques used in identifying hazards 29 CFR 1926 - Subpart K • • • • • • • • • 1926.400 – Introduction 1926.402 – Applicability 1926.403 – General requirements 1926.404 – Wiring design and protection 1926.405 – Wiring methods, components, and equipment 1926.406 – Specific purpose equipment and installations 1926.407 – Hazardous (classified) locations 1926.408 – Special systems 1926.416, 417, 431, 432, 441 – Safety-related practices and maintenance • 1926.449 - Definitions Common Electrical Hazards • Electric shock/electrocution occurs, when current flows through the body damaging the body. • Electrical burns are caused by arc blast or hot conductors. • Indirect falls from ladders, scaffolds or other walking and working surfaces. Common Electrical Hazards • Explosions can be caused when electricity provides a source of ignition for an explosive mixture in the atmosphere. • Fires are caused by overloading a circuit or appliance or by current flowing through high resistance due to faulty wiring, setting fire to insulation and surrounding materials. General Requirements 1926.403(a) General Requirements • Electrical equipment must be free from recognized hazards that can cause death or serious physical harm to employees – Suitability for installation – Mechanical strength and durability – Electrical insulation – Heating effects under condition of use – Arcing effects – Classification by type, size, voltage, 1926.403(b)(1) current capacity, specific use General Requirements • Listed, labeled, or certified equipment must be installed and used in accordance with instructions included in the listing, labeling or certification 1926.403(b)(2) Nationally Recognized Testing Laboratories • • • • • • • • • • • • • • • Canadian Standards Association (CSA International) Communication Certification Laboratory, Inc. (CCL) Curtis-Straus LLC (CSL) FM Approvals LLC (FM) Intertek Testing Services NA, Inc. (ITSNA) MET Laboratories, Inc. (MET) NSF International (NSF) National Technical Systems, Inc. (NTS) SGS U.S. Testing Company, Inc. (SGSUS) Southwest Research Institute (SWRI) TUV SUD America, Inc. (TUVAM) TUV SUD Product Services GmbH (TUVPSG) TUV Rheinland of North America, Inc. (TUV) Underwriters laboratory Inc. (UL) Wyle Laboratories, Inc. (WL) Box Not Approved as a Pendant General Requirements • Equipment shall be installed and used in accordance with instructions. 1926.403(b)(2) Used in Accordance With Instructions General Requirements • Splices – Splicing devices suitable for use – Welding/brazing/soldering – Mechanically/electrically secure before soldering – Covered with insulation equivalent to that of the conductors – Insulating device suitable for purpose 1926.403(e) General Requirements • Each service, feeder, and branch circuit, at its disconnecting means or over current device, shall be legibly marked to indicate its purpose. 1926.403(h) General Requirements • Live parts of electric equipment operating at 50 volts or more shall be guarded against accidental contact by cabinets or other forms of enclosures, or by another suitable method. 1926.403(i) Wiring Design and Protection • Polarity of connections – No grounded conductor may be attached to any terminal or lead so as to reverse designated polarity Correct Polarity Hot Neutral Ground Hot Ground Neutral Reversed Polarity 1926.404(a)(2) Wiring Design and Protection • Employer shall use either ground fault circuit interrupters, or • An assured equipment grounding conductor program to protect employees 1926.404(b)(1)(i) Wiring Design and Protection • Portable generators need not be grounded if: – Supplies only equipment mounted on the generator and/or cord and plug equipment is plugged into receptacle mounted on the generator – Noncurrent-carrying metal parts of equipment and grounding conductor terminals of the receptacle are bonded to generator frame 1926.404(f)(3) Wiring Design and Protection • Vehicle-mounted generators; vehicle frame may serve as system grounding if: – The frame of the generator is bonded to the vehicle frame and …. – Generator supplies only equipment located on the vehicle and/or equipment plugged into the generator and …. 1926.404(f)(3) Wiring Design and Protection – The noncurrent-carrying metal parts of equipment and grounding conductor terminals of the receptacles are bonded to the generator frame, and …. – The system complies with all other provisions of this section. 1926.404(f)(3) Wiring Design and Protection • The path to ground from circuits, equipment, enclosures must be permanent and continuous. 1926.404(f)(6) Wiring Design and Protection • Equipment connected by cord and plug – Noncurrent-carrying metal parts which may become energized must be grounded 1926.404(f)(7)(iv) Wiring Design and Protection • Equipment connected by cord and plug must be grounded, if: – In a hazardous location – Operated at over 150 V to ground • Except guarded motors and appliances permanently insulated from ground – Hand held motor-operated tools – Equipment used in wet and/or conductive locations – Portable hand lamps 1926.404(f)(7)(iv) Wiring Design and Protection • Flexible cords and cables must be protected from damage. 1926.404(a)(2)(ii)(I) Wiring Design and Protection • Extension cord sets used with portable electric tools and appliances must be of three-wire type and must be designed for hard or extra-hard usage. 1926.404(a)(2)(ii)(J) Wiring Design and Protection • Conductors entering boxes, cabinets, or fittings must be protected from abrasion. 1926.404(b)(1) American Wire Gauge Note: The larger the gauge number, the smaller the wire. Wire Rating Wire Size: Handles up to: Allowable ampacities: #10 AWG 30 amps 28 amps 30 amps #12 AWG 25 amps 23 amps 20 amps #14 AWG 20 amps 17 amps 15 amps #16 AWG 18 amps 8 amps -------- Unless permitted in NEC 240.4(E-G): Safety factor of 20% Tool Estimated Watts Amperage Used Receptacle Amperage 25 40 Maximum Amperage Load (less 20%) Jig Saw 300 2.5 (*5.0 motor startup) Table Saw 1800 15 7 ¼” Circular Saw 1200 10 Chop Saw 1550 13 Total Usage 4850 43 (* includes startup) 20 32 Wiring Design and Protection 1926.405(b)(1) Wiring Design and Protection • Unused openings in cabinets, boxes and fittings must be effectively closed. 1926.405(b)(1) Wiring Design and Protection • All pull boxes, junction boxes, and fittings must be provided with a cover. • If metal covers are used, they must be grounded. 1926.405(b)(2) Wiring Design and Protection • Flexible cords and cables must be suitable for conditions of use and location. 1926.405(g)(1) Wiring Design and Protection • Permitted uses of flexible cords and cables – Pendants – Fixture wiring – Portable lamps and appliances – Elevators cables, cranes, and hoists – Stationary equipment – Frequent interchange – Appliances – to permit removal for maintenance and repair 1926.405(g)(1) Wiring Design and Protection • Prohibited uses of flexible cords and cables – As substitute for fixed wiring of structure – Run through holes in walls, ceilings or floors – Run through doors, windows or similar openings – Attached to building surfaces – Concealed behind building walls, ceilings, or floors 1926.405(g)(1)(iii) Flexible Cord Run Above Ceiling Wiring Design and Protection • Flexible cords shall be connected to devices and fittings so that strain relief is provided. – Will prevent pull from being directly transmitted to joints or terminal screws 1926.405(g)(2)(iv) Wiring Design and Protection Safety-Related Work Practices • Employer must not permit an employee to work in such proximity to any part of an electric power circuit. – If employee could contact the power circuit, it must be de-energized or guarded. 1926.416(a)(1) Safety-Related Work Practices • Working spaces, walkways, and similar locations shall be kept clear of cords so as not to create a hazard to employees. 1926.416(b)(2) Safety-Related Work Practices • Worn or frayed electric cords must not be used. • Extension cords shall not be stapled, hung from nails or suspended by wire. 1926.416(e) Tools for Identifying Hazards • An electrical receptacle voltage tester with GFCI tester. – Line voltage probes Summary In this course, we discussed: – Common electrical hazards – Standards relating to those hazards – Electrical equipment defects/hazards – Tools/techniques used in identifying hazards Recognize Any Hazard(s)? 44 Yes No employer shall permit a worker to work in such proximity to any part of an electric power circuit that the worker could contact the electric power circuit in the course of work 45 Recognize Any Hazard(s)? 46 Yes Crossing electrical line must be supported, protected or removed to safeguard workers 47 Recognize Any Hazard(s)? 48 Yes Spliced electrical extension cords. Extension cords should be marked DO NOT USE. Also, bad housekeeping, trip hazard and unprotected hole in photograph 49 Recognize Any Hazard(s)? 50 YES 1. No GFCI 2. System not grounded 3. Openings where conductors entered not closed 4. No cover on boxes 5. Panel boards were not dead front 51 Recognize Any Hazard(s)? 52 YES Electric drill flexible cord was spliced to a non-flexible conductor with damaged insulation 53 Recognize Any Hazard(s)? 54 Yes Scaffold was erected 4 ½ feet from 7.2 kV power lines 55 Recognize Any Hazard(s)? 56 YES Continuous path to ground not maintained; multiple cords used for fixed equipment 57 Recognize Any Hazard(s)? 58 YES Employer was operating a stand fan without grounding protection 59 Recognize Any Hazard(s)? 60 Yes Conductors entering boxes, cabinets, or fittings shall be protected from abrasion. Openings through which conductors enter shall be effectively closed 61 Recognize Any Hazard(s)? 62 Yes Flexible cords and cables may pass through doorways or other pinch points, if protection is provided to avoid damage 63 Your Questions?