Electrical& Welding · 2019. 4. 22. · Electrical& Welding. Serious Exposure. Electrocution is one of the top four causes of construction fatalities Nearly half of those fatalities

Electrical & Welding

Serious Exposure

Electrocution is one of the top four causes of construction fatalitiesNearly half of those fatalities were

the result of contact with overhead power lines OSHA is focusing more attention to

these exposures

Applicable Standards

Electrical standards are among the most frequently cited by OSHANo Lock Out/Tag OutImproper Wiring MethodsInadequate Components and Equipment

OSHA references the following for guidelinesElectric Safety Requirements for Employee Workplaces and

codes (NFPA 70E)

Basic Terminology

Conductor – A material that has very low resistance to the flow of electric currentInsulator – Material that resists electric currentGrounding – A low resistance path to the earth

for electric currentAmps – The amount of electricity flowingVolts – The force at which the power flows

Grounding• Service Ground – Protects machinery/equipment• Equipment Ground – Protects worker from tool

malfunction• 2 options for safe grounding:

• Assured Grounding Program• Written Program• Testing (continuity and terminal connection)• Test Schedule• Completed by Competent person

• GFCI (Ground Fault Circuit Interruption)

Ground Fault Circuit Interruption

• Must be provided for all 120v single phase 15 and 20 amp circuits that are not part of the permanent wiring

• Permanent wiring using an extension cord is considered temporary power and requires a GFCI

• All temporary power sources must have GFCI protection either at main box, extension cord, or tool.

Ground Fault Circuit Interruption

Ground Fault Circuit Interrupters (GFCI’s) sense changes in current (5 milliamps) and stop energy flow.Devices stop current in 1/40

of a secondNever bypass any protective

system or device designed to keep you from contact with electrical current.

Electric Shock

• Body becomes part of the electrical current• Current enters the body at one point and leaves at

another (path to ground)• Shocks can occur when a person contacts:

• Both wires• Wire to ground• Any conductor that is energized

Physical Effects

Amps are the true measure of current absorbed, not voltsWe are good conductors, the

human body is 70% waterInvoluntary muscle contraction

is the reason we are affectedCan’t let go of energized objectBreathing is impairedHeart rhythm is disrupted

Physical Effects

1 mA

16 mA

20 mA

100 mA

2 amps

15 to 20 amps

Barely perceptible

Max current an average man can grasp and let goParalysis of respiratory muscles

Ventricular fibrillation threshold

Cardiac standstill and internal organ damage

Current required to trip common household breaker

Influencing Factors of a Shock

Circumstances that affect the outcome of an electric shock;Circuit voltageThe bodies external (skin) and

internal resistanceTotal current flowing through the

bodyCurrent pathThe duration of the shock

Employer Responsibilities

Equipment must be:Free from recognized hazards Suitable and identified through listing,

labeling, or certification of purpose.Designed with adequate mechanical

strength and durability

Other items for consideration Electrical insulation Heating effects /conditions of use Arcing effects Use classifications

GuardingLive parts of electrical equipment operating at 50 volts or more

must be guarded against accidental contact.Means of acceptable guarding include:Isolation in a cabinet, room, or vault accessible only by

qualified personsUse of partitions or screens to exclude unqualified personsElevation of eight feet or more above the floor

Electric installations over 600 require special protectionmetal-enclosedVaultcontrolled by lock

Lock Out / Tag Out

LOTO written program Components

Documented energy control proceduresEmployee Training

programInspection

program

Lock Out / Tag Out

Purpose is to draw attention to and disable a live energy source during service and repair work.Lock Out physically disables

the energy source, Tag Out provides a warning onlyOnly the employee who

placed the lock or tag may remove it!

Safe Power Shutdown- 5 Steps -Preparation and Notification– Understanding

energy source and alerting all affected employees

Shutdown – De-energizing procedureIsolation – Properly locking all power sourcesLock & Tag Application

Color coding for different tradesEmployee assigned locksPhoto tags, helps locate employee, makes

associationControl and Verification– Control stored and

residual energy with locks in place

Re-energizing- 3 Steps -

Inspection – checking the work area and surrounding machinery and for employeesNotification – Make notice

to all affected employees as to what will be re-energizedRemoval of Tags and Locks

Tags and Locks

Tags and Locks must be:Durable – resist conditions of environmentStandardized – color code and formatSubstantial – strong enough to minimize false

removalIdentifiable – clear message, know who it is

protecting

Extension Cords

Service RatingsHard Service (types S, ST, SO, STO)

Junior Hard Service (types SJ, SJO, SJT, SJTO)

Home use, small appliance (type SP)

Cords with missing ground prongs, broken insulation, crimping or crushing must be removed from service.

Splicing is prohibited but new end can be installed Unplug at the receptacle Any cord that has to cross a pthway must be protected OSHA considers an extension cord temporary power, no matter the power

source!

Portable GeneratorsNever use a generator indoors or

in an attached garage.Use extension cords with adequate

duty ratings. To prevent electrical shock, make

sure your generator is properly grounded.

Do not store fuel indoors or try to refuel a generator while it's running.

Turn off all equipment powered by the generator before shutting it down.

Other Considerations

Environmental Deterioration of Equipment - Unless specified for use in such an environment, no conductors or equipment should be exposed to; Damp or wet locations Gases, fumes, vapors, liquids, or other deteriorating agents Excessive Temperatures

Electrical ChecklistExtension cords:

- No crimping or crushing- No missing insulation- No signs of stress at plug

All extension cords out of high traffic areas:

- Road ways (protective cover)- Driveways- Hallway, entrance, stairwell

Lock Out / Tag Out plan for all maintenance operations

Equipment rated for duty and environment

Proper PPE when necessary GFCI protection at box, cord, or tool

Awareness of all overhead power lines

All tools double insulated

Pre-job identification of all underground utilities

Generators must have earth ground

WeldingPotentially Hazardous Fumes and Gases Fumes – Solid particles that originate

from the welding media, base metal, orcoating

Gas – Generated by the shielding gas or process radiation Nickel Zinc Iron Oxide Copper Cadmium Fluorides Manganese Chrome & Gases

Effects of Overexposure Acute Effects

Irritation of eyes, skin, respiratory system

nausea, headaches, dizziness

Metal Fume Fever Asphyxiation (confined

space) Chronic Effects

Central nervous system impairment

Respiratory illness Reproductive disorders Possible links to

Parkinson’s

Radiation

Visible – intense light emitted during welding operations

Infrared - produced by electric arc and other flame cutting equipment

Ultraviolet - generated by all arc processes

Radiation Effects - Influencing Factors

WavelengthIntensityDuration of

exposureExposure may result

in skin burns or eyedamage

Common Welding Techniques

MIG WeldingTIG WeldingMAPP GasOxy-fuel Welding

MIG Welding “Metal Inert Gas” Semi-automatic or automatic arc welding process

in which a continuous and consumable wire electrode and a shielding gas are fed through a welding gun.

Can use alternating or direct current, DC is most common

Typically used with steel Fast welding technique

TIG Welding “Tungsten Inert Gas”Uses a nonconsumable tungsten electrode and

filler metal to produce the weld.A shielding gas such as argon protects the

process from atmospheric contamination Commonly used with Aluminum, Magnesium,

Copper, light gauge Stainless Steel Slower than other welding techniquesHarder to master than other forms of welding but

produces higher quality and stronger welds

MAPP Gas “Methyl Acetylene Propodiene” Consists of LPG mixed with MAPPDoes not require dilution or special container

fillers during transport which allows a greater volume of gas to be transported at the same givenweight

Most commonly used for brazing and soldering Ideal for aluminum and copper

Oxy-fuel Welding“Oxyacetylene Welding” aka Gas WeldingTwo pieces are heated to a temperature

that produces a shared pool of molten metal.The molten pool is supplied with

additional metal called filler.

Safe Work Practices The surrounding work area should be clean and free of

potentially combustible material A fire extinguisher should be kept on hand at all

times Good ventilation is a must for all welding operations Personal protective equipment (PPE) should include eye

and face protection as well as protective clothing Less toxic materials should be substituted when

possible Cadmium-free silver solders Asbestos-free electrodes

Pre-Shift Inspection

Leads – insulation breech, kinks Torch – tip, valves, tool bodyHoses & Fittings Bottles & Valves Cart or other CG Bottle Support Surrounding Area Fire ProtectionAny defective equipment must be replaced,

repaired, or removed from service

Personal Protective Equipment

HelmetMust Comply with

ANSI Z87.1Most equipped with

auto-darken features, 1/10,000 of a second

OSHA 1926.102Tables E-1 and E-2 specify minimum protection levels

Personal Protective Equipment

GlovesANSI Z49.1Must be flame resistantGloves should be in

good shapeMust resist potential

electric shock from welding unit

Personal Protective Equipment

ApronANSI Z49.1 Produced in

variety of fire retardant materials LeatherNomexChemically treated

textiles

Compressed Gas Cylinders

Typical Oxygen cylinder pressures are around 2600 lbs/in²

Oxy fittings should be kept clean and free of oil and grease

Hose colors determine use:Red – fuel gas hoseGreen – OxygenBlack – Inert gas

Compressed Gas Cylinders

Cylinder valves must be protected at all times

Cylinders should be stored in an upright and secure position

The tilt and roll method is accepted practice for movement, never attempt to hoist with chokers

Valve caps must be secure any time the cylinder is not in use

When stored, oxygen cylinders should be separated from other gas cylinders. The required separation is 20’

or A five foot high fire wall with an

approved fire-resistance rating

Welding Torch - Cutting Torch Comparison

Cutting Torch Safety

Take appropriate precautions forflooring surface

Work benches made of steel or other fire retardant material isacceptable

Adequate ventilationConfined SpacesToxic Fumes

Cutting Torch Safety

Appropriate personal protective equipmentControl potentially combustible materials

around work areaFire extinguisher handy at all timesEquipment maintenance

Safe Welding ChecklistFamiliarization with all applicable Material Safety Data Sheets (MSDS)

Surrounding area free of potentially combustible materials

Leeds should be fully insulated, no kinks or deformation

Fire extinguisher readily available, fully charged and functional

Torch tip, valves, and tool body in good working order

Proper face, hand, and body protection in use

Hoses and fittings tight and free of wear, dry rot

Surrounding work areas protected by welding curtains

Bottles secured and upright whether stored or in use, cap secured

Adequate ventilation for all processes at all locations

Bottles free of excessive corrosion, no dents, collar threads intact, clean fitting

Insure proper grounding of welding machine

Valves and gauges secured and operational

Any defective equipment replaced or repaired prior to the start of work