UNL Safety UNL Safety ColloquiumColloquium Laboratory Electrical Laboratory Electrical SafetySafety

Fall, 2006Fall, 2006

Robert W. HaydenRobert W. Hayden, , M.A., PMPM.A., PMP

Lincoln Electric System (LES)Lincoln Electric System (LES)

Why is this relevant to Why is this relevant to me?me?

• You work in a laboratoryYou work in a laboratory (Electrical accidents are…)(Electrical accidents are…)

• Accident statsAccident stats• Injury statsInjury stats difficult to find, difficult to find, • Fatality statsFatality stats probably rare probably rare

(but, (but, why why be famousbe famous?) ?)

Major characteristic of Major characteristic of electrical accidentselectrical accidents• You work in a laboratoryYou work in a laboratory

• Accident statsAccident stats• Injury statsInjury stats difficult to find,difficult to find, • Fatality statsFatality stats probably rareprobably rare

(but, why (but, why be famous?)be famous?)

RATIORATIO of fatalities to injuries is of fatalities to injuries is HIGH 1

for ALL electrical type injuries.

Electrical hazards in a Electrical hazards in a lablab

Electrocution from INSTALLED Electrocution from INSTALLED equipmentequipment

Electrocution from Electrocution from TEMPORARY wiringTEMPORARY wiring

Electrocution from Electrocution from APPARATUS or POWER APPARATUS or POWER SUPPLIESSUPPLIES

But, first some basics . . . . . But, first some basics . . . . .

Electricity comes in Electricity comes in only two flavors, only two flavors, ACAC and and DCDC AC is AC is AAlternating lternating CCurrent. It flows urrent. It flows

both directions, in varying potential, both directions, in varying potential, at a given frequency. In the U.S., at a given frequency. In the U.S., 120v at 60 Hz is the standard. In 120v at 60 Hz is the standard. In other countries both the voltage and other countries both the voltage and frequency may be different. frequency may be different. (230v (230v @50Hz)@50Hz)

DC is DC is DDirect irect CCurrent. It flows in only urrent. It flows in only one direction, at a set potential. one direction, at a set potential.

What What AAlternatinglternating C Currenturrentlooks like on an looks like on an oscilloscopeoscilloscope

Frequency (one cycle or hertz)

What What DDirectirect C Current urrent (steady (steady

state)state) looks like on an looks like on an oscilloscopeoscilloscope

0

+

What a What a DDirectirect C CurrenturrentPULSEPULSE looks like on an looks like on an oscilloscopeoscilloscope

0

But let’s talk safety.But let’s talk safety.

Both AC and DC need a ‘path’ in Both AC and DC need a ‘path’ in order to complete a ‘circuit’. Only order to complete a ‘circuit’. Only when a circuit is completed will when a circuit is completed will current flow.current flow.

PEOPLE get hurt when THEY get PEOPLE get hurt when THEY get inin the path (circuit). the path (circuit). – HOWEVER- electricity travels at (nearly) the HOWEVER- electricity travels at (nearly) the

speed of light, therefore ALL your precautions speed of light, therefore ALL your precautions have to focus on preventing a path because have to focus on preventing a path because afterafter a path (circuit) is established it may be a path (circuit) is established it may be too latetoo late. .

The risks?

There are four types of electrical-related There are four types of electrical-related injuries:injuries:– Electrocution (Electrocution (death due to electrical due to electrical

shock)shock)– Electrical shock (may cause tissue damage, Electrical shock (may cause tissue damage,

initially invisible).initially invisible).– Burns (visible, obvious)Burns (visible, obvious)– Falls (secondary injury)Falls (secondary injury)

Electrical BurnsElectrical Burns

• A common, nonfatal shock-related injury

• May occur when you touch electrical wiring or equipment that is improperly grounded, used, or maintained

• Typically occurs on the hands

• Electrical burns are very serious injuries that need immediate attention

Falls or Contact injuries

• Electric shock can also cause Electric shock can also cause indirect indirect or secondary or secondary injuriesinjuries

• Workers in elevated locations Workers in elevated locations who experience a shock can who experience a shock can fallfall, resulting in serious injury , resulting in serious injury or deathor death

• OR, workers can be OR, workers can be thrownthrown into others or into solid or into others or into solid or sharp objectssharp objects

So, how much So, how much electricity does it electricity does it reallyreally take to hurt take to hurt me?me? It varies. Sex, weight, skin It varies. Sex, weight, skin

moisture, hydration, and path moisture, hydration, and path through the body all contribute.through the body all contribute.

Some Some general general threshold threshold values:values:– Sensation. ~1 mA AC / 5mA DCSensation. ~1 mA AC / 5mA DC– ‘‘Let-go’. ~15 mA AC / 75 mA DCLet-go’. ~15 mA AC / 75 mA DC– V-fib. ~75-100 mA AC / 300 mA DCV-fib. ~75-100 mA AC / 300 mA DC

COMPARECOMPARE

The values in the previous slide The values in the previous slide are in units called milliamps (mA). are in units called milliamps (mA). One milliamp is 1/1000 of an One milliamp is 1/1000 of an amp.amp.

What is the TYPICAL current What is the TYPICAL current rating (in amps) of a 120v circuit rating (in amps) of a 120v circuit breaker? breaker?

COMPARECOMPARE

the TYPICAL current rating (in amps) of a the TYPICAL current rating (in amps) of a 120v circuit breaker?120v circuit breaker? Let’s say 15 amp.Let’s say 15 amp.

15 amp = 15,000 mA / 150 mA = 15 amp = 15,000 mA / 150 mA =

100 times enough current to kill enough current to kill youyou (without tripping the breaker, of course)(without tripping the breaker, of course)

So, if the circuit So, if the circuit breaker doesn’t breaker doesn’t protect protect meme, what’s it , what’s it for?for?

Electrical Protective DevicesElectrical Protective Devices Protective devices shut off the flow Protective devices shut off the flow

of electricity in the event of of electricity in the event of either an over current an over current oror a ground-fault a ground-fault condition in the circuit. They condition in the circuit. They include fuses, circuit breakers, include fuses, circuit breakers, and ground-fault circuit and ground-fault circuit interrupters (GFCI’s).interrupters (GFCI’s).

BUTBUT, they protect different things., they protect different things.

Over Current DevicesOver Current Devices

Fuses and circuit breakers are Fuses and circuit breakers are over currentover current devices. devices. When there is too much current:When there is too much current:

Fuses meltFuses melt Circuit breakers trip openCircuit breakers trip open

Fuses and circuit breakers Fuses and circuit breakers protect protect WIRING and EQUIPMENT.WIRING and EQUIPMENT.

They are designed to prevent fires.They are designed to prevent fires. Their Their primaryprimary purpose is NOT to purpose is NOT to

protect people. protect people.

Ground Fault DevicesGround Fault Devices

In contrast, GFCIs protect against ‘imbalanced’ loads (wrong path to ground) also known as a ‘fault’, or a ‘ground fault’.

Only GFCIs are designed to protect PEOPLE.

BarbiDEMO

a.k.a. Why you need a GFCI

Electrocution from Electrocution from INSTALLED INSTALLED equipmentequipment Non-UL (Underwriter’s Non-UL (Underwriter’s

Laboratory) equipment.Laboratory) equipment. Improperly installed Improperly installed (wired)(wired)

equipment equipment (for example switching the neutral wire).

Ungrounded equipment Ungrounded equipment (two prong)

Unprotected (non Ground Fault) Unprotected (non Ground Fault) equipment or outletsequipment or outlets– Especially around Especially around

liquids/water/plumbing.liquids/water/plumbing.

Electrocution from Electrocution from TEMPORARY wiringTEMPORARY wiringContributors Include:

–Non-GFCI cords or non-GFCI outlets

–Damaged cords–Modified cords– Improper use or application of cords

“The path to ground from circuits, equipment, and enclosures must be permanent and continuous.”

PermissiblePermissible Uses of Flexible Uses of Flexible CordsCords

Pendant, orFixture Wiring

Portable lamps,tools or appliances

Stationary equipment-to facilitate interchange

ProhibitedProhibited Uses of Flexible Uses of Flexible CordsCords

Substitute for fixed wiring

Run through walls, ceilings, floors, doors, or windows

Concealed behind or attached to building surfaces

Electrocution from Electrocution from POWER SUPPLIES or POWER SUPPLIES or APPARATUSAPPARATUSo In these cases (most often) the In these cases (most often) the

apparatus or power supply is apparatus or power supply is doing just what it’s supposed to. . It is putting out voltage – at a It is putting out voltage – at a given current and/or frequency.given current and/or frequency.

o BUT – People (you) have BUT – People (you) have managed to get yourself managed to get yourself intointo the the circuit (path).circuit (path).

The Results? The Results? They range from . . .They range from . . .

Ooops / Ouch (small shocks)Ooops / Ouch (small shocks) Secondary injuries or damageSecondary injuries or damage

SparksSparks FiresFires Falls or cutsFalls or cuts Breakage or equipment damageBreakage or equipment damage

Big shocks. Burns or even death.Big shocks. Burns or even death.

ElectrocutionElectrocution– Minor shockMinor shock– Major shockMajor shock

@ approximately let-go threshold = @ approximately let-go threshold = invisible invisible (often latent) tissue damage (often latent) tissue damage beginsbegins to occur to occur

Visible burn(s)Visible burn(s)

– FatalityFatality Most often due to V-fibrillationMost often due to V-fibrillation Can also be from the burn (internal or Can also be from the burn (internal or

external) external)

Known POWER SUPPLIES Known POWER SUPPLIES or APPARATUS valuesor APPARATUS values

• Electrophoresis (power supplies)Electrophoresis (power supplies)• Various manufacturers’ spec models from 0 Various manufacturers’ spec models from 0

to 6000v, 0 to 2000mA. to 6000v, 0 to 2000mA. • Electroporation (equipment itself)Electroporation (equipment itself)

• Pulses of 1,000’s of voltsPulses of 1,000’s of volts• Other (physics) power suppliesOther (physics) power supplies

• LasersLasers• Particle study equipment Particle study equipment (Especially anything (Especially anything

with large capacitors)with large capacitors)

QUITE capable of injury if not properly handled.QUITE capable of injury if not properly handled.

The Barriers Installed equipment

– Purchase UL listed equipment, if possible– Have equipment installed by a licensed

electrician. (if it’s not ‘plug-in’ type)– Have any non-UL equipment checked for

grounding/wiring by a licensed electrician– STRONGLY consider having all equipment

circuits operating around liquids or in proximity to plumbing (sinks) plugged into GFCI outlets or GFCI pigtails

– LABEL all outlets/circuit breakers

The Barriers Temporary wiring

– Use only cords with proper ratings (amperage as well as environment [wet =‘W’])

Jacket codes in Nat’l Electric Code (NEC)

– Again, all equipment circuits operating around liquids or in proximity to plumbing (sinks) should be plugged into GFCI outlets or have GFCI pigtails

– Don’t ‘daisy-chain’ cords. Especially multiple outlet cords

The Barriers

Technique / procedure– Follow procedural guidance (SOPs) for

setting up, terminating, and adjusting equipment / apparatus (for example …)

Power OFF before touching wires Double check connections before powering

ON

– Don’t defeat electrical interlocks– Be especially careful whenever working

with both electricity and any liquid or plumbing

SummarySummary

Know that electricity can hurt or even kill Know that electricity can hurt or even kill youyou

Don’t get Don’t get tootoo comfortable around electricity, comfortable around electricity, especiallyespecially when also around liquids when also around liquids

Inspect your equipment/apparatus Inspect your equipment/apparatus (frequently)(frequently) Follow procedures for setup, adjustment, etc.Follow procedures for setup, adjustment, etc. If you have Safety questions, ask the If you have Safety questions, ask the

Occupational Health and Safety department Occupational Health and Safety department staff staff

Questions Questions ??