Welding Hazards Welding Hazards Mitigating the Mitigating the

RiskRiskPresented by Dave Hisey to Presented by Dave Hisey to

the WMEA Conferencethe WMEA ConferenceJune 12, 2003June 12, 2003

Welding HazardsWelding HazardsMitigating the RiskMitigating the Risk

Electric shockElectric shock

Stray welding currentsStray welding currents

Welding fumeWelding fume

Mobile Gas Welding SystemsMobile Gas Welding Systems

Welding HazardsWelding HazardsElectric ShockElectric Shock

Electric Shock from welding will killElectric Shock from welding will killProvince of Ontario StatsProvince of Ontario Stats

August 15, 1988August 15, 1988Sept. 15, 1993Sept. 15, 1993August 04, 1994August 04, 1994Nov. 02, 2001Nov. 02, 2001

Each date represents a fatality involving Each date represents a fatality involving electric weldingelectric welding

Welding HazardsWelding HazardsElectric ShockElectric Shock

Electric Shock from welding will killElectric Shock from welding will killRecent US Mining FatalitiesRecent US Mining Fatalities

August 30, 2000August 30, 2000Sept. 16, 2002Sept. 16, 2002

Both fatalities involved stick welding in Both fatalities involved stick welding in confined work areas while the welder was confined work areas while the welder was lying on the base metallying on the base metal

Welding HazardsWelding HazardsElectric ShockElectric Shock

Welding machines Welding machines can and do operate can and do operate at up to 100 VDCat up to 100 VDCWe must prevent the We must prevent the welder from welder from receiving electric receiving electric shockshockJohn Richards is John Richards is going to explain how going to explain how this device worksthis device works

Shock Stop Design Shock Stop Design CriteriaCriteria

Reduce the OCV Reduce the OCV when the welder when the welder is not in use and is not in use and return power the return power the instant an arc is instant an arc is stuck.stuck.Seamless Seamless operation for operation for welder no impact welder no impact on quality.on quality.

Shock Stop ComponentsShock Stop ComponentsMicroProcessor MicroProcessor Based.Based.Solid State Switching Solid State Switching up to 720 Amps.up to 720 Amps.Powered by the Powered by the available OCV.available OCV.Mounted in a Mounted in a Fibreglass Enclosure.Fibreglass Enclosure.

Shock Stop Theory of Shock Stop Theory of OperationOperation

The human body The human body normallynormally provides a provides a high resistance high resistance value.value.A number of factors A number of factors reduce the effective reduce the effective resistance.resistance.

TemperatureTemperatureHumidity/MoistureHumidity/MoistureDistanceDistanceSurface AreaSurface Area

Shock Stop Theory Of Shock Stop Theory Of OperationOperation

Shock Stop measures Shock Stop measures the resistance of the the resistance of the welding circuit.welding circuit.The Threshold The Threshold Resistance is in the Resistance is in the Range of 40Range of 40--50 50 Ohms.Ohms.When the electrode When the electrode is struck on the work is struck on the work the resistance drops the resistance drops below the threshold below the threshold level and Shock Stop level and Shock Stop output is energized.output is energized.

Shock Stop Theory Of Shock Stop Theory Of OperationOperation

To allow the weld to To allow the weld to be established the be established the output is energized output is energized for a minimum of 3 for a minimum of 3 seconds.seconds.The microprocessor The microprocessor is fast enough that is fast enough that the turn on and off the turn on and off time is not time is not noticeable to the noticeable to the user.user.

Shock Stop DiagnosticsShock Stop DiagnosticsInternalInternal

SCR, Trigger Devices, SCR, Trigger Devices, MPUMPU

ExternalExternalWelding Cables, Welding Cables, Ground PathGround Path

Shock Stop is an Shock Stop is an additional Safety additional Safety device to be used device to be used with existing safety with existing safety practices.practices.

Shock Stop SummaryShock Stop SummaryWelders accept Welders accept electric shock as part electric shock as part of their job.of their job.The risks associated The risks associated with shock are not with shock are not known by welders known by welders nor their supervisors.nor their supervisors.Technology is Technology is available to reduce available to reduce risk and improve risk and improve working conditions.working conditions.

Stray Welding CurrentsStray Welding CurrentsCause damage toCause damage to

Pins and bushingsPins and bushingsBearingsBearingsBuilding structureBuilding structureBuilding electrical systemsBuilding electrical systems

ConduitsConduitsGround/Bond wiresGround/Bond wiresTech cable jacketsTech cable jacketsBonding screwsBonding screws

Electronics Electronics –– computer driven equipmentcomputer driven equipmentPeoplePeople

Stray Welding CurrentsStray Welding Currents

Responsible for Responsible for fatalitiesfatalities

Nov. 02, 2001 Nov. 02, 2001 Cambridge Ontario Cambridge Ontario

Electrical service was diagonally opposite welding location

Proof of multiple current paths – this circuit was not involved in powering welder

Main

400 amp splitter

Welder

Failure point

Worker suffers fatal shock when opening a 600 volt attachment device

Work Lead

30 amp welder switch

Service Ground

Building Steel

EMT Connector which failed

Connection to Splitter

The connector which the victim was attempting to open when he died

Burn marks where welding machine was located

Main

400 amp splitter

Welder

Failure point

Worker suffers fatal shock when opening a 600 volt attachment device

Work Lead

30 amp welder switch

Service Ground

Building Steel

Condition of Welding Cables Condition of Welding Cables is Importantis Important

Unacceptable damage

Unacceptable risk!

Examples of Welding Current Examples of Welding Current DamageDamage

Examples of Welding Current Examples of Welding Current DamageDamage

Costs of Welding Current Costs of Welding Current DamageDamage

Engine overhaul Engine overhaul costs can be as high costs can be as high as $350,000.00as $350,000.00

Destroy that engine Destroy that engine due to welding due to welding damagedamage

Costs can be as high Costs can be as high as $600,000.00as $600,000.00

Why Do Stray Welding Why Do Stray Welding Currents OccurCurrents Occur

Because multiple parallel Because multiple parallel current paths existcurrent paths exist

TYPICAL WELDER CIRCUIT600V POWER OUTLET

POWER SUPPLY600V, 3PHASECABLE

3 POWER +GRNDCONDUCTORS

STRUCTURALGROUND

WELDER

MACHINE FRAMEGROUND

WORK LEADTERMINAL

ELECTRODETERMINALDC OUTPUT

ELECTRODEWORKPIECE

TABLE

FLOOR/GROUND

DC WELDING CURRENT FOLLOWS CONTROLLED PATH THRU THE CABLES

FAULT CONDITION DC WORK LEAD TERMINAL

WORKPIECE

FAULT

IF WORK CLAMPIS NOT IN PLACEOR HIGHRESISTANCE

POWER TOOL

(WELDING IN PROGRESS)

CURRENT THRUGROUND COND.OF POWER TOOL& GROUND SYSTEM OF BLDG OR EQUIP

FAULT CONDITION DC ELECTRODE TERMINAL(NO WELDING IN PROGRESS)

NOTE: ELECTRODENOT IN USE

WORKTERMINAL

ELECTRODETERMINAL

FAULT

POWER TOOL

When Using Steel as When Using Steel as Current PathCurrent Path

The multiplier is X The multiplier is X 77

4/0 welding cable = 1 4/0 welding cable = 1 5/8 5/8 round barround bar

This Major Company This Major Company Experienced Serious Stray Experienced Serious Stray Welding Current ProblemsWelding Current Problems

This flat bar is only 22 gauge material – it got very hot!

These mats were melted by the heat generated from welding current passing through 22 gauge sheet metal strip

Clamp used here only amplifies the problems

Tack weld will not carry the current

Stopping the DamageStopping the Damage

Work Lead Position is KeyWork Lead Position is Key

W117.2W117.2--01 S 5.3.2.4 ….. The work lead 01 S 5.3.2.4 ….. The work lead shall be connected as close as practicable to shall be connected as close as practicable to the location being welded uponthe location being welded upon

to ensure welding current returns directly to to ensure welding current returns directly to the source the source through the work leadthrough the work lead

W117.2W117.2--0101 …..…..

The work lead shall be of the same crossThe work lead shall be of the same cross--sectional area as the greater portion of the sectional area as the greater portion of the electrode cable.electrode cable.

Damaged cables shall be replacedDamaged cables shall be replaced

Cable length shall not exceed that specified by Cable length shall not exceed that specified by the welding equipment manufacturer.the welding equipment manufacturer.

W117.2W117.2--0101 …..…..

Electrical grounds connected to a building Electrical grounds connected to a building framework or other locations remote from the framework or other locations remote from the work area increase the possibility of output work area increase the possibility of output current passing through lifting chains, crane current passing through lifting chains, crane cables, or other electrical paths.cables, or other electrical paths.

This passage of current through building This passage of current through building systems can cause extensive damage to systems can cause extensive damage to equipment and electrical circuits if the work equipment and electrical circuits if the work lead isnlead isn’’t properly installed.t properly installed.

From This From This –– To ThisTo This

Correct Work Lead Correct Work Lead ConnectionsConnections

Note the amount Note the amount of steel contained of steel contained in the designed in the designed for purpose 600 for purpose 600 amp welding amp welding clamp when clamp when compared with compared with the standard “C” the standard “C” clampclamp

Welding Fume DiseaseWelding Fume Disease

Manganese IssueManganese IssueRelationship to Parkinson’sRelationship to Parkinson’s

Pregnant Welder ConcernsPregnant Welder ConcernsNo published studiesNo published studies

Welding Fume DiseaseWelding Fume Disease

ACGIH reduced Manganese TLV to ACGIH reduced Manganese TLV to .2mg/m.2mg/m3 3 in 1996in 1996Notice of Change to .03mg/mNotice of Change to .03mg/m33

How it is measured has also changedHow it is measured has also changed

Relationship of manganese to Relationship of manganese to Parkinson's under study at Harvard Parkinson's under study at Harvard --AWSAWS2 year study Dr. Joseph Brain2 year study Dr. Joseph Brain

What’s wrong with What’s wrong with this picture?this picture?

The Female WelderThe Female Welder

Alberta StatisticsAlberta Statistics3.67% of all licensed welders female 3.67% of all licensed welders female Over 200 welders Over 200 welders -- femalefemale59 steamfitters 59 steamfitters -- female (additional) plus female (additional) plus apprenticesapprentices13.37% of apprentice welders female13.37% of apprentice welders femaleCurrently there are over 5000 apprentice Currently there are over 5000 apprentice welders in Alberta welders in Alberta –– 670 female670 female

SyncrudeSyncrude Canada Ltd., CSA, The LAC, & Canada Ltd., CSA, The LAC, & Keyano College are working together to Keyano College are working together to make this a reality. make this a reality.

Thank YouThank You

Are there any questions for Are there any questions for myself or John Richards?myself or John Richards?