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Welding fume Management

Welding fume Management

• In what units is fume generation measured?

• What units apply to particulate TLV’s?

• A FCAW welder produces how much fumes per year?

Fume emission level versus shielding atmosphereFume emission level versus shielding atmosphere

100

0

0

20

0

80

10

5

85

5

5

90

0

8

92

0

1,5

98,5

200

400

600

800

1.000

740

470

350290

190150

Fumes (mg/min.)

CO2

O2

Ar

Wire ER 70S3 dia.: 1,2mm280 - 300 A

28 - 30 V

Ar + 18% CO2

Ar + 13% CO2 + 5% He

Ar + 10% CO2

Ar + 6% CO2 + 2% O2

Ar + 5% CO2 + 4,5% O2

Ar + 3,5% O2

Influence of CO2 content in the shielding gas on CO emissionsInfluence of CO2 content in the shielding gas on CO emissions

0

50

100

150

200

160

130120

80

40

0

CO content (ppm)

Ar

+ 3

,5%

O2

Wire ER 70S3 1,2mm

Wire = 10 m/min

I = 280 / 300 A U= 32 / 34 V

I

Airborne particulatesTypical size range

Atmospheric dust

Very fine (10E-8 cm) Fine (10E-4 cm) Coarse (1 cm )

Welding fume and dust

Tobacco smoke

Coal dust

Cement dust

Respirable particles

Factors affecting fume generation rate

Type of shielding gas if applicable to the process Welding current Welding voltage Arc length Polarity Current density Humidity Base plate Electrode angle Electrode type Formulation of the electrode and wire

Fume emission testing device

• Filters weighed before and after test

• Welding time known• 30 seconds/1 min

exhaust• fume emission rate

calculated: average of five readings

• measurements in mg/minute

•Air exhaust fan•Filters

•Conical column

•Rotating table• FCAW gun mount

•Observation window

•AWS F 1.2-92( Laboratory method for measuring fume generation rates• and total fume emission for Welding and Allied Processes)•20mm plate, 20 inch dia, 4 inch efffective, 120 lbs .

Typical fume generation Rates

Process Range g/minSMAW 0.2 - 1.2

FCAW 0.5 - 3.5

GMAW 0.1 - 0.5

GMAW(AL) 0.1 - 1.5

The filter is about the size of a medium PIZZA!

• Clean and used filter, after 30 seconds!

Welding fumes composition

EEEllleeemmmeeennnttt CCCooommmpppooouuunnndddsss

Fe Fe3O4 - MnFe2O4 - K3FeF6 - CaFeSi2O6

Mn MnFe2O4 - MnSiO3 - MnTiO3

Si Fe2SiO4 - K2SiF6 - CaFeSi2O6

Ti MnTiO3

Ca CaF2 - KCaFe2O4 - CaSiO3

K KCaF3 - K3FeF6 - K2SiF6

Welding fumes composition

EElleemmeenntt CCoommppoouunnddss

Na NaF - NaFeO2

F CaF2 - KCaF3 - K3FeF6 - K2SiF6 - NaF

Ni ( Fe,Ni)O

Cr III Cr2O3 - FeCr2O4 - K2NaCrF6

Cr VI K2CrO4 - Na2CrO4 - NaK3(CrO4)2

Potential Health EffectsFumes Potential health hazard

Iron Oxide Respiratory irritant in highconcentrations

Cadmiumoxide

Lung irritants and kidney toxins

Chromium Cr VI is a recognized carcinogenCopperoxides

Irritant, may cause fume fever

Fluoride At high exposures, lung irritant & canaffect bones and kidneys

Lead Systematic poisoning and affects thenervous systems

Magnesiumoxide

Fume fever

Nickel Dermatitis and respiratory irritantZinc oxide Fume feverManganese Nervous system disorders – Parkinson

disease like symptoms

Hexavalent Chromium

Hexavalent chromium is a known lung carcinogen

SMAW stainless steel electrodes produce high level of Cr VI ( 50% - 70% of total chromium)

Lithium compounds reduce Cr VI significantlyFCAW stainless steel electrodes produce high

level of Cr VI ( 30% - 60% of total Chromium)GMAW of stainless steel produces very little

Cr VI ( < 10% of total Chromium)ANSI/AWS F3.1 - 89 : Guide for Welding Fume

Control

Composition by % weight:GMAW

Element Mild steel StainlessFe 45 - 55 30 - 45Mn 5 - 10 1 - 20Si 3 - 5 1 - 4

Ni N/A 2 - 8Cr Total N/A 8 - 25

Cr VI N/A 0.2 - 1Li N/A N/A

Composition by % weight:FCAW

Element Mild steel StainlessFe 30 - 50 10 – 20Mn 5 - 15 4 - 20Si 2 – 4 2 - 8Ti 0.02 - 4 0.5 - 5Ca 0 – 20 0.1 - 5K 0 - 10 3 - 10

Na 0 - 10 2 - 20F 1 – 20 2 - 10Ni N/A 1 – 5

Cr Total 6 - 12Cr VI 1 – 4

Li 0 – 1

Welding fumes

Welding amperage

fumegenerationg/min

?

Influence of the shielding gas and parameter set up on fume emission level in GMAW

Influence of the shielding gas and parameter set up on fume emission level in GMAW

(Wire: ER 70S3)

Ar + 3% CO2 + 1% O2 Ar + 10% CO2 Ar + 18% CO2

Tension (V)

15 20 25 30 35 400

200

400

600

800

1.000

170 A

Fumes (mg/min)

300 A

350 A

100 A

3-D representation of fume generation for non pulsed GMAW

• For a given wire feed speed or amperage:– Low fume generation in

short circuit range

– As voltage is increased, transfer transits through globular range causing a first maxima

– Fine tuning of spray transfer gives a minima

– As voltage increased beyond the optimum, fume generation rate increases

Fume Concentration

Fume concentration is measured inMilligrams per cubic meter (mg/m3)

Some terms used in the welding fume legislation

• OSHA: Occupational Health and Safety Administration• PEL: Permissible Exposure Limit (8 hours)• TWA: Time weighted average (8 hour exposure)• NIOSH: National Institute of Occupational Safety and Health• ACGIH: American Conference of Governmental Industrial Hygienists• OEL: Occupational Exposure Limits (8 hours)• TLV: Thresh hold Limit Value (8 hours)• TWAEV: Time Weighted Average Exposure Value (8 hours)• STEL: Short Term Exposure Limit ( TLV-STEL : 15 minutes)• C: Ceiling value ( TLV-C : instanteneous max value not to be exceeded)• General ventilation must move 2,000 cu feet per minute• Each welder should have 10,000 cu feet of barrier free work space• Serious violation : $ 7,000 per violation• Repeat violation: $ 70,000 per violation

Occupational Exposure Limits(OEL) for Ontario, Canada

Welding fume 5.0 mg/m3Chromium Metal 0.5 mg/m3

Chromium - trivalent 0.5 mg/m3Chromium - hexavalent 0.05 mg/m3

Nickel metal 0.5 mg/m3Manganese 1.0 mg/m3 ( 0.2 mg/m3)Fluorides 2.5 mg/m3

Barium soluble 0.5 mg/m3NO2 3.0 ppmNO 25 ppm

Ozone 0.1 ppmCO 35 ppm

Air Sampling Meter

Daily variation of Fume Concentration

08:00 12:00 16:00

Fumeconcentrationmg/m3

Exposure limit

Time weightedAverage

Actual Exposure

Fume weight per welder per year ?

• Fume generation rate of 1g/minute• 2000 hours/yr at 20% duty cycle = 400 hours welding time• 400 hours X 1 g/minute X 60 = 24,000 grams = 52.8 pounds

• Equal to the weight of one coil of wire per year!

FUME GENERATION – 1.6 mm FCAW : 200,000 HOURS OF ARC TIME NOTE:NOTE: 200,000 hours of arc time at 18% duty cycle translates to 200,000 hours of arc time at 18% duty cycle translates to

approximately 556 welders.approximately 556 welders.

STATUS WIRE Fume g/min Wire feed i.p.m VOLTAGE GAS Fume Burden

Current Wire A 1.066 350 29 V CO2 12.79 MTProposed Wire B 0.783 380 29 V B/S8 9.39 MTProposed Wire A 0.881 380 29 V B/S8 10.57 MTProposed Wire C 0.949 380 29 V B/S8 11.38 MTBenchmark Wire B 0.67 350 29 V Arcal 211 8.04 MT

Through choice of gas and wire fumes reducedAnnually by 4.75 MT!!

Source capture

Applications?

Source capture?

Fume extracting gun

Test results of air quality

Sample Location Sampling time in

minutes

Volume sampled

inliters

Lab results(micro

grams per sample)

Concentration(mg/m3)

99V001 Welder under general exhaust fume hood, fume hood switched

OFF61 122.1 3424 28.0

99V002 Welder under general exhaust, fume hood

switched ON 61 122.1 1969 16.1

99V003 Welder under fume hood, with a smoke

extracting gun 62 122.4 171 1.38

           

Ontario Ministry of Labour, TWAEV for welding fumes 5.00

Welding Fume management

Questions?