Control of Welding Fume Exposures in Shipbuilding Confined Spaces

purpose of the studyTo develop and assess a ventilation training program to reduce welding exposures in confined spaces.

To determine if training welders can change ventilation practices.

Motivation: excessive exposures to welding fume

welding fume• ultrafine particles • hazardous components

• metals, gases, particulate matter

health risks:• respiratory

• lung disease (COPD, Asthma)• “metal fume fever” (galvanized)• Cancer (SS)

• cardiovascular diseases

Develop training conceptsValidation of training conceptsDevelop training programPre-intervention assessmentPost intervention changeDirections for future

STUDY OVERVIEW

Ventilation “lab” tests

After observations in shipyards, we used a more controlled space to test which parameters had the most effect on fume control, such as:

• Duct height• Duct proximity• Air flow• Room mixing

This helped us develop ventilation training guidelines.

Simple, pictorialBox modelExhaust placement

Local, General New concept: Regional Exhaust Ventilation

Mixing Exhaust vs. Supply

Cross draft “Mini-fan”

Common problems Short circuiting Dead space

TRAINING CONCEPTS

ventilation training:Basic Ventilation Concepts

ventilation training:Practical Questions

Minifan-induced crossdraft

CROSS DRAFT AND MIXING

ventilation training:Short circuit

ventilation trainingCommon Problems

verifying our recommendationsWe tested our recommendations by monitoring the fume exposure by measuring

exposure before and after adjustments.

Exhaust at floor: Poor control

Exhaust high: Good Control

010

2030

Geo

met

ric M

ean

mg/

m3

High Low Near Far Cross MixPre Post Pre Post Pre Post Pre Post Pre Post Pre Post

Location of Ventilation

for Control and InterventionGeometric Mean Concentration

verifying our training principles

Simple ventilation adjustments reduce worker’s exposure

Pre-Assessment Questionnaire on trainees Monitoring in typical conditions

Training In groups of up to 20 at a time Primarily new construction at Vigor and Dakota Creek

Post-Assessment Questionnaire on same trainees Monitoring in typical conditions

INTERVENTION ASSESSMENT

ventilation trainingAbout 100 workers participated in the ventilation training program at Vigor in Seattle and Dakota Creek, in Anacortes.• Five sessions with

about 20 people

• Combination of discussion, lecture, and ventilation problem-solving exercises

• Training was led by an industrial hygienist with a background in designing temporary ventilation for welding in similar situations in refineries.

Participants filled out a survey about their knowledge and use of ventilation before the class and again several weeks later.

Observed conditions and welding fume exposure levels

n (%)GM (GSD)

mg/m3 All Samples 65 (100%) 2.4 (4.2)

Space ConfinementPartially Enclosed 5 (8%) 1.3 (2.4)Enclosed 28 (43%) 2.2 (3.2)Confined 32 (49% 2.9 (5.4)

Welding TypeSMAW 5 (8%) 0.8 (4.5)FCAW (Dual Shield) 49 (75%) 3.2 (3.6)FCAW (Inner Shield) 5 (8%) 3.7 (4.9)Oxyacetylene 6 (9%) 0.4 (2.9)

Ventilation TypeNo ventilation 19 (29%) 2.3 (4.4)Supply blowers 19 (29%) 4.3 (4.2)Exhaust blowers 25 (38%) 1.8 (3.7)Supply & exhaust blowers 2 (3%) 0.6 (7.2)

n (%)GM (GSD)

mg/m3 Exhaust Vent Proximity

Local 2 (7%) 1.1 (47.1)Regional 6 (22%) 2.1 (1.9)General 19 (70%) 1.6 (3.5)

DeadspaceNo 31 (48%) 2.4 (3.8)Yes 34 (52%) 2.4 (4.7)

CrossdraftNo 55 (85%) 2.7 (4.5)Yes 10 (15%) 1.4 (2.6)

Respirator UsedNo 11 (17%) 0.9 (3.3)Yes 54 (83%) 2.9 (4.1)

QUESTIONNAIRE RESULTSCHANGE IN SCORE ~ 1 MONTH POST TRAINING

 n

Post-Pre improveme

ntSE

Worthwhile setting up for short job71 0.11 0.13

Too much work for any length job.70 0.17 0.14

Takes too much time to set up69 0 0.13

Confidence in my ability to decide what vent works best 70 0.17 0.1

Confidence in my ability to set up ventilation71 0.1 0.83

Properly used vents can reduce my exposure71 -0.01 0.08

Properly used vents will increase the comfort and visibility 71 -0.28 0.09

Properly used vents will reduce exposures of others 71 -0.03 0.07

Mean score based on a 1 to 5 scale

 

Pre-training% correct

Post-training

% correct

Change in % correct

You may need a respirator even when using vents 100 100 0

When exhausting the length of duct does not matter 86 85 -1

Weld quality is always reduced if air is moving past you 78 69 -9

Welding smoke is heavy and settles 72 75 3

The number of blowers needed depends on number of welders 69 79 10**

How many blowers are needed to ventilate 9x9x9 ft space? 56 71 15**

Which of the images shows short-circuiting? 22 18 -4

Which type of exhaust ventilation is practical and effective? 25 34 9

What advantage does blowing have over exhausting? 60 56 -4

QUESTIONNAIRE RESULTSCHANGE IN % CORRECT ~ 1 MONTH POST

TRAINING

** McNemar’s test of proportions, p<0.05

Shipyard environment is very challenging For environmental control For conducting research

Ventilation CAN be set up in confined spaces to significantly reduce exposure to welders Sufficient fresh air supply Strategically placed for fume removal Dissipation where appropriate

But it is not being effectively used in many conditionsA single training for welders is NOT sufficient to

change practices Many barriers and organizational constraints which training

alone cannot overcome

STUDY RESULTS AND CONCLUSION

Recommendations Continue to develop expertise within welding and support

trades to increase effectiveness of ventilation

Develop system to identify adequacy of ventilation during work

Continue supporting use of respirators as needed

Next steps: Further analysis Dissemination of results and training materials through:

Scientific journals Research group website: https://blogs.uw.edu/uwseixas/

Suggestions for additional dissemination?

THANK YOU!We greatly appreciate the participation and support from:

• Puget Sound Shipbuilders Association• Vigor Shipyards• Dakota Creek• Foss Maritime• Lake Union Dry Dock

• Contributors: • Faculty: Noah Seixas, Hendrika Meischke, Mike Yost, Lianne Sheppard• Staff: Chris Warner, Rick Neitzel, Marc Beaudreau, Bert Stover, Gerry Croteau• Students: Jane Pouzou, Jeff Walls, Lea Duffin, Eddie Kasner

air monitoring and observations

We measured how well different ventilation setups worked in real situations by observing and monitoring the fume levels in the spaces where welders were working.

Hundreds of assessments of ventilation were made at Vigor, Dakota Creek, Foss, and Lake Union Dry Dock.

common ventilation problems

“Short-circuiting” of the air

Excessive bends or kinks in duct

Inadequate equipment for space and amount of welding (many spaces that needed multiple blowers only had one)

Poor placement of the duct• Too far from the fume• Too low to the ground

Use of venti lat ion:• 3% used local exhaust ventilation • 29% used dilution ventilation (either

exhaust or supply)• 68% did not use LEV or DV

Use of a respirator: 41%

Exceedance of the 5 mg/m 3 8-hour TWA PEL:• Overall: 82%• Confined spaces: 94%• Enclosed spaces: 70%• Spaces with dilution ventilation: 31%• Spaces with local exhaust ventilation:

100%

a preliminary study in other shipyards showed: