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Group burning operation |
After the plates have been stacked, they are joined with small connecting
parts and burned together to form cell elements or groups. This operation is
conducted either manually at a burning station or by using an automatic
cast-on-strap (COS) machine. The major source of lead exposure in the group
burning process comes from
lead fumes that workers may inhale during the following
operations:
| Automatic
COS Machines |
Figure 1. Ventilated COS machine
Figure 2. Vacuum plates before use
Figure 3. Tamp plates over ventilated work station
Figure 4. Enclosed COS machine
Figure 5. Automatic COS machine |
Potential Sources of Exposure
- Exposure to lead may increase from handling dry plates or moving plates in and out of the workstation.
- Lead oxide that accumulates on racks, equipment, and floors may become airborne.
- Lead particles may become airborne when groups are dropped into the cases.
- Lead particles may become airborne during cleaning and roughing
with a wire brush.
- Increased exposure to lead may occur during drossing or charging the lead pot.
Possible Engineering Controls
- Install down draft or slot ventilation at the feed end (Figure 3).
Stacking Table
Single Exhaust Booth Hood
- Enclose machine and place in a ventilated room (Figure 4).
Cast on Strap Machine (Farmer) Total Enclosure with Exhaust
Cast on
Strap Machine (Dynacast II) Emission controls
- Provide an access door for maintenance and a small port for drossing and loading the lead
pot.
- Provide local exhaust ventilation at the melting pot, mold heating section, dross pot, lug brush, and the casing
areas.
- Position ventilation slot in the direction of the generated lead
particulate, not behind the brush.
- Install an exhausted semi-enclosure around the brush to help collect particulate entrained in the
brush.
- Install a laminar
flow (supplied-air) island above the workstation.
- Use slot ventilation at burning and group dropping stations.
- Use an enclosed Lazy Susan for holding the stacked groups for the team
stack and burn operations.
- Place a plastic sheet at the stacking side to control the height of the
stacks and prevent cross drafts.
- Provide an exhaust ventilated enclosure for the lead pot and dross
container.
Possible Work Practice Controls
- Avoid setting torches at excessive temperatures.
- Tamp plates only over ventilated workstations (Figure 3).
- Do not bang plates excessively.
- Use a grating or perforated plate tamping stand.
- When dropping groups into container, place opening toward exhaust
ventilation.
- Handle groups only with hands; do not lean them against the stomach,
chest, or chin.
- Wear an apron.
- Maximize the distance between the operators breathing zone and the plates by not stacking assembled groups more than three
high.
- Stand on platform when practical.
- Keep openings to unventilated enclosures to a minimum.
- Close access doors to ventilated enclosures.
- Place, do not throw, defective plates into a ventilated scrap
barrel.
Scrap
Handling Barrel/Drum Exhaust Hood
- Cover drums with a plastic bag before removing.
- Provide rubbers or gratings for walking surfaces.
- Provide adequate PPE, a change of clothes, and shower rooms (see OSHA Lead Requirements for PPE, Housekeeping, and Hygiene Facilities).
- See Grid Production and Parts Casting for additional
possible engineering and work practice controls.
- Maintenance:
- Ensure that local exhaust ventilation is working properly.
- Prevent cross drafts.
- Substitute cooler flames such as air-propane or air-MAP gas for
oxy-acetylene.
- Change torch head to decrease time required for burning.
- Provide a plastic or glass plate between the breathing zone and the
plates.
- Housekeeping:
- Vacuum work stations and adjacent areas to prevent accumulation of oxide
dust.
- Vacuum off each row of plates or groups before use.
- Vacuum tops of plate trays.
- Vacuum clean out trays (do not dump them into barrels).
- Use dust suppression techniques such as keeping floors wet, using dust suppression compounds,
or vacuuming.
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| Manual
Group Burning |
Figure 6. Exhaust burning box
Figure
7. Manual post burning operation
Figure 8. Ventilated torch
|
Potential Sources of Exposure
- Exposure to lead fumes may occur when burning with torches.
- Exposure to lead may result from moving groups in and out of the workstation and
in and out of the burning box.
- Lead cross contamination can
occur between the stacking and the burning stations during the manual group burning process.
- Lead particles may become airborne when groups are dropped into the cases.
- Exhaust ports of pneumatic systems may cause settled dust to become airborne.
Possible Engineering Controls
Possible Work Practice Controls
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| Group Repair Operations |
Figure 9. Handle groups carefully |
Potential Sources of Exposure
- Exposure to lead may occur while repairing groups.
Possible Engineering and Work Practice Controls
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| Cleaning Molds |
Figure 10. Clean molds carefully |
Potential Sources of Exposure
- Lead particulate may become airborne while cleaning molds using compressed air or torches.
Possible Engineering and Work Practice Controls
- Clean molds using alternative methods, such as vacuuming, that do not produce airborne lead
particulate (Figure 10).
- Use local exhaust ventilation around torch head.
Ventilated Torch
- Use portable side draft or slot ventilation.
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| Adjusting/Repairing Equipment |
Potential Sources of Exposure
- Lead exposure may increase while adjusting and repairing equipment, or during changeovers.
Possible Engineering and Work Practice Controls
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