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Furnace that melts lead for the Barton Process
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Lead oxide, which is used to create
the paste used on the battery plates, is
either produced by the Ball
Mill Process or the Barton-Like Process.
It may also be purchased from an oxide producer (see receiving).
The major source of lead exposure in the
oxide production process comes
from leaking equipment and system upsets.
| Oxide Production |
Figure 1. Drossing out the lead pot
Figure 2. Barton Process
Figure 3. Enclosed screw conveyor
Figure 4. Inspect leaking equipment
Figure 5. Work station for analyzing oxide samples
Figure 6. Vacuum frequently
Figure 7. Ball mill
Figure 8. Barton pot
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Potential Sources of Exposure
- Lead dust can become airborne due to improper air flow or exhaust ventilation, which results in "puffing" of lead oxide at the mill inlet.
- Exposure may occur from handling lead pigs while loading the mill pots
or the ball mill.
- Lead oxide dust may spill or leak from trunnion seals, bearing seals, conveying systems, and transfer points.
- Exposure to lead may occur when drossing the lead pots during the Barton
process (Figure 1) and during maintenance operations that require entry into the pot for
cleanout.
- Lead oxide may leak or spill during drive fitting and transfer operations.
- Lead exposure may occur while collecting and testing oxide samples.
- Operators may be exposed to lead oxide while cleaning the oxide
production line.
- Exposure may be due to vehicular traffic in adjacent roadways stirring up oxide.
Possible Engineering Controls
- Use local exhaust ventilation:
- Install a hood enclosure for the lead melting pot.
Gas
Fired Lead Pot Canopy Hood
- Install a hood enclosure on the dross pot or barrel.
- Install tightly enclosed conveyer systems with ventilation at transfer
stations (Figures 3 and 4).
- Use exhaust ventilation at the sampling and process test stations (Figure 5).
- Use exhaust ventilation around the agitator shaft or air intake of the Barton pot.
- Place a hooded duct in close proximity to the air intake to contain the
volume of a "puff" in order to prevent it from entering the workplace.
- Place local exhaust ventilation around dust generation points.
- Ensure that drum filling operations are ventilated and enclosed.
Oxide Drum Filling Local Exhaust Ventilation
Oxide Barrel Filling Local Exhaust Ventilation
Gas Fired Lead Pot Canopy Hood
- Add a pressure relief valve, vented through a
filtering system, to the screw conveyer to vent dust generated
during the transfer operation.
- Isolate the process:
- Separate the operation from the rest of the plant and keep it under negative
pressure.
- Build a positive pressure control room for the operator.
- Use pneumatic conveyers for handling barrels rather than handling them
manually.
- Use automatic sampling instead of manual sampling.
- Install a vertical classifier ahead of the normal classifier and oxide
collection equipment to reduce "puffing" of the Barton Process
equipment.
- Protect or insulate storage tanks from the weather to prevent water condensation on the inside
walls.
- Mechanize the system of feeding lead pots or mills.
Possible Work Practice
Controls
- Notify supervisor of oxide leaks and perform temporary repairs
immediately.
- Fill drums inside ventilated hoods or enclosures.
- Wipe down the exterior of drums before transferring them to storage or to other
areas.
- Cap the drums before vacuuming.
- Prevent lead buildup on the inside perimeter of the pot because it can slough off and cause
puffing.
- Provide adequate PPE, a change of clothes, and shower rooms (see OSHA Lead Requirements for PPE, Housekeeping, and Hygiene Facilities).
- Maintenance:
- Ensure that the local exhaust ventilation is working properly (Figure 2).
- Develop a written schedule of inspections for oxide mill operators.
- The
schedule should include weekly inspections of equipment such as overhead
ducts and rotary valves.
- Housekeeping:
- Vacuum all oxide spills immediately with a central
vacuum system or a HEPA vacuum.
- Vacuum equipment surfaces and floors whenever possible during each
shift (Figure 6).
- Use dust suppression compounds in place of
water for dust suppression in the mill area to prevent the
possibility of oxide fires and the mixing of water and molten lead.
- Periodically shut down the plant to perform a thorough cleanup of settled
dust.
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