Oxide and Grid Processing » Oxide Production

Furnace that melts lead for the Barton Process
Furnace that melts lead for the Barton Process

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).

Figure 1. Drossing out the lead pot

Potential Sources of Exposure

Figure 2. Barton Process Figure 2. Barton Process
  • 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.

Figure 3. Enclosed screw conveyor

Possible Engineering Controls

Figure 4. Inspect leaking equipment
  • Use local exhaust ventilation:
    • Install a hood enclosure for the lead melting pot.
    • 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.
    • 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.

Figure 5. Work station for analyzing oxide samples

Possible Work Practice Controls

Figure 6. Vacuum frequently
  • 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.

Figure 7. Ball mill
Figure 8. Barton pot