Grid production machine |
Grid production and parts casting involves book casting,
continuous casting, and strip casting. In
all of these processes, lead pigs are melted down and the molten lead is
poured into molds or continuously cast into
grids, strips, or parts. Expanded
metal grid production involves mechanical
operations on the cast strip and is not a source
of airborne lead dust or oxide. The major source of lead exposure in this process is from lead
fumes and lead
oxide which can become easily airborne.
|
|
Potential Sources of
Exposure
- Drossing the lead pot may increase lead exposure.
- High levels of
lead fumes are generated when
a flame is put in contact with lead, such as when cutting out frozen
pots.
- Settled lead dust on surfaces and equipment may become airborne due to exhaust from fuel-powered fork-lifts
or vehicular traffic.
- High exposure to lead fumes can occur when the pig is
loaded
into the lead pot.
- Airborne lead dust can migrate from other
areas of the plant
depending on the plant
layout.
- Separator boards may become contaminated by using lead contaminated pallets that have not been cleaned
after being returned from the pasting
line.
- Dust may become airborne
as a result of using a rotary sander for cleaning
molds.
- Oxide that has collected
on the dross ladle may become airborne while cleaning
or storing it in
an area outside the hood.
Possible Engineering
Controls
- Develop
a system to minimize the
formation of dross.
- Place a local exhaust ventilation on the lead melting pot and the dross
pot
(Figures
1, 2, and 3).
Lead Pot and Dross Hood
Scrap Pot and Dross Hood
- Dross with a ladle with holes
in it to allow lead to drain back into the
pot.
- Install Laminar
Flow (Supplied Air) Islands at the drossing
station if
exposures exceed the PEL.
- Provide local slot ventilation or a ventilated torch for cutting out frozen
pots.
Ventilated Torch
- Suspend plastic curtains to separate the casting areas from the traffic
areas.
- Isolate the lead pots from casting
operations.
Possible Work Practice
Controls
- Handle dross carefully within a ventilated
enclosure.
- Keep the doors closed on the dross cabinets when drossing into the
containers.
- Keep the dross covered where air turbulence may cause powdery dross to become
airborne.
- Cool waste drums under exhaust
ventilation.
- Enclose cooled waste drums with a plastic bag prior to storage (Figure 3).
- Do not add sawdust to the
dross.
- Keep dross from calcium and antimonial alloys separate and dry since arsine and stibine
gases could be emitted.
- Slide pigs into the casting pots, where feasible.
- Use a long-handled push rod or mechanical system to feed the pigs into the
pot.
- Use separate pallets for grid storage and
pasted plate storage (Figure 4).
- Provide adequate PPE, change of clothes, and shower
rooms (see OSHA Lead Requirements for PPE, Housekeeping, and Hygiene Facilities).
- Maintenance:
- Ensure ventilation is working
properly.
- Use electric powered fork
lifts.
- Use an automatic conveyance
system.
- Avoid using a rotary sander to clean
molds.
- Housekeeping:
- Use dust suppression techniques, such as, using
dust suppression compounds or
vacuuming.
- Keep the floor areas and work surfaces around the lead pots and lead storage areas free of oxide
dust.
- Scrape metal splashes with a shovel or long-handled
scraper.
|
|
|
|
Back to Top 
www.osha.gov
Figure 3. Ventilated and automated
Figure 5. Lead-contaminated separator boards
