Apple today confirmed that explosions last year at Chinese plants of two of its parts suppliers were caused by excessive aluminum dust. In its annual report on its suppliers' efforts in worker safety, labor rights and environmental impact, Apple said the explosions at facilities operated by Hon Hai Precision Industry -- better known by its trade name, Foxconn -- and Pegatron last year were traced to small airborne particles. The Foxconn plant explosion in May 2011 in Chengdu, China, killed four and injured 18 others. A December explosion at a Shanghai factory run by RiTeng Computer Accessory, a subsidiary of Pegatron, injured 59, Apple said.
Other reports had put the injured
tally at the latter explosion at 61. According to the Apple report, both
explosions involved combustible aluminum dust.
Reports at the time of each
explosion had identified aluminum dust -- produced while milling and polishing
the casings of such Apple products as its iMac, MacBook and iPad -- as the
likely culprit.
Interviews with air-quality
experts last May after the Foxconn explosion also pointed to combustible dust.
Very fine particles of all kinds
of materials can trigger an explosion, said Brian Edwards, director of
engineering at Atlanta-based Professional Engineering, in an interview at the
time.
"By creating fine particles
or dust powder, you increase the surface area of the material, which with a
spark, can cause a rapid exothermic reaction," said Edwards, using a more
technical term for an explosion. "That decreases the minimum energy needed
for ignition and speeds up the reaction."
Aluminum is more explosive than
either sugar or grain dust, Edwards added, talking about two typical causes of
dust explosions in the U.S.
"You need a perfect
storm," Edwards said. "You have to the have the right concentrations
of dust in the air, you need sufficient oxygen, and you need an ignition
source."
Edwards speculated that the cause
of the Foxconn explosion was aluminum dust that had collected in the ductwork
that drew off dust from polishing or grinding equipment, which in turn ignited
dust in the actual workspace.
Such explosions can be massive,
he noted. "In a dust explosion, you typically see structural damage,"
Edwards said.
Christopher Haase, director of
environmental, health and safety at Environmentally Sensitive Solutions, a
Milwaukee, WI-based firm that develops industrial cleaning products, said that
Chinese factories badly lagged behind American plants in their dust-explosion
prevention methods, in part because government censorship prevents managers and
specialists from getting the information they need to create safer workplaces.
"The last few years, the
Great Firewall means they can't talk to others, or complain about the work
environment," said Haase. "They're asking for help, but they have to
use proxies and things like Hotmail to open a dialog with Western
experts."
The "Great Firewall" is
the name many have slapped on the Chinese government's attempt to control what
its citizens are able to access on the Web.
In its report, Apple said that it
had worked with external experts to audit all its suppliers that handled
aluminum dust, and with one exception, put new measures into place. "We
have established new requirements for handling combustible dust throughout our
supply chain," said Apple. The company ticked off several action items,
including ventilation requirements, regular inspections of ductwork, and
banning the use of compressed air for cleaning, a practice that makes more dust
airborne.
"All suppliers except one
have implemented the counter-measures identified by the team of external
experts," Apple said. "The one supplier that has not will remain shut
down until modifications are in place."
Apple did not identify the supplier
that was shutdown.
The Apple report can be viewed
from the company's website ( download PDF )
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