A 20-foot section of a construction crane fell 30 floors in Miami, Fla., Tuesday, smashing into a home below and killing two people. The accident comes 10 days after a crane collapsed in New York, killing seven people. New York City is re-inspecting high-rise cranes following the crane collapse that killed seven people nearly two weeks ago.

Earlier in the year and farther south, a February explosion at a sugar refinery in Georgia left at least 13 dead. Investigators said the explosion was caused by combustible sugar dust, according to Occupational Hazards.

These tragedies have once again led to national concern over industrial safety.

Crane Collapses
Investigators believe that the March 15 accident in Manhattan occurred as workers high on the 22-story crane were installing steel bracing to stabilize it so that additional sections could be added to make the crane taller, a process known as “jumping” the crane.

At the time of the accident, the crane was being lengthened with a new section. Apparently a heavy-duty steel collar used to tie the crane to the building’s side fell; when the steel collar fell, another collar on the ninth floor — a major anchor securing the crane to the building — was damaged. Without the support at the ninth floor, the counterweights at the top of the crane’s tower caused the entire crane to fall, according to a buildings department spokeswoman.

However, New York City’s mayor and other city officials insist that braces on the third and ninth floors appeared to have been adequate. Nonetheless, the city yesterday ordered “broad changes [...] to the way it inspects and regulates tower cranes,” The New York Times reports.

Laing O’Rourke, the largest privately owned construction firm in the United Kingdom, provides a few basic points to consider when it comes to safe crane operations:

• Erecting a tower crane is a potentially hazardous operation, and any site activities that could impinge on the operation must be suspended while it is done.

• As an additional precaution, an exclusion zone must be established around the operational area.

• Procedures must conform to the manufacturer's instructions and to the method statement both supplied by the erection supervisor and approved by the project manager.

• The tower crane must be satisfactorily tested. If the crane is to be subsequently climbed and tied (connected) to the structure, a further test will be required each time before the crane is returned to service.

• If the tower crane is from an external supplier, the inspection and testing department must be given due notification. An examination must be made before the tower crane is delivered to site, and the test of the installed crane must be witnessed.

Investigators with the U.S. Occupational Safety and Health Administration (OSHA) were at the Miami site yesterday. A crane expert will also help in the investigation.

Since the crane collapse on the East Side of Manhattan, city officials have increased safety and inspection requirements. The Buildings Department said a city inspector will now have to be present every time a crane is erected, jumped or dismantled. It will require the project engineer who submitted the original permit application for a crane to produce a “written protocol” for each jump, including guidelines for how the work should be done. The engineer will have to inspect the crane to certify that it was built and assembled according to plans. The city has already shut down several cranes for violations.

Combustible Dust
As for the recent refinery blast in Georgia, IndustryWeek points out the U.S. Chemical Safety Board’s November 2006 study “that identified 281 combustible dust incidents at U.S. plants between 1980 and 2005.”

“In many accidents, employers and employees were unaware that a hazard even existed,” OSHA notes. In addition to knowing the type of dust in the processing plant, the following are other tips to consider:

• Frequently clean floors and horizontal surfaces, such as ducts, pipes, hoods, ledges and beams.

• If dust surpasses 1/32 of an inch in depth on floors, structural members, and other surfaces, remove all of it.

• Design the dust-containing systems (ducts and dust collectors) so fugitive dusts do not accumulate.

• Aim relief venting to a safe location away from employees.

• Where dust occurs, use an ignition control program, such as grounding and other methods for dissipating any electrostatic charge that could occur while transporting the dust through the ductwork.

• Employ only electrically powered cleaning devices, such as sweepers or vacuum cleaners used in dusty areas, approved for the hazard classification, as required under 910.307(b).

• Install many “no smoking” signs in areas in and near dusty places and only allow people to smoke where there is no danger of causing an explosion.

• Use only dust collector systems with spark detection and explosion/deflagration suppression systems. (There are other alternative measures.)

• Construct all components of the dust collection system of noncombustible materials.

• Maintain sufficient velocity in ducts to ensure the transport of coarse and fine particles.

• Ground duct systems, dust collectors and dust-producing machinery.

• Ensure that all electrical wiring and equipment comply with 1910.307(b) requirements.

• Train workers and supervisors about the hazards of combustible dust.

The February blast in the Georgia refinery near Savannah has prompted OSHA to inspect hundreds of plants where combustible dust is a workplace hazard. There are currently 17 different standards that are applicable to combustible dust.

Resources

Two Workers Are Killed In Miami Crane Accident
by Damien Cave and Solange Reyner
The New York Times, March 26, 2008

Probe Begins in fatal Miami Crane Crash
by Matt Sedensky
The Associated Press, March 26, 2008

Three Bodies Pulled From Rubble of Crane Collapse
by Rocco Parascandola
Newsday, March 17, 2008

City Tightens Its Regulations and Inspection of Cranes
by William Neuman
The New York Times, March 26, 2008

Safe Operation of Cranes (page 23)
Laing O’Rourke, 2004

Refinery Blast Reinforces Calls for Process Safety
by Jonathan Katz
IndustryWeek.com, April 1, 2008

Combustible Dust National Emphasis Program (Reissued)
OSHA, March 11, 2008