Eliminating and controlling dust explosion hazards starts with a thorough understanding of explosion characteristics – and that takes laboratory testing, according to Brian J. Kingsley of Chilworth Global Technologies. Kingsley presented a seminar this morning at AIHce 2011 entitled, “Dust Explosion Hazard Assessment – including OSHA’s Combustible Dust National Emphasis Program.” (NEP)
“You have the ability to get data from many places,” Kingsley said, but cautioned that level of confidence industrial hygienists can have in data depends upon it being applicable to the specific kind of dust in a given facility.
Lab data can reveal how material will ignite (its minimum ignition energy, minimum ignition temperature and thermal instability), what will happen if it does ignite (i.,e. maximum explosion pressure, off-gassing potential). Additionally, data can provide the basis for controlling atmospheres and can supply information on electrostatic properties.
“Some materials can even be ignited by the human body,” said Kingsley. Devices like anti-static footwear can reduce explosion hazards in facilities where these materials are present.
In addition to a knowledge of explosion characteristics, dust explosion hazard management should also include a site audit, proper process and facility design and the regular inspection and maintenance of equipment.
Data can also help in the design of relief ventilation devices that will safely release the pressure without destroying the vessel, said Kingsley. “Relevant laboratory testing needs to be undertaken in order to understand the profile (of materials),” He emphasized that venting devices are not suitable for toxic material, and must be directed to the exterior of a building. “Always vent to a safe place.”
Factors affecting combustibility data include temperature, pressure, particle size and turbulence.
Controlling the spread of combustible dust atmospheres can be accomplished through equipment maintenance, continuous local exhaust ventilation and housekeeping. Kingsley said that compressed air was not recommended, but if it is used, the surfaces should be vacuum cleaned first, electrical power should be shut down, there should be no hot surfaces and only low gauge pressure should be used.
Preparing for an OSHA NED also involves good housekeeping to reduce risk of a dust explosion. Kingsley also recommended that companies become familiar with OSHA NEP documents, paying close attention to how to identify and assess hazards.