Dust explosion

There is one more dust explosion at Hoeganaes facility, Tennessee on May 27th in which two persons died and another is seriously injured. Earlier in the explosion on 31st January, two persons died and a person was injured during the flash fire on 29th March. My post on 14th May gives some details of iron dust explosion provided at CSB website. The latest incident appears to be initiated by hydrogen gas leak from 3x7 inch hole on a hydrogen pipe in a trench. The trench also contains nitrogen and water lines. After hearing hissing sound from the trench, nearby annealing furnace operators informed maintenance who unsuccessfully tried to remove the trench cover. Later tried to open with the metal chain hooked to a forklift and during cover opening, a flash and explosion occurred. The statement for news conference on June 3, 2011 by CSB gives status of their investigations and a short video (1:16 min) on iron dust flash fire experiment.
The shortfalls at the plant identified are poor containment of dust, improper dust collection, thick layers of dust, unsuitable electrical fittings and availability of various ignition sources nearby.These types of causes are well reported and NFPA Standard 484 and we fail to take measures to eliminate these types of causes.
Providing dust containment and collection, elimination of ignition sources, flameproof electrical fittings, providing and maintaining obstruction-free aisles, regular wet mopping and incineration of mops at safe distance, testing of electrical continuity between equipment and earth pits, maintaining 50-60% humidity, use of antistatic uniform and PPE are some of the measures that will surely help in avoiding such incidents.

Fatality at a Zirconium-Titanium Facility

It is reported that two persons died in a facility that handles zirconium-Titanium. Read the information from the link here. The incident occurred during packing of titanium powder into bricks. Federal Investigators Seek Cause Of Fatal Hancock Co. Blast - News Story - WTOV Steubenville. CSB in a statement stated that it is deploying 4-member investigating team. Internet search shows some accidents/injuries during the handling of pyrophoric materials, in which some useful information can be found in these links. LINK1, LINK2. 

1. Zirconium, titanium, thorium and other metal fires have great potential to cause injuries and fatalities as the thermal radiation can initiate fires in the surrounding areas. They can easily ignite and explode when subjected to friction/impact. It is well known that explosions be devastating in confined spaces. 
2. In combination with insufficient water, the metal fires can grow bigger due to release of hydrogen and can also cause sputtering leading to flying of burning splinters all around (some times to a few hundred meters distance - source: internet search) and cause secondary fires.
3. The zirconium fires are intense and bright and can cause retinal damage when viewed with naked eye. The fire once initiated can reach great heights in no time depending upon the quantity of material involved and size, when turnings are involved. It is reported extensively in literature and NFPA that metal powder/dust can cause dust explosion and friction is sufficient to initiate this.
4. TEC powder in portable extinguishers is effective only for small fires and big fires can be extinguished only by application of large quantities of water from all directions by experienced fire fighters. Further, continuous watch for at least a day is required after extinguishing as it is likely that the material under the heap can keep burning for a long time.
5. As per the safety advice mentioned in MSDS/NFPA, and as it is with any chemical, lesser the inventory, the more safer it is. We can't sit assuming that everything is safe when we are only storing and not handling / processing, which proved very costly during the famous Bhopal accident.
6. Pyrophoric materials need very little energy to catch fire / explode and it is stated that the static charge accumulated on a person is sufficient to initiate fire of this dust/powder. For a safe work place, it is recommended to use antistatic apparel, provide earthing to discharge static charge on the equipment/containers, flameproof/explosion proof electrical fittings, maintain at least 60% humidity, etc in the work area.
7. The powder generated should be incinerated every shift / day (depending upon the quantity) under controlled conditions so that the material can be rendered safe and can be disposed off as landfill.