Grain Elevator Explosion 1

[dik]

http://www.winnipegfreepress.com/wo...-shoots-a-fireball-high-in-sky-132874423.html

 

[ishvaaag]

I muse that these things should be avoidable by now by just proper monitorization of the air mix inside or through vents, filters or whatever.

A reference for those needing to deal with the matter:

Dust Explosions in the Process Industries
Second Edition
Rolf K. Eckhoff
Butterworth-Heinemann
Linacre House, Jordan Hill, Oxford OX2 8DP
225 Wildwood Avenue, Woburn, MA 01801-2041
A division of the Reed Educational and Professional Publishing Ltd

 

[MiketheEngineer]

You would think!! But unfortunately it happens too frequently and usually quite deadly.

I used to work for a company that sold explosion suppression systems. It literally sensed the beginning of an explosion and flooded the area with Halon - a cousin to Freon. IT WORKED. I saw a number of films that showed it. Even talked to a guy that was in a propane filling room when an explosion was averted by the system we had installed. Other than soiling his pants - he was fine.

System wasn't cheap - back then in the $25,000 range. But a lot cheaper than 3 lives.

FENWAL made the system - not sure if they are still in business but Halon has kind of been banned - I think - or it is very expensive. I think race cars still use them. Not sure why airlines don't??

You can breathe the stuff as the concentration is only in the 5-7% range and just displaces a fraction of the oxygen content whereas nitrogen need to be in the 30%+ range - which can suffocate you.

 

[dik]

I understand there are several methods of significantly reducing the hazard of dust explosions... Some of these were implimented in saw mill projects I've been involved with.

I suspect that the lack of implimentation is due to the cost... The three deaths may not be a significant cost saving to the company.

Dik

 

[TXStructural]

It is almost impossible to avoid an explosive level of dust in grain elevators, so the controls are typically in place to avoid ignition sources. While dust can be controlled generally, there will still be, at minimum, localized concentrations. Many such explosions are the result of steel getting past screens and magnets, and causing a spark in the area of high concentration. Also, a small event can liberate a large dust cloud, leading to a second, larger explosion.

During cleaning, even small sparks can result in big booms.

 

[Lemony]

I believe the rule of thumb for LEL of dust was "if you can't see a mining lamp at 10 feet". Is their ventilation that poor?

 

[JLNJ]

The agricultural industry has always been more accepting of risk. It's part of the American Way.

 

[MiketheEngineer]

Now 6 lives

 

[dik]

From an NFPA explosion report for a grain explosion in Kansas in 1998 where 7 people were killed, "However, the potential for these hazards continues to exist at many older facilities where modern technology has not been implemented. These facilities must rely on the human factors of proper housekeeping and preventive maintenance programs to limit the potential for fire or explosion. The basic method of limiting the explosion hazard is to reduce the potential fuel load. This is accomplished through a comprehensive housekeeping program, where dust accumulations are promptly and regularly cleaned. This should include a complete dust collection system as well as manual housekeeping, such as removing dust from inaccessible places where dust collection systems cannot reach."

Be interesting to see the new report... doesn't seem like they've learned very much...

Dik

 

[TXStructural]

Every time the elevator is filled, dust accumulates on top of every surface (pipes, ledges, etc.), and if something disturbs the dust, for instance a sudden vibration like a small, initial explosion near the grain handling area, the collected dust shakes loose and mixes quickly with enough air to make a larger explosion. You will not eliminate the fuel where grain is actively being handled, so keeping the risk of ignition low is the primary control. To prevent a secondary explosion, housekeeping is most important.

On a smaller scale in a past career, I designed high speed explosion detection-suppression systems using UV/IR detectors and high speed water as well as CO2 suppression. The challenge with this size of a vessel is the rapid detection-suppression sequence required over a very large area. Some grain silo facilities will be a quarter to half mile long, and then each silo is quite tall. Water cannot be used effectively since the silo will not be maintained above freezing temperature as all times. Halon is not an option - very expensive (if you can get it, hundreds of thousand of dollars per silo and deadly once you get the discharge required for an empty silo into a partially filled one.) There is probably a suppression system one could design, but prevention is far less expensive, however that requires the rather undependable human element.

 

[dik]

TXS...

I sort of agree... but, proper housekeeping is essential and employee training is also imperative...

I've worked on projects in chemical plants where even the flash from a digital camera will detonate stuff... powder that can ignite by friction, as well as the potential for toxic gas release... and these firms have a significant training program as well and the trained employees are also up with the program... every action is almost safety related.

It would be interesting to know what part of their program is dedicated to safety and housekeeping. I'm not making any comment on what this firm did or didn't do for safety, but, in my experience it can be done... There are far more dangerous environments. There is also a cost associated with this... staying alive is 'non-productive'.

I don't know... six lives have been forfeit in the process.

 

[MiketheEngineer]

And the pay isn't that great. Jest read an article where a supervisor's average pay is $45,000 - $47,000 and the peons make much less. I guess that is OK in Outback, Kansas. But not my cup of tea!!

 

[MikeHalloran]

I wonder how/if things might change if worker deaths caused a direct business cost, rather than an actuarial possibility of a cost.

I.e.. suppose OSHA said, "There are no rules for equipment, procedures, or documentation. The only rule is this: Each worker death results in a fine, due immediately, in cash, of 1,000,000 USD, (inflation adjusted)."

I suppose it would need a "whichever is greater" clause to cover the case where $1E6 is petty cash, but you get the idea.



Mike Halloran
Pembroke Pines, FL, USA

 

[TXStructural]

Realizing that we are only speculating on cause right now, and only speaking in general terms:
OSHA regulations actually never include the "it's just too darn expensive" option. And I certainly agree that housekeeping is paramount, but the safety profession and the insurance industry recognize that relying upon the human element is seldom satisfactory for high-risk systems and situations. Some events remind us how unreliable methods requiring human intervention can be.

Engineered controls are always preferred because of their reliability. But the grain industry has very few workable engineering methods for dust control. Some methods include suppressing dust with sprayed oils (causes significant fire, storage, and processing problems of its own), dust extraction (which doesn't work very close to where the grain is handled), or inerting the entire silo (expensive and creates a lethal environment inside the silo.)

I'm not excusing poor practices, only emphasizing that the issue is not so simple as some would make it out to be.