Friday, May 4, 2018

Some Thoughts on the Anniversary of the West Explosion

I wrote this article on 23 April,  2018.  A slightly-edited form of it appeared in the Waco "Tribune-Herald" on 26 April,  2018.  By way of disclosure,  I am on the board of contributors for that newspaper.  And a few years ago,  I worked in fire protection engineering,  which gave me much more than just a nodding familiarity with the various fire codes.

For those from out-of-state,  the "Trib" is the Waco,  Texas,  USA,  newspaper.  The agricultural plant in nearby West,  Texas,  caught fire and suffered an ammonium nitrate fertilizer explosion,  some 5 years ago.  Recovery from that devastation is now complete. And devastation it was.


The 5 year anniversary of the West fertilizer plant explosion recently passed,  with excellent coverage on TV and in the newspaper regarding recovery since.  That recovery is now said to be complete,  and is a testimony to the people of West,  and to all who helped them.

Many things in life are a sort of “double-edged sword” that can either help you or hurt you.  Ammonium nitrate is one of those things.  It makes a wonderful fertilizer as a source of fixed nitrogen.  It is also a mass-detonable explosive in its pure form,  which is type 100-0-0 fertilizer,  something well-known from a long history of such explosions.

When combined with other fertilizer compounds as something other than 100-0-0 fertilizer,  the explosive risk goes away.  But there is still an enhanced fire danger,  as the ammonium nitrate decomposes when exposed to fire,  releasing oxygen into the fire.  That makes the fire very intense.

Now,  neat 100-0-0 ammonium nitrate fertilizer is hard to detonate,  requiring either the same sort of detonator as dynamite (just larger),  or confinement when decomposing in a fire.  Without confinement,  decomposing the material in a deliberate fire is actually the best way to dispose of mass quantities. 

The confinement comes from anything heavy resting on top of the fertilizer (including large amounts of the fertilizer itself,  as at Texas City),  or containing the fertilizer within some physical structure as it decomposes from the heat of a fire.  The fertilizer itself doesn’t burn,  it decomposes. It also melts and runs as a liquid down into any holes or spaces,  even floor drains.

In a building fire such as happened at the West fertilizer plant,  the confinement is generated by either (1) the burning building collapses down upon the decomposing fertilizer,  or (2) the melted fertilizer flows down a floor drain into a pipe.  Either will start the tremendous explosion. 

At the West fertilizer plant,  it was the building collapse that prompted the explosion.  This event actually happened after the majority of the stored fertilizer had already decomposed in the building fire.  Had it happened sooner,  much more of (perhaps all) the town of West would have been obliterated,  and the death toll would have been much,  much higher.

The way to positively prevent ammonium nitrate explosions is to positively prevent the building fire from collapsing the building in the first place.  Wooden structures,  feed,  and grain,  plus other building interior furnishings,  are all flammable:  fuel for the fire. 

In a new facility,  you simply eliminate all those materials from where ammonium nitrate is processed and stored.  But because the fertilizer is stored in paper bags,  there is still fuel next to the fertilizer that enhances the fire. 

So,  you fire-sprinkle the building according to the specific standards for fertilizer storage (and these already exist,  courtesy of the National Fire Protection Association).  There is no other way to be certain.

In an existing facility,  there are likely to be wooden floors,  wooden building structure,  wooden storage racks or pallets,  and perhaps even wooden handling and process equipment.  These are all flammable,  fuel for the fire.  That makes the fire-sprinkling of the building even more crucial,  plus it is prudent to seriously over-design the sprinkler system.

Most of these facilities now lie within the city limits of small towns all over Texas.  Many of them were outside the city limits when originally built,  putting them under county (or state) jurisdiction.  If there is no authorization for a county to impose the fire code standards upon these facilities,  then it is the Legislature’s job to authorize them to do so,  or else to make it a statewide mandate. 

And,  believe me,  they should do so!  There have been many of these explosions over the past century.  There is no excuse to let money trump public safety.  Official both in public service and in private organizations should be judged by how they prioritize public safety versus profit.

There is also the problem of urban sprawl.  As already mentioned,  towns grow toward and engulf these facilities.  Without thinking about the threat,  residences,  businesses,  and schools get built right next to facilities handling what amounts to a high explosive,  if mishandled. 

What that really means is that local officials need to understand the true nature of the threat from ammonium nitrate.  They need to zone around these facilities as their locations are annexed into the city,  to restrict development to a safe distance.  This has not been happening,  but ignorance should not be an excuse!

As for anhydrous ammonia,  it poses much less of an explosion hazard,  but something of a toxic gas release hazard,  even in a plant fire.  However,  there are standards for these,  too.  If applied,  the risks are reduced quite effectively.  Again,  this starts as a county or state requirement for rural construction,  and those same requirements should be applied by the cities as they engulf these facilities,  as well as proper zoning.

Citizens,  you render your judgements at the polls!