Our thoughts and prayers are with those whose lives were lost, and those injured, as well as their families in last week’s fertilizer plant explosion in West Texas. A few statements made in the press were a bit surprising and I wanted to share those with you. Before I begin, let me be clear that I do not have detailed knowledge of the functional safety culture at the West fertilizer plant nor was anyone from exida involved in any functional safety services for this plant.
- The plant’s June 2011 risk management plan (RMP), filed with the Environmental Protection Agency, identified several potential hazards, … The report asserted that the worst-case scenario for the plant “would be the release of the total contents of a storage tank released as a gas over 10 minutes.” It reported no flammable material on site, despite listing 54,000 pounds of anhydrous ammonia at the plant.” Full article here
- Ammonium nitrate disasters
If you look at the overview of Ammonium Nitrate Disasters, you will see 28 incidents listed (excluding the West plant explosion). There are several stated as “plant explosions.” The one I remember best was the AZF fertilizer factory in Toulouse, France specifically because it happened right after 9/11 and there were initial speculations that it may have been a terrorist attack.
In the AZF factory three hundred tons of ammonium nitrate was stored (the maximum capacity was 2,000 tons) in the hangar #221. The whole factory was destroyed making a crater of depth 20 to 30 m (65 to 100 ft), with a diameter of 200 m (650 ft); steel girders were found 3 km (2 mi) away from the explosion. The blast measured 3.4 on the Richter scale, with an estimated power equivalent to 20-40 tons of TNT. The results of the official enquiry were that a warehouse of ammonium nitrate had exploded following improper handling of this dangerous material. The disaster caused 29 deaths (28 from the factory, 1 secondary school pupil from a neighboring school), 2,500 seriously wounded, and 8,000 light casualties.
So what does this mean? How can the worst case scenario identified in a Process Hazard Analysis (PHA) for a plant storing Ammonium Nitrate not be complete plant explosion? OSHA PSM requires that we redo our PHAs every 5 years or when there are changes to the process and/or plant, so yes they are a must. However when we do our PHAs we need to realize that they are a MUST to identify ALL POTENTIAL hazards so we can ensure our own safety. If we want to do a good PHA we need to think outside the box, consider unmitigated (without safeguards) consequences.
Take a look at my “That is impossible! It has never happened before…” blog entry. I’m blogging about an “unimaginable” travel experience. The Ammonium Nitrate Disasters are not unimaginable.
The unfortunate events at the West Texas fertilizer plant quite easily allowed me to collect these statements/statistics. The scenario where a PHA does not identify the “worst case scenario” is however not uncommon. At exida we have seen this quite a bit. I don’t know if it’s the difference between a “commodity” PHA and a “functional safety” PHA. However, we must realize that for our safety PHAs are a MUST and need to be conducted by highly experienced personnel and/or independent third parties. Commodity PHA is not the answer just because it may be done cheaper and enables the engineering contractor and/or client to just “tick the box.”