Posted By steve e ashton Sorry I can't offer example documents, and I don't want to teach my granny how to suck eggs, but I guess you will already have "Googled" the large amount of info on the web about things that can go wrong with Ammonia plant to ensure your plans take account of the 'worst case scenario' as required by COMAH? Despite a view that Ammonia is 'normally' difficult to ignite, having high LEL and high energy ignition requirements, there have been more fires / explosions involving the material than most might expect, and the toxic cloud / chilling effect are not the only risks. As a case study: Place & Date: Azotas Fertiliser Plant, Jonova, Lithuania – 20th March 1989 Type of release: Ammonia Overview of Incident: A storage tank experienced over-pressurisation and burst on one side, releasing ammonia. At the same time, the whole tank was dislodged from the foundation (reaction force) and smashed through the surrounding retention wall of reinforced concrete. Devastation around the tank was enormous and liquid ammonia around the fertiliser factory and stores was up to 0.70m in depth. Large quantities of ammonia evaporated and suddenly the vapour caught fire and the whole area was engulfed in flames. The ammonia vapour and nitrous fumes (resulting from fertiliser decomposition) spread up to 35km, forming a contamination zone with an area up to 400km2. After 12 hours all the ammonia had evaporated but the fertiliser continued to burn for three days, evolving great quantities of nitrous fumes. The official number of fatalities was seven. The retention wall surrounding the ammonia tank was made of reinforced concrete with a thickness of 0.4m and a height of 14.1m, so there were secondary containment provisions in place. However, the design was not sufficient to prevent the ammonia tank crashing through the wall and the subsequent loss of ammonia. Hope this is of interest if you hadn't already picked up on it... Steve

Posted By Coy Tanger Steve, thanks for this. Our worst case is of this order but we have not been looking at ignition (but we will now). Thanks for your effort and time, really appreciated.

Posted By steve e ashton The HPA link given by CHAS above suggests that Ammonia "is not flammable but may explode". I would suggest the data is wrong... Ammonia can and does burn. There have been a number of serious fires involving anhydrous ammonia. The Jonova ammonia spill referenced in the HSE Research report burned for around 12 hours. (and the resulting fertiliser fires for a further three days). It may require high concentrations, and high ignition energy -but it does burn. I have posted on the HPA feedback page to let ‘em know they are publishing potentially dangerously misleading information. Steve