Evaluation of techniques for in situ determination of explosion hazards in asphalt tanks

Abstract It is clear from recent work in our laboratory and elsewhere that the traditional method of assessing the explosion hazards in asphalt tanks, by comparing storage temperature to material flash point, is not reliable in many circumstances. In response to the need for better evaluation methods, several techniques for monitoring the composition of the vapour space of asphalt tanks have been evaluated. Methods were investigated which determine the combustibility of the vapour space and which analyse for more specific compounds which are indicators of smouldering coke deposits — a major ignition hazard in asphalt tanks. Simple methods, easily applied routinely by manufacturing personnel, are shown to be of adequate accuracy by comparison to more complex methods yielding more complete information but also requiring more extensive equipment and expertise. Applicability of each method to five different classes of asphalt is discussed. Strengths and weaknesses of conventional flash point tests are also discussed; they are shown to be of limited use in assessing explosion hazards with air blown asphalt and solvent deasphalting residuum.