(186d) How Stressed Is Your Facility? Past Events Resulting from Structural Stress

When we think about process safety, we tend to focus on the process related elements, such as flow, temperature, pressure etc. However, a key element that is very important is the physical structures that thank form part of or support the process. How stress is applied to structures or equipment can have a significant effect on the process safety outcomes. A well know process safety incident that involved a stress related failure was the Flixborough explosion, where the stresses in the temporary pipe were not considered. Another is the structural failure in the Formosa Point Comfort fire, where structural steel lacked passive fire protection, and was not able to withstand its load in a fire scenario. Failures due to stress loading are not limited to the processing industries, for example in 1970 the Westgate Bridge in Victoria Australia collapsed during construction due to stress loads in in the box girder. Similarly, in 1969 and 1970 two other box girder bridges collapsed during construction. Stress related failures can also be seen in liquid tankers that ‘break their back’ during loading or unloading, atmospheric storage tanks that implode on discharge due to the vacuum pressure or the in-flight break-up incidents that occurred with the de Havilland Comet. All these types of failures are related to the structural stresses, though the reason for the stress may be different. This paper will explore some case studies of stress related failures highlighting possible learnings for the processing sector in identifying and managing structural stress.