Domino effect accident
A domino effect accident is an accident in which a primary undesired event sequentially or simultaneously triggers one or more secondary undesired events in nearby equipment or facilities, leading to secondary accidents more severe than the primary event. Thus, a domino effect accident is actually a chain of multiple events, which can be likened to a falling row of dominoes. The term knock-on accident is also used.
Domino effect accidents are an important process safety issue affecting process plants where significant amounts of hazardous materials are stored, transported, and processed. Losses of containment that result in fires or explosions can escalate to nearby equipment, due to thermal radiation, blast overpressure or other mechanisms, thus potentially causing further fires, explosions, or toxic gas clouds.
Characteristics of domino effect accidents
The consequences of the domino effects of an accident are often more severe than the primary event. Escalation is caused by the physical effects induced by the primary event, which are referred to as escalation vectors. Domino effect accidents mainly consist of three elements: the primary scenario, the escalation vectors, and one or more secondary accidents.Primary scenarios
The primary scenarios include various types of fire, unconfined vapor cloud explosion, confined explosion, and mechanical explosion. Normally, there is only one primary event, such as a tank fire in a gasoline storage farm. However, if the process is triggered by intentional attacks or natural disasters, multi-primary events may apply. In that case, it can be very difficult to prevent the escalation of domino effects due to the synergistic effects caused by multiple hazardous events. For example, an earthquake may lead to multiple equipment failures in a process plant, which can in turn cause further accidents.Escalation vectors
The escalation vectors are the hazardous effects caused by the primary scenarios. The escalation vectors of pool fires, jet fires, and fireballs is thermal radiation and fire impingement. For BLEVE, ME, and VCE it is blast overpressure and fragment projection. Fire-induced domino effects are time-dependent, while explosion-induced domino effects are not related to time, as the failure of the affected equipment will occur instantaneously.Single and multiple secondary accidents
If the primary scenario successfully escalates to other installations nearby, one or more secondary events occur. Escalation from the primary event to the secondary event is called the first-level escalation, while escalation from secondary event to a potential tertiary event is called second-level escalation, and so on. When lower-level event triggers multiple higher-level events, these are called parallel effects. A higher-level event caused by multiple lower-level events is a case of synergistic effects. Time-dependent escalation vectors from different sources and acting at different times may result in a synergic effect over a secondary target; this is called superimposed effects.Types
Intentional and unintentional domino effect accidents
According to whether the primary event is deliberate or not, domino effect accidents can be divided into unintentional and intentional. The primary events of unintentional domino effects are caused by accidental events or natural hazards. Intentional domino effects are cause by deliberate attacks such as acts of terrorism and sabotage.Fire-induced and explosion-induced domino effect accidents
According to the physical nature of the primary event, domino effects can be divided into fire-induced and explosion-induced. According to some sources, toxic release may also directly induce domino effects via the movement of toxic gases, e.g., if poisoning induces plant operators to errors that result in secondary accidents.Internal and external domino effect accidents
In a chemical cluster or a process plant industrial park, there are multiple hazardous materials sites located next to each other. An accident occurring in a site may escalate to the neighboring plants. Internal domino effect accidents are those accidents that occur within a plant, while external ones are those escalating to outside the primary plant boundaries. Preventing external domino effect accidents is especially complex, as these require managing the hazard across multiple companies. Encouraging the cooperation between different neighboring companies within a cluster of sites is essential for the management of domino effect hazards.Examples
The consequences of domino effect accidents can be much more severe than the primary events. Past process industry catastrophes that involved domino effects significantly greater than the initiating event are the San Juanico disaster, the Piper Alpha disaster, the Esso Longford disaster of 1998, the 2005 Buncefield fire, the 2009 Jaipur fire, the 2009 Cataño [oil refinery fire], the 2019 Xiangshui [chemical plant explosion], etc. For example, at the 2019 Xiangshui chemical plant explosion, which led to more than 78 deaths and 617 injuries, many facilities near the chemical plant where the accident started were damaged.File:Buncefield explosion from M1 motorway.jpg|thumb|Buncefield fire seen from the M1 motorway