Normal Accidents | Charles Perrow

Summary of: Normal Accidents: Living with High Risk Technologies – Updated Edition
By: Charles Perrow


Dive into the world of high-risk technologies with the summary of Charles Perrow’s insightful book, “Normal Accidents: Living with High Risk Technologies – Updated Edition.” This summary explores the complex systems that govern our modern world, and examines the intricacies of human-made accidents and disasters within these systems. Perrow discusses system accidents and their various facets, including Design, Equipment, Procedure, Operator, Supplies, and Environment (DEPOSE). Further, you’ll discover the role of complexity and coupling, which play a significant part in determining the safety and reliability of various technologies such as nuclear reactors, chemical plants, dam structures, and aircraft.

Understanding System Accidents

The occurrence of system accidents is often unexpected and can be complex. These accidents arise from various errors in Design, Equipment, Procedure, Operator, Supplies and Environment, commonly referred to as DEPOSE. Failure in any of these areas can cause the whole system to fail. This point is illustrated in a situation where a series of events led to a job interview being missed. A forgotten key, a friend with it, a neighbor’s car that wouldn’t start, and a bus drivers’ strike prevented a taxi from being available. The interdependent nature of all these systems resulted in the entire system, in this case, the interview, collapsing. Although such accidents may not always lead to a disastrous outcome, the implications in nuclear or chemical plants, for example, can be catastrophic.

Complex vs. Linear Systems

Complex interactions and tight coupling can lead to catastrophic failures in systems. While complex systems have multiple interconnected components that may be hard to predict, they can be flexible enough to recover from component failures. Linear systems, on the other hand, are easy to predict, but a single component failure can trigger failure in other components, leading to catastrophe. The Grand Teton Dam collapse in 1976 is an example of how a tightly coupled linear system failed due to an insufficient solution to a known problem. Understanding the characteristics of different systems can help prevent disasters and improve functionality.

Lessons Learned from the Three Mile Island Disaster

The partial meltdown at the Three Mile Island (TMI) nuclear power plant in 1979 provides a valuable lesson on the dangers of complexity and coupling in high-risk industries. The accident resulted from four small, seemingly unrelated failures that occurred within 13 seconds of each other, causing the core temperature and pressure to rise. Safety devices that were meant to prevent disasters sometimes fail or even contribute to the problem.

The first failure occurred when water leakage caused a false signal to shut down the turbine used to generate power. The emergency water pumps were then inoperable due to valves that were closed, causing the core to overheat. An automatic safety device designed to relieve pressure got stuck and signaled that it had closed when it remained open. This failure led to the unstable core overheating the coolants, which created hydrogen gas. Despite the operators following safety protocols and reducing the cold water feed, the core remained uncovered, and a hydrogen bubble had formed.

The lesson learned from TMI is that complex and tightly coupled systems, like those in high-risk industries, are unpredictable. Trivial failures can interact and cause a system accident. In such industries, safety devices are installed to prevent disasters, but they can sometimes become ineffective or even damage recovery. Thus, the system must always be monitored to ensure its safety.

The Inherent Risks of Flying

Flying has become increasingly safe over the years due to improved designs, safety measures, and a reduction in complexity and coupling. However, crashes will always occur due to the inherent complexity of flying. Even with the great improvements in air traffic safety, a single component failure caused by a maintenance error and design error in the slats led to hundreds of deaths in the DC-10 airplane crash. Flying, with its multitude of components and unpredictable interactions, will never be risk-free.

The Hidden Risks of Petrochemical Plants

The dangers of petrochemical plants are often overlooked, but they pose a significant risk. Similar to the nuclear industry, the petrochemical business also employs processes that can be hazardous. Although the industry has been in operation for over a century, accidents have occurred. While some are unpreventable, others, such as the Bhopal gas tragedy, are avoidable and can result in thousands of deaths due to negligence. Safety precautions are put in place, but it only takes a mixture of circumstances for a catastrophic system accident to occur. By understanding the potential dangers and risks associated with petrochemical plants, we can be better informed and take steps to prevent such tragedies from happening.

The Dangers of Production Pressure

In a bid to meet up with deadlines and expectations, production pressures oftentimes lead to the creation of small errors that can cascade into something uncontrollable. This is similar to what happens with system accidents. While technology designed to aid safety and navigation can be helpful, they can actually increase the chances of accidents if not used correctly. A case in point is the BP oil tanker incident that was caused by the captain’s poor judgment due to the pressure to deliver his cargo fast. Marine accidents caused by operator’s haste and poor judgment are on the rise despite the adoption of collision avoidance systems and better communication between vessels. Companies and operators prioritize quicker delivery and lower expenses, oftentimes without considering the potential risks. This highlights the need for companies to put safety first and for operators to resist the urge to take unnecessary risks in a bid to meet up with production demands.

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