Heat Exchanger Rupture Incident Using the Information

Heat Exchanger Rupture Incident

Using the information in the CSB Case Study, identify probable direct causes, contributing causes, and root causes of the incident. Explain the reasoning you used to reach these causes. You may make assumptions concerning any missing investigative information as long as you clearly state your assumptions. Discuss how and where your proposed causal factors fit into the causation model on page 356 of the course textbook. For the root causes only, provide recommended corrective actions.

The United States Chemical Safety and Hazard Investigation Board (CSB) is an independent federal agency tasked with protecting workers and the public by investigating and preventing chemical accidents, and after each investigation is completed a comprehensive case study is released to detail probable causes and proposed responses. When an ammonia heat exchanger ruptured and released deadly gas inside Houston's Goodyear Tire and Rubber Company plant on June 11, 2008, an incident which killed one employee and injured six others, the CSB conducted a rigorous examination of the equipment being used that day, the employees charged with managing the initial emergency, and the preventative maintenance programs in place at the time. The CSB ultimately concluded that operator error, lack of preventative maintenance, and equipment malfunction combined to create the circumstances which directly caused the ammonia heat exchanger to rupture and explode.

According to the CSB's final report on the Goodyear Tire and Rubber ammonia release, after a round of routine maintenance was performed to close "an isolation valve between the heat exchanger shell (ammonia cooling side) and a relief valve to replace a burst rupture disk under the relief valve that provided overpressure protection" (2011), the closed isolation valve was never reopened. This oversight began a chain reaction of events in which operators then performed a separate task, requiring them to close the block valve necessary to prevent the first mistake from becoming catastrophic. When the flow of steam during the routine cleaning process began to heat the ammonia to dangerous levels, the redundant failsafe in place had been bypassed, allowing internal pressure to increase until the deadly rupture occurred.

The CSB observed and documented "evidence of breakdowns in both the work order and lockout/tagout programs that contributed to the incident" (2011), and this supervisory oversight undoubtedly precipitated the heat exchanger rupture incident. By not ensuring that proper maintenance protocols had been adhered to each and every time repairs were made to sensitive equipment, workers left operators without vital knowledge that may have warned them that over-pressurization was likely to occur.

The CSB also concluded that "Goodyear's maintenance procedures did not address over-pressurization by the ammonia when the relief line was blocked, nor did it require maintenance and operations staff to post a worker at the vessel to open the isolation valve if the pressure increased above the operating limit" (2011), despite standards established by the American Society of Mechanical Engineers (ASME). Had the Goodyear plant adhered to the regulations provided by ASME's Boiler and Pressure Vessel Code, Section VII, the first incidence of human error would not have been permitted to create over-pressurization in the ammonia heat exchanger.