June, 2008

This is a repeating event

200811JunAll DayGoodyear Heat Exchanger Rupture 2008Goodyear Houston (US-TX) Origin: CSB Lessons:Asset integrity,Control of Work,Emergency PreparednessIndustry:ChemicalsCountry:United StatesLanguage:ENLoC:Overpressure

Summary

On June 10, 2008, Goodyear operators closed 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 over-pressure protection. Maintenance workers replaced the rupture disk on that day; however, the closed isolation valve was not reopened.

On the morning of June 11, an operator closed a block valve isolating the ammonia pressure control valve from the heat exchanger. The operator then connected a steam line to the process line to clean the piping. The steam flowed through the heat exchanger tubes, heated the liquid ammonia in the exchanger shell, and increased the pressure in the shell. The closed isolation and block valves prevented the increasing ammonia pressure from safely venting through either the ammonia pressure control valve or the rupture disk and relief valve. The pressure in the heat exchanger shell continued climbing until it violently ruptured at about 7:30 a.m.

The catastrophic rupture threw debris that struck and killed a Goodyear employee walking through the area. The rupture also released ammonia, exposing five nearby workers to the chemical. One additional worker was injured while exiting the area.

KEY ISSUES:
• EMERGENCY RESPONSE & ACCOUNTABILITY
• MAINTENANCE COMPLETION
• PRESSURE VESSEL OVER-PRESSURE PROTECTION

ROOT CAUSES:
1. Although maintenance workers had replaced the rupture disk by about 4:30 p.m. on June 10, the primary over-pressure protection for the heat exchanger remained isolated until the heat exchanger ruptured at about 7:30 a.m. on June 11.


Image credit: CSB

Origin

CSBUS Chemical Safety Board

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