Chapter 11 - Emergency Shutdown

Abstract

An emergency shutdown (ESD) system is a method to rapidly discontinue the operation of the process and isolate it from incoming or outgoing connections or flows to reduce the likelihood of an unwanted event from occurring, continuing, or escalating. The aim of an ESD system is to protect personnel, afford protection to the facility, and prevent an environmental impact from a process event. Most ESD systems are designed so that several mechanisms can initiate a facility shutdown. These mechanisms are provided by both manual and automatic means. The design of an ESD system is normally based on independence and fail-safe component utilization. Independence is obtained by physical separation using separate process locations, impulse lines, instruments, logic devices, and wiring. This avoids common failures in the system. Fail safe features are obtained by ensuring that selected components in an ESD system are such that during a failure of a component, the process reverts to a condition considered “safe.” Safe implies that the process or facility is not vulnerable to a catastrophic, destructive event because of the release of hydrocarbons. For most facilities, this implies that pipelines that supplies fuel to the incident (i.e., incoming and outgoing) are shut off and that high pressure, high volume gas supplies that are located in the incident are relieved to a remote disposal system.