Time to consequence (TTC) is the time between initiation of the safety system by a failure and the moment the hazardous consequence occurs. Dynamic simulations can help to determine TTC and ensure safety systems are adequate.
Dynamic simulations have become indispensable for process design and validation, control system verification, startup support, and troubleshooting. Recent developments in simulation software and technology have enabled their use for developing large-scale dynamic models that can be used throughout a project’s life.
Time-to-consequence (TTC) calculations are one area where these models can be used to ensure the suitability of safety systems for a process. TTC is important because it determines the maximum amount of time the safety system has to respond, including sensing the out-of-control condition and actuating the control devices, as well as other tasks.
This article describes how to use dynamic simulations to calculate TTC (sometimes referred to as process safety time, PST). Case studies from a liquefied natural gas (LNG) plant illustrate the concepts.
Deputy Chief for the Process Safety Engineering Group , Bechtel Oil, Gas, and Chemicals
Sameera ThakoreSenior Process Engineer, Bechtel Oil, Gas, and Chemicals
Haribabu ChittibabuSenior Process Engineer, Bechtel Oil, Gas, and Chemicals
Jaleel ValappilPrincipal Process Engineer , Bechtel Oil, Gas, and Chemicals
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