MSL93
Structural
- Aug 10, 2017
- 6
It is common in my industry to design a flare stack for a pressure of roughly 7 barg that is solely intended to account for the pressure in the system if a deflagration event were to occur. In fact, several customers have this language put into their specifications. From my research, this looks to be a safe and simple way to handle the design of the system for deflagration. However, it is my understanding that the nature of a deflagration event is that it results in a rapid increase in pressure from the combustion of the internal gases that then propagates to the exit of the stack and into the atmosphere. If this understanding is correct, then this would be a rather transient load case where designing the stack for a static (sustained) design pressure of 7 barg may be unnecessarily conservative.
Do note that the stack system I am describing is downstream of all block valves and open to the atmosphere.
In general, this isn't a problem (designing the stack for an internal design pressure of 7 barg) for small diameter stacks where this pressure is relatively minor, but for stacks where some segments are over 10 ft in diameter, this 7 barg design pressure can result in a large increase in wall thickness and overall system weight. When all other load cases have operating pressures less than 1 barg, I want to be positive that I am not unnecessarily designing the stack for a sustained internal design pressure of 7 barg to account for deflagration.
Does anyone on here have an insights or references to add that may provide guidance to my scenario?
Do note that the stack system I am describing is downstream of all block valves and open to the atmosphere.
In general, this isn't a problem (designing the stack for an internal design pressure of 7 barg) for small diameter stacks where this pressure is relatively minor, but for stacks where some segments are over 10 ft in diameter, this 7 barg design pressure can result in a large increase in wall thickness and overall system weight. When all other load cases have operating pressures less than 1 barg, I want to be positive that I am not unnecessarily designing the stack for a sustained internal design pressure of 7 barg to account for deflagration.
Does anyone on here have an insights or references to add that may provide guidance to my scenario?
