Methane (blast) containment pit
Methane (blast) containment pit
(OP)
Need to design a concrete cover for a concrete methane spill containment pit (5'x25'x4'deep). It's sized for 3' of spilled methane with 1' extra to the bottom of any vents.
Is there an industry generated code for the possible explosion pressure? What about depth of concrete cover for fire protection of reinforcing steel? We would like to place vents along two sides to direct flames away from the storage tank and pumps. How big should the vents be?
Is there an industry generated code for the possible explosion pressure? What about depth of concrete cover for fire protection of reinforcing steel? We would like to place vents along two sides to direct flames away from the storage tank and pumps. How big should the vents be?






RE: Methane (blast) containment pit
With regard to fire resistant structural design, you'll have to do some research (there's plenty on the web). You'll have to consider:
What is the temperature of the fire (depends on the type of fuel - methane)?;
How long will the cover be exposed to the heat after the initial reaction (explosion)?;
Do you expect the cover to remain serviceable after exposure to a "containment event" (chances of the event occurring vs. cost of the cover)
If the cover design indicates that the self wt of the cover is not sufficient to counteract the pressure of the explosion, and if it's not economically feasible to design the cover to that effect, then vents would probably be designed considering fluid dynamics with regard to flow rate, pressure, vent opening, serviceability, etc.
Where safety against personal injury is a concern, you should increase any safety factors accordingly.
It's an interesting question, and I wish I could have been of more (or some) help.
good luck.
RE: Methane (blast) containment pit
At least that's what I have seen in the aftermath of pipeline explosions, anyway.
Please see FAQ731-376 by VPL for tips on how to make the best use of Eng-Tips Fora.
RE: Methane (blast) containment pit
The stored material is methanol (not methane, my mistake) and I have found references to methods for quantifying explosion pressures in NFPA 30, 68 and 69. they mention determining an "energy-equivalent mass of TNT, but I haven't found a reference yet that relates methanol to TNT. And, of course it makes a difference how big the vapor cloud is and how close you are to it.
Focht3 is right, it won't burn for long, and NFPA gives clear cover recommendations for concrete exposed to heat (fire), so I feel certain that I can protect the reinforcing. Still, I need to come up with a reasonable and rational design pressure.