natural gas explosion reference

[MA_PE]

So we've got a situation where a water supply pipe crosses below a natural gas main.   The water pipe people want to know what the risk of damage to the water pipe is if the gas pipe explodes.  We know the diameter and pressure of the gas pipes and can assess damage potential for water pipe, but need to know the extent of the energy from the gas line explosion.  Does anyone have any industry accepted procedures for estimating the energy from the gas explosion or the relationship between the crater formed from explosion of the buried gas line?  @mudpuppy are you in the as business? Any EBer's in th gas business that might be able to provide some insight or someone to cotact?

 

[wilheldp_PE]

I found a reference describing a model to estimate blast radius, but it doesn't deal with crater depth.  Maybe some of the references in this paper would answer your question?

https://pstrust.org/docs/C-FerCircle.pdf

 

[Dleg]

I don't have access to anything but I do believe that such information exists. Way back in my oilfield days, I recall having to review penetration data for explosive perforating charges. As I recall, there were empirical relations available that would tell you the depth of penetration (e.g. crater depth) depending on the explosive energy and the concavity of the charge. For a gas line that would just be zero (or 1 or whatever the terms used).  So see if you can look that up.  Search terms shaped charge, explosive casing perforation, etc. (just be prepared to be flagged by the FBI and NSA!)

 

[pbrme]

I found a reference describing a model to estimate blast radius, but it doesn't deal with crater depth. Maybe some of the references in this paper would answer your question?

https://pstrust.org/docs/C-FerCircle.pdf

I don't have access to anything but I do believe that such information exists. Way back in my oilfield days, I recall having to review penetration data for explosive perforating charges. As I recall, there were empirical relations available that would tell you the depth of penetration (e.g. crater depth) depending on the explosive energy and the concavity of the charge. For a gas line that would just be zero (or 1 or whatever the terms used). So see if you can look that up. Search terms shaped charge, explosive casing perforation, etc. (just be prepared to be flagged by the FBI and NSA!)

^& @MA_PE
I'm a little late to the party, but I'm currently working on a somewhat similar analysis. In my case, I'm looking at a mobile hydrogen storage tube bundle skid and trying to determine the blast force psi on it's surroundings at certain distances away. It's being requested by our client per mandated review by a local fire marshal. I'm using an older calculation we did for the same client 10 years ago, which converts the stored volume into an equivalent mass of TNT using the stored work principles. I can then take the equivalent mass of TNT and use scaling laws to calculate the distance equivalent to reference 1kg TNT at set distances. There are charts available for referencing a 1kg TNT explosion on a Peak Overpressures (psi) to Distance (m) charts. FEMA has charts which you can use to compare this data.

I'm actually looking for any input from others on this topic as well, since the approach I mentioned above is giving me excessively high quantities. I found an excel calculator on the NRC website (Google "hydrogen blast calculation excel", top of the list) which provides an approach taken from the SFPE Handbook, but still gives high mass equivalents. I'm just having trouble determining the Yield% to use in the calculation. The calculator notes on Yield: "The fraction of available combustion is 1% for unconfined mass release and 100% for confined vapor release energy participating in blast wave generation." This is out of my wheelhouse, and I've heard arguments for both extremes... unconfined as the storage tubes will release to atmosphere and confined as they are in essentially pipes. This calculator has various other fuel gases, one of which is propane, so it may also be useful for someone else.

 

[Dleg]

Assume worst case? It's hard to be faulted when you take that approach. In a review after an accident, of course. You'll probably be faulted a lot when they see the bill for construction, though.

 

[pbrme]

Assume worst case? It's hard to be faulted when you take that approach. In a review after an accident, of course. You'll probably be faulted a lot when they see the bill for construction, though.

"When in doubt - make it stout" is definitely the mantra, just not sure in this case. I have in the neighborhood of 108K gal of H2 at 200 bar, and at 100% yield calcs out on the NRC spreadsheet to close to 3.3M lbs TNT!!! This puts me way outside of the FEMA charts and is pretty much weapons grade something. I've got some queries out to some local FPE's and a local fuel gas supplier (the one suppling the storage skid in fact) on what other AHJ regulations they're used to seeing. This can't be that unusual of a situation as there are similar installations around my neck of the woods. Just thought I'd check with you all in case someone here had experience.

 

[Dleg]

Wow 1.6 kilotons? Yeah can't exactly design for a tactical nuke....