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# Equivalent Static Load of an Enclosed Explosion

## Equivalent Static Load of an Enclosed Explosion

(OP)
Hello,

I am new to the forum so if this belongs somewhere else I apologize.

I am working on a product built to contain an arc flash explosion in a metal box with spring loaded latches on the door. This allows the door to "burp" gasses out during the arc flash event which reduces stress on the overall structure.

Customers ask for door mounted accessories, which can blow out of the door during an arc event.

What I would like to do is calculate an equivalent force that I can test door mounted devices to see if they will remain in place during the arc blast without running an expensive dangerous arc flash test.

Is there a way to calculate the force/pressure on the interior wall of a box that contains an explosion? Could I use burst panels on the door to measure the pressure during an actual arc flash and then solve for an equivalent static force. The idea would be to build a jig that holds the doors and press on door mounted devices with the equivalent load and if they break/push out of the door then they can't be used.

I hope I explained it well, your thoughts are welcome!

### RE: Equivalent Static Load of an Enclosed Explosion

If the door opens using spring loaded catches, can't you just measure the force with a spring tension device to open the door and then calculate pressure by using the area of the door.

Or slowly pressurise the chamber until the door flies open?

Or mount a pressure transmitter and measure peak pressure?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

### RE: Equivalent Static Load of an Enclosed Explosion

(OP)
The door opening and leaking some of the gas kinda complicates the problem, the arc blast is a huge violent explosion. There is a massive blast and huge fireball/smoke/vaporized copper etc.

The risk I am trying to mitigate is a device (usually like a VFD keypad or electric meter) getting blown out of the door during the arc blast. A pressure transmitter may work if the sample rate was fast enough.

After I measure the pressure I need to calculate the force it's putting on an object (simple enough) but then figure out how to recreate that force without the massive explosion (like an arbor press or something)to check devices.

Is the equivalent force from an explosion pressure just the pressure x area or does it have an "impact" type of equivalent static force? Does the wave of the explosion "impact" the door or can I just treat it like a pressure spike?

### RE: Equivalent Static Load of an Enclosed Explosion

The US Army has done a lot of research on the effects of blasts.
They are more like an impact, there is no static load equivalent.
I believe that many of the papers are available if you search for them.
Blast damage and blast protection would be key words.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

### RE: Equivalent Static Load of an Enclosed Explosion

If the explosion is as big as you imply then your looking at a different issue. I can't really get my head around "huge violent explosion" and "burping out gasses".

Seems to be two end of the spectrum hear??

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

### RE: Equivalent Static Load of an Enclosed Explosion

(OP)
Yes, the explosion is huge and violent and the doors burp some of the gas but most of the fire/vaporized copper etc is contained inside the cabinet. That is the reason I need to keep door mounted devices from blowing out, the fire will come out behind them and pose a threat.

Also I found some blast damage papers but they were with respect to structures, effects on beams etc.

There may be no shortcut around performing actual testing for each type of device, I was hoping there was a shortcut to model it.

### RE: Equivalent Static Load of an Enclosed Explosion

In Europe there's EN 14460 Explosion Resistant Equipment. It defines:
- explosion pressure resistant components = those that withstand explosion without being deformed
- explosion pressure shock resistant = those that do not break but are permanently deformed.
For the the former the design criteria is not very clear. For the latter you need materials with minimum elongation of 14% and design the component with the EN 13445 (ASME VIII Div 2) criteria against the maximum explosion pressure (and try to reduce the stress concentrations).

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