BALL MILL BLAST BUNKERS

[oldguy]

.A lot of folks think a blast bunker should be solidly built.

That is true to a degree, to keep people out & restrain an explosion to a certain extent.

 

The reality is, a blast bunker should be built to accommodate a possible blast in such a way that potential debris doesn't go flying in all directions.

High velocity debris flying through the air is what usually kills people.

 

To curtail a pipe bomb type flying debris effect you want the bunker built to allow gas to escape.

Meaning well vented on all walls, as well as the ceiling.

The walls should be thick & heavy but built in a way that if an explosion happens they will expand to an extent absorbing the blast , rather than fly apart at high velocity for long distances.

 

Blast gases go towards the least resistance.

That is called "relief". If you provide for various types of gas "relief" in the bunker construction, that will minimize the chance of fly debris.

Which minimizes the chance of fatalities from flying debris.

 

Sand bags are great, in that they will absorb much of a blast.

They will also come apart & the sand itself will restrain expanding blast gases.

For example, you can throw a metal nut, bolt, large nail or a jagged piece of sheet metal for a considerable distance.

Then ponder it is impossible to throw a hand full of sand for a long distance.

 

So, in building a blast bunker. Always provide for several avenues of blast gas relief to minimize any possible solid flying debris.

For example, in a thick solid concrete bunker, the weakest point is usually the door.

Blast gas will generally blow the door off & create a cannon barrel effect.

Meaning most of the blast force will exit at the point of least resistance (the door) & channel flying debris out the door in the direction the door is facing.

So, its best to have the door situated pointing at a sand bag blast wall or hill side, or open space rather than anyplace people might be.

 

After the door, the roof is usually what gets blown upward & outward.

A sheet of plywood roof flying through will severally injure or kill anyone it might hit.

So if you use a plywood roof. Cut the sheets into 12 inch widths & leave an inch of space between each width, as you apply them.

That space will create "relief" where blast gas can escape, rather than send the sheet flying like a Frisbee.

 

To waterproof the roof, rather than tin or sheet metal use pond liner or EDPM type roofing membrane.

It is pliable, will bend & expand providing that much more gas relief, rather than flying away like a Frisbee.

With sand bags on top of that waterproof liner, the roof might raise up a few feet if an explosion occurs inside the bunker. But, it will not go far.

 

All thoughts to ponder.

Edited April 28, 2011 by oldguy

[Peret]

Firework factory blast rooms - so I have read, anyway - are often made with 3 stout concrete walls and one end open, or with a light partition and door, and a lightweight roof of corrugated plastic.

[dan999ification]

that sure is food for thought, i wouldn't expect less considering the size of your mill, for most milling rooms that i have seen the roof is the part that gives "relief" with the walls being stronger and sometimes double skinned the cavity filled with sand and piled up outside to the roof the blast is directed upwards, a thick [unliftable by bp]concrete slab that is propped up above the walls allowing 4 inches for more"relief" and ive seen the door facing sand banks or solid external walls. i think the size of the room also plays a part in containing the blast where a bigger one would allow the expanding gasses to expand and not ask for too much relief from the construction.

ive seen a re-enactment where a 7 metre thick reinforced concrete wall was broken and moved some distance by a bp blast even though the roof was wood and should have given way sooner the walls still moved. there was alot of bp.

a scale ive not considered with my 50g batches.

dan

[madmandotcom]

Perfect timing, i'm just building mine now, the questions i have are:

I am currently building a new shed with bunker underneath, i have all planks spaced loosely but would putting carpet over that affect the relief?

and if so, would the trapdoor going down into the bunker be sufficient relief?

[dagabu]

*SARCASM* Just make sure you and everything that burns in on top of the trap door so that there is no evidence of the shed after the ball mill explodes. *SARCASM*

 

NO, that is a terrible idea, the explosion would over pressure the building and reduce it to kindling.

 

-dag

[killforfood]

MMDC you are the Chum Lee of APC.

 

I built a 10'X 16' Chicken coop out back that is currently empty. My Son set up tables in it and uses it occasionally as a dry place to work on motors and tranny's. It has a sunken dirt floor, solid 4X4 framing and an industrial grade tin roof scrounged from an industrial park remodel project BUT… Three of the walls are lined about halfway up with ½" hardware cloth. I think should I ever have a ball mill accident that the open walls should keep the roof on. I'm just an occasional hobbyist and the ball mill only runs a few times a year.

 

[dagabu]

MMDC you are the Chum Lee of APC.

 

I built a 10'X 16' Chicken coop out back that is currently empty. My Son set up tables in it and uses it occasionally as a dry place to work on motors and tranny's. It has a sunken dirt floor, solid 4X4 framing and an industrial grade tin roof scrounged from an industrial park remodel project BUT… Three of the walls are lined about halfway up with ½" hardware cloth. I think should I ever have a ball mill accident that the open walls should keep the roof on. I'm just an occasional hobbyist and the ball mill only runs a few times a year.

 

I love it!

[MadMax]

MMDC,

 

Why bother with the shed? Seriously? Assuming the ball mill itself is small then all you'd need is just enough stacked sand bags to surround it stacked just high enough to block horizontal and some diagonal blast debris. So if my ball mill is a cubic foot then I'd stick it in a 2x2 foot sand bag enclosure roughly 2 feet off the ground. Leave the top of the sand enclosure open. Then put a cloth tent over that.

 

The problem with the whole bunker under the shed thing is by adding a shed to the mix all you are doing is adding potential debris to the mix. Putting it underground in theory is good but remember that what goes up must come down. So whatever you put on top of it may arc outward hitting property and god forbid... people.

 

If anyone was serious about the safety of a design plan then why not test it - in a safe and legal way of course. That's what I did. We have a good amount of woods enclosed land in the country where blasting is not heard by anyone nearby and if they do no one kicks up much of a fuss. I have tested the effects of sand bag enclosed explosions and believe me when I tell you that SAND BAGS SAVE LIVES!

 

Another idea that could be used instead of sand bags is water. Granted it doesn't absorb as much of the energy of sand bags but it's not too hard to setup if one wanted to. I have a friend in the EOD who told me about a special truck they have setup that has a large tank of water in the back the top open. When they are transporting a suspect device they will enclose it in a waterproof bag and sink it to about half way down and drive it to a destruction site.

 

So do yourself a favor and don't intentionally build an unnecessary shrapnel box around an otherwise safe sandbag box. I mean it's not like it's going to double as a tool shed right? The enclosure should be only for the ball mill and that's it.

Edited April 30, 2011 by MadMax

[madmandotcom]

I mean it's not like it's going to double as a tool shed right?

no, its going to double as workshop

i also have plenty of releif in the walls of the above shed

[gsmkkji]

does anyone no why i cant post my own topic?

i says cant post a topic try replying instead

[killforfood]

Sand bags are probably the safest. I don't have any sand or bags around but I do have clay soil without rocks. I could probably dig a small pit in the ground and set the mill in the bottom. At least that would direct every thing straight up. I think the ultimate would be a sandbagged mill inside of a chain link dog kennel.The sand and blast force would go right through the kennel and any big pieces of the mill would be caught by it. In the late 70's I saw a chain link fence stop a Funny Car's blower from going into the crowd. It looked like a sack of wires stretched right to the front row with a blower in it.

 

 

 

[killforfood]

no, its going to double as workshop

i also have plenty of releif in the walls of the above shed

I would not be milling and working in the shop at the same time.

[killforfood]

does anyone no why i cant post my own topic?

i says cant post a topic try replying instead

 

Just guessing: I think you need to make a minimum number of replys before you can start a new thread.

 

I gotta go rototill, I'm out

Edited April 30, 2011 by killforfood

[MadMax]

Look dude, I don't think this is a good idea. You want to setup a workshop on top of your ballmill? If it blows then all your equipment gets destroyed. If there are any comps there then you could be talking about a major disaster. And if you're in it working when it goes, then you could even die. Don't screw around seriously. If you want to do it right and be safe then have an isolated area exclusively for the ballmill. I am not trying to be a dick but if you want a shed for a workshop that's cool and all but why does the ballmill need to be under it?

 

no, its going to double as workshop

i also have plenty of releif in the walls of the above shed

[dan999ification]

madman here is an example of the flaws in that design[from the re-enactment i mentioned]

please for your safety dont do it.

though i doubt anyone would be silly enough to have such a large amount of bp that it fills a room

http://www.youtube.com/watch?v=eFytcsA9mU8 the action starts at 1.50

since this is a thread on blast bunker design i think its appropriate to use this as an example on how not to go about it.

its also an intersting documentary[part 7]

dan

[dagabu]

Remember, remember.....

[goldwingnut54]

Dagabu, what do we need to remember? I can speculate on a handful of things to which you might refer. PM me if it is a verboten topic.

 

I have little to contribute here so far. (Too soon old, and too late smart methinks.) But I do NOT want to miss something important in my education. So please forgive me if I've missed something obvious.

 

Stan

 

And dan999, that is a fascinating video. I'm trying to come up with a mill bunker that would contain a milljar full of just over 4 OZ of "unthinkable". Actually, that needs restated. UNthinkable is a poor concept for the purposes of this conversation. I should think "INevitable" and plan/build accordingly. Up til now, I've never milled my 75-15-10 together. And to do so with ultimate safety, I'll probably have to drive to my son's farm about 85 miles one way, as the crow flies.

[dagabu]

Guy Fawkes & the Gunpowder Plot

Words of "Remember Remember" refer to Guy Fawkes with origins in 17th century English history. On the 5th November 1605 Guy Fawkes was caught in the cellars of the Houses of Parliament with several dozen barrels of gunpowder. Guy Fawkes was subsequently tried as a traitor with his co-conspirators for plotting against the government. He was tried by Judge Popham who came to London specifically for the trial from his country manor Littlecote House in Hungerford, Gloucestershire. Fawkes was sentenced to death and the form of the execution was one of the most horrendous ever practised (hung, drawn and quartered) which reflected the serious nature of the crime of treason.

 

The Tradition begins...

The following year in 1606 it became an annual custom for the King and Parliament to commission a sermon to commemorate the event. Lancelot Andrewes delivered the first of many Gunpowder Plot Sermons. This practice, together with the nursery rhyme, ensured that this crime would never be forgotten! Hence the words "Remember, remember the 5th of November"

 

The poem is sometimes referred to as 'Please to remember the fifth of November'. It serves as a warning to each new generation that treason will never be forgotten. In England the 5th of November is still commemorated each year with fireworks and bonfires culminating with the burning of effigies of Guy Fawkes (the guy). The 'guys' are made by children by filling old clothes with crumpled newspapers to look like a man. Tradition allows British children to display their 'guys' to passers-by and asking for " A penny for the guy".

 

 

 

Guy Fawkes Day Poem

 

Traditional British

 

 

Remember, remember, the 5th of November

The Gunpowder Treason and plot ;

I know of no reason why Gunpowder Treason

Should ever be forgot.

Guy Fawkes, Guy Fawkes,

'Twas his intent.

To blow up the King and the Parliament.

Three score barrels of powder below.

Poor old England to overthrow.

By God's providence he was catch'd,

With a dark lantern and burning match

 

Holloa boys, Holloa boys, let the bells ring

Holloa boys, Holloa boys, God save the King!

 

Hip hip Hoorah !

Hip hip Hoorah !

 

A penny loaf to feed ol'Pope,

A farthing cheese to choke him.

A pint of beer to rinse it down,

A faggot of sticks to burn him.

Burn him in a tub of tar,'

Burn him like a blazing star.

Burn his body from his head,

Then we'll say: ol'Pope is dead.

[Shadowcat1969]

Goldwing - if you've seen the movie "V for Vendetta" the mask that Hugo Weaving (V) wore is a caricature of Guy Fawkes and references to the Gunpowder plot and the rhyme Dagabu listed above are all through the movie.

[goldwingnut54]

Wow....

 

I had heard of Guy Fawkes of course, but not the plot.

 

And interestingly enough, V for Vendetta is on my want to see video list.

 

Thanks!

Stan

[Arthur]

The BEST blast screen I have seen is a circular mound of old tyres with a staggered entrance. This is used on a HE Range in England. The blast gets out muffled but the shrapnel doesn't get out. However at about 25feet outside diameter and 10 feet high it's a lot of tyres to find -then dispose later and maybe a bit big for some gardens.

[dagabu]

They use tractor trailer tires with the side walls cut off to achieve the same thing for portable containment over the pond here but the tires are just stacked with overlapping treads (they make these tires in many ODs). They contain energetic materials well and allow the blast to travel up and not out.

[TheExplosionist]

I dug a massive hole in '07 almost as deep as me for my ball mill. It suppressed the noise completely but was ridiculously impractical and messy. It took ages to get rid of all the soil too and refill the hole.