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View Full Version : Merits of a shipping container as a faraday cage


thenodnarb
11-27-2011, 3:04 PM
All this talk about EMP has been interesting, and some friends of mine are interested in preparing for SHTF. They are especially concerned about EMP(me not so much but whatever gets them prepping!).
We may collectively buy a shipping container and store it at a central point(which happens to be my place) and keep a portion of our preps in it. I prefer an insulated one for storing food because I can keep it cool with an A/C. It seems to me that a shipping container should make a nice big faraday cage as well. It conducts electricity, and if kept on the ground, should make for exceptional grounding. I know the non insulated ones have wood floors. Could/should it be modified to work as a big faraday cage?

Discuss :)

http://renaissanceronin.files.wordpress.com/2008/09/shipping-container.jpg

Icypu
11-27-2011, 3:27 PM
This sounds like a cool idea. Would you bury it underground?

orangeusa
11-27-2011, 3:37 PM
If you add A/C, what's to prevent EMP from conducting into your container through the power cord? And if you go with an internal generator - you still needs exhaust outlet / air intake..

Remember - radiated AND conducted are both types of interference.......

I havent't read the EMP threads, but assuming that where there's EMP, there's a nuke. I don't think your storage container will stop gamma rays, pressure waves, thermals, etc.... And it's not a Faraday cage unless you modify the doors to be completely electrically sealed, not to mention any minor holes etc in the container...

I dunno. Just an EE trying to help...

.

thenodnarb
11-27-2011, 3:57 PM
First off: no burying. Containers can't be buried because the sides and top can't take a load. reinforcement would be needed, like concrete walls, and then, no container needed since the concrete itself is the shelter. Its a common misconception that containers can be buried.

The container isn't meant to be a fallout shelter or nuke shelter(obviously). Yes, gamma rays would penetrate. Needs to be underground to protect against radiation.
My friends are more worried about a high atmosphere air burst, which in theory maximizes the EMP and has little if any fallout(since fallout is usually radiated debris from a nuke that detonates on or near the ground.)

A faraday cage itself was designed as a cage, meaning that it had holes in it(well its was a mesh). So it doesn't have to be totally sealed. In a recent post, someone posted a video about EMP and the US govt. has several planes that are designed to be EMP proof. The windows have a metal mesh in them to conduct the EMP. The inside electronics are all insulated from the exterior of the plane.

So really all that is needed is a metal box that conducts the electricity and hopefully sends that energy to the ground. The slight gaps around the door should be no problem since the metal around it conducts the electricity. A microwave sends microwaves into the compartment and, because it is metal, blocks the microwaves from escaping. They also have a glass window with a metal mesh inside to prevent the waves escaping out the door. You can see in, but the waves don't make it out.

As far as the air conditioner, I would cut a hole in the back where the reefer unit would normally go, and put a window style air con in there. The air conditioner itself is metal so it shouldn't be any different than a wall from an EMP standpoint. If necessary, I would weld a metal mesh around the outside of the A/C. Even if the EMP affected the A/C, so what? If A/C craps out, the preps are still saved...right?

This is my understanding, but its purely academic. Hopefully an expert chimes in, or someone who has done the research on faraday cages and how they function will chime in.
Thanks for responses so far. Good to vet out concerns.

orangeusa
11-27-2011, 4:05 PM
Yes, there can be holes - but they need to be 1/10th the size of the wavelength you are trying to filter out or less. And they need to be perfectly consistent - no slots or holes/gaps larger than wavelength above...

Othewise you have a slotted waveguide and is as good as nothing against interference from outside electrical sources. Just re-radiates like an antenna inside - almost no attenuation even though you've spent all this time making the rest of the container EMI proof...

So, yeah, some EMI shielding is done with copper screen or have small diameter holes, but doors typically need EMI braid or copper fingers to make perfect contact.....

..

Cokebottle
11-27-2011, 4:22 PM
Yes, there can be holes - but they need to be 1/10th the size of the wavelength you are trying to filter out or less.
^^^^This:

http://upload.wikimedia.org/wikipedia/commons/thumb/e/eb/Light_spectrum.svg/324px-Light_spectrum.svg.png


300Ghz = 1mm... no opening can be larger than 0.1mm in any dimension... and that's still a fairly low frequency when we're talking about EMP.

damon1272
11-27-2011, 4:27 PM
I do not know where to get them but I have heard it mentioned that you can change the door gasket to a conductive type for emp proofing. As for burying, it depends on how much. Containers are designed to take a top load but at the four corners as the stack these things for shipping.

bill_k_lopez
11-27-2011, 4:41 PM
I'm not an expert - but if it was just that easy, why wouldn't the government just store all their electronics in grounded shipping containers rather than paying big bucks for real faraday cages? Why would test labs bother making cages out of copper or silver if just plain old aluminium would work?

Its a hell of an investment to only find out that it didn't work.

thenodnarb
11-27-2011, 4:41 PM
Yes, there can be holes - but they need to be 1/10th the size of the wavelength you are trying to filter out or less. And they need to be perfectly consistent - no slots or holes/gaps larger than wavelength above...

Othewise you have a slotted waveguide and is as good as nothing against interference from outside electrical sources. Just re-radiates like an antenna inside - almost no attenuation even though you've spent all this time making the rest of the container EMI proof...

So, yeah, some EMI shielding is done with copper screen or have small diameter holes, but doors typically need EMI braid or copper fingers to make perfect contact.....

..

Good info! So then with some custom copper braid door seals, and no hole cut in the container, it should work right? What about the floor?
Also, in this video, tune to the part about the govt's EMP proof planes at 30:25. They show the windows at 31:04. That doesn't look like .01mm mesh.
dI4qKg5UBxU

edit: my wife made a good point. Maybe the windows have gold film as well.

thenodnarb
11-27-2011, 4:51 PM
I'm not an expert - but if it was just that easy, why wouldn't the government just store all their electronics in grounded shipping containers rather than paying big bucks for real faraday cages? Why would test labs bother making cages out of copper or silver if just plain old aluminium would work?

Its a hell of an investment to only find out that it didn't work.

I think the deal there is that they need the electronics inside to work while also being shielded. For me, its SHTF/backup stuff. I don't need a cord to power the things. The power cord itself can deliver the energy to destroy the components pluged into it inside.

I'm no expert either!

wash
11-27-2011, 4:51 PM
A shipping container has holes in it and the rubber gasket creates a gap for electric fields to get through.

I'm not sure how solid the floor is either (the interior has a plywood floor but I'm not sure if it's continuous steel under that).

I think some corrugated steel drain pipe with the ends welded shut would be cheaper and probably buriable.

The problem is you have to keep it sealed up to get the benefit.

wheels
11-27-2011, 5:06 PM
Unless all your gear needs EMP protection maybe just get some metal boxes to store the EMP sensitive items inside with all the other stuff. Food is not EMP sensitive. That wooden bottom would certainly require mitigation.

TheChief
11-27-2011, 5:15 PM
Some thoughts...

Experts, there aren't many other than theoretical. At least publically. The last EMP was in the 60s so everything is guess work given the considerable change in infrastructure, manufacturing techniques, electrical design and grounding techniques used today.

Dont rely on the container sitting on the dirt as sufficiant grounding. Ground it with proper grounding rods and cables.

Bury it and only lightly back fill, don't attempt to compact and dont cover the top. This reduces the conductive surface space and provides some level of camo as well.

Instead of working on sealing up doors, maybe create a mesh wall just inside the door like those old hippie bead doors. Stainless mesh might be cheaper than copper. The wall can be quickly broken down to allow access into the container.

Lastly, keep the AC unit off of the container to shield the container from any surge that might come through the power lines and into the AC unit...Use non-conductive ducting to get the air there and back with mesh over the holes. Off the top of my head I am thinking about large diameter garden drain hose (with no stiffening wire). Given the theoretical power of an EMP, and how well you may have this container grounded, I would keep the AC unit and all power lines a good distance from the container so there is no chance of sparking the gap. I would do something like 10 feet to feel comfortable. That is a gut call, not calculated.

Good luck.

What are peoples thoughts on wrapping individual small items in tin foil or some other conductive material to allow the power to run over the material and not through the device?

GrizzlyGuy
11-27-2011, 5:31 PM
It seems to me that a shipping container should make a nice big faraday cage as well. It conducts electricity, and if kept on the ground, should make for exceptional grounding. I know the non insulated ones have wood floors. Could/should it be modified to work as a big faraday cage?

Discuss :)


It will be an excellent EMP-proof storage container as-is and doesn't need to be modified at all. It also doesn't need to be grounded unless you are planning to run wires into it (you aren't). From here on pg. 3-6: EP 1110-3-2, ELECTROMAGNETIC PULSE (EMP) AND TEMPEST PROTECTION FOR FACILITIES (31 DEC 1990) (http://www.everyspec.com/ARMY/ARMY+(General)/EP_1110-3-2_1990_18942/)

(6) Grounding. Some form of grounding is required in any electrical or electronic system for protecting personnel from electrical shock, controlling interference, proper shunting of transient currents around sensitive electronics, and other reasons. (Grounding does not directly provide protection against EMP, but must be done properly to prevent creation of more serious EMP vulnerabilities.) Ideally, grounding would keep all system components at a common potential.

The "more serious EMP vulnerabilities" they are talking about are common mode currents and voltage differentials that can result from the inbound cabling serving as inadvertent antennas. You have no cabling so don't sweat it.

You also don't need to worry about the gaps or other holes that would be in a typical shipping container. Virtually all of the energy from a HEMP is below 500 MHz (see figure 2-6 on page 2-30 of that document) so the holes would need to be at least a few inches across before you'd need to worry about them. Go here (http://www.k5rmg.org/calc/waveguide.html) if you want to play with the numbers.

damon1272
11-27-2011, 6:07 PM
If you are really worried then I would put whatever electronic equipment in a steel trash can within the container. This would remove any doubt and would allow the installation of an a/c unit.

cranemech
11-27-2011, 7:16 PM
If you are really worried then I would put whatever electronic equipment in a steel trash can within the container. This would remove any doubt and would allow the installation of an a/c unit.

http://www.industrialladder.com/productDetails.do?productID=2936&categoryID=228

I've heard of people using these for larger items. I've seen various sizes on CL for $200-$500.

11HE9
11-27-2011, 8:16 PM
I've been waiting for a thread like this to pop up. I am very aware of EMP, but have been out of the loop (military) on how to protect electronics from it for some time.

I have a sea container that I use for a shop and some storage. The only things in there that I'd be concerned about in a EMP event would be the gensets, and some spare "old school" truck parts. The spare parts are for a '72 Landcruiser, and parts needed to convert the '91 Landcruiser to points & carberator after a EMP event ;)

I really want to run power to the container, so it looks like I need a "isolation area" for the parts & gensets :rolleyes:

thenodnarb
11-27-2011, 8:26 PM
It will be an excellent EMP-proof storage container as-is and doesn't need to be modified at all. It also doesn't need to be grounded unless you are planning to run wires into it (you aren't). From here on pg. 3-6: EP 1110-3-2, ELECTROMAGNETIC PULSE (EMP) AND TEMPEST PROTECTION FOR FACILITIES (31 DEC 1990) (http://www.everyspec.com/ARMY/ARMY+(General)/EP_1110-3-2_1990_18942/)



The "more serious EMP vulnerabilities" they are talking about are common mode currents and voltage differentials that can result from the inbound cabling serving as inadvertent antennas. You have no cabling so don't sweat it.

You also don't need to worry about the gaps or other holes that would be in a typical shipping container. Virtually all of the energy from a HEMP is below 500 MHz (see figure 2-6 on page 2-30 of that document) so the holes would need to be at least a few inches across before you'd need to worry about them. Go here (http://www.k5rmg.org/calc/waveguide.html) if you want to play with the numbers.

This is awesome. Military manual on how EMP works, Shielding theory and how to harden a facility/equipment. Perfect! I'm reading it now.
:thumbsup:

problemchild
11-27-2011, 9:01 PM
If an am/fm radio wont work inside your are gtg.

KevinB
11-27-2011, 9:25 PM
We have a 40 ft container buried. We welded 2in square tubing on 16in centers on all the sides and installed a very thick set of front doors. We use ours for a powder magazine. The top has to remain unburied as in case of a explosion the blast goes up.

I wonder how well a 2 mile deep mine shaft will work for shelter. I wonder if We have to worry about EMP other than the fact of the nuke blast that caused it.

thenodnarb
11-27-2011, 10:49 PM
I wonder if We have to worry about EMP other than the fact of the nuke blast that caused it.

the sun can cause EMP as well. Some people believe that this is more likely than a terrorist nuke. They predict 2012 will be the year of a big solar storm that causes an EMP. Apparently the sun has major eruptions every so often(about 11 years on avg.) and 2012 we are due for the next series.

Good idea on how you reinforced your container. I'm going to run that by my architect friend and see what he thinks. If its kosher, that may be the cheapest way to bury a container.

xgi1991
11-28-2011, 7:06 AM
All this talk about EMP has been interesting, and some friends of mine are interested in preparing for SHTF. They are especially concerned about EMP(me not so much but whatever gets them prepping!).
We may collectively buy a shipping container and store it at a central point(which happens to be my place) and keep a portion of our preps in it. I prefer an insulated one for storing food because I can keep it cool with an A/C. It seems to me that a shipping container should make a nice big faraday cage as well. It conducts electricity, and if kept on the ground, should make for exceptional grounding. I know the non insulated ones have wood floors. Could/should it be modified to work as a big faraday cage?

Discuss :)

http://renaissanceronin.files.wordpress.com/2008/09/shipping-container.jpg
We use shipping containers exclusively in the ROV industry; we convert them to control vans for the vehicles. And yes, they provide a measure of shielding; cell phones, radios, and hand held VHF radios do not function inside without an external antenna.

Ripon83
11-28-2011, 11:09 AM
My wife would be pissed if I put one of those in the back yard....

thenodnarb
11-28-2011, 11:45 AM
My wife would be pissed if I put one of those in the back yard....

My wife WANTS one!

TheChief
11-28-2011, 12:10 PM
My wife would be pissed if I put one of those in the back yard....

Then put it "under" the back yard ;) Wonder how that would go over...

11HE9
11-28-2011, 12:19 PM
My wife WANTS one!

My wife has been looking for a (cheap) second container to convert into a play house for the kids :D

Cokebottle
11-28-2011, 4:30 PM
the sun can cause EMP as well. Some people believe that this is more likely than a terrorist nuke. They predict 2012 will be the year of a big solar storm that causes an EMP. Apparently the sun has major eruptions every so often(about 11 years on avg.) and 2012 we are due for the next series.
We just had a HUGE eruption a couple of months ago.
Fortunately, it was not directed at Earth, but even if it had been, only satellites (including the space station) would have been at risk.

There was a moderately large eruption a couple of weeks ago.
The result? Aurora Borealis were seen as far south as central California and Mississippi.

Check http://www.spaceweather.com every few days to stay on top of what is actually happening rather than what some :TFH: guy proclaims is going to happen a year from now.

Yes, solar activity runs in 11 year cycles, and so far, this cycle has been extremely mellow with the exception of a couple of major CMEs.

Ripon83
11-29-2011, 8:20 AM
If I could get that done on one of her 10 hr shifts and she didn't know - maybe :)


Then put it "under" the back yard ;) Wonder how that would go over...

Californio
11-30-2011, 3:23 PM
So I am running a backup today on my computer. Disk would be fried in an EMP Burst. I want my family pictures and videos to be safe. Would a DVD disk survive EMP?

mej16489
11-30-2011, 4:14 PM
Would a DVD disk survive EMP?

A manufactured optical disk generally has metal in it, so those actually might not survive. I know you can certainly destroy them in a microwave...

...but 'burned' optical disks I think are nearly entirely based on 'ink' and 'dye'. So they are probably safe from EMP - but they do have long-term degradation issues.

From http://www.cd-info.com/archiving/degradation/index.html

CD-R/DVD-R/BD-R employs recording layers made with dye that can be prone to accelerated decay. Since the dye is chemically altered when a drive's laser reads or writes its data, it is extremely photosensitive. Even mild exposure to UV rays can affect the longevity of the discs. The disc's reflective side will visibly convey dye degradation over time through dark color discrepancies that don't match the green, gold, blue or silver appearance of a new disc.