aldofad
Hazard to Self
Posts: 56
Registered: 30-6-2013
Member Is Offline
Mood: No Mood
|
|
The most dangerous moment in a blast and its solution
Hello world,
do you all agree that the most dangerous moment in a blast is when we insert the detonator in the main tertiary explosive charge (or in a booster)?
I'm asking that because I can develop a cheap robotic detonator that mechanically insert itself in the main tertiary explosive charge (or in a
booster) providing feedback when totally inserted to the remote user.
I can really do that but it will take me some time and a good effort to realize and put in production such invention, so I wish to know first what do
you think about this.
I love getting fun with energetics but I feel really unsafe when i put the detonator inside the main charge. I want to reduce that small risk further.
Please let me know your thoughts,
cheers!
|
|
|
Dany
Hazard to Others
Posts: 482
Registered: 3-8-2013
Member Is Offline
Mood: No Mood
|
|
It depend on many factors. First, if your main charge is made up of sensitive explosive (peroxides) it is already dangerous even before you insert the
detonator. How you insert the detonator is important. DO NOT USE THE DETONATOR TO MAKE THE ENTRY HOLE! use a wooden stick or other material that do
not accumulate static charge to make a hole in the explosive. If you try force the detonator to enter the main charge, pressure or friction (due to
deformation of the detonator) can lead to detonation of the sensitive explosive and thus the main charge. For this reason other detonator can replace
the traditional compound detonators made up of primary sensitive charge and secondary high explosive (for output enhancement). These detonators are
the Exploding- Bridge Wire (EBW) detonator that contain only secondary explosive (PETN, RDX or PBX based explosives) or the Exploding-Foil Iniator
(EFI) also called the slapper detonator. The EFI [2] (invented in Lawrance Livermore National Laboratory by John Stroud in 1965), is a detonator
without explosive in it. it is made of copper foil or other materials in contact with a polymer (e.g., KAPTON) once the foil explode (due to high
electric current) the KAPTON is accelerated to several km/s (e.g., 4km/s) and ''slap'' the main charge. if the pressure and duration of the ''Slap''
or the shock induced is sufficient for that particular explosive, a detonation of main charge is possible. a whole chapter in [1] is dedicated to EBW.
For EFI read paper [2].
[1] Cooper,W.P. Explosive Engineering (1996).
[2] CHARACTERISATION OF AN EXPLODING FOIL INITIATOR (EFI) SYSTEM (http://www.smf.phy.cam.ac.uk/Publications/Energetics%20paper...)
Dany.
[Edited on 19-9-2013 by Dany]
|
|
|
aldofad
Hazard to Self
Posts: 56
Registered: 30-6-2013
Member Is Offline
Mood: No Mood
|
|
Compared to EBW detonators my idea of robotizing the detonator insertion looks crazy.
EBW looks really a safe way to detonate and realizable.
Is there anyone here who has ever realized an EBW power generator?
There is some data needed to realize an EBW detonated explosion:
- the explosive type intended to be directly detonated by an EBW detonator (ex.: PETN)
- bridgewire material, section and length of the small piece of wire connecting the main bipolar cable
- voltage to be applied and total capacitance (ex.: 20 µF ?). In my opinion it doesn't make sense considering current for this application. Its much
more practical directly considering the final capacitance and voltage of a capacitor serie
- main bipolar wire cable length and diameter
There are also different ways to obtain an high voltage and several ways to discharge it.
Using a micro controller I can easily charge several capacitors in parallel and then obtain an high voltage reconfiguring the capacitors in series.
A very fast solid state relay may be a good choice to discharge the high voltage
Makes sense?
Cheers 
[Edited on 19-9-2013 by aldofad]
|
|
|
NeonPulse
Hazard to Others
Posts: 417
Registered: 29-6-2013
Location: The other end of the internet.
Member Is Offline
Mood: Isolated from Reality! For Real this time....
|
|
sounds like an interesting concept. i wonder though would it be mobile enough to be used in most situations? many people like to use shaped charges
so it would have to be precise enough to insert it deep and centred enough to be useful to that particular charge and without knocking it over. and
charges that are attached to things off the ground. or if the charge needs burying well human interaction in doing that would defeat the purpose of a
remote insertion. there are many things to consider so i guess that learning about and developing an EBW setup that is 100%reliable would be more
worthwhile from a blasters perspective. as we know saftey is a huge thing not to be skipped or done half assed as mistakes are often fatal or at the
least injurious, and if there were a system that put distance between the blaster and initiating unit that was not too costly but also useful in a
variety of situations people would be interested i think.
|
|
|
aldofad
Hazard to Self
Posts: 56
Registered: 30-6-2013
Member Is Offline
Mood: No Mood
|
|
Quote: Originally posted by aldofad  | Compared to EBW detonators my idea of robotizing the detonator insertion looks crazy.
EBW looks really a safe way to detonate and realizable.
Is there anyone here who has ever realized an EBW power generator?
There is some data needed to realize an EBW detonated explosion:
- the explosive type intended to be directly detonated by an EBW detonator (ex.: PETN)
- bridgewire material, section and length of the small piece of wire connecting the main bipolar cable
- voltage to be applied and total capacitance (ex.: 20 µF ?). In my opinion it doesn't make sense considering current for this application. Its much
more practical directly considering the final capacitance and voltage of a capacitor serie
- main bipolar wire cable length and diameter
There are also different ways to obtain an high voltage and several ways to discharge it.
Using a micro controller I can easily charge several capacitors in parallel and then obtain an high voltage reconfiguring the capacitors in series.
A very fast solid state relay may be a good choice to discharge the high voltage
|
I've found a commercial EBW detonator datasheet obtaining all the answers:
http://www.teledynerisi.com/products/0products_2fs_page46.as...
- The voltage required is 4000V
- The capacitance at least 1 microFarad
Charging a couple of this Capacitors would sure be enough.
From my perspective the circuit is very easy. I can charge the capacitors with an induction, a good transistor and a microcontroller.
I can build the circuit, test it, verify requirements are meet, and provide detailed instructions to this forum to replicate it. I'll be happy if
someone will test the circuit with PETN because at moment I've only been able to make Urea Nitrate, and I don't think it can be easily ignited as
PETN.
Makes sense?
|
|
|
Melmoth
Harmless
Posts: 28
Registered: 15-7-2002
Location: The Netherlands
Member Is Offline
Mood: No Mood
|
|
Sound like an interesting DIY project, but the firing system would be an easy one compared to the EBW Detonator itself.
Almost all of them consist of a pure gold or gold alloy bridgewire, 1.5mil (0.0015in) in diameter..
"This species has amused itself to death"
|
|
|
aldofad
Hazard to Self
Posts: 56
Registered: 30-6-2013
Member Is Offline
Mood: No Mood
|
|
| Quote: Originally posted by Melmoth | Sound like an interesting DIY project, but the firing system would be an easy one compared to the EBW Detonator itself.
Almost all of them consist of a pure gold or gold alloy bridgewire, 1.5mil (0.0015in) in diameter.. |
Uhmm... I don't think will be an issue finding some gold/platinum wire, I'll take infos. Should bridgewire diameter be too large, won't be a problem
raising current putting other capacitors in parallel.
|
|
|
Melmoth
Harmless
Posts: 28
Registered: 15-7-2002
Location: The Netherlands
Member Is Offline
Mood: No Mood
|
|
For the bridgewire to explode with sufficient output to detonate the initial pressed explosive, high input power and current are required. Around
200A/µs are the nominal values required. Increasing the diameter of the bridgewire means drastically increasing the current required..
The explosive to be used requires a low critical energy fluence and short run distance. Almost all EBW's use PETN, at low density and small particle
size. (superfine, high surface area RDX is also used successfully)
"This species has amused itself to death"
|
|
|
Fuse
Harmless
Posts: 16
Registered: 25-2-2013
Member Is Offline
Mood: No Mood
|
|
I’ve built more EBW systems and all works great.
Have a look on my youtube channel I’ve posted some videos.
http://www.youtube.com/watch?v=VqEnXz41IRU
In general EBW has this configurations:
Capacitor bank voltage: 4kV, 1uF, low ESR, high dV/dt (electrolytic capacitors are not suitable, use ceramic or, better, polypropylene)
Discharge current must be at least 500A/uS order
Wire diameter of the bridge-wire must be in the 0,05-0,07mm order
Line cable must to be a low impedance cable
If someone is interested I can sell the EBW in the video.
If someone need help in the construction of the EBW I’m happy to reply here.
PS if you like my videos click on “I like” 
|
|
|
aldofad
Hazard to Self
Posts: 56
Registered: 30-6-2013
Member Is Offline
Mood: No Mood
|
|
Your reply is much appreciated and thanks for offering help.
From my point of view this is just a beautiful hobby were to apply my best for personal satisfaction
|
|
|
Fantasma4500
International Hazard
Posts: 1677
Registered: 12-12-2012
Location: Dysrope (aka europe)
Member Is Offline
Mood: dangerously practical
|
|
what about this little thing?
http://www.youtube.com/watch?v=nMil37G1F2Q
somehow i first realised how it works now
basically you put distance to target and primary, and its first shot into the main charge when its ready to set it all off
this is quite simple stuff to get, all of it, and seemingly it works very reliable
|
|
|
Simbani
Hazard to Self
Posts: 50
Registered: 12-12-2012
Member Is Offline
Mood: No Mood
|
|
Fuse, i´m working on a EBW-system at the moment, and my main problem is the switching.
How do you switch the cap in your system? Spark-gap, electron tube or semiconductor? I don´t want to use a spark-gap
or even a mechanical switch for several reasons, namely the long switching-times and the energy-losses..
Aldofad, the capacitors you´ve linked are not suitable for this application, they are way too small. Maybe it would be possible to somehow get it
working,
but for us amateurs it´s better to just use a big high voltage capacitor. These are not that hard to get and as a plus you´ll have a
energy-reservoir which makes
the system far more reliable.
I acquired a pulse-rated 3.5KV 10µF capacitor (I-peak=25kA) for about 20USD.. I should´ve bought all 4 of them, but I waited too long 
When everything is ready, you can test your cap with your desired wire (BTW, the commercial ones use gold or platinum mainly because of
corrosion-resistance, you are good to go with 0.05mm aluminum wire).
You achieved detonation-status when you hear a deafening, very sharp bang when connecting the wires. Another way to prove you created a shockwave
which is capable of detonating sec. explosives, is to put your wire onto a piece of thicker paper. If the paper directly beneath the wire is
disintegrated or torn apart then you´ve won ;D
All you need is now is a good switch and you´re good to go.
|
|
|
Fuse
Harmless
Posts: 16
Registered: 25-2-2013
Member Is Offline
Mood: No Mood
|
|
@Antiswat I saw the video and it’s a good idea, it can be a great solution, obviously the cap must be in contact inside with secondary. I watched
all the videos from Vvideoupl but now the author seems to be disappeared..
@Simbani I’ve already test discharging by SCR arrays, IGBT arrays, also big SCR (not cheaper) but I had bad results… The solution for me was to
build a simple trigatron and I must to say it works very well. I had thousand of amperes/uS in discharge.
1uF is sufficient to create shock during wire explosion, 10uF is plenty for sure but can be dangerous for you in case of accindental contact with high
voltage
|
|
|
Fantasma4500
International Hazard
Posts: 1677
Registered: 12-12-2012
Location: Dysrope (aka europe)
Member Is Offline
Mood: dangerously practical
|
|
i still remain questioning when i realise you guys still use primaries (= haha
come on, do it properly, and make it fail, and i will kiss your shoes if you send them to me, lol really...
|
|
|
Pyrotrons
Harmless
Posts: 38
Registered: 13-10-2013
Member Is Offline
Mood: No Mood
|
|
I've done it successfully with ETN. I liquified a brass rifle cartridge case that the ETN was contained in, so I assume that the ETN went high-order.
It splashed the brass everywhere into the steel around it. I unfortunately didn't have a chance to do plate-dent or Pb-expansion tests to compare it
to say, HMTD.
There is a lot more science to EBW's than meets the eye, but a few notes from me should help:
- No need to go big on the capacitor, 2uF (2 microfarads) is more than adequate.
- I highly recommend capacitors from a defibrillator unit. They are perfect for this application. The defib of course also contains the power supply
to charge it. ** (edit): AND it's battery powered...portable.
- How to switch the energy from the cap into your bridgewire? By dropping a bolt across two other bolts, of course. Just make a manual switch to
complete the circuit. Put a bolt on the end of a reasonably long insulator so you don't kill yourself, and drop that bolt across two other bolts.
Keep the two other bolts far enough apart so that your high voltage won't arc across them by itself, detonating the charge on the other end 
- Voltage doesn't matter as long as it's more than a few kV. ***EDIT: Probably should go with 6,000V minimum for reliability.
- As has been stated before - Use the right capacitor type. The capacitor MUST be designated as a pulse capacitor (high speed, meaning low ESL and/or
ESR).
- 50 ohm coax cable, of length less than 50 feet, is just fine. This will get you 50 feet away from the blast. Want more, you'll probably have to
parallel multiple sections of 50-ohm coax to reduce the impedance.
- Bridgewire: LOL, just use the damn smallest copper wire you can find. Strip some lamp cord, and use one of the individual strands. Solder it
directly across the business-end of the coax. Stick that in your ETN or PETN.
* If you fuck the electronics up and something arcs over, your EBW+charge can detonate unexpectedly
* You must use coax
* The capacitor is specialized for speed and energy
* The high voltage alone can stop your heart
EBW's are the holy grail of safe amateur explosives work, I highly recommend them to ANYONE that enjoys energetic chemistry. I no longer have a need
to synthesize primary explosives, and I'm thrilled about that.
[Edited on 14-10-2013 by Pyrotrons]
[Edited on 14-10-2013 by Pyrotrons]
|
|
|
Fantasma4500
International Hazard
Posts: 1677
Registered: 12-12-2012
Location: Dysrope (aka europe)
Member Is Offline
Mood: dangerously practical
|
|
btw now that im reading above written...
theres a thread on this guy, experienced with explosives.. he mentions that taking a bridgewire and dipping it in hot concentrated methanol/ETN
solution works as blasting cap...
perhaps you could try this some time?
for those who need to walk abit it might not be a good thing to have 50 metres of cable, a power source, a blasting cap and a secondary charge to walk
about with .. lol ..
im considering to try unconfined EBW tho, just to see
anyways about skipping the first part in the explosive train, some remain very very doubtful to say the least
good to hear other agree that the first part of the explosive train is unnessecary
|
|
|
Simbani
Hazard to Self
Posts: 50
Registered: 12-12-2012
Member Is Offline
Mood: No Mood
|
|
| Quote: Originally posted by Pyrotrons |
No need to go big on the capacitor, 2uF (2 microfarads) is more than adequate.[Edited on 14-10-2013 by Pyrotrons] |
In fact, commercial slapper-ignition systems use 100nF, 15kV capacitors. Those are enough for EFI´s, but for an EBW you need at least 1µF and 5kV.
| Quote: | | I highly recommend capacitors from a defibrillator unit. They are perfect for this application. The defib of course also contains the power supply to
charge it. ** (edit): AND it's battery powered...portable. |
Sorry, but they are far from perfect for this task.. Of course they store quite a bit of energy, but they are NOT pulse rated!! They are designed to
have Ipeak=300A, you cannot compare this to real pulse capacitors. Let´s not even start about ESL/ESR..
As stated before, I use 3.5kV 10µF with Ipeak=25kA and even with this monster I have my problems when 50m of cable are connected (too low voltage).
| Quote: | | How to switch the energy from the cap into your bridgewire? By dropping a bolt across two other bolts, of course. |
This is a terrible idea in terms of safety and switching-time. Build at least a pneumatic or spring-powered switch for your own comfort.
| Quote: | | Voltage doesn't matter as long as it's more than a few kV. |
It does matter, voltage is a critical factor for fast current-rise times. You should go with at least 5kV, 10 to 15kV are MUCH better.
You won´t get past a (few) hundred of A/µs with your system, destroying the capacitor after prolonged useage.
|
|
|
Pyrotrons
Harmless
Posts: 38
Registered: 13-10-2013
Member Is Offline
Mood: No Mood
|
|
I'm glad to see that there are others here that have experience with homemade EBW's, and are willing to share it.
Simbani, thank you for your input.
I said that defibrillator capacitors were perfect for this application. I agree with you, that they are NOT perfect. There are two perspectives - I
was taking the perspective of an average forum member that has no experience with pulsed discharge equipment.
To the amateur - defib cap's are reasonably small, readily identifiable, store enough initiation energy, and they're fast enough. They do the job.
To you and I - they're slow, possess too much ESL and ESR, and have limited lifetime. You and I would much prefer something from General Atomics
wouldn't we?
Referring to my statement about a simple spark-gap, actuated by a bolt dropped across two other bolts, you said:
| Quote: |
This is a terrible idea in terms of safety and switching-time.
|
I could suggest that the forum members just machine a trigatron. But that wouldn't be very helpful. What would be helpful, is my suggesting
something that is simple, cheap, safe, and works.
| Quote: |
Put a bolt on the end of a reasonably long insulator so you don't kill yourself, and drop that bolt across two other bolts
|
Most people understand that you don't go near the wires when there is high voltage present. I suggested a means to stay entirely safe - a plastic
rod. So how again is my spark gap suggestion unsafe?
| Quote: |
Build at least a pneumatic or spring-powered switch for your own comfort.
|
Respectfully, that was right from the spoon. No big deal.
| Quote: |
It does matter, voltage is a critical factor for fast current-rise times. You should go with at least 5kV, 10 to 15kV are MUCH better.
|
Thank for bringing it to our attention, 6kV is what I was using at the time. I'll edit my original post to be a minimum of 6kV, as I experienced
excellent results with that under the aforementioned conditions (defib cap, 50' coax, bolt spark gap).
| Quote: |
You won´t get past a (few) hundred of A/µs with your system
|
That's quite an assumption there sir. Why don't you tell that to my Pearson current transformer and TDS210 oscilloscope that clearly showed upwards
of 800A/uS? And while you're at it, tell it to the glitter of brass that used to be a rifle cartridge...
|
|
|
Fuse
Harmless
Posts: 16
Registered: 25-2-2013
Member Is Offline
Mood: No Mood
|
|
Trigatron is very simple, safe, cheap and works well.
Switching electrodes manually is prehistoric IMO.
|
|
|
DubaiAmateurRocketry
National Hazard
Posts: 841
Registered: 10-5-2013
Location: LA, CA, USA
Member Is Offline
Mood: In research
|
|
If your machine is a remote booster inserter, then dosnt it have to be near the explosives ? Wouldnt it destroy your invention in the end ?
|
|
|
Simbani
Hazard to Self
Posts: 50
Registered: 12-12-2012
Member Is Offline
Mood: No Mood
|
|
I suspect these 800A/µs were measured without long cables? It´s quite unlikely that you get these values during field-operation with 50-100m of
cable.
|
|
|
Pyrotrons
Harmless
Posts: 38
Registered: 13-10-2013
Member Is Offline
Mood: No Mood
|
|
@Simbani: Heh heh, you got me interested in these fun devices again. I re-visited the hard disk that I have my notes on, and found that I had
excellent notes from Yr. 2008. Full technical details of my setup are in a new thread here in Energetic Materials:
http://www.sciencemadness.org/talk/viewthread.php?tid=26800
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
