Sparking would be bad: Newsletter Challenge (01/02/08)

Vacuum or mechanical pick-and-place systems have failed

I'd want to know why. If they can't solve the problem this way I wouldn't trust them to handle a box of matches, much less a crate of explosives. (OK , I'd also like to be the first to gripe about a question aimed only at those with a specific knowledge area. Challenge questions are best when open to all, and requiring applied logic/general engineering sense. rant, rant, rant,,,,,,)

Hear, hear, but should we cater to a broad section, this is not a problem I can tackle, it belongs to those in the know, this accusation can be levelled at quite a few questions, so should we just lay back and learn?

Clad the Ferrous Materials with the blend of nonferrous metal alloys, or composites, properly manufactured the electro magnetic lift will work properly.

How about a form fitting shell cansister holder that is made of metal that is incased in rubber that the electro magnet can lift while carrying the non-ferrous shell along the production line.

Or how about sticky tape or gum?

This is the intro. to a US Patent, granted 2nd July, 1957. Looks as if it could have some bearing on this problem. (This is from http://www.freepatentsonline.com).

I guess I would investigate embedding a steel plate within a non-sparking material. I would shy away from non-metals (rubber, urethane) for durability reasons. Seems like the best of both worlds.

Several years ago I did some drawings for an overhead crane system to be used in a potentially explosive environment (liquidified gases, IIRC). Wheels had to be made of bronze to reduce the possibility of sparking.

Containers could be made of bronze with an embedded, battery-powered, copper wire electromagnet. This electromagnet doesn't need a very strong magnetic field because the magentic field of the electromagnet used to move the containers can be made strong enough to lift and hold the largest container used.

Another possibility is to use rare earth magnetic alloys. I know some mobile ham radio antenna magnetic mounts use rare earth magnets. I tried looking online for a suitable alloy online, but the info I was looking for wasn't easy to reach.

Copper Beryllium is used to make non sparking hi strength tools. That takes care of the 200,000Ksi parts. at RC40. But these two seem to make me want to be far away.

Brad

who is the dingbat that gave them the idea to use magnets of any kind?

automating a h.e. line with anything that will have magnetic properties to it is like wondering why your tongue sticks to a frozen water pipe.

C.I.L made copper alloy tools avaialble and specially built drum buggies for carrying guncotton barrels around the plant with . just how fast does this guy want the process to go?

since they have air packs they have a compresor what stops them from using a air floater cushion these are used for moving heavy cabinet makers machinery or equipment in the medium sized wood working shops? 400# is 400# whether it is in a drum or in the form of a casting.

List of Heusler alloys: all are magnetic.

• Cu₂MnAl, Cu₂MnIn, Cu₂MnSn,
• Ni₂MnAl, Ni₂MnIn, Ni₂MnSn, Ni₂MnSb
• Co₂MnAl, Co₂MnSi, Co₂MnGa, Co₂MnGe
• Pd₂MnAl, Pd₂MnIn, Pd₂MnSn, Pd₂MnSb

If not this way I would clad or glue two sheet of metal to make the container walls, outer from the well known bronze (CuBe is not necessary as no high strength is needed) or brass and the inner one from ferromagnetice (stainless or ordinary) steel.

RHABE

So you need a grip of a pick & place robot that do not spark?

You may have more than one solution differ from non-sparking magnetic allow to be a part of a magnetic circuit (of the picking grib). Right?

It is one of " the concept critical verification".

I am BEGGING all the surviving experimenters to NOT try and solve this EXPLOSIVE problem with WAG's . The potential for fatalities is near 100% with a 'try this and see if it works' approach.

We should all understand what DuPont went through learning how to manufacture explosives without blowing up people. Also the lead anti-knock industry (DuPont, Ethyl Corporation, Octel) developed absolutely fail-safe methods for making, handling, storing, using an extremely hazardous and unforgiving material and still have the BEST safety record.

Explosives are not to play around with. Fortunately, the explosives used in modern ammunition are designed and manufactured to be stable, hard to ignite unintentionally, and relatively safe to handle.

Since vacume and mechanical lift systems have failed and elctromagnetic lifting is found suitable, nickle is the only non ferrous and ferromagnetic metal which could be used. Either Nickle claded copper should used for fabricating the outer walls or nickle+copper alloy should be used for fabricating the containers. As for me nickle claded copper should serve best, in case strength and non corrosion are the criterias. Better Nickle should form the outer surface.

Option II : Nickle+Alluminium alloy also can be used for fabricating the containers. The advantage of this alloy would be :- Light in weight (Alluminium being low density material) and thus low energy magnetic field can work.

For me, not being an engineer but a technician especialized in automotive repairs your answer is quite simple, thanks.

This sounds like an excellent test of evolution, as long as you are able to lure potential employees. I wonder why they both have Hispanic names. Is some larger context implied here? The solution is to use rubber-enclosed ceramic magnets in a cylindrical shape and a wire coil rather than an electromagnet to lift the munitions containers. The coil would pull the ceramic magnet into its center when the juice is applied and would drop the ceramic magnet when the juice is cut off.

The whole question reminds me of two munitions offloads I participated in as an enlisted man in the US Navy. Nonsparking sailors were used to pick up the munitions containers and transport them across a deck, down a flight of stairs (known as a ladder in the Navy), and to deposit the containers on a pallet for offloading by cranes operated by steam-driven winches. The day of the offload came up misty and rainy with a cutting crosswind, resulting in slick decking and slick steps on the ladder. No sooner than my boondocker hit the first step on the ladder, it flew out from under me, and I grabbed the handrail to prevent me from mowing down the half dozen or so fellow sailors on the lower rungs of the ladder. This had the effect of letting the explosive round fall several feet to the deck below, where it landed without incident. I was excused from the rest of the offload. Another time, after the second Forrestal fire (not the one started by rockets on John McCain's jet; this was a later fire started by a sailor on drugs who didn't want the ship to go to the Mediterranean for some reason, and most of the damage done was not done by the fire but by overeager fire parties pouring an ocean of water into spaces full of very expensive computers), the marine contingent was offloading our nuclear warheads in impressive racks pulled across the hangar deck by a towmotor. Liberty was called and a long line of sailors formed on the hangar deck waiting to salute the officer of the deck and the ensign and go get drunk. Winding his way among the resentful sailors, the marine on the towmotor lost track of his load of nukes and slammed one rack solidly into another. I'm sure there was no danger and there were no casualties. There were no officers around, so the incident probably was never reported. The moral of this tale is: Never put explosives or arms of any kind in the hands of enlisted men in any branch of the service.

Sorry I must have my dumb hat on today. Please be gentle. But how can you have an alloy that's non-ferrous but ferromagnetic at the same time. It's that "ferro" prefix that's spinning me out. Ferrous in latin means "containing iron".

How about using Cobalt? It's non-ferrous but still magnetic.

Nickel?

As stated by others, there is no shortage of ferromagnetic materials that contain no iron, and some of these can even be coated with approved materials if need-be.

But:

I imagine that ferromagnetism itself will introduce some additional risks, and
(other than weight or ferromagnetism) what is the rational basis for avoiding iron-containing alloys in the first instance?

The rational basiss is that if you give steels a good hard clout with a hard rock/concrete/steel surface they will spark and risk detonating the explosives, believe me it will clear an explosives building in no time if a spark occurs. Having spent sixteen years in an explosives factory I would use slings and hoops on the containers and forget any clever quick release ideas.

The idea of not using iron in the first place is the chance of it sparking - as in having the metal particles produced from an impact igniting in the atmosphere.

I myself would avoid most rubber or plastics due their nature of being able to generate large electrostatic charges on their surfaces from such things as moving air or friction with other materials - you just gotta love the dielectric effect. For example Teflon would be a great coating for chemical resistance and electrical insulation ability but in a stream of dry air will make a great electrostatic generator. (don't Teflon coat your ceiling fan blades)

The properties we need to look at is ferromagnetic ability, conductivity to dissipate any electric charges quickly and safely, and a very high resistance to producing sparks (burning metal fragments) under impact.

A lot of alloys have been mentioned but which ones meet the last requirement?

Thanks. As you say, ferrous alloys are not alone with regard to the tendency for the surfaces to produce sparks - so the "non-ferrous but ferromagnetic" specification is clearly inadequate. I have a vague memory that ferrous materials with more attractive surface properties had been developed for the mining industry - but I could easily be wrong about this.

Might plastics or rubbers with bulk dissipative properties make suitable (thick) coatings? (I believe a range of such materials are used in the semiconductor industry).

Neither these, nor those metals are the solution to the sparking problem. Coming from the semiconductor user side, there is a whole litany of ways to avoid static buildup. But the bottom line is:

1,. Do not generate static charges. It means artifical fibres in clothing are out. Rubber soles on shoes are out, leather in. The floor cannot be a good insulator.

2,. Have everywhere high, but limited resistance paths for discharge. A path, that limits the discharge to a few microAmps will not do damage in contrast to a metal to metal uncontrolled discharge and sparking.

3,. Keep the humidity, say over 70% constantly. Use ion generators, if needed.

So it means for our example, the gripper can be made from any metal, but the touching and gripping should take place with somewhat conducting rubber surfaces of sufficient thickness to force all the (slow) discharge thru it.

No spark = no headache (at least from that single cause).

Very basic questions:

Are there an atmosphere where sparks do not create initial explosion?

In petro-chemistry (I guess) there are purging or neutral gas problem solutions.

Raising the relative humidity in the work area does increase safety during the movement and handling of explosive materials.

However other precautions must be taken as well. All electrical devices such as lighting, relays, process logic controllers (PLC's), electrical motors, and switches must be designated as "explosion proof". All surfaces should be coated with conductive materials to reduce the chance of unintended ignition of rapidly oxidating compounds.

Grounding, shielding and non-triboelectric handling devices must be designed as essential non-substitutable elements in the transportation and handling systems of sensitive materials and monitored by systems which will stop the transportation of sensitive materials if there is a malfunction or human error.

Substitution of handling components is best left to those trained in this highly specialized field. To paraphrase one contributor who so wisely observed, people can die because of the smallest of engineering errors.

Poor old Juan and Tomas seem to have to work in this place without breathing apparatus. Oxygen-free atmosphere would solve one problem.

Yes, that would improve the human element of this problem.

Another stabilizer of fast oxidants is temp. Before Dupont and Nobel, Nitro was frozen to transport. Wagon wrecks were not an explosive problem unless product thawed then you didn't want to be around. Not at 25,000 ft per sec.

The evaporation plants was another place to steer clear of. Vaporized Nitro took only a bad thought to ignite. Steep learning curve when there was no building left to find what the mistake was. Would have hated to be in failure analysis then.

Brad

Am I missing something here - I can't see what problem an oxygen-free atmosphere would solve?

SFIK, explosives come with a solid (occasionally liquid) reactants ready-mixed - indeed, in some cases both reactants form part of the basic molecular structure of the explosive material. That is the reason the chemical action can proceed fast enough for the purpose.

an inert atmosphere would prevent the initial spark which sets of the reactants in the explosive

"Inert atmosphere prevents sparks". It would prevent the temperature of the sparks being maintained by oxidising reaction, but would not prevent them arising in the first instance. That is clearly helpful, but do you have knowledge/evidence that it is sufficient?

I don't know whether these containers ever need to move between plants, but presumably that too would become more complex.

An electromagnetic lift system utilizing eddy currents should allow the use of aluminum containers.

I would be interested to hear how that principle works?

John.

What is the number for ICE? Juan and Thomas are illegal. Thomas' real name is Jose. Do not expect them to perform the function at hand. Instead, rely on us to solve it for them, they perform the work and when they lose an appendage, etc... you can surely bet that we will foot the bill.

Eddy current separators are widely used in the recycling industry. Eddy currents induced by spinning permanent magnetic rotors repel non-ferrous metals, pushing them from the waste stream. While this is not my field, I think that eddy currents induced by an AC-powered electromagnet should be able to push a non-ferrous container against a suitably-designed pickup arm, capturing it, and allowing it to be picked up.

Wouldn't you need to cater for the situation where three containers are initially touching (allowing circulating eddy currents to be set up between them) and then separated?

If the containers cannot be redesigned to allow safe automated mechanical handling, I find it hard to see how eddy-current repulsion would improve the situation.

Having said that, it's not clear to me that the extra degree of freedom that could be provided by magnetic attraction would make a huge difference either; perhaps I'm trying to say that, rather than looking for high-tech solutions the real solution might be to work smarter on handling using existing material (even if it meant redesigning the containers, that would be no more costly than rebuilding them using ferromagnetic materials)

The rest of you apparently don't understand the objective to this game. It is an open question to anyone who thinks they can squeak out an answer. If you can't do it then you can't do it. Don't whine about it. Just admit that this isn't your subject and move on. Haven't any of you taken tests where you didn't know the answers.

By the way, this particular question involves brainstorming. No one answer is right. The key is to come up with the best answer using what you know or can find out.

Logically there shouldn't be any types of metals around that when friction happens a spark flies. So start with a metal of this type. Next. Since vacuum systems aren't really a good idea to begin with ( if the seal breaks or malfunction causes seal to break), we need to open the next door and see if it could help. Why not embed the metal with magnetic beads? Theory (mine) says that any two magnets close enough will either attact or push apart. Even an electromagnet should pick up a magnet, provided the polarity was controlled.

Nor is there any proper way to brainstorm. If it works use it, if it don't file it.

Brad

They could use a Ferromagnetic Stainless Steel Alloy such as a Martensitic Alloy or a Ferritic Alloy. See below.

Martensitic stainless steels are essentially alloys of chromium and carbon that possess a martensitic crystal structure in the hardened condition. They are ferromagnetic, hardenable by heat treatments, and are usually less resistant to corrosion than some other grades of stainless steel. Chromium content usually does not exceed 18%, while carbon content may exceed 1.0 %. The chromium and carbon contents are adjusted to ensure a martensitic structure after hardening. Excess carbides may be present to enhance wear resistance or as in the case of knife blades, to maintain cutting edges.

Ferritic stainless steels are chromium containing alloys with Ferritic, body centered cubic (bcc) crystal structures. Chromium content is typically less than 30%. The ferritic stainless steels are ferromagnetic. They may have good ductility and formability, but high-temperature mechanical properties are relatively inferior to the austenitic stainless steels. Toughness is limited at low temperatures and in heavy sections.

Thanks,

Adolfo S. Leal, Sr.

Are these non-sparking?

They don't need to make a special container for fabrication. Just bring all the materials to same electrical potential. Everything at same potential no spark.

Knock container against a different material -> spark -> bang. End of facility, death of employees, go to jail (do not pass go, do not collect $200)

Why not think "inside" the box this time.

You really don't need a fancy allow at all, just plate or otherwise embed a magnetic form of steel or iron in the non-ferrous alloy container. Sparking won't happen and the magnetic lift won't be impaired by the non-ferrous plating.

Tony

Magnetic Brass????? We have a load of brass parts that were made in China and they stick to our MRI room test magnet "there full of tin". Takes a big magnet, but it is good for a laugh.

m.r.i. room test magnets.

where do you or your employer source them from?

what is thier guass rating?

Could guest mean the superconducting electromagnets usually used to provide the steady field in MRI scanners?

I had a full body MRI scan once. The technician got me to remove jacket and all metallic objects (ring etc). He said not to bother with my trouser belt, even though I pointed out that it had a metal buckle. The 'pull' on the thing was astonishing as I got scanned. They were only looking at my head ( well there's a surprise) so hopefully it didn't mangle the results. Feeling the magnetic pull certainly took my mind off those nasty noises you get inside a scanner.

The Idea of using a strong magnetic field in a uncontrolled environment where interaction with any conductor is possible is at the very least doomed to boom. Since just passing a magnetic field through a conductor causes a current this in itself can create an electrical spark as opposed to a friction spark. Unless their intention is sabotage I would relieve them of their duties as soon as possible.

thank god somebody out there can think . any magnetic field has the potential to create electrical sparks , and as electrical sparks tend to be considerably hotter than impact generated sparks , are always going to be a more significant risk . hence these darwin award applicants really should not be working in the h.e. industry in the first place ...

Glue a bunch of rubber refrigerator magnets all over the containers ;)

Non-sparking rubber, of course. Interested to see what happens when you place two such containers side by side

I have had a look at most of the answers, and am very impressed with your engineering knowledge. My only concern, as perhaps it is to many people reading this is that none of you have given any consideration as to the cost of providing some of these alloys, which I would suggest would be prohibitive. My opinion would be to go with electro magnetic fields where possible, and insulate the cables in a hard nylon to keep cost down.

Neil

You are right in general.

In most cases I had to design in Ex environment, costs were the last factor considered.

In this case eliminate of sparking ( or its explosion initiative) is First Thing to solve, and solve even in redundancy. Exi rules e.g. apply to electric sparks.

How about modifying the site instead of the containers. Use tennis balls and raised floor. Enough tennis balls to cover the raised floor area and underneath it. Let the containers rolloff the tennis balls while the balls would fall under the raised floors and be pushed back up to the floor area at the opposite end (departing side). The raised floor should have space for balls to fall near the walls and have a curve to let the balls roll under the raised floor and back upwards at the other end.

There is something I haven't seen brought up (or missed).

What happens when the electromagnetic containers touch when the electrons are massed close to the contact point of one and the electron holes are massed close to the contact point of the other. It should create a spark, air or not.

One would have to be overly careful with this system to prevent the electromagnetic field from inducing or directly causing an ignition source.

Making motherboards ESD was a big issue. Just rolling a cart across a floor could create a large voltage potential. One metal cart that was suppose to be ESD certified was shocking the handlers and the Brass (bosses) didn't believe us until we measured a 35,000 volt static charge buildup and more or less forced them to observe it.

Any conductor that has an EMF field applied to it strong enough to propel it would induce the free electrons of the conductor to move, creating a potential.

So my opinion is: Bad Idea.

Brad

Missed it, see 44

Admittedly being a utility tech. I don't know alot about manufacturing processes. I've read thru quite a few of the responses and some sound pretty good to me. I have one concern though. In an enviroment using an electro-magnetic system regardless of what materials are being used isn't this type of enviroment prone to static discharges caused by the electro-magnet itself? I do know a bit about electrical fields and anything running a current thru it such as this builds capacitance. Maybe I'm wrong?

Thanks all. We enjoyed the discussion.

Just add to my knowledge, whether like AlNiCo, this alloy of copper-manganese-Aluminium or Manganese-Aluminium Bronze also retains the magnetism (Or traces of it) and under what condition our quick release mechanism can work with maximum efficiency.

During handeling heat-treatable Aluminium alloy (With 1 per cent Managanese and 1 per cent Magnessium) starts retaning electrostatic charges.

Whether any body has observed the same phenominon.