Why does metal spark?

[knowlittle]

If I am handling tools in a potentially explosive atmosphere, I must use tools that don't spark.
1) Why does metal spark? S
2) What metals are known for not sparking?
3) How do I test the sparking tendency of a new tool?
Thanks.

 

[unclesyd]

Here is a very good paper from Canada this explains in detail you question.

http://www.ccohs.ca/oshanswers/safety_haz/hand_tools/nonsparking.html

The spark is mainly due to oxidation of a metal or one of it's constituents. There are relatively minor reasons for generating a spark when two materials come together with a little force.

 

[knowlittle]

Thanks for the link. Unfortunately, it does not say much about the science behind sparking.

I have a set of tools sitting on my desk. They are blue Crastsman combination wrenches. According to web, they are physical vapor depositied of some titanium. I have to run tests for safety in potentially hazardous environment, one of which would be sparking.

 

[TVP]

The blue Craftsman tools to which you refer are still manufactured by forging steel into the desired shape, it's just the blue coating that is applied by PVD. The coating is actually a thin film of titanium oxynitride (TiO_xN_y).

 

[saberblue]

You will probably need to buy special non sparking tools. They are typically made out of berillium - copper and of course that sets up its own set of issues as berillium dust is toxic.

In my experience sparking occures where there is a static electric discharge or when two materials come togeather hard enough for a chip to be produced. If the resulting chip then contains enough energy that the chip eill react with the oxygen in the air and burn>

You might want to talk to the people at the fire department for some nuts and bolts help.

the devil is often in the details!

 

[knowlittle]

We have non-sparking, yellow colored tools in our tool drawers. Also, I earn bread and butter by dealing with static charge. But metal sparks I am unfamiliar with. Thanks for explaining how metal spark is generated and what the blue coating is.

 

[jedward]

Ampco metal (beryllim free) is used to make non-sparking tools along with beryllium copper
are available thru suppliers such as mcmaster-carr and grainger

 

[unclesyd]

Even though these "spark- resistant" tools are called "non-sparking" they still can be instrumental in creating a spark under certain conditions.

One case is where something is painted with Aluminum and has been hot. An example that I used many times are where Cast iron steam traps and strainers are painted with Al paint. If you strike the surface of the painted component a glancing blow with a "non-sparking" tool the majority of the time it will create a spark due to the thermite reaction.

For a tool to be certified "spark resistant" it has to be approved by the Factory Mutual Research Corporation and marked as such. No other testing mitigates this approval. This is the only specific/approval (FM 7910) that satisfies all insurance requirements.
There are other specifications if the tool has to be "non-magnetic"

http://www.fmglobal.com/assets/pdf/fmapprovals/7910.pdf

 

[EdStainless]

I can't locate the NASA document, but they discuss the ignition of fumes from non-sparking tools. Even though no spark was formed the local temperature at impact exceeded the ignition temp of the mixture and boom.

Tools for your application must have FM approval.

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Plymouth Tube

 

[knowlittle]

Thank you ladies and gentlemen. Based on what I learned from you, I can say that the thin blue surface coating is not going to improve sparking resistance whole lot. If that's the case, I don't see a need to run non-sparking tests. (thanks for fmgloval.com link). I will go ahead with other tests that need to be done. Thanks again.

 

[PeterCharles]

I notice the phrase "potentially explosive atmosphere". Is this related to the European ATEX directives? If so what Zone will you be working in? If it's high (0 or 20) should you actually be working there at all?

 

[knowlittle]

Thanks for the reply, PeterCharles,
The term "European ATEX Directive" I don't recognize. I work in the space exploration industry. The "potentially explosive atmosphere" in this case is if a hypergolic fluid leaks out to the air. If fuel/air mixture is right, it can ignite from a spark (mechanical impact, abrasive wear, static electricity).

 

[btrueblood]

If your hypergolic fuel is hydrazine or one of its derivatives, you won't be able to work in a potentially explosive atmosphere without breathing equipment (and possibly not even then, due to regulatory restrictions)...but you probably know that. Another potential ignition source you should worry about, however, is catalysts, both conventional and photo- (light) assisted. Copper and hydrazines...not a good mix.

 

[btrueblood]

Also, if you are dealing with hydrazines, you should have a copy of Eckhardt Schmidt's Hydrazine and Its Derivatives, McGraw-Hill. He was revising it when I worked with him back in the late '90s, so it should be out in revised edition. If the information you need about fuels is not in that book, then either you don't really need it or, you will need to start thinking about a science project.

 

[knowlittle]

Thanks for the reminder to purchase the second edition of Hydrazine and Its Derivatives. We have several copies in our areas but I want one FOR MYSELF! I need to study the book and pick up some more basic knowledge.

 

[0707]

go to

http://www.touchoilandgas.com/master-sparking-tools-a704-1.html

maybe it helps

Luis Marques

 

[riskengr]

The American Pertroleum Institute (API) has completed a lot of research on this topic and has published their findings in their Publ 2214. You may want to lookit over if your not familiar with it.

In applying it you will need to consider the differences in the ignition energy requirements between the fuels your dealing with and typical hydrocarbons. At the end of the day they found that non-sparking HANDTOOLS (Does not apply to handheld power tools) were unnecessary for most hydrocarbon applications, as the human body could not generate a spark of suffciient energy.

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