Explosion risk analysis

Posted in: , on 16. Jan. 2006 - 00:36

The company I am working for is designing a slotting machine for carbon blocks (anodes) for aluminum industry.

Our customer rated that machine as ATEX 21. He gave us the folloming data, based on crushed calcined material:

· Maximum explosion pressure Pmax: 7.9 bar

· Maximum pressure increase: dP/dtmax: 276

· Dust explosion factor Kst: 75 bar*m/s

· Dust explosion class St 1

· Minimum ignition temperature (MIT): 690 oC

· Minimum ignition energy (MIE): >1,000 mJ

· Smoldering temperature >400oC

From these data, how should we proceed to analyse the risk of explosion?

The customer says that an electric spark cannot create an explosion, considering dust MIE he estimates. Our preliminary analyse makes us think that the only possible source of explosion remaining is surface temperature. See MIT and MIE listed above.

We are looking for people who are used to dealing with that type of risk analysis. ■

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Carbon Anode Risk

Posted on 16. Jan. 2006 - 09:04

Is your slotting machine closed in? If so, is it being aspirated? If so, you may need explosion protection, but I doubt it. You should check to see if there are any losses for the aluminum industry or for slotting machines and related equipment that occured because of a dust explosion. I would hazard a guess that it would be very low probability that such a machine could contain a concentration of flammable dust great enough to support a chain reaction. There is also a low likelihood that there would be credible ignition source in this type of process.

Regards,

Bill ■

Re: Explosion Risk Analysis

Posted on 17. Jan. 2006 - 04:26

An important question I want to ask: is carbon dust, made from slotting anodes, considered as flammable material? If not, does ATEX still apply? ■

Re: Explosion Risk Analysis

Posted on 17. Jan. 2006 - 01:30

I assume that the data contained in your initial post relates to the dust that will be generated in your machining operation.

If so then clearly the dust is combustible and it follows that an explosion is possible.

But your client has already established that the applicable ATEX Zone is Zone 21 and you should carry out your risk assessment accordingly, implimenting its findings in your design. The previous references I quoted will guide you on this. Alternatively you could employ a consultant to do the work for you. ■