4 replies to this topic

[Hash90]

Hi All,

 

I am trying to work out if the conditions within a mixing vessel could potentially create a dust explosion.

 

The vessel is sealed by the lowering of a mixing head. The vacuum pump is turned on and the vessel is pulled to 0.95bar - so only a small vacuum is pulled.

 

What would the oxygen concentration be inside the vessel at this point? An explosive powder is added to the vessel at this point under vacuum and I want to prove that the oxygen concentration in the vessel head space is <14% which would mean a dust explosion is unlikely.

 

Edited just to clarify - pulling vacuum in the vessel so that we can draw in a powder which is held in a sealed bag. A lance is pierced into the bag and the other end of the lance is a hose with a camlock which is connected to a nozzle on the vessel head. Not much oxygen in the bag itself.

 

Thanks for any help

Edited by Hash90, 26 July 2024 - 04:39 AM.

[shvet1]

No way if you introduce into a vessel no a gas other than air. For some guide for inerting see CEN/TR 15281.

Edited by shvet1, 26 July 2024 - 04:24 AM.

[Pilesar]

There is more to the process than you describe. Some other secret ingredient is mixing with the bag's mystery contents. The hazard scenarios seem to be for non-normal operation. 1) vacuum pulled, bag is busted, mixer seal breaks and air fills the vessel. 2) vacuum pulled, bag is busted, second secret ingredient does not enter and no one notices, operators empty vessel except the contents are not as usual and some explosive powder remains, air is allowed into supposedly empty vessel. When evaluating hazards, it is the unplanned events that generally cause problems.

[breizh]

Hi,

Let you perform a HAZOP study! 

What is the powder? Did you get the relevant data about the powder (particle size distribution, KST, Maxi pressure ,...)

I share with you a nice document about dust explosion, unfortunately in French. I'm sure you have a translator in your PC to support the work.

Another document is about the mitigation of the risks.

Edit:

A more sophisticated option:

https://www.dedietri...ing/powder-pump

 

Good luck.

Breizh 

Attached Files

•  prevent-combustible-dust-explosions-with-n2-inerting.pdf   418.23KB   4 downloads
•  Explosion poussiere.pdf   1.35MB   4 downloads

[shvet1]

Note that powder itself may contain the large amount of air having enough potential to interfere inerting,