Soot and sparks with HVOF

[Shawn Callahan]

I have a JP5000 torch:

Why am I seeing a sooty buildup on the outside of the combustion chamber part?

-AND-

Occasionally there are white sparks that come out with the flame. Most likely source is...?

Thanks

[KevGarty]

I have a JP5000 torch:

Why am I seeing a sooty buildup on the outside of the combustion chamber part?

-AND-

Occasionally there are white sparks that come out with the flame. Most likely source is...?

Thanks

The sparks you are seeing is more than likely barrel loading the powder builds up inside the barrel then eventually heats up and comes out the end of the gun or causes your feed lines to burn off (Check your parameters i.e Flows, Barrel Length, feed rate etc) Also check the quality of your Interconnector and Stabilizer make sure everything is still in tolerance

Not sure what you mean by sooty build up on the outside. Inside the combustion chamber you will get Carbon Build up but never seen it on the outside. What I have seen it the combustion chamber becoming discoloured and almost rusting due to poor quality cooling water. Make sure your water is Deionized.

See how you get on with the above

Cheers

Kev

[Shawn Callahan]

Thanks Kev.

I'm getting the sparks with no powder flow and long after powder has been switched off. I had a thought it was the result of a small leak (though not visible when I run the pump with the torch off) and was indirectly leading to the sparks by accelerating the degradation of the chamber wall. Problem with that theory is there are no obvious o-ring or seating issues when I take the torch apart.

As for the sooty outside; total head scratcher for me too. It is every bit as dark and friable as the carbon build up typical for the inside but in much less quantity; more like a film. Water is DI and fresh as could be save for producing it on site.

Thanks for your consideration.

Shawn

[KevGarty]

Thanks Kev.

I'm getting the sparks with no powder flow and long after powder has been switched off. I had a thought it was the result of a small leak (though not visible when I run the pump with the torch off) and was indirectly leading to the sparks by accelerating the degradation of the chamber wall. Problem with that theory is there are no obvious o-ring or seating issues when I take the torch apart.

As for the sooty outside; total head scratcher for me too. It is every bit as dark and friable as the carbon build up typical for the inside but in much less quantity; more like a film. Water is DI and fresh as could be save for producing it on site.

Thanks for your consideration.

Shawn

Head scratcher indeed !

There doesnt need to be powder flowing to cause the sparks as the barrel could have loaded previously and it has stuck to the barrel wall and when you light the gun it causes the loaded powder to detach (hope that makes sense) if your carrier flow is incorrect then the spped it is injected into the flame could be too slow or fast causing the powder to stick to the barrel and doing the above?

Have you done a spot test ? etc.

Cheers

Kev

[Brent]

i had been told that the white sparks that leave the gun were just bits of the carbon buildup leaving the combustion chamber??

[GMA thermal spray systems]

Hello I build liquid fuel system type JP5000. The problem is simple use correct powder and not agglomerated fine powder grains. The energy in the combustion chamber is around 300KW and is sufficient to break in the sphere balls glued together into smaller spheres. It makes also a tribo-electric effect and sparks can be seen in the plastic hoses specially if you are using argon as carrier gas. This stop using nitrogen instead. IT happens when you buy cheaper and cheaper powder so stay with the old classical powder who have made their proof and reliable. Of course worn out parts can be in cause but the smaller particles fly back, stick to unburn fuel and goes to injectors then bang you have the hoses melted.
yves.plusquin@skynet.be