Technopriest
Mechanical
We have a little problem on the ATEX protection on a horizontal dryer.
The dryer is little more of a stainless steel cylinder with an agitator in the middle. There is a jacket for heating, usually at about 60°C.
The dryer will have to dry a powder that is nonconductive and potentially explosive. The customer requires a Zone 0 protection (so class 1).
The cylinder itself is safe; the agitator is slow-moving, and with the same electric potential of the cylinder's walls. There is also a temperature control device on the wall that prevents a dangerous overheating of the walls.
So the machine itself do not present any active ignition source. However the powder (the product to be dryed) can have electric discharges on it's own, due to it's nonconductive nature.
My questions are:
1) do the static discharges that are due to the product inside the machine (the powder) need to be contemplated in our ATEX protection? They are not an ignition cause due to the machine..
2) If the powder has to be protected from it's own static discharges, are there any other ways than inert atmosphere/vacuum?
3) During discharge and load (when it is not possible to have vacuum or inert atmosphere inside the machine), is there any need of ATEX protection? If yes, do you have any suggestions?
Any help will be greatly appreciated. Any reference to directives or such will be, too.
Che Dio ce la mandi buona, o almeno ce la mandi- Massimiliano Eusebi
Check eng-tips rules: faq731-376
The dryer is little more of a stainless steel cylinder with an agitator in the middle. There is a jacket for heating, usually at about 60°C.
The dryer will have to dry a powder that is nonconductive and potentially explosive. The customer requires a Zone 0 protection (so class 1).
The cylinder itself is safe; the agitator is slow-moving, and with the same electric potential of the cylinder's walls. There is also a temperature control device on the wall that prevents a dangerous overheating of the walls.
So the machine itself do not present any active ignition source. However the powder (the product to be dryed) can have electric discharges on it's own, due to it's nonconductive nature.
My questions are:
1) do the static discharges that are due to the product inside the machine (the powder) need to be contemplated in our ATEX protection? They are not an ignition cause due to the machine..
2) If the powder has to be protected from it's own static discharges, are there any other ways than inert atmosphere/vacuum?
3) During discharge and load (when it is not possible to have vacuum or inert atmosphere inside the machine), is there any need of ATEX protection? If yes, do you have any suggestions?
Any help will be greatly appreciated. Any reference to directives or such will be, too.
Che Dio ce la mandi buona, o almeno ce la mandi- Massimiliano Eusebi
Check eng-tips rules: faq731-376